1. Home
  2. General Electronics
  3. MOSFET driver killed with no particular reason

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 a direct reason 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
Loading thread data ...

All Bridge drivers have the potential for short-circuit failure unless there is a safety circuit to prevent this. With separate drive circuits for simultaneous complementary switching , it is cruicial to control the switch delay to allow some dead-time in the switches and have each one protected for reverse pulses. Asymmetric delays for rising and falling pulses and reactive loads all contribute to this risk. Try to design the pulse delays so that the turn-off delay is always shorter than the complementary switch's turn-on delay. This can be controlled by adding turn-on delay only in the pre-driver signal to compensate for the natural longer off delay of the switch. Examine worst case time delays with temperature effects and best case to calculate the dead-time needed to avoid short-circuiting the high-side and low side switches thru each other to power. A power transistor will have a safe operating area for voltage and current but also look for deratings from thermal effects and pulse speed. Once these limits are all observed, your MOSFETs will last a long happy life.

Tony EE'75

Reply to
tony.sunnysky

Thanks for your reply. I understand the necessity of deadtime to prevent shoot through in bridge, and as said in driver's datasheet such prevention is already built in. Moreover, it's not MOSFETs, but the driver itself get destroyed by just playing with input rails H/L, even haven't connected them to high switching frequency yet.

This picture shows what I did:

formatting link
(NOTE: bootstrap diode is built in)

Reply to
w2kwong

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.