Monday, January 7, 2013

Using the SG3525 PWM Controller - Explanation and Example: Circuit Diagram / Schematic of Push-Pull Converter


PWM is used in all sorts of power control and converter circuits. Some common examples include motor control, DC-DC converters, DC-AC inverters and lamp dimmers. There are numerous PWM controllers available that make the use and application of PWM quite easy. One of the most popular of such controllers is the versatile and ubiquitous SG3525 produced by multiple manufacturers – ST Microelectronics, Fairchild Semiconductors, On Semiconductors, to name a few.

SG3525 is used extensively in DC-DC converters, DC-AC inverters, home UPS systems, solar inverters, power supplies, battery chargers and numerous other applications. With proper understanding, you can soon start using SG3525 yourself in such applications or any other application really that demands PWM control.

Before going on to the description and application, let’s first take a look at the block diagram and the pin layout.







Pins 1 (Inverting Input) and 2 (Non Inverting Input) are the inputs to the on-board error amplifier. If you are wondering what that is, you can think of it as a comparator that controls the increase or decrease of the duty cycle for the “feedback” that you associate with Pulse Width Modulation (PWM).

This functions either to increase or decrease the duty cycle depending on the voltage levels on the Inverting and Non-Inverting Inputs – pins 1 and 2 respectively.

  • When voltage on the Inverting Input (pin 1) is greater than voltage on the Non-Inverting Input (pin 2), duty cycle is decreased.
  • When voltage on the Non-Inverting Input (pin 2) is greater than voltage on the Inverting Input (pin 1), duty cycle is increased.
 
The frequency of PWM is dependent on the timing capacitance and the timing resistance. The timing capacitor (CT) is connected between pin 5 and ground. The timing resistor (RT) is connected between pin 6 and ground. The resistance between pins 5 and 7 (RD) determines the deadtime (and also slightly affects the frequency). 

The frequency is related to RT, CT and RD by the relationship:


With RT and RD in Ω and CT in F, f is in Hz.

Typical values of RD are in the range 10Ω to 47Ω. The range of values usable (as specified by the manufacturers of SG3525) is 0Ω to 500Ω.

RT must be within the range 2kΩ to 150kΩ. CT must be within the range 1nF (code 102) to 0.2µF (code 224). The oscillator frequency must be within the range 100Hz to 400kHz. There is a flip-flop before the driver stage, due to which your output signals will have frequencies half that of the oscillator frequency that is calculated using the above mentioned formula. So, if you are looking to use this for a 50Hz inverter, you require drive signals of 50Hz. So, the oscillator frequency must be 100Hz.

A capacitance connected between pin 8 and ground provides the soft-start functionality. The larger the capacitance, the larger the soft-start time. This means that the time taken to go from 0% duty cycle to the desired duty cycle or maximum duty cycle is larger. So, the duty cycle increases more slowly initially. Keep in mind that this only affects initial rate of increase of duty cycle, ie, the rate of increase of duty cycle after the SG3525 starts up.

Typical values of the soft-start capacitance lie within the range 1µF to 22µF depending on the desired soft-start time.

Pin 16 is the output from the voltage reference section. SG3525 contains an internal voltage reference module rated at +5.1V that is trimmed to provide a ±1% accuracy. This reference is often used to provide a reference voltage to the error amplifier for setting the feedback reference voltage. It can be directly connected to one of the inputs or a voltage divider can be used to further scale down the voltage.

Pin 15 is VCC – the supply voltage to the SG3525 that makes it run. VCC must lie within the range 8V to 35V. SG3525 has an under-voltage lockout circuit that prevents operation when VCC is below 8V, thus preventing erroneous operation or malfunction.

Pin 13 is VC – the supply voltage to the SG3525 driver stage. It is connected to the collectors of the NPN transistors in the output totem-pole stage. Hence the name VC. VC must lie within the range 4.5V to 35V. The output drive voltage will be one transistor voltage drop below VC. So when driving Power MOSFETs, VC should be within the range 9V to 18V (as most Power MOSFETs require minimum 8V to be fully on and have a maximum VGS breakdown voltage of 20V). For driving logic level MOSFETs, lower VC may be used. Care must be taken to ensure that the maximum VGS breakdown voltage of the MOSFET is not crossed. Similarly when the SG3525 outputs are fed to another driver or IGBT, VC must be selected accordingly, keeping in mind the required voltage for the device being fed or driven. It is common practice to tie VC to VCC when VCC is below 20V.

Pin 12 is the Ground connection and should be connected to the circuit ground. It must share a common ground with the device it drives.

Pins 11 and 14 are the outputs from which the drive signals are to be taken. They are the outputs of the SG3525 internal driver stage and can be used to directly drive MOSFETs and IGBTs. They have a continuous current rating of 100mA and a peak rating of 500mA. When greater current or better drive is required, a further driver stage using discrete transistors or a dedicated driver stage should be used. Similarly a driver stage should be used when driving the device causing excessive power dissipation and heating of SG3525. When driving MOSFETs in a bridge configuration, high-low side drivers or gate-drive transformers must be used as the SG3525 is designed only for low-side drive.

Pin 10 is shutdown. When this pin is low, PWM is enabled. When this pin is high, the PWM latch is immediately set. This provides the fastest turn-off signal to the outputs. At the same time the soft-start capacitor is discharged with a 150µA current source. An alternative method of shutting down the SG3525 is to pull either pin 8 or pin 9 low. However, this is not as quick as using the shutdown pin. So, when quick shutdown is required, a high signal must be applied to pin 10. This pin should not be left floating as it could pick up noise and cause problems. So, this pin is usually held low with a pull-down resistor.

Pin 9 is compensation. It may be used in conjunction with pin 1 to provide feedback compensation.

Now that we’ve seen the function of each pin, let’s design a circuit with the SG3525 and see how it is put to use practically.

Let’s make a circuit running at 50kHz, driving MOSFETs (in a push-pull configuration) that drive a ferrite core which then steps up the high frequency AC and then is rectified and filtered to give a 290V regulated output DC that can be used to run one or more CFLs.

For the turns calculation, check out my article "Ferrite Transformer Turns Calculation for High-Frequency/SMPS Inverter": http://tahmidmc.blogspot.com/2012/12/ferrite-transformer-turns-calculation.html

So here’s the circuit (click on the circuit to enlarge the image):



Let’s analyze it and see what I’ve done.

You can firstly see that the supply voltage has been provided and ground has been connected. Also notice that VC has been connected to VCC. I’ve added a bulk and a decoupling capacitor across the supply pins. The decoupling capacitor (0.1µF) should be placed as close to the SG3525 as possible. You should always use this in all your designs. Do not omit the bulk capacitor either, although you may use a smaller value.

Let’s see pins 5, 6 and 7. I’ve added a small resistance RD (between pins 5 and 7) that provides a little deadtime. I’ve connected RT between pin 6 and ground and CT between pin 5 and ground. RD = 22, CT = 1nF (Code: 102) and RT = 15k. This gives an oscillator frequency of:


As the oscillator frequency is 94.6kHz, the switching frequency is 0.5 * 94.6kHz = 47.3kHz and this is close enough to our target frequency of 50kHz. Now if you had needed 50kHz accurate, then the best way would have been to use a pot (variable resistor) in series with RT and adjust the pot, or to use a pot (variable resistor) as RT, although I prefer the first as it allows for fine tuning the frequency.

Let’s look at pin 8 now. I’ve connected a 1µF capacitor from pin 8 to ground and this provides a small soft-start. I’ve avoided using too large a soft-start as the slow duty cycle increase (and thus the slow increase in voltage) causes problems when using CFLs at the output.

Let’s look at pin 10 now. Initially it’s pulled up to VREF with a pull-up resistor. So, PWM is disabled and does not run. However, when the switch is on, pin 10 is now at ground and so PWM is enabled. So, we’ve made use of the SG3525 shutdown option (via pin 10). Thus the switch acts like an on/off switch.

Pin 2 is connected to VREF and is thus at a potential of +5.1V (±1%). The output of the converter is connected to pin 1 through a voltage divider with resistances 56kΩ and 1kΩ. Voltage ratio is 57:1. At feedback “equilibrium”, voltage at pin 1 is 5.1V as well as this is the target of the error amplifier – to adjust the duty cycle to adjust the voltage at pin 1 so that it is equal to that of pin 2. So, when voltage at pin 1 is 5.1V, voltage at output is 5.1V * 57 = 290.7V and this is close enough to our 290V target. If greater accuracy is required, one of the resistors can be either replaced with a pot or in series with a pot and the pot adjusted to give required reading.

The parallel combination of the resistor and capacitor between pins 1 and 9 provides feedback compensation. I won’t go into detail into feedback compensation as it is a vast topic on its own.

Pins 11 and 14 drive the MOSFETs. There are resistors in series with the gate to limit gate current. The resistors from gate-to-source ensure that MOSFETs don’t get accidentally turned on.

So that’s about it. You can see that this is quite an easy circuit to design. If you’ve understood all of this, you can now design circuits with SG3525 yourself. Try to make a few, eg for 50Hz output and with isolated feedback. If you can’t don’t worry, I’ll put up another article with a few more circuits using SG3525 so that you become completely clear with it (if you haven’t already).

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Reference documents:

Ferrite Transformer Turns Calculation for High-Frequency/SMPS Inverter: http://tahmidmc.blogspot.com/2012/12/ferrite-transformer-turns-calculation.html

266 comments:

  1. A tip you got some good information here but, the colour scheme you choose are not good for readability, its really bad.. Try white on black instead if the inverse (as you have it currently).

    ReplyDelete
    Replies
    1. I'll keep that in mind and will make changes if necessary. Thanks for the input.

      Regards,
      Tahmid.

      Delete
    2. hello tahmid I have a question here. I am building a high frequency inverter. I use irfz46 in the dc to dc section and the dc voltage stands up good under a load of 300 watt when I use irf3205 in stead which can handle more current the dc voltage falls off to 35v from 165v . Could this be defective 3205 fets or I need to change components to match the irf3205. Thanks for ur support

      Delete
    3. It could be defective IRF3205's. But before that, you should make sure that the MOSFETs are properly driven. If they aren't properly driven to turn them fully on, the problem could lie there. So, add a driver circuit (totem-pole or discrete driver based, eg TC427) and then test again.

      See here: http://tahmidmc.blogspot.com/2012/12/low-side-mosfet-drive-circuits-and_23.html

      Regards,
      Tahmid.

      Delete
    4. Oh thank you Tahmid i will try this driver and let you know the results.keep the good work going

      Delete
  2. Hi Tahmid,
    What is the role of R3 in the above circuit?

    Regards,
    Prasanth.

    ReplyDelete
  3. Hi Prasanth,

    R3 pulls up pin 2 to the level of VREF and is thus used as reference voltage (at pin 2) for the error amplifier.

    Regards,
    Tahmid.

    ReplyDelete
  4. Hi Tahmid,
    I am sorry if u misunderstood my question. I mean if the value of R3 is made 0 ohms, is it going to make any difference? If I am right, the input of the comparators are having very high impedance.

    Regards,
    Prasanth.

    ReplyDelete
    Replies
    1. Yeah, it shouldn't be a problem. If you won't use pin 2 with any voltage divider circuit and just need to provide 5V, you should just be able to connect it to VREF. The inputs to the error amplifier should have high impedance.

      Regards,
      Tahmid.

      Delete
  5. hi,
    tahmid i really need your help i already mailed you some info may be you didnt chek it kindly reply me i m in trouble.
    Regards:
    Waqas.(mah****le@hotmail.com)

    ReplyDelete
    Replies
    1. Check your inbox.

      I'll answer your question here as well:

      The PIC, in a sine wave inverter, is used to generate the SPWM signals and do the "housekeeping" tasks as well - battery low cut, overload, battery high cut and other protection, etc. And you also have the benefit of not being able to copy someone else's work!

      Regards,
      Tahmid.

      Delete
  6. thanks tahmid for your tutorials.

    please can you guide me on how to use TL431 and optocoupler as feeback for sg3525.

    thanks..

    ReplyDelete
    Replies
    1. Hi abm,

      I'm glad that the tutorials were of help.

      I'll try to write up an article on TL431 and optocoupler for feedback for SG3525.

      Regards,
      Tahmid.

      Delete
    2. thanks tahmid i will be looking forward to that.

      you just made these SG3525 a plaything for me i am enjoying it. i have placed order fro ferrite inductors hope to start learning smps, atleast enough of simulation.

      thanks for all your effort may God grant you more ease of wisdom and knowledge (amen).

      Delete
  7. hi tahmid """"

    my name is mohamed mustafa from egypt please help me to design my power inverter >>> i bought ferrite core ETD34 and i find that at 100 khz this transformer give 321 watt " from data sheet " can i operate irfz44n at 100 khz or this not advisable and i calculate but with 75 khz the number of turns of primary and secondary and i found it :::: Np= 3 turns and Ns= 96 turns >>>> what is the thickness of this wire of both primary and secondary
    my email :: ENG_MOHAMEDMUSTAFA@YAHOO.COM

    ReplyDelete
    Replies
    1. Hi,

      321W mentioned in the datasheet is the absolute maximum. You should use it at a considerably lower power level.

      The thickness of the wire of the primary and secondary will depend on your selected power level. Remember that you can't use too thick wires due to skin effect, especially since you're operating at 100kHz. Don't use wires thicker than 26 SWG. Then, use multiple 26 SWG wires to handle the required current.

      Regards,
      Tahmid.

      Delete
    2. for input 12v 21A 75KHZ 250 watt ...
      for output 310V 0.9A 75KHZ 250 watt...
      i wound the primary with wire thick = 22SWG
      and the secondary with wire thick = 27SWG
      Is that satisfied ?
      thank you for helping me

      Delete
  8. Is there any way to make duty cycle control on SG IC to be from 1 to 99%?....I built few circuits and i tryed many things but i can reach this range on 300Khz.

    ReplyDelete
    Replies
    1. Are you attempting to control the duty cycle without a feedback loop?

      Delete
  9. hi tahmid ::
    my design: for my ferrite ETD34transformer
    for input 12v 21A 75KHZ 250 watt ...
    for output 310V 0.9A 75KHZ 250 watt...
    i wound the primary with wire thick = 22SWG
    and the secondary with wire thick = 27SWG
    Is that satisfied ?
    thank you for helping me

    ReplyDelete
    Replies
    1. Before I go on to check for current rating, I will let you know that SWG 22 wire is too thick for use at 75kHz. Skin effect will play a large part and at high load, the wire will overheat. Use quite a few SWG 26 in parallel to make up the wire with required current handling capacity.

      Regards,
      Tahmid.

      Delete
  10. hi tahmid :
    i purchase the component of above design but i have a question .... in the LC filter of the output the capacitor is 10 micro ..1- what is the withstand voltage of the capacitor ?????
    2-what is the specification of this capacitor ?
    3-have you pcb lay out of this design?
    thank you very much ..........

    ReplyDelete
    Replies
    1. 1) Make sure the voltage is higher than the maximum output voltage. A 400V capacitor would be good since I assume your output voltage would be lower than 330V. If it's higher than that and close to 400V, use 630V.

      2) It is an electrolytic capacitor. Try to use a low-ESR capacitor.

      3) Unfortunately, I don't have the PCB design for this. There are many free PCB design software you can use to design the PCB yourself.

      ExpressPCB: http://www.expresspcb.com/expresspcbhtm/download.htm
      Cadsoft EAGLE (freeware with limitation): http://www.cadsoftusa.com/download-eagle/freeware/
      PCB123: http://www.sunstone.com/pcb123.aspx
      DesignSpark PCB: http://www.designspark.com/page/designspark-pcb-home-page
      DipTrace (freeware with limitation): http://www.diptrace.com/
      TINA: http://www.tina.com/English/tina/
      gEDA: http://www.gpleda.org/
      KiCad EDA: http://www.kicad-pcb.org/display/KICAD/KiCad+EDA+Software+Suite

      There are other free PCB design software available as well.

      So, download one. Go through the manual and start using it.

      I've used ExpressPCB and PCB123 (a little bit of EAGLE as well). I'd say they're pretty good and certainly good enough for your purpose.

      Hope this helps!

      Regards,
      Tahmid.

      Delete
  11. Hi,
    it's really an interesting topic "Using the SG3525 PWM Controller - Explanation and Example: Circuit Diagram / Schematic of Push-Pull Converter ".As far as my consolation it is an excellent explanation.Thank you dear.
    Inverter charger

    ReplyDelete
    Replies
    1. You're welcome!

      I'm glad you found it helpful.

      Regards,
      Tahmid.

      Delete
  12. hello tahmid keep up the good work. I have a question i see ur calculations for transformer.if I calculate the primary turns for a 12 dc supply to 330v say I want to step up my system to 24dc can i use the same primary turns and adjust the secondary for the 330v or my primary turns would also have to be different for 24v.. Thank u for ur support

    ReplyDelete
    Replies
    1. You should recalculate for 24VDC. Keeping the same primary turns means that you'll have twice the flux density you'll do for 12VDC.

      Regards,
      Tahmid.

      Delete
  13. hi tahmid ",,,,,
    plz .. i want PCB of this design

    ReplyDelete
    Replies
    1. I haven't designed PCB for this. There are many free PCB design software you can use to design the PCB yourself.

      ExpressPCB: http://www.expresspcb.com/expresspcbhtm/download.htm
      Cadsoft EAGLE (freeware with limitation): http://www.cadsoftusa.com/download-eagle/freeware/
      PCB123: http://www.sunstone.com/pcb123.aspx
      DesignSpark PCB: http://www.designspark.com/page/designspark-pcb-home-page
      DipTrace (freeware with limitation): http://www.diptrace.com/
      TINA: http://www.tina.com/English/tina/
      gEDA: http://www.gpleda.org/
      KiCad EDA: http://www.kicad-pcb.org/display/KICAD/KiCad+EDA+Software+Suite

      There are other free PCB design software available as well.

      So, download one. Go through the manual and start using it.

      I've used ExpressPCB and PCB123 (a little bit of EAGLE as well). I'd say they're pretty good and certainly good enough for your purpose.

      Regards,
      Tahmid.

      Delete
  14. hi tahmid you are doing some excellent work i see your calculations for the number of primary turns for transformer from 12VDC to 330V could you please calculate from 24VDC TO 330V the number of primary turns because i dont fully understand the steps after setting out the equasion thanks in advance

    ReplyDelete
    Replies
    1. You should try it yourself by following the steps mentioned here: http://tahmidmc.blogspot.com/2012/12/ferrite-transformer-turns-calculation.html

      Specify the problems you have. Then, you can learn by doing it yourself and I can help you if you are stuck.

      Regards,
      Tahmid.

      Delete
    2. If i change the number of Transformer turn ratio accordingly for 24V Dc , should the values of other parameters remain same ??? @tahmid

      Delete
  15. hi tahmid ::
    my design: for my ferrite ETD34transformer
    for input 12v 21A 75KHZ 250 watt ...
    for output 310V 0.9A 75KHZ 250 watt...
    i wound the primary with wire thick = 26SWG*4
    and the secondary with wire thick = 35SWG*3
    when applying 12v the circuit give 310 v but the transformer make noise sound .... is this noise sound refer to problem?

    ReplyDelete
    Replies
    1. How loud is the sound?

      Ensure that the transformer and winding are tight and that there's no scope for any sort of "movement". Dipping the transformer in varnish should help.

      Many a times, the reason for the audible noise is due to problems in the feedback circuitry. The oscillations in the unstable feedback circuitry cause the noise. Stabilizing the feedback loop should help.

      Regards,
      Tahmid.

      Delete
  16. hiiiiiiiiiii
    you are very genius
    plz ...i have done 12v to 310 v circuit and i want circuit diagram of H-bridge to produce 220 v , 50 hz pure sine wave ...thank you very much

    ReplyDelete
    Replies
    1. Hi,

      Thanks for the compliment.

      You can find many circuits if you search on Google. I think you should first search on Google, if you haven't done so already. If you are unable to choose one due to problems in understanding criteria, etc, feel free to ask for help.

      Regards,
      Tahmid.

      Delete
    2. i had search on internet but useless have you circuit diagram for driving h-bridge ..... i'm so sorry for disturbing you.....

      Delete
    3. What are the specifications? I can help you design one.

      Regards,
      Tahmid.

      Delete
    4. i want 250 watt 220v 50 hz pure sine wave circuit diagram... .i have done 12v to 310 v circuit and i want circuit diagram of H-bridge to produce 220 v , 50 hz pure sine wave ...thank you very much

      Delete
    5. i want 250 watt 220v 50 hz pure sine wave circuit diagram ... .i have done 12v to 310 v circuit and i want circuit diagram of H-bridge to produce 220 v , 50 hz pure sine wave ...thank you very much

      Delete
    6. Please go through this thoroughly:

      http://tahmidmc.blogspot.com/2013/01/using-high-low-side-driver-ir2110-with.html

      Regards,
      Tahmid.

      Delete
  17. Hi tahmid, your blog is awesome. ı know u from edaboard. ı have a project to do and now ı just need to do push pull dc to dc converter which converts 36VDC to 311VDC. I cant simulate the circuit above and also ı need to implement this circuit. Does this circuit really work ? ı need a ferrite transformer but ı cant implement this circuit without this transformer. ı mean should ı select proper ferrite first right ? and then ı can implement this circuit. Which article should ı read on your blog about ferrite transformer calculation ? My project has 1kVA output power. So ferrite transformer must be 1kVA. My question is that how should start to implement this circuit ? because ı cant simulate it in proteus, multisim, ltspice etc.

    ReplyDelete
    Replies
    1. Hi,

      Thanks for the compliment. May I know your edaboard username?

      Yes, the circuit works. But, for your project, don't just "copy-paste" this circuit into the application. If you go through this entire tutorial on SG3525 thoroughly, you should be able to design the circuit yourself.

      Regarding ferrite core transformer calculation, I have written a tutorial as well. You can find it here:

      http://tahmidmc.blogspot.com/2012/12/ferrite-transformer-turns-calculation.html

      Regards,
      Tahmid.

      Delete
    2. My edaboard username is fethiyeli. ı guess ı can modify this circuit for my requirements but if ı have a question, ı ask u in this blog. Because of lacking of the ferrite transformer model in simulation software, ı cant simulate it. So, do u have any idea how ı can implement this circuit without simulating ? Should I calculate ferrite core transformer calculation first ? I dont know which step ı should start =) thnx again.

      Delete
    3. You should start with the design of the PWM controller stage, then the driver stage and then the ferrite transformer stage. For the ferrite transformer, first select your core and then calculate the number of turns. Then decide which wire to use and then wind the transformer carefully and tightly.

      Regards,
      Tahmid.

      Delete
  18. hi tahmid
    i want smps battery charger 10 A .... i want circuit diagram ... can you help me?

    ReplyDelete
    Replies
    1. You can design one using SG3525 and IR2110. Go through this tutorial and the one on IR2110 as well. Also go through the tutorial regarding transformer design for half-bridge converters.

      http://tahmidmc.blogspot.com/2013/01/using-sg3525-pwm-controller-explanation.html
      http://tahmidmc.blogspot.com/2013/01/using-high-low-side-driver-ir2110-with.html
      http://tahmidmc.blogspot.com/2013/02/ferrite-transformer-turns-calculation_22.html

      Regards,
      Tahmid.

      Delete
  19. hi tahmid
    i want smps battery charger 10 A .... i want circuit diagram ... can you help me?

    ReplyDelete
    Replies
    1. You can design one using SG3525 and IR2110. Go through this tutorial and the one on IR2110 as well. Also go through the tutorial regarding transformer design for half-bridge converters.

      http://tahmidmc.blogspot.com/2013/01/using-sg3525-pwm-controller-explanation.html
      http://tahmidmc.blogspot.com/2013/01/using-high-low-side-driver-ir2110-with.html
      http://tahmidmc.blogspot.com/2013/02/ferrite-transformer-turns-calculation_22.html

      Regards,
      Tahmid.

      Delete
    2. http://sandysplash.blogspot.in/

      Delete
  20. After visiting your blog and reading your posts I did like to be communicating with you henceforth.

    ReplyDelete
    Replies
    1. You can email me at inferno-rage (at) hotmail (dot) com

      Regards,
      Tahmid.

      Delete
  21. hi tahmid ...
    what's the difference between sg3525 & sg3525an if i place SG3525AN instead of SG3525 at push pull application ??????????

    ReplyDelete
    Replies
    1. You can use SG3525AN directly for push-pull application. SG3525AN and SG3525 are the same chip. Different manufacturers use different suffixes, AN being one of them.

      Regards,
      Tahmid.

      Delete
  22. Dear Tahmid, I've found your tutorial very helpful, especially since the data sheet of the SG3525 chip lacks the proper information, regarding the associated circuit design. For example a profound information given by the Linear Technology, which comes along their buck/boost controller chips, is poles apart different from the information misery offered by the SG3525 manufacturers. I think those guys owe you a lot of money so far, as your information serves their customers.. Just one thing, IMHO, your voltage divider is slightly wrongly calculated. When you have that resistances, your actual resultant voltage will be V= 280x 1/(56+1)= 4.91V, not 5.1, hence 5.1x 57= 290.7V. But apart from that, your work is excellent. Thanks for your efforts, just keep it up, I wish you all the best, mate, Alex, Krakow, Poland. (Temporarly in London, UK)

    ReplyDelete
    Replies
    1. I'm glad to hear that you found my tutorial helpful. I'm happy to be able to help whenever I can.

      Thanks for pointing out the error. I've fixed it by adjusting the output voltage requirement so that the output desired is 290V. So, the current combination works. Thanks for pointing it out.

      Your comments and suggestions regarding the blog and any further material are welcome and will be appreciated.

      Regards,
      Tahmid.

      Delete
  23. in capacitor 8 how many vlotages will be used.....?

    ReplyDelete
    Replies
    1. C8 should be rated for 400V or more.

      Regards,
      Tahmid.

      Delete
  24. Hello,
    The block diagram of SG3525 is fabulous.And the description is really helpful for knowing this circuit.Thanks a lot for sharing this blog.
    DC to AC power inverter

    ReplyDelete
    Replies
    1. You're welcome. I'm glad that you've found it useful.

      Regards,
      Tahmid.

      Delete
  25. Cool! thank you very very much!

    ReplyDelete
    Replies
    1. You're welcome. I'm glad that you've found it useful.

      Regards,
      Tahmid.

      Delete
  26. Great resource! Greetings from South Africa :)

    I have just one question. I've noticed that I am able to only obtain a max of 50% duty cycle at the outputs of A and B respectively. Could I join these outputs together somewhere to obtain a higher duty cycle? If so, how would I achieve this?

    I am thinking of using an adder op-amp? What do you think?

    Kind Regards.

    ReplyDelete
    Replies
    1. Hi,

      The internal circuitry of the SG3525 is such that the outputs of A and B can only go up to 50% duty cycle. That is where the usefulness of the SG3525 lies. If you need higher duty cycle, you could use 2 diodes, the anodes of which are connected to pins 11 and 14, and the cathode of both are shorted. Then you take the output from this point - the cathode of the diodes. Make sure you use ultrafast recovery diodes for higher frequencies. If you use this method, remember that you're blocking the pulling down / sinking ability of the internal totem pole of the SG3525. So, you should use an external (totem-pole based or driver chip based) driver to drive the MOSFET.

      Hope this helps!

      Regards,
      Tahmid.

      Delete
  27. hi everybody i'm a french so i don't talk english very well!
    i just want to know if we suply 18V instead of 12v, will it work???
    thak's
    regards

    ReplyDelete
    Replies
    1. Hi,

      I've mentioned this in the article above:

      Pin 15 is VCC – the supply voltage to the SG3525 that makes it run. VCC must lie within the range 8V to 35V. SG3525 has an under-voltage lockout circuit that prevents operation when VCC is below 8V, thus preventing erroneous operation or malfunction.

      Pin 13 is VC – the supply voltage to the SG3525 driver stage. It is connected to the collectors of the NPN transistors in the output totem-pole stage. Hence the name VC. VC must lie within the range 4.5V to 35V. The output drive voltage will be one transistor voltage drop below VC. So when driving Power MOSFETs, VC should be within the range 9V to 18V (as most Power MOSFETs require minimum 8V to be fully on and have a maximum VGS breakdown voltage of 20V). For driving logic level MOSFETs, lower VC may be used. Care must be taken to ensure that the maximum VGS breakdown voltage of the MOSFET is not crossed. Similarly when the SG3525 outputs are fed to another driver or IGBT, VC must be selected accordingly, keeping in mind the required voltage for the device being fed or driven. It is common practice to tie VC to VCC when VCC is below 20V.

      I hope that answers your question!

      Regards,
      Tahmid.

      Delete
  28. my sg3525 is always heat up.after d heat ,it(sg3525) get damage & cant take reading of d frequency at the gate of the mosfet once the source is connected to the ground.pls kindly guide me in rectifing this problem.av already damage like 3 sg3525 ic

    ReplyDelete
    Replies
    1. Check the power connections to the SG3525. Ensure that pin 16 (VREF) isn't shorted to ground or VCC. Ensure that none of the outputs are shorted to ground or VCC. Ensure that VCC is within acceptable limits.

      Remove the connections to the MOSFETs all together and then check the outputs of the SG3525. Measure both the frequency and the voltage. Check the shape using an oscilloscope, if possible.

      You might even have damaged MOSFETs that are damaging the SG3525. So, if the outputs seem to be correct without the MOSFETs connected, replace the MOSFETs with new ones.

      Hope this helps!

      Regards,
      Tahmid.

      Delete
  29. Hi Tahmid,
    I am trying your circuit out, I get 48.8Khz from pin 11 (output A) but nothing at pin 14 (ouput B). What could be the problem? I have just connected the SG3525 chip to 12V. I have not connected this to a MOSFET driver of CFL circuit yet?Just tryin this chip first to get a frequency close to 50Khz.
    Thanks for your help in advance?

    ReplyDelete
    Replies
    1. Have you designed the circuit correctly? Exactly as I've shown? Did you make any changes? If you have, what changes did you make? Can you try with another SG3525?

      Regards,
      Tahmid.

      Delete
  30. Hi Tahmid,
    great blog and thanks for sharing this valuable information!!!
    last night I tried this circuit and it seems to work fine, but the r10 for feedback
    was very hot..

    I have just one question:
    the net format of R10 and R11 is 57kohm, the current flowing is 290v/57kohm = 5.08mA more or less...
    the power dissipated is P = R*I^2 = 57000*(5.08mA)^2 = 1.47W
    is not too high?

    In This configuration should I Use a 1W resistors?
    It's not better to increase the value of the net resistance and limit the current flow while
    maintaining the same ratio of divider?

    for example R10 = 120Kohm and R11 = 2.2kohm
    so the current flow is 290v/124.2kohm = 2,33mA
    and the power dissipation is (2.33mA)^2*124200 = 0.67 W
    So can use the half-watt resistors...
    I am right?

    Greetings from Italy
    Pier

    ReplyDelete
    Replies
    1. Yes, 1.47W is a little high. But you can use 3W resistors safely. 1W resistors won't do. You need to select a resistor with a power dissipation capacity higher than the actual max dissipation. Twice the actual dissipation is a good figure. And that's why I mentioned 3W.

      Yes, you can use larger resistance to lower the current and thus the power dissipation. If you get a 0.67W power dissipation (calculated), then you should use a resistor with a power dissipation capacity of at least 1W.

      Remember that this is for R10. R11 won't get hot.

      Hope this helps.

      Regards,
      Tahmid.

      Delete
    2. Thanks.... :-)
      Pier

      Delete
  31. I have made circuit as per your procedure but 25 watt energy saver is not working properly making fluctuating while i am using 12v 3amp charger to switch on inverter. You are requested to explain why bulb is not working properly.

    ReplyDelete
    Replies
    1. My first suspicion is that the output voltage is too low. So, before checking for other things, use a high voltage DC voltmeter to measure the output voltage.

      Also you may want to use an oscilloscope to check the outputs of the SG3525 to observe the output pulses and determine if they are ok.

      Post your findings and then we may proceed to fixing the problem.

      Regards,
      Tahmid.

      Delete
  32. Replies
    1. Which ETD core are you using? eg ETD34, ETD39, ETD44, etc.....

      What frequency did you select?

      How many primary turns did you use? How many secondary turns did you use?

      What are the input and output voltage specifications you have defined?

      Regards,
      Tahmid.

      Delete
  33. tahmid plz reply very quickly..... and thanks also will be for supporting.....

    ReplyDelete
    Replies
    1. I am extremely busy with my exams. Know that I will reply to your posts and will be glad to do so. Please be patient. Thanks.

      Regards,
      Tahmid.

      Delete
  34. pls.my mosfet is burnin out.wot shud i do

    ReplyDelete
    Replies
    1. Could you describe your situation with more details? Specifications? Circuit connections/ configuration? Transformer core? Turns used?

      Without knowing these, there's no way I can tell you why your MOSFETs are burning.

      Regards,
      Tahmid.

      Delete
  35. my core is ETD44... i given in primary turns 4+4...and in secondary turns 200+200... so then you tell me am i right?

    ReplyDelete
    Replies
    1. What is your desired output voltage? What is the input voltage? Did you use feedback for output regulation?

      Your answering the above questions will help determine where the problem lies.

      Regards,
      Tahmid.

      Delete
    2. Another problem you may have is that the "soft-start" may be too slow. What is the value of the soft-start capacitor that you used?

      Delete
  36. am using sg3524.rt=20 Pot,ct=1nf.100khz frequency.transformer ee42.primary =4.. 0.. 4,sec= 66turn.mosfet= 75N06.from pin 11 & 14 10ohm and 1k to d ground.duty cyle arud 51% .pls y is my mosfet burnin out.am gettin frustrated.i opt for sg3524 bcus my sg3525 keeps burn at high frequency i.e 100KHZ

    ReplyDelete
    Replies
    1. There could be many reasons.

      Ensure that you've got a good enough driver in place and that you've got sufficient deadtime.

      The 51% duty cycle seems erroneous, if it's on one output. If both outputs have 51% duty cycle, that's what's causing the MOSFETs to burn.

      Regards,
      Tahmid.

      Delete
  37. This comment has been removed by the author.

    ReplyDelete
  38. tahmid...
    i check do their inverter output voltage is 240V.....

    ReplyDelete
    Replies
    1. For a CFL, that could be too low. Of course it depends on the bulb too. I would recommend you increase the output voltage to about 280V.

      Regards,
      Tahmid.

      Delete
  39. Thanks Tahmid,
    I tried another SG3525 chip and it worked.
    Cheers brother.

    ReplyDelete
  40. am using sg3524.rt=20
    Pot,ct=1nf.100khz
    frequency.transformer
    ee42.primary =4.. 0.. 4,sec=
    66turn.mosfet=
    75N06.from pin 11 & 14
    10ohm and 1k to d
    ground.duty cyle arud
    51% .pls y is my mosfet
    burnin out.am gettin
    frustrated.i opt for sg3524
    bcus my sg3525 keeps
    burn at high frequency i.e
    100KHZ

    ReplyDelete
    Replies
    1. Use a good MOSFET driver circuit between the SG3525 and the MOSFET. This is critical, especially at higher frequencies like 100kHz. You can design a simple circuit using dedicated gate driver like TC427. You can also use simple transistors.

      Refer to this:
      tahmidmc.blogspot.com/2012/12/low-side-mosfet-drive-circuits-and_23.html

      Regards,
      Tahmid.

      Delete
  41. i want to design a 50hz pure sine wave which has 10V peak to peak output and around 100mA ouput current. please tell me the circuit for that and the exact specifications of all components required.(I tried making it using phase shift oscillator using BJT but frequency would not come below 150hz)
    PLZ HELP

    ReplyDelete
    Replies
    1. For such low power, using a microcontroller + bridge would be overkill. There are many sine wave oscillator circuits you can find online, with BJTs and also with operational amplifiers.

      Regards,
      Tahmid.

      Delete
  42. Tahmid, more grease to your elbow. Plz can you explian to me the compensation network and how it works.
    Another thing I want to know is if I can use the output from the transformer directly to appliances assuming it is approximately 230V, 50Hz. Plz reply. Thanks

    ReplyDelete
    Replies
    1. There's quite a bit I have to learn about compensation network before I can write a tutorial about that.

      Yes, you can connect the output directly. Add a 1uF capacitor across the output for filtering.

      Regards,
      Tahmid.

      Delete
  43. Hi Tahmid
    will current flow through R5 i.e 2.2k ??

    ReplyDelete
    Replies
    1. There will be a very small amount of current. You might find it helpful to think of R5 as a "pull-up resistor".

      Regards,
      Tahmid.

      Delete
  44. Electronics is a study of flow of electrons in electrical circuits. You made some good points about electronics. I have read your post it is genuine and helpful. Thanks
    Aerospace and Electronics Systems

    ReplyDelete
  45. Dear Tahmid,

    I have following issues in SMPS Inverter.

    I am making a 1KVA system.Is ETD-49 enaugh for 24V to 350V DC-DC Boost Converter working @ 40KHz Push-Pull ?
    What are the steps to calculate number of turns for high frequency transformer ? I have calculated according to mentioned calculation but it is not workig.

    Thanks in Advance

    Regards
    Gapoo

    ReplyDelete
    Replies
    1. For transformer winding, refer to this:

      tahmidmc.blogspot.com/2012/12/ferrite-transformer-turns-calculation.html

      ETD49 could be enough. You could move up to ETD54.

      Regards,
      Tahmid.

      Delete
    2. I got 350V at output but as I put any small load output reduces to zero.

      Delete
    3. Do the MOSFETs heat up and get damaged after the load is put on?

      Delete
  46. Hi Tahmid,
    I am designing sine wave inverter.
    Input : 8V to 16V DC Battery
    Push-pull Out : 325V/ 0.5A
    Full Bridge Inverter : 230V/50Hz output

    Now, in push-pull, how to use SG3525 in isolated voltage feedback? Can you share any idea or circuit?
    I want to regulate 325V but with isolation (any isolator with 100% or 200% CTR).

    Regards
    NKG

    ReplyDelete
    Replies
    1. You may use a simple auxiliary winding (that can also be used to power the secondary side circuits) along with optocoupler + TL431 for isolated feedback.

      PC817B has a CTR between 130% to 260%. PC817C: 200% to 400%. PC817D: 300% to 600%.

      Regards,
      Tahmid.

      Delete
  47. pls i need ur help,one of my mosfet get hot fast than the other one

    ReplyDelete
    Replies
    1. Which MOSFETs are you using? Are you driving them directly from SG3525? What is the frequency you set for SG3525? Did you use a deadtime resistor?

      Delete
    2. am using irfp250.am driving it from the sg3525.65khz frequency and no deadtime resistor.i connected pin 7 directly to pin 5

      Delete
    3. Use a small deadtime.

      You may need to use a driver circuit for the MOSFETs. You can use a simple totem-pole driver or a dedicated driver-based design. Take a look here:

      tahmidmc.blogspot.com/2012/12/low-side-mosfet-drive-circuits-and_23.html

      Regards,
      Tahmid.

      Delete
    4. thanks. now am driving the mosfet from a totem pole and also 39ohm between pin 7 and 5.have also reduced d frequency to 31KHZ but after 5minutes without load both mosfet will start getting hot slowly

      Delete
    5. Have you ensured that the transformer has been wound properly?

      You might need to use snubbers - you might be facing problems due to spikes at the MOSFET drains, ie the transformer primary. Use an oscilloscope and observe the waveform at the MOSFET drains.

      Regards,
      Tahmid.

      Delete
    6. i don't have access to oscilloscope.i savage my transformer from a t.v without having any information on it.so i rewinds it by just assuming it a particular core.please what can i do now since i don't have access to oscilloscope.

      Delete
    7. Use a snubber circuit. Without an oscilloscope it will be difficult to understand the nature of the spikes, but you may experiment with different values to find which works best.

      Does the transformer you use have a large gapped cores?

      Delete
    8. av use snubber still d same tin i.e 47ohm resistor den 1nf cap.bt wen i put cap of 100nf my resistors burns out.am using 12v 88ah battery.note no feedback yet.

      Delete
    9. another tin again is that wen i switch on my circuit wen d mosfet is not hot,i do av like a thousand volt for some seconds before it drops to like 7 hundred something volt

      Delete
    10. That voltage is way too high!

      I think you have a problem with your transformer winding. The leakage inductance is too high and that contributes to high spikes. Also, the windings may not be perfectly symmetrical, causing the heating.

      Try with snubber values of about 56 ohm resistance (2W-5W depending on how much heat you dissipate) and 68nF 100V capacitance. Then experiment further with the resistor and capacitor values.

      Regards,
      Tahmid.

      Delete
  48. Hi Tahmid,

    great website! saves me a lot time ....

    so, I don't think you saw my last post about a uc2845 ic, looks like they call it a flyback converter (what I was building), simple design but since my e-core transformers made anoying noise (can't really explain it, nothing to do with lose windings with toroids there was no problem) even at 48khz specialy with litle or no load, under "heavy" load it was better, and after removing some secundary windings it was also better but the output voltage was dropping under higher load.

    So I started building the 3525 circuit
    My goal was still 24--> +-200VDC

    I made everything like your schematic and it worked! Except I put in a lm7818 for feeding the
    3525 and mosfets.
    Since the efficiency was crap with a first test (I used the 1N4007 for the bridge rectifier), maybe the output capacitor of 470uF 450V is to big, they were also getting hot. I swaped the diodes for Buy27.

    So now I got 209V 0.63A output @ 75% efficiency and 208V 0.17A @ 74% efficiency. No load (only about 1W for the voltage sensing feedback resistors ) the circuit draws about 2.2W .
    I'm using 2 times 7 turns prim, and 70 turns sec. So my turn ratio is a bit on the high side, maybe I could remove 5 turns. The fets 250v 38A 0.075mohm and are not warm, mounted on a big heatsink I must say. @ 0.2A output the transformer is not getting warm, at 0.6A the windings are warming up, but the core stays cool. (with 48khz I could even be save with only 3 prim turns)
    I'm using 0.28mm² wire for the transformer. I think I need to parallel more wires for my primary coil since it is recomended to use 3A/mm² right? 0.28mm² is to low I guess since my prim pulls 6-7A.
    I'm not using the output riple/snubber? coil so I will experiment later with that.

    NOw , I want to higher my efficiency, since I'm losing almost 45W with an output of 130W, there must be something in the chain that is losing a lot of power! Now I cant notice parts that are heating up more than they should, any tips? My multimeter is decent and made no calculation mistakes.

    Btw is it possible to make a current protection with the 3525 or do I need a more complicated driver?

    thanks!







    ReplyDelete
    Replies
    1. Use a driver circuit between the SG3525 outputs and the MOSFET gates.

      Bring the primary turns down from 2 x 7 turns to 2 x 4 turns or 2 x 5 turns. Adjust the secondary accordingly.

      0.28mm^2 is what, SWG 24, right? With a primary current of 6-7A, use 3 x SWG 26 wires in parallel. That should help - improved current handling + reduced losses from skin effecy.

      Use ultrafast diodes at the output. What are the specifications for BUY27? I regularly use UF4007 diodes. DO NOT use regular rectifier diodes like 1N4007 as they are too slow. Just take a look at the reverse recovery time in the datasheet!

      Reduce the output capacitance to about 100uF.

      Try with these changes and let me know the result. Good luck!

      Regards,
      Tahmid.

      Delete
    2. For (over) current protection, you need to use an external circuit. The SG3525 itself doesn't provide over current protection. Use an external circuit that shuts down the SG3525 when the current is too high. You can use a shunt resistor, hall-effect sensor or current transformer for current sense.

      Regards,
      Tahmid.

      Delete
    3. Hi Tahmid,

      I want my output 230VDC, 500 real watt( 50A input), so i think i should wind pri 3 turn+3 turn, sec 75 turn. Can you tell me how to choose cooper wire for pri and sec coils?

      By my calculation, i wind 72x 26 SWG wires in parallel for pri , but due to skin effect,i think 65x 26 SWG is OK!

      Plz help me this doubt.

      Regards,

      Quynh

      Delete
    4. 72 x 26 SWG is not required! If you can use that many, 72 or even 65, there's no harm. It's even better due to lower winding resistance. But about 15-20 x 26 SWG should be more than enough. Of course, the actual capacity will depend on the specific wire itself, due to its properties such as insulating material, etc. So, oversizing may actually be a good idea if you have space.

      For frequencies less than about 100kHz, I don't think you really need to worry about skin effect for SWG #26 wire.

      Regards,
      Tahmid.

      Delete
  49. Hi, can I put a pwm signal on the shutdown pin?

    ( for a solar project I want to control the output power, because the load will be a battery and I don't want the input voltage to collapse or go lower than a certain level, since it is powered by a solar panel about 5times the outputvoltage)

    ReplyDelete
    Replies
    1. Don't apply PWM signals to the shutdown pin. Instead, I think, it'll be better if you use the MOSFETs for the switching and drive them off when required and back on when required, ie control the MOSFET on/off via the drive signals instead of using the shutdown pin.

      Regards,
      Tahmid.

      Delete
  50. Hello,
    thank you for the information about this type of power inverter.I love to read this post because it is very useful and easy to understand, after reading this page I will see the other pages of this web hopefully have a lot of good information.
    Power inverters

    ReplyDelete
    Replies
    1. I'm glad you're finding my posts helpful!

      Delete
  51. What is the formula for calculating the value of feedback resistors supposing the ferrite transformer would be wound to produce lets say 340v??

    ReplyDelete
    Replies
    1. It's the same formula as the normal voltage divider formula. Take Vin to be 340V and Vout to be 5.1V (as that's the reference voltage used). Make sure you use large enough resistances so that current through the resistors is very small.

      Regards,
      Tahmid.

      Delete
  52. hi Tahmid
    why pin 1 connect to inverter output ? can we use with out connect it
    how select primary and secondary wire thick ?

    ReplyDelete
    Replies
    1. The given connection (with pin 1 connected to output via the resistors) provides feedback. Please go through the article thoroughly and you can understand the feedback implementation.

      You can avoid connecting pin 1 as shown if you choose not to use feedback.

      The thickness of the primary and secondary wires are selected depending on the current through them. Use multiple thin wires in parallel - don't use wires that are too thick. Google "wire skin effect" and read about it to know more about this.

      Regards,
      Tahmid.

      Delete
  53. Hi, Dear

    I cant find sg3524 or sg3525 Proteouse liberary Can u please help in this ?
    i 'll be thankfull

    ReplyDelete
    Replies
    1. Take a look on this page: http://320volt.com/proteus-isis-smps-pwm-entegre-modelleri-library-dosyalari/

      The links given on the above mentioned page are:

      https://dl.dropbox.com/s/z6axv7owsnt73ax/proteus-isis-smps-pwm-entegre-modelleri-library-dosyalari.rar?dl=1

      https://rapidshare.com/files/2895824845/proteus-isis-smps-pwm-entegre-modelleri-library-dosyalari.rar

      http://www.mediafire.com/?0sz11ua84ah3v2d

      http://320volt.com/wp-content/uploads/2011/10/proteus-isis-smps-pwm-entegre-modelleri-library-dosyalari.rar

      Regards,
      Tahmid.

      Delete
  54. Aoa! how to design feedback of the given cct.

    ReplyDelete
    Replies
    1. The circuit shown has non-isolated feedback implemented. Please read the article thoroughly and you can understand the feedback implementation.

      Regards,
      Tahmid.

      Delete
    2. Aoa!i mean how to design feedback compensation b/w pin 1 and 9.or give general values of resistor and capacitor b/w pin 1 and 9.also can u give me reference for understanding this topic.thanks

      Delete
    3. If you want to understand feedback compensation, refer to "Switching Power Supply Design" by Abraham Pressman. To learn about quickly implementing it, refer to "Power Supply Cookbook" by Marty Brown.

      Regards,
      Tahmid.

      Delete
  55. Please Tahmid, I designed 50HZ sine wave signal using OP-AMP and carrier signal of 20KHZ using OP-AMP. Can you tell me how to use SG3525 as PWM with this two signals to produce 50HZ PURE SINE WAVE signal for inverter . Because this SG3525 has shut down pin and the pin will be used for overload,battery low and AC ON shut down.

    ReplyDelete
    Replies
    1. SG3525 should not be used for generating SPWM signals. You can use the analog method as you described. But better would be to use a microcontroller to generate the SPWM signals. Take a look at these:

      http://tahmidmc.blogspot.com/2011/01/generation-and-implementation-of-sine.html

      http://tahmidmc.blogspot.com/2012/10/smart-sine-software-to-generate-sine.html

      http://tahmidmc.blogspot.com/2012/10/generation-of-sine-wave-using-spwm-in_10.html

      http://tahmidmc.blogspot.com/2012/10/600w-50hz-sine-wave-inverter-test.html

      http://tahmidmc.blogspot.com/2012/11/feedback-in-sine-wave-inverter-pic16f.html

      http://tahmidmc.blogspot.com/2013/02/demystifying-use-of-table-pointer-in.html

      http://tahmidmc.blogspot.com/2013/02/generation-of-sine-wave-without-eccp_16.html

      http://tahmidmc.blogspot.com/2013/02/sine-wave-generation-with-fast-pwm-mode_2525.html

      http://tahmidmc.blogspot.com/2013/07/sine-wave-generation-and-implementation.html

      Hope this helps!

      Regards,
      Tahmid.

      Delete
    2. http://sandysplash.blogspot.in/

      Delete
  56. Hi Tahmid,

    Nice blog.You did not need a snubber circuit for your MOSFETs ?

    ReplyDelete
    Replies
    1. In most of my experimental low-voltage input DC-DC converter circuits I did not need snubbers as the peak spike was not high enough to damage the MOSFETs. However, for high power circuits and for final commercial products, a snubber circuit should be used.

      Regards,
      Tahmid.

      Delete
  57. And I do wish,you would consider using a black on white background for your blog :)

    ReplyDelete
    Replies
    1. I did get that suggestion once before. However I like the white on black background and most people don't mind it. However, I will keep your suggestion in mind.

      With thanks,
      Tahmid.

      Delete
  58. Dear Tahmid.

    Can you please provide the schematic for 300VA Inverter.

    Regards,
    Anvaya

    ReplyDelete
    Replies
    1. I can't give you any complete circuit, but go through these:

      http://tahmidmc.blogspot.com/2013/01/using-sg3525-pwm-controller-explanation.html

      http://tahmidmc.blogspot.com/2013/01/using-high-low-side-driver-ir2110-with.html

      http://tahmidmc.blogspot.com/2012/12/ferrite-transformer-turns-calculation.html

      http://tahmidmc.blogspot.com/2013/03/output-inductance-calculation-for-smps.html

      http://tahmidmc.blogspot.com/2013/02/n-channel-mosfet-high-side-drive-when.html

      http://tahmidmc.blogspot.com/2012/12/low-side-mosfet-drive-circuits-and_23.html

      http://tahmidmc.blogspot.com/2013/05/debugging-bridge-tips-to-successfully.html

      http://tahmidmc.blogspot.com/2012/12/learning-smps-hard-way.html

      Hope this helps!

      Regards,
      Tahmid.

      Delete
    2. http://sandysplash.blogspot.in/

      Delete
  59. Aoa!i have core saturation problem with my push pull converter.By now, i have tested it without load.plz guide me about its solution.

    ReplyDelete
    Replies
    1. How do you know that the problem is with core saturation?

      Provide more details of the PWM section, the MOSFET drive section, the MOSFET connection section, and most importantly, transformer parameters and specifications.

      Regards,
      Tahmid.

      Delete
  60. Hi,
    The topic about Using the SG3525 PWM Controller - Explanation and Example: Circuit Diagram / Schematic of Push-Pull Converter is fabulous.It's a good post for me because I am always interesting to know about the Inverters,it's shelling and products .Thanks Sir for this useful post which is very much important for me.Thanks again
    DC power inverter

    ReplyDelete
  61. hello Tahmid keep the good work going. Ihave a problem with a modified sine wave inverter i built. Its running at 60hz on the output when ever i plug appliances in it like tv radio fridge lights etc the frequency at the output remains at 60hz but when i plug a fan into it I see my meter showing frequency change like 158hz and it is not stable if I use one leg of my meter and touch one leg of the ac out it reads 60hz but accross two legs I see an increase but this only happens with a fan pluged in. Please help me here. Thank you

    ReplyDelete
    Replies
    1. Does the fan operate properly? Does it run smoothly without any unusual noise?

      What meter are you using?

      Can you test with other fans too and post the result?

      Delete
    2. thank u Tahmid for your support. The fan runs smoothely just the usual low hum being modified sine wave I am using a fluke multimeter. I tried other fans and the same thing happens but if I have the tv pluged in at the same time with the fan I dont see a difference in the picture on the screen or operation of the tv so I dont know how to explain this so I ask u. Thank u

      Delete
    3. It could be that everything's okay but the meter is giving some kind of a false reading. Maybe the fan contributes to this somehow. I'm not sure but it's possible. Like you say, everything else seems fine.

      See if you get the same results with a different fan. See if you get the same results with a different meter. If possible, see the output with an oscilloscope and see if there really is a change in the output. That should clear things up.

      Regards,
      Tahmid.

      Delete
  62. hello Tahmid, iam rahul lalu a electronics Engineering Diploma student from trivandrum, in India, now iam trying to make a 12Vdc/24Vdc 500W transformer-less pure sine wave(pwm) inverter for my class room, but i don't have any good circuit, so can you give me a good circuit??
    iam waiting for your favorable reply (my email id:rahulmarch1986@gmail.com)
    thank you....

    ReplyDelete
    Replies
    1. I can't give you any complete circuit, but go through these:

      http://tahmidmc.blogspot.com/2013/01/using-sg3525-pwm-controller-explanation.html

      http://tahmidmc.blogspot.com/2013/01/using-high-low-side-driver-ir2110-with.html

      http://tahmidmc.blogspot.com/2012/12/ferrite-transformer-turns-calculation.html

      http://tahmidmc.blogspot.com/2013/03/output-inductance-calculation-for-smps.html

      http://tahmidmc.blogspot.com/2013/02/n-channel-mosfet-high-side-drive-when.html

      http://tahmidmc.blogspot.com/2012/12/low-side-mosfet-drive-circuits-and_23.html

      http://tahmidmc.blogspot.com/2013/05/debugging-bridge-tips-to-successfully.html

      http://tahmidmc.blogspot.com/2012/12/learning-smps-hard-way.html

      Hope this helps!

      Regards,
      Tahmid.

      Delete
  63. This comment has been removed by the author.

    ReplyDelete
  64. i have simple question that this circuit is designed for 12V input , what changes should i made for 40V input

    ReplyDelete
    Replies
    1. You need to add a low voltage regulator (eg for 12V output) to supply the SG3525. The rest is pretty much the same.

      You may want to consider a switching regulator over a linear regulator for lower losses and higher efficiency.

      Regards,
      Tahmid.

      Delete
  65. Hi Tahmid,

    Can you show me how increase efficency of DC-DC converter SG3525 and reduce temparature on each MOSFET?

    I think that i should forced turn off MOSFET with negative voltage? But i havent konwn yet what i should do?

    Plz help me.

    Best regards,

    Quỳnh.

    ReplyDelete
    Replies
    1. 1) Use MOSFETs with very low RDS(on) to reduce on-state resistance, thus reducing power loss and increasing efficiency. If necessary, connect MOSFETs in parallel to reduce RDS(on). This reduces conduction power losses.

      2) Negative voltage is not required. But use a good driver circuit to turn the MOSFET off as quickly as possible and to ensure that the MOSFET is turned fully on when it is on.

      3) Don't use too high a frequency that the switching losses are increased.

      4) Use good transformers with low leakage inductance.

      Hope this helps.

      Regards,
      Tahmid.

      Delete
  66. Bro , ur blog is very exellent , may ALLAH reward u for ur effort , i haveto ask that if i use 4 mosfets ( instead of 2 due to large power ) then how should i connect them ??? plz reply

    ReplyDelete
    Replies
    1. You have to connect MOSFETs in parallel. Connect the drains of the paralleled MOSFETs together and connect the sources of the paralleled MOSFETs together. Use individual gate resistors for all the MOSFETs and connect them all to the common input signal.

      If you have 4 MOSFETs instead of 2, that means that you have 2 MOSFETs paralleled in each junction.

      Regards,
      Tahmid.

      Delete
  67. how to calculate the value of inductor ( L1) ??? and will there be any difference if C5,C6 are not used ? and what is the purpose of C8 ?? actually i m new in power electronics . can u plz help
    Regards
    Qamar

    ReplyDelete
    Replies
    1. C5 and C6 must be used. C6 should be placed as close to the SG3525 as possible.

      C8 is the output bulk/filter capacitor.

      For calculation of the output inductor, go here:
      http://tahmidmc.blogspot.com/2013/03/output-inductance-calculation-for-smps.html

      Regards,
      Tahmid.

      Delete
    2. thanks alot sir :)

      Delete
  68. how do i make my output duty cycle 50%? wen i connect one end of my output pin 11 or pin 14 ,then one end to the negative terminal of my battery,d duty cycle is always around 50.9%.but when i test both output pin 11 & 14 together without put it on the negative,is always around 52.2%.any solution why is not 50%? my mosfet is gettin hot too

    ReplyDelete
    Replies
    1. hello, i need to set my duty cycle to 58% how do i do this?

      Delete
  69. Hi Your blog is very good. The times I have been using in my learning. congratulations for your blog. Regarding the SG3525am wondering how do I connect several controllers to synchronize them

    ReplyDelete
    Replies
    1. I haven't yet tried to synchronize multiple controllers. May I know why you are trying to synchronize multiple controllers?

      I will take a look around and experiment on this, and I'll get back to you.

      Regards,
      Tahmid.

      Delete
    2. I'm trying to make a converter using SG3525 as PWM controller for a wind generator that will work with variable voltage from 80 to 240 VAC and the output voltage of the converter should be 50Vdc power to not be very high in each module, the timing would be for connecting modules in parallel converters put without timing they do not work perfectly pwm a feedback influence on the other. I await any idea thanks for your attention ...

      Delete
    3. Hi, I found a datasheet where timing is shown it calls TC35C25 of TELCOM. If this is also the doubts I have helped someone ...

      Delete
  70. Hi Tahmid,

    How to get sine wave output with this ckt. Without using any microcontroller.

    The sinewave frequency should be 50Hz only.

    Because with this modified sine wave the inductive loads will not work.

    Like fans and motors are not work with modified sine wave.

    So, can you please tell me.

    Regards,
    Anvaya

    ReplyDelete
    Replies
    1. You can't get sine wave output with this circuit. You should look to use a microcontroller for this purpose. If you do have a problem with using microcontroller (eg if you aren't sure in your abilities in using microcontrollers), then you can try to implement sine wave generation without microcontroller, using circuits similar to this:

      http://www.wpi.edu/Pubs/E-project/Available/E-project-042507-092653/unrestricted/MQP_D_1_2.pdf

      Regards,
      Tahmid.

      Delete
    2. Thanku Tahmid.

      But this concept is work practically.

      This is just a academic project. We are the manufacturing Company. In large volumes this design is not correct choice.

      Can you please tell me that how much efficient this design.

      Is there any practicale issues with design.

      I saw some where else Bubba Oscillator is not efficient . And this having max current capacity of 200mA only.

      But for my application
      Input = 12VDC
      output = 230VAC, 50Hz,
      It is going to rural areas so in India rural areas having Inductive Loads only.

      It should Work with inductive loads.

      And more over the above design (SG3525) is useful for Inductive designs.
      With High frequency DC Voltages.

      In http://tahmidmc.blogspot.in/2012/12/ferrite-transformer-turns-calculation.html you have mentioned that only number of turns.

      But we cant able to construct Ferrite Transformer without knowing inductance.

      So, can you please tell me the inductance.

      So finally i need 2 clarifications High Frequency DC is suitable for Inductive loads or not & Formula for inductance.

      Thanks in advance.

      Regards,
      Anvaya Designs


      Delete
    3. You can build pretty high power systems with it. But I think I've read that Bubba oscillators are unstable and take quite an effort to get stable.

      For commercial applications with high efficiency, I think your best choice is to use microcontrollers. Go to this page:

      http://tahmidmc.blogspot.com/p/blog-page.html

      Scroll down to "SPWM and sine wave generation and inverter:" and see all the related articles. I've got loads of articles/tutorials on sine wave generation and implementation using the Microchip PIC, Atmel AVR and the Microchip dsPIC.

      SG3525 is used for just regular PWM - for obtaining square wave / quasi sine wave outputs.

      For forward-type converters, such as forward, push-pull, bridge, what's important is the number of turns and the relevant flux density. Don't worry about the inductacne.

      I don't get this last part: "So finally i need 2 clarifications High Frequency DC is suitable for Inductive loads or not & Formula for inductance." Could you clarify?

      Hope this helps.
      Tahmid.

      Delete
    4. Hi Tahmid,

      Inductive loads are work with high frequency inverter or not.

      Inductive loads means sealing fans. High frequency inverter design based on SG3525.

      Can we design Inverter with 50HZ frequency with SG3525 or not.

      I feel that, if we design inverter at 50HZ the ferrite core is not suitable for design.

      So please tell me ..

      Thanks in advance

      Anvaya

      Delete
  71. Hello Tahmid I have benn following ur info all over the net and I must say I appreciate your support. I have a question here . I am building a pushpull transformer output inverter. The circuit uses 1k as gate resistors and 10k from gate to source. I want to use about 24 irf260 fets . I want to know if lowering the gate resistor from 1k down to about half ( 500ohm) if this would give me more power from the fets. I am using one of your totem driver circuits to drive the fets. Thank u for ur support

    ReplyDelete
  72. Tahmid can i avoid connecting the ref to pin10..bcos i will like to use it with other control circuit for shut down...and plz can u mail me a well details feedback loop complete circuit diagram using 4n35 with sg3524 and sg3525.i will need it as soon as possible thanks. princequint@gmail.com

    ReplyDelete
  73. can i use this circuit for both of 24v and 12v i watt to make 12v-24v to 250v transformer using your formula can i do it

    ReplyDelete
  74. Hi Tahmid,

    You can explain for me 10^ -9 calculator from ? . and formula thick (Sorry my english slightly less. I using Google trans,I'm from VN) . I hope you help good work

    ReplyDelete
    Replies
    1. Hi,

      That's the timing capacitor CT. I used CT = 1nF (as mentioned). The formula uses capacitance in Farads and resistance in ohms to give frequency in Hertz. So I need to convert from nF to F:

      1nF = 10^(-9) F.

      Regards,
      Tahmid.

      Delete
  75. hi
    how to convert this sg3525 circuit to 24v

    ReplyDelete
  76. hie can someone help me with explaining the frequency formular calculations im having problems understanding it

    ReplyDelete
  77. Hy Tahmid,i hope you will be fine...
    i am having a problem in making inverter.i'm making inverter using tl494 and sg3524.i'm using push pull topology to drive transformer and tl494 to drive push pull mosfet and sg3524 to drive full bridge mosfet...but there is no feedback.its just a simple circuit.can you send me the tl494 and sg3524 circuit with proper feedback.i have shared the only tl494 circuit file.link is
    http://rapidshare.com/share/C59EB1590CB87009A651BB5C6251E3D8
    my email is dowson.jack17@yahoo.com

    ReplyDelete
  78. Hi Tahmid
    can you tell me how to change this circuit and FET for 24v
    i calculate transformer for 24v but this circuit not work 24v FET burn every time i supply 24v can you help me please
    my email tdilshan100@gmail.com
    thanks

    ReplyDelete
  79. hi thmid thanks for this blog it is great and so usefull, on pin 3 sync there is nothing? i've tryed this on proteus but nothing hapenned and so i connect it to +vcc and it works, could you tell me if it was a mistake or can you explain me for what is this pin? thanks

    ReplyDelete
  80. Hi Tahmid, My name is Mubarak. I have been successful in making the 310 VDC with your circuit. I have a strange problem. When i connect the 310 VDC to a CFL bulb, my MOSFET is getting very hot and blowing. I have made your circuit in 3 parts PCB, one is PWM stage, MOSFET Stage and Transformer Stage and last one is rectification stage. Is the mosfet getting hot because i have separated each stage and connected through wire? How to solve the Mosfet heating issue?

    ReplyDelete
    Replies
    1. I was able to make it work. The problem of MOSFET getting hot and blowing is because of a faulty CFL. When i tried with a 100W bulb, its working like a charm. :) I am happy to see get things working after so much struggle in making it work.

      Delete
  81. how this use to drive dc motor 35v to 180v for treadmill. plc draw a circuit for us how will do it
    thanks

    ReplyDelete
  82. greetings !!!
    Hope so your fine...
    I, Mohammad Tawheed Kibria. I need to build a buck-boost regulator using a micro controller for my thesis work. for this work the regulators input may vary from 12V to 20V with constant output at 165V/150V. and max. power capacity should be 100W.
    Please help me to find out the work.

    ReplyDelete
  83. hi tahmid could you tell me what happen if the feedback voltage on pin 1 is greater than 5.1v? in this case in your example when the voltage is less of 290V the duty cycle is increased but what happen if the voltage goes up for example to 300V in this case the voltage on pin 1 will be more than 5.1V in this case the duty cycle is decreased to reduce the output voltage? or what happen in this case?. thanks for your time.
    Regards from colombia

    ReplyDelete
  84. this is push-pull circuit right?this circuit can apply for photovoltaic system?i mean, the supply 12VDC will convert to 12VAC by push-pull and step-up transformer will change the value of 12VAC to 240VAC..that i'm right?

    ReplyDelete
  85. That Was a very Great Circuit, I made it,, It was Awesome. but I have a lil problem.
    we reduced the Frequency of output to 350Hz, to use a transformer of iron core,E I 6630
    the problem is that the output is not stable after a while of usage.
    anther problem is that when we change the value of the load, the voltage is dropped from 36 to 20V DC
    at 600mA output is 36VDC, if 1.2A, out 30V, and if 1.8A - 20VDC. we changed the CT value (Pin5 and ground ) from 1u, to 530nF. and we use MOSFET SSF7509 as
    How to solve the problem,.

    ReplyDelete
  86. Hello Tahmid,
    I am sorry if the following question seems to be redundant but I have always been confused with the difference between Transformer frequency, switching frequency and oscillator frequency. I know that the Oscillator Frequency(Fosc) is the Frequency set by the Resistor Capacitor values of the SG3525A IC and also,that the Power transistor Switching frequency is half of the Fosc but when Calculating Number of Primary Turn and Power Handling capacity of the HF transformer I am confuse which frequency to use( Do I use Fosc or Fosc/2?)

    Please, your reply will be greatly appreciated.

    Regards

    Faruq (Nigeria)

    ReplyDelete
  87. dear Tahmid
    Is it necessary to connect the IC to the transistor to check its performance?
    We applied a voltage between 1-5V to pin1 and pin connected to pin 16 via 1 kohm resistor but error amplifier output at pin 9 its not correct its only five. why?

    ReplyDelete
  88. Hello Tahmid,
    I am sorry. I don't know about compensation pins. Can you explain about it?

    ReplyDelete
  89. Hello Tahmid
    Really like your tutorials on the electronics.... I have read a few of them now and used some the circuits, ie: TLP250, high side MOSFET switching....
    I have a question for you: I am designing a variable output voltage (500-2000VDC) push-pull converter/inverter using the same SG3525A chip. Basically, I will need the 500-2000vdc voltage range to be constantly adjustable, but only need 15-20ma. current. This is to be used as the power supply for a Don Smith/Tang device. I can send you more information if you like.....
    OK, I understand that the Output voltage can be varied by using a potentiometer from PIN#1 to Voltage divider from Output feed back> Ground cross connected to PIN #9 thru appropriate resister.
    My question pertains to the calculations for the transformer; I can't seem to find information on the construction/calculations for a variable output voltage transformer to use with the SG2525A push-pull circuit.
    What do you recommend I do to wind such a variable voltage transformer?
    I would greatly appreciate any hints or advice you can give me pertaining to developing this circuit.
    I have some photos of a completed variable (500-2000vdc) push-pull circuit, but they do not show underneath side of the circuit board or discuss the principals involved with the calculation for the transformer.
    Thanks in advance for taking the time to read this...
    Have a great day1
    mjd

    ReplyDelete
  90. thanks tahmid.this is really useful
    -hafiz, Malaysia-

    ReplyDelete
  91. hi tahmid
    i am very impress with ur FERRITE TRANSFORMER CALCULATION but i always dream of designing inverter with chopper transformer so plz can u help me with d circuit diagram using sg3525 which i will used d ferrite transformer with
    plz comment

    ReplyDelete