Biasing from the anode of the opto driver.

Furkan Eroglu

Hello everone ,

Sorry for my question I'm newbie.

There is a bootstrap circuit that I take the project of a graduate student as a reference and it works. But there are a few things that I don't understand in this circuit.

Like ;

-Why does the PWM signal come from the cathode to the anode?
-Why is a capacitor placed between the cathode and the anode?
-Why 12V is given externally to the anode?

Thank you.

over 5 years ago

0 Mike O' over 5 years ago

TI__Guru* 85826 points

Hello,

It looks like you are just sending a PWM signal across the opto isolators.

I have not seen isolators like this, generally there is a photo diode and a photo transistor.

Regards,

0 Peter Repka over 5 years ago in reply to Mike O'

Prodigy 210 points

Hello Mike, This may be an optical relay and the bootstrap he is talking about may be an on/off control. Just speculating here. I would like to know the part number of the device to see what it really is. I have used Anode biasing with mosfet drivers to stop all sorts of driver issues. Regards , Peter

0 Furkan Eroglu over 5 years ago in reply to Peter Repka

Prodigy 120 points

Hi team I'm sorry for the late reply.
I Was not at work these last day cause of the virus.
The part number is Broadcom's HCPL3120 also I've solve the problem.
Thank you for answering the question!

0 Peter Repka over 5 years ago in reply to Furkan Eroglu

Prodigy 210 points

This is an older device originally from Hewlett-Packard and it is an isolated gate driver For mosfet and igbts. I used this same device to drive large 100A IGBT blocks in a modified sine inverter design over two decades ago and it worked great. Glad you Fixed the problem.

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Biasing from the anode of the opto driver.