[SOLVED] TLP 250 or IR 2110 , Which one to use?

lxmn said:

Hi Everybody,

I am currently trying to build a 500W, 100kHz buck boost converter, with Vin = 25to 35 Vout = 25 / 50 V. Switch MOSFET : IRF 3710
I am a bit confused about a number of things.

1. Should i be using a high side + low side driver like IR 2110 or a optocoupler based TLP 250 would suffice?
i feel ir 2110 is redundant since i need to drive only one mosfet. But i have heard TLP works satisfactorily only upto 25 kHz or so (?????).

2. Do i need to use a bootstrap circuit at all or is it required since the output / source is not at ground zero potential ( i am clearly a bit confused about when and where the bootstrap circuit is needed )

3. I have tried using ir 2110 , following the design equations given in the application note ( C> .1 uF) , i had used bootstrap capacitor ( electrolytic) C = 1uF , lower C = uF and bootstrap diode 1N4148. The resistor in series with the gate was 100 ohm ( random selection ). But with these values the test circuit didnt workout . I would like to know , on what basis do we fix the values of the R and the lower C?

Thanks in advance.....

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Tahmid said:

1. What kind of a buck boost converter are you using? Is it a single switch inverting buck-boost converter or 2/3 switch non-inverting converter?

2. When source is not at ground potential, and the load is taken through source to ground, the MOSFET is configured as a high-side switch and then, high-side driving is required. One such way to drive the high-side MOSFET is through a diode-capacitor bootstrap method. So, if you're driving a high-side MOSFET this way, you need to use bootstrap.

3. What, in the test circuit, did not work out? Did the circuit simply not work? Did it get burnt? Did you verify that input is correct? You should upload your schematic. There may be errors there.

The TLP250 on its own is a low-side driver. You can design high-side driving circuitry employing a TLP250 using bootstrapping or an isolated power supply, but it's not designed as a high-side driver.

Hope this helps.
Tahmid.

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lxmn said:

I have attached the schematics that i used to test the ir 2110 driver.

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mtwieg said:

This isn't a buck boost converter (it's not a DC-DC converter of any kind, just a DC chopper). But it should still be able to turn on the FET and power the load. Are you sure the SD pin is pulled low? Does the LO output work if you provide PWM to the LIN pin?

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Tahmid said:

From where are you giving the signal? Microcontroller or PWM IC?

You need to pull pin 11 low. You should use a smaller gate resistor although that won't stop the MOSFET from turning on.

Connect pin 11 to ground. Provide the input and observe the output across the load.

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Tahmid said:

What is the frequency of the signal? 10 ohm is okay for most frequencies unless it's very high. But, seeing as the input is from a microcontroller, the frequency won't be too high (assuming that you're using a PIC/AVR/ other 8-bit microcontroller) and you can use 10 ohm resistor.

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mtwieg said:

100KHz should be doable with a IR2110, so long as the fet is not very huge. And if you use an external gate resistor then that should dissipate most of the gate drive power, rather than the IR2110.

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lxmn said:

The frequency is 100 kHz, with 65 % duty cycle.
In fact i have tried out with 22 ohm and i got the output .
The problem with the circuit now is that ir2110 is getting heated up. what could be wrong now?

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Orson Cart said:

Hello there, there is a limit to the max duty cycle you can have as the bootstrap cap needs to charge thru the load in your test circuit, so 100% is not possible, if the recharge in the off time is not sufficient (even at 50% duty) then after a while the high side driver wil stop due to the UVLO on the IC, then the cap will charge thru the load and the process repeat...

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