Problem:
I have a James sub woofer amp that blew two Output FETs. This amp Has two IR2011 chips driving two FETs. One High (+60v) and one Low (-60V). One pair drives the speaker negative and the other pair drives the speaker positive. One of the pairs blew. I changed all the FETs. The amplifier worked but the output filter inductors got very hot after running for five minutes while the heat sinks remained cool. While probing the input OpAmp the FETs blew again. It seems only the low side FETs were working as the Bootstrap caps show no voltage. The problem should be something common to both amps but I am at a loss.
Here's where I'm at:
I think the problem is that the IR2011 high side won’t start even though the high input is present. There is no voltage across the Bootstrap caps. This seems to be due to an incorrect startup sequence to charge these caps. I downloaded a reference design from International Rectifier that is an amplifier that is almost exactly the same (See attached). I metered out everything in the Vcc circuitry and found nothing wrong. I changed some caps, pre-drivers and the IR2011's to no avail. If there is no 13V across the Bootstrap Caps the High out signal won’t work. There’s something wrong with the Bootstrap Circuit which I don’t understand. Please help!
Gary
I have a James sub woofer amp that blew two Output FETs. This amp Has two IR2011 chips driving two FETs. One High (+60v) and one Low (-60V). One pair drives the speaker negative and the other pair drives the speaker positive. One of the pairs blew. I changed all the FETs. The amplifier worked but the output filter inductors got very hot after running for five minutes while the heat sinks remained cool. While probing the input OpAmp the FETs blew again. It seems only the low side FETs were working as the Bootstrap caps show no voltage. The problem should be something common to both amps but I am at a loss.
Here's where I'm at:
I think the problem is that the IR2011 high side won’t start even though the high input is present. There is no voltage across the Bootstrap caps. This seems to be due to an incorrect startup sequence to charge these caps. I downloaded a reference design from International Rectifier that is an amplifier that is almost exactly the same (See attached). I metered out everything in the Vcc circuitry and found nothing wrong. I changed some caps, pre-drivers and the IR2011's to no avail. If there is no 13V across the Bootstrap Caps the High out signal won’t work. There’s something wrong with the Bootstrap Circuit which I don’t understand. Please help!
Gary