Tuesday, April 30, 2013

Using the TLP250 Isolated MOSFET Driver - Explanation and Example Circuits


I’ve already shown how to drive an N-channel MOSFET (or even an IGBT) in both high-side and low-side configurations in a multitude of ways. I’ve also explained the principles of driving the MOSFETs in these configurations. The dedicated drivers I’ve shown so far are the TC427 and IR2110. Some people have requested me to write up on MOSFET drive using the very popular TLP250. And I’ll explain that here.

The TLP250, like any driver, has an input stage, an output stage and a power supply connection. What’s special about the TLP250 is that the TLP250 is an optically isolated driver, meaning that the input and output are “optically isolated”. The isolation is optical – the input stage is an LED and the receiving output stage is light sensitive (think “photodetector”).

Before delving any further, let’s look at the pin configuration and the truth table.

Fig. 1 - TLP250 Pin Configuration


Fig. 2 - TLP250 Truth Table


Fig. 1 clearly shows the input LED side and the receiving photodetector as well as the totem-pole driver stage. Pins 1 and 4 are not internally connected to anything, and hence are labeled N.C. meaning no connection.

Pin 8 is VCC – the positive supply. Pin 5 is GND – the ground supply or the return path for the driving power supply. The supply voltage must be at least 10V. The maximum voltage is dependent on the operating temperature. If the temperature is lower than 70°C, up to 30V can be used. For temperatures between 70°C and 85°C, up to 20V can be used. However, there shouldn’t be a need to use higher than 20V anyways. In most cases, you’ll be using 12V or 15V or perhaps in some cases 18V.

Pins 2 and 3 are the inputs to the LED, anode and cathode respectively. Like regular LEDs, it has an input forward voltage and a peak forward current. The forward voltage will typically be between 1.6V and 1.8V. The forward current should be less than 20mA. The threshold input current for output transition from low to high is typically 1.2mA, but may be as high as 5mA. Thus, 10mA current should be good.

Even though pins 6 and 7 are shown to be internally connected, the output should be taken from pin 6 as the image - datasheet - shows pin 6 labeled as Vo (Output). Output voltage will tend to rise to supply voltage when high (it will actually be slightly lower) and fall to ground level when low.

The TLP250, being an optically isolated driver, has relatively slow propagation delays (not to say that optically isolated drivers can’t be fast; there are optically isolated drivers faster than TLP250). The propagation delay time will typically lie between 0.15µs and 0.5µs. An important thing to remember is that the datasheet specifies the maximum operating frequency to be 25kHz. I’ve used the TLP250 for frequencies up to about 16kHz.

That covers the different parameters related to TLP250. Now let’s go to the design stage and look at a few circuits. One thing you MUST remember to do when designing circuits with TLP250 is that, a 0.1µF bypass capacitor (ceramic capacitor) should be connected between V+ (pin 8) and V- (pin 5). This capacitor stabilizes the operation of the high gain linear amplifier in the TLP250. Failure to provide this capacitor may impair the switching property. The capacitor should be placed as close to the TLP250 as possible. The closer, the better.


Fig. 3 - Non-Inverting Isolated Low-Side MOSFET Driver


Fig. 3 shows a typical circuit for using the TLP250 as a MOSFET driver. VIN is the input drive signal that dictates the output state. Remember that VIN is referenced to Signal Ground. And that the TLP250 ground and load ground are referenced to the power ground, ie Vsupply and VMOS share the same reference ground as can clearly be seen from the circuit diagram and this ground is separate from Signal Ground. This clearly illustrates the isolation in MOSFET drive as the driving signal is isolated from the load supply.

When VIN = 1, Q1 is driven from the supply voltage (Vsupply) – the gate is pulled up to Vsupply level. Q1 turns on and current flows through the load – the load is driven from VMOS via the MOSFET.

When VIN = 0, Q1 is driven low – the gate is pulled down to its source level. Q1 turns off and the load is off.

Vsupply could be between 10V and 15V – 12V being a very common level used. R1 should be calculated by you depending on the amplitude of the input signal. I’ll give an example to clearly show you how (if you don’t know that already).

I’ve said above that 10mA (= 0.01A) for the forward current for the LED is a good value to use. So I’ll take that. Let’s say that the TLP250 is being driven from a microcontroller and the amplitude for the signal is 5V. I’ve said above that the forward voltage for the LED would typically be between 1.6V and 1.8V – I’ll take it to be 1.8V for this example.

So, V = (5.0 – 1.8)V = 3.2V
V = IR
R = V/I = 3.2V/(0.01A) = 320

R2 is the gate resistor. If you’re curious about why I used R3, read here:


C1 is the decoupling capacitor I talked about above. This MUST always be used and MUST not be omitted. I’ve added C2 for filtering/smoothing, as a bulk capacitor.

Let’s look at a few more circuits:

Fig. 4 - Inverting Isolated Low-Side MOSFET Driver


This circuit in Fig. 4 is similar to the above circuit in Fig. 3, with the difference being that the circuit in Fig. 3 shows a non-inverting driver (VIN = 1 drives the MOSFET on and VIN = 0 drives the MOSFET off) whereas Fig. 4 shows an inverting driver (VIN = 0 drives the MOSFET on and VIN = 1 drives the MOSFET off). How this has been configured to be an inverting driver is extremely simple to understand – the LED now turns on when VIN = 0 and turns off when VIN = 1. Like Fig. 3, Fig. 4 also shows an isolated driver: +VS is isolated from Vsupply and VMOS.

 Fig. 5 - Non-Inverting Non-Isolated Low-Side MOSFET Driver


Fig. 5 shows a non-inverting non-isolated driver. By shorting Signal Ground and Power Ground, isolation has been gotten rid of. Vsupply and VMOS share the same ground as the signal ground to which VIN is referenced.

 Fig. 6 - Non-Inverting Isolated High-Side MOSFET Driver



Fig. 6 shows the TLP250 being used as a high-side driver. Here in this circuit, there are 3 “grounds” – that of the signal ground to which VIN is referenced, that of Vsupply and that of VMOS.

When VIN = 1, Q1 gate is pulled up to the level of Vsupply (with respect to source). Since this is above the level of the source (which is connected to Vsupply return/ground), the MOSFET turns on and there is a current from VMOS through Q1 through the load, turning the load on.

When VIN = 0, Q1 gate is pulled down to the level of source and Q1 is turned off. There is no current through the load and the load is off.

By having the MOSFET source share the same ground as the TLP250 drive section and keeping this ground separate from the VMOS ground, Vsupply is easily used by the TLP250 to drive the MOSFET operating as a high-side switch.

And that’s it. The TLP250 is a useful little chip, making isolated MOSFET drive extremely simple. One last note is that while I've shown the circuits for MOSFET drive, they can easily be used (with the same circuit) for IGBT drive (of course, you replace the MOSFET with the IGBT).

I hope that my explanation of the application of the TLP250 and the circuit examples I provided help you in designing your own circuits using the TLP250 for optically isolated MOSFET (or IGBT) drive. Feel free to post your comments, feedback and suggestions!

77 comments:

  1. hi thanks for very helpful imformation.....get i get ur email please, cause i wanna show u the circuit of buck converter based on pwm and optocoupler....i got problem with my circuit, when give supply, the output is not come out...but if i short it with vcc at output of optocoupler it working....

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

      Regards,
      Tahmid.

      Delete
    2. thanks i already email u.....

      Delete
  2. Dear Tahmid
    I fabricated the 5 level inverter circuit using opto-coupler the input to opto is sine pwm but the output I got from the opto-coupler was normal square wave. What is wrong in my circuit.

    Regards
    Veera...!

    ReplyDelete
    Replies
    1. The drive signals from the driver are supposed to be square wave. By driving the MOSFETs/IGBTs with square wave signals with variable duty cycles (varying sinusoidally - as required for sine wave approximation) and then filtering the output, a sine wave is obtained.

      Regards,
      Tahmid.

      Delete
    2. Sir, shall I use this tlp250 for my MOSFET switching in buck boost converter circuit. My dsp30f2010 is producing a pwm in the range of 1my kHz. Weather this circuit work for me

      Delete
  3. Dear Tahmid

    Thanks...!
    Regards
    Veera...!

    ReplyDelete
  4. hi,
    i am doing a circuit of openloop boost converter using sg3524.. generated pulses at 50khz. but getting problem in the next part.. i have used the circuit given shown by you for isolation using tlp250. i am getting 50kHz pulses on the otherside of tlp which is fine... but i connected th tlp output to Mosfet with power circuit off. to gate n drain.. on cro when i see the pulses suddenly disappear to show it is getting shorted.. thin spike kind of lines appear between tlp output terminals.. please help me with ur valuable suggestions

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  5. hi, i'm planning on using the TLP250 for my IGBT inverter circuit using the proteus simulator. TLP250 is not available on the simulator. pls can u suggest the suitable driver i could use. i am designing a drive for a 0.5hp, 415v, 3 phase induction motor.

    ReplyDelete
    Replies
    1. You can get the TLP250 model from here:

      http://320volt.com/en/proteus-isis-smps-pwm-entegre-modelleri-library-dosyalari/

      Regards,
      Tahmid.

      Delete
  6. Please, can explain to me on how to use TLP250 to drive 24v supply and shut down when voltage is 18v or using TLP352 that has 15v minimum input voltage.

    ReplyDelete
  7. Is it possible for me to use LM350 to supply 15v to TLP250 for 24v inverter so that when voltage from the battery is 17.9v,there will be no output from the regulator to the inverter and the inverter will shut down.

    ReplyDelete
    Replies
    1. You can use a 12V regulator. That will be enough for driving MOSFETs and gives a lot of headroom at battery low voltage.

      Regards,
      Tahmid.

      Delete
  8. an HCPL3120 has similar delay time, but is an IGBT / MOSFET driver up to much higher frequencies (<500 ns switching speed)

    Regards

    ReplyDelete
    Replies
    1. Thanks for the input. You can also look at TLP350.

      Regards,
      Tahmid.

      Delete
  9. Dear tahmid,
    I have designed the dc switching relay using IGBT,the driver is tlp 250,the part of IGBT is AP30G120SW.THE problem is with vce its greater than 3V,but according to the datasheet VCE saturation is 3V,so how to reduce that drop.otherwise please send the circuit, using IGBT and tlp 250.

    ReplyDelete
    Replies
    1. The datasheet mentions VCE(sat) at a given temperature. Also remember that this is the drop if you drive the IGBT to saturation. Did you use sufficient drive current? How much larger is VCE than 3V?

      Delete
  10. Dear Tahmid:
    I have designed a switching circuit using the "Non-Inverting Non-Isolated Low-Side MOSFET Driver" pattern you mentioned above. In order to test its function, I input a square function into the TLP250. Furthermore, I set the frequency to be very low(i.e. 2HZ), then I discovered something really strange: Vmos was scaled down by about 0.5V. I'm eager to find out whether it was a loss or it was because of operation under low frequency?? BTW, I really found your info above helpful!! Thanks for your great job and your willing to share :)

    ReplyDelete
  11. Dear Tahmid,

    I've designed a full-bridge inverter using TLP250. I have the trouble in high-side mosfet. The both high-side mosfet heat-up in a few second. Let me ask you a couple question?
    1. Each supply for TLP250 (for 4 set) must be separated from the other ?
    2. How to use the "Bootstrap" for High-side Mosfet by TLP250 ?

    Thank you so much.
    Song

    ReplyDelete
    Replies
    1. 1) The 2 high side TLP250's must have separate supplies, separate from each other and from circuit supply and low-side drive supply. The 2 low-side TLP250's must have supplies separate from the high side supplies, but they may share the same supply?

      2) The bootstrap method relies on charging a capacitor to a specified voltage above the drive voltage (while the high-side MOSFET is off), and then relying on this voltage to drive the high-side MOSFET when on. See here: http://tahmidmc.blogspot.com/2013/02/n-channel-mosfet-high-side-drive-when.html

      You should consider using dedicated high-low side drivers, such as IR2110, L6385E, etc. Take a look here: http://tahmidmc.blogspot.com/2013/01/using-high-low-side-driver-ir2110-with.html

      Regards,
      Tahmid.

      Delete
  12. Can VMOS and VSupply be the same 12V power source?

    ReplyDelete
    Replies
    1. Only if you're using one of the non-isolated drive circuits, and if your load drive circuit works with 12V.

      Regards,
      Tahmid.

      Delete
  13. Hi Tahmid, this is a DC MOTOR controller TLP 250 circuit.

    http://img196.imagevenue.com/img.php?image=108102761_Image1a_122_98lo.jpg

    Can you guess the 2 transistors TO 220 package in the right upperside near the MUR 1660 power diode (its numbers are erased).

    Thanks.

    ReplyDelete
    Replies
    1. It's not possible to just guess without further information.

      Further information such as DC motor rating, controller specifications, control type, etc are required.

      Those may be BJTs or Power MOSFETs. The specific part number would depend on circuit parameters such as voltage, current, efficiency, drive mechanism, etc

      Regards,
      Tahmid.

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

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  15. do you have the hcpl3120 library for proteus?

    ReplyDelete
  16. Well done! What an excellent article!
    I landed here while I was looking for some info; In my setup, B1 is a bridge /cap combination directly from the mains supply ~310v. Is it possible to omit B2 and just use a voltage divider from 310v to feed ~15v to TLP250 ? Is IR2110 a better choice for that purpose?

    Thanks

    ReplyDelete
    Replies
    1. Which diagram are you referring to?

      If you're talking about a low-side driver, then you can use a non-isolated power supply to provide the 15V. A voltage divider just won't have the current drive capacity. If it does (low resistances, or transistor follower), it'll have way too much power dissipation and heat, with abysmal efficiency.

      If you're talking about a high-side driver, you'll need to use an isolated power supply.

      Even if you choose to use an IR2110 (which would be for only a high/high-low side configuration), you'd need a separate low voltage power supply.

      Regards,
      Tahmid.

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

      Delete
  17. Thank you, very helpful (but, please consider how hard it is for some people to read white text on a black background).

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  18. Hi tahmid, i wanna ask value of R2 from your circuit. Is it 10 ohm or 10 kohm ?

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  19. hi tahmid, i really appreciate ur blog, well done sir
    my question is why is R2 used ?? is it ok not using it?? and how its value is calculated??
    regards
    ehab

    ReplyDelete
    Replies
    1. You should use R2. Don't omit it. It's value isn't too critical. Think of it as a current limiter for driving the MOSFET gate. The critical thing is not to choose too large a resistance such that it prevents driving the MOSFET completely (fully on). 10R should be good for up to relatively high frequencies (about 100kHz).

      Regards,
      Tahmid.

      Delete
  20. Hi, Tahmid
    Your blog is so awesome with great information.
    I also followed your hints with this tutor, but something is wrong. can you suggest me some tips to solve my problems.
    In my case, load is AC and I try to fire MosFET by TLP250 but not success. Could you help me, please?

    ReplyDelete
    Replies
    1. Could you give a schematic of your setup? That would help me better understand the situation.

      For driving AC loads with MOSFET, use the circuit as shown in Figure 6. Take a look at this as well:

      http://tahmidmc.blogspot.com/2012/11/controlling-ac-load-with-mosfet.html

      Regards,
      Tahmid.

      Delete
    2. Hi Tahmid,
      I am sorry for late response because recently I am very busy.
      In my case, I also followed your recommend schematic to control ac load, Rg approximately 100ohm and Rgs about 10kohm. My MOSFET I use in this application is FQP6N80C and be controlled by TLP250. I tried several times but still not success. I think the output current of TLP250 is not enough to open FET(with maximum about 1.5A)? or maybe iam wrong some point of view?
      Thank you so much
      Sincerely
      Lavie

      Delete
    3. https://www.dropbox.com/s/eyybmf4fqykb27a/20140226_165526.jpg
      this is my schematic. was I wrong something?

      Delete
  21. Hello Sir,

    i have a scenario like in Fig. 6 - Non-Inverting Isolated High-Side MOSFET Driver. but i have a common ground supply for the microcontroller and gate driver. so the isolation in gate driver will be no more. and i think i should use a isolated supply for that and there is no other solution. could you please update it with flyback converter design.

    regards
    Zeeshan

    ReplyDelete
  22. Hello, love your work, you're an accomplished young man

    Of all the low side gate driver ICs which would be best to use if I am making a boost converter at PWM frequency 30-50k Hz? to give a double boost.
    Thank you in advance

    ReplyDelete
    Replies
    1. I would recommend using a dedicated low-side driver. The TC427 is one for example - take a look at the TC429 if you need higher drive current.

      Delete
  23. Dear Tahmid, I have a buck boost converter, I designed the controller for outer voltage loop with an PI and the inductor current is being controlled by Slope compensation.I simulated that all in PSIm, and it works all ok as calculateed and expected, now I want to Implement it in Multisim, The Mosfet driver is giving me problem. The parameters are; Vin =30Vdc Vout is 60 V, L=100u, say C= 697u or 680u, equivalent load resistance is = 8 Ohms. and The converter works in CCM, with Switching frequency of at least 100kHz. I was using Mosfet IRCZ44, if you need I can send you some of my simulation results, but How. I am Tareq , and from Bangladesh. If you can help me , I appreciate it.

    ReplyDelete
  24. Dear Tamid, or to anyone who could help, on the case of the TLP250, used for an inverter. My question is: if mosfets blows up, would the optoisolator blows too. Pls help: u can post the answer here or reply me on richiereigns@gmail.com

    ReplyDelete
  25. Dear Tamid, or to anyone who could help, on the case of the TLP250, used for an inverter. My question is: if mosfets blows up, would the optoisolator blows too. Pls help: u can post the answer here or reply me on richiereigns@gmail.com

    ReplyDelete
    Replies
    1. I can't say for sure. Depends on why the MOSFET blows. For example, if the gate gets shorted to drain for example, the optoisolator is going to be gone.

      Delete
  26. I want to ask about multi mosfet. we want to use 4 parralel mosfet (for share the power) and can we use only one tlp250?

    ReplyDelete
    Replies
    1. Depends on which circuit you're using and the frequency. For low side drive, at low frequencies (50Hz for example), you can use one TLP250.

      Delete
  27. Hello Tahmid, thanks for the earlier help. i am designing an smps inverter which i have been able to finish but i now intend to create another design which would have multiple ferrite transformers of the same type driven by their separate mosfets and tlp250. i want to be able to shutdown each dc to dc converter without shutting it down from the sg3525. can i design a shutdown function for tlp 250

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  28. Hi tahmid can I replace 350 with 250

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  29. CAN U GIVE THE PROTEUS LIBRARY FOR TLP250

    ReplyDelete
  30. GREAT WORK :) .. I NEED UR HELP TO DESIGN CIRCUIT FOR JUST SWITCHING DC MOTOR ( BOMBER CAR IN FUN LAND ) ..BUT I NEED HIGH SIDE SWITCH . ( MOTOR RATING 100VDC . 15A) . THE SUPPLY VOLTAGE BETWEEN 75~100 VDC FROM RECTIFIER. I USED DC DC SSR . IT WORKS GOOOD BUT IT DAMAGED EASILY FOR ANY SHORT CIRCUIT AND IT IS EXPENSIVE .. I NEED DESIGN OTHER CIRCUIT using tlp250 DO LIKE SSR WITH LOW COST AND MAKE SOME PROTECTION

    PLZ HELP ME MY EMAIL : ESSAMYOWAKIM@GMAIL.COM

    ReplyDelete
  31. Dear Tahmid,
    I have to use TLP250 in my Proteus design. It is not available in Proteus. How i can add it.

    ReplyDelete
  32. It's really a mind blowing project!!! Very well explained in this video

    https://www.youtube.com/watch?v=fOyZuAd3NlM&feature=youtube_gdata_player

    ReplyDelete
  33. Hi Tamid,
    Can you please share us about TLP350.I need the designing of resistors and capacitors.It is really urgent.

    ReplyDelete
  34. Dear Tahmid,
    can you help me about tlp250. actually i want to design dc to ac converter using arduino .in my design i m getting an error (input current is outside specified range) and the error is happened when i connect tlp250 with arduino. now can you tell me how can i solve this problem.my email id is (smartsinger.mds@gmail.com) please mail me some idea about tlp250..

    ReplyDelete
  35. hello,
    im using a h bridge comprising of 4 n channel mosfets (IRF540N). Im using hcpl 3120 to drive each of the mosfets from seperate supplies and the circuit is similar to the one uve posted. my hcpl has a supply of 12V and my inverter works at 30V and a switching frequency of 40kHz. Should i be worried about the high side switching?? im not using any bootstrap circuit.

    ReplyDelete
  36. Hello,
    I am looking for high side High Voltage switching and the Fig 6 configuration looks the best for me. Am using isolated 12V DC DC Converter for supply B2. Can I use another isolated DC DC converter of 1500V as Supply B1?
    Please reply. How can I send you my circuit for reference?
    Thanks

    ReplyDelete
  37. Dear Tahmid
    can i use your circuit diagram with arduino or pic micro controller pwm to control 24 v dc proportional solenoid valve
    regards

    ReplyDelete
  38. Dear Tahmid
    can i use your circuit diagram with arduino or pic micro controller pwm to control 24 v dc proportional solenoid valve
    regards

    ReplyDelete
  39. Hi tahmid
    Can we drive ac motors like inverter i mean with this configuration withing range of 1kw

    ReplyDelete
  40. Hello! This is Sanjeev Pandey from India. Your blog is really helping me for my understanding about dc-dc converters. Currently, I am working on buck converter and my switching frequency is 100kHz. Please suggest me a MOSFET driver IC. I know only two driver IC TLP250 and 350. And these are not going to help me in this application.

    ReplyDelete
  41. Sir If I only use tantalum capacitor if it could for driving high side?

    ReplyDelete
  42. we have two circuits one is sg3524 and ir2101 but we cannot connect grounds together. if we connect its become short circuit. Actually we are doing full brige inverter circuit which is converter ac to dc .

    ReplyDelete
  43. VIN to TLP250 is pwm input or direct dc volt?

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  44. HCPL3120 LIB FILE...IF ANYONE HAVE KINDLY SEND IT TO ME THANKS

    ReplyDelete
  45. Hi,
    I have a very common question that if I want to use bjt or fet the base/gate voltage should be equal to the collector/drain voltage to get the same at the emitter/source.so how tlp 250 in H bridge configuration in high side switch transfer the same(310v)or any high voltage than tlp250 supply voltage to load while we are using 12/15 volt gate drive supply voltage.

    ReplyDelete
  46. i have given all the above connections for isolated high side driver but still i am getting no response in output..please help me

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  47. Hello sir... can you pls explain the difference between MCT2E and TLP250 driver circuit. which one is the best..how?

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  48. Is there any full form of TLP in tlp250 ??

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  49. Can I made H bridge inverter gate driver circuit using single battery or supply instead of using 4 for each MOSFET???

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  50. For convert 24 volt dc to dc to 5.2 volt dc to dc what type tlp will be used?

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  51. This comment has been removed by the author.

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  52. Do you have library of eagle cadsoft for tlp250?
    thank you

    ReplyDelete
  53. Hey Can anybody sign me up the real TypeNr of Mosfet to use? For example de FQP6N80C is the only one listed in the forum below. I only need a Typenr for a mosfet that can sink 10A or a littlebit More. As seen in:

    Fig. 5 - Non-Inverting Non-Isolated Low-Side MOSFET Driver

    With friendly greets, and please rather refer to: woutervanwegen@mijnplinq.nl

    ReplyDelete