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convert open-circuit fault to short-circuit-fault (IGBT)

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kappa_am

kappa_am

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Hi all,
Is there any way (gate driver) by which I can convert open-circuit fault caused by missing firing signal or driver fault to the short-circuit fault?

Thank you for your helps.
 

A typical de-saturation detection circuit should detect both open circuit fault and short circuit fault as a common fault. You don't need to convert anything. For example PC929, HCPL-316 etc. are optically isolated gate drivers with built-in de-saturation detection circuit.
 

Hi,
Thank you for your reply.
I know about them. what I need is when the firing signal is missing the IGBT get fired.
 

Are you talking about the miller capacitance coupling from the Collector to the Gate and turning it on? The addition of a small capacitor from gate to emitter solves this. The preferable approach (although not economically feasible in small devices) is to use negative gate drive to ensure the device stays off during aggressive dv/dt on the collector emitter when the device is off.
 

I believe we can avoid much guessing if we first hear a clear question.

"convert to the short-circuit fault" means exactly what?
 

I am working on a multilevel inverter, I have designed a fault remedy algorithm, that works perfectly under short circuit condition ( experimentally verified).
Since in multilevel inverter energy level is not enough high to evaporate silicon surface, the possibility of this kind of open-circuit fault is very low. but because of numerious switches and connection there is still possibility of open-circuit fault because of missing firing signal. To avoid bypass switch, I'd like the switch be closed (switch ON) when its firing signal is missed. I'd like to have most economical way.

Thank you for your helps.

Sorry for first vague question
 

To avoid bypass switch, I'd like the switch be closed (switch ON) when its firing signal is missed. I'd like to have most economical way.
Click to expand...

Doesn't sound well considered.

1. What's your exact criterion to detect that a "firing signal is missing"?
2. On which circuit level should the automatic close signal be generated?
3. It's normal operation that some switches of a multilevel inverter are not fired for some time. Closing these switches automatically would result in bus voltage short after some time?
 

Hi all,
Suppose the following circuit.
I detect that a switch is failed short/open or healthy using commanded firing signals and charging states of the capacitors.
I would like it to be in the power section close to the switches as much as possible.
I know that some switches are not fired in some intervals, but the charging states will be same as the desired ones. Therefore, any fault interrupt will not be generated.
closing a switch short two capacitors with different voltages. Since the current decays rapidly it is ok.

Any comment is appreciated.
fc.jpg
 

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