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MOSFET driver killed with no particular reason

hi to everyone. I mysteriously killed 5 MOSFET half bridge drivers and wish to see if anyone can help.

I'm making a N-MOSFET H bridge circuit that switch a sine wave output using unipolar PWM for an inverter project. The gate driver I choose was IR21834 and I began testing half of the bridge on breadboard according to the datasheet circuit. Connecting input lines manually to V+ or GND to produce the output, the lower MOSFET would first work, but it always happened that somehow after changing the circuit such as connecting driver input here and there or switching the value of boostrap capacitor, at a random time the chip would go crazy . The chip would feel hot touch, followed by increase in current drawn, all of which signifying an internal short circuit. It seems the hide side circuit is causing problem, since the low side output would usually still functioning afterwards.

I believe such short circuit behavior can only be caused by shorting high side output to ground or to V+, and I swear I didn't, nor did I connect bootstrap diode and capacitor wrongly (I redid the circuit several times and same error can't happen over and over again). I thought it might be chip design problem but as I tried chip from other manufacture, L6388 from ST, the same happened. Now I'm really threatened as I don't want to kill any more chips. Although I might find out the reason myself but that would probably take another 10 chips dedicated to destroy, and this is why I ask for help here.

While not expecting direct reasons to the problem, I am REALLY REALLY glad if someone who have killed MOSFET driver before (for whatever reasons) to share his/her story, and also tell me what to avoid when working with drivers, thousands thanks in advance!

Reply to
w2kwong
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Did you read the appnotes? Can you post a schematic? (on ABSE or with a link to a website or ASCII here)

Ed

Reply to
ehsjr

Hi,

There are several issues but usually the gate resistor is not large enough plus you must have a diode around this resistor and a resistor in series with the diode. ( the current mirror issue ) the Crss is being charged with the turn on gate resistor. The resistor in series with the diode ( turn off resistor ) should about 1/10th the value of the turn resistor. This is because when you turn on the fet the other fet in series is seeing the same dv/dt. so the turn off resistor should be low enough to keep from pulling the gate up to the threshold voltage. When you have selected the turn on resistor the driver chip will run cooler because it will have to deliver less charge. It is totally impossible to drive fets in a half bridge or full bridge( with any current ) with out series gate resistors. Ray

Reply to
Ray King

Hi again I forgot something, The boot strap diode must be at least as fast as 200ns. The boot strap cap should be 1 uf and the ground cap at the anode end of the fast diode should be at least 10uf. I hope this is helpful Ray

Reply to
Ray King

my guess your loaded with static.. try putting on some anti-static straps on your wrists.

--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5
Reply to
Jamie

First thanks for replying.

Humidity last night was 60% and this excludes possibility of electrostatic, plus I have played with CMOS gates 74HC, 40XX without anti-static for ages without encountering a single chip killed for this. Ray suggested that Rg is source of problem, but I was only manually bring the input on and off, not yet with high frequency. The gate is in order of nF and can't see how a single charge up could cause current large enough to blow the driver. With IR21834 which have more then 1A capability, the chip actually burned and drawed more then

1A from 12V supply, obviously an internal short circuit...

This picture shows what I did:

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(NOTE: bootstrap diode is built in)

Reply to
w2kwong

Don't use plug-in boards for power control circuits.

RL

Reply to
legg

You have stray inductance all over the place with those plug in boards. Also they are capacitive and radiate like a Son of a gun. This is fine for low speed digital or simple analog opamp circuits but definately not for high speed PWM. When you thrn the FETs on and off, you're getting spikes all over.

You need a PCB with wide, short traces to minimize the inductance.

I have tried making switching power supplies on perf board using copper tape and short wires and it never even came close to the performance of a proper PCB layout. The perf projects were usually unsuable.

Reply to
Mook Johnson

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