I am building a Single-ended Class D audio amplifier with +-30V voltage supply and the half brdige MOSFETs are switched with an IRS20957s driver. The PWM input is obtained comparing the audio signal (+-1V max) and a carrier signal 260kHz frequency. The load is a LC filter with a cut-off frequency of 40kHz approx and a 4ohm resistance.
I have done the design of the Driver stage folllowing the application notes from IR:
http://www.irf.com/technical-info/appnotes/an-1144.pdf
My problem is that HO and LO outputs are kept low all time and I could not find the reason. The timing capacitor of the Over-current protection is continously charging and discharging all time, going from the high threshold to the low threshold, but I can assure that the current limits are not exceeded, since I am using a laboratory power supply that can deliver a maximum of 3A and the limit is set to more than 7A. But anyway, the driver, as far as I can see, never starts. So that is why I think that the problem may be due to the bootstraping circuit, even though I can't say exactly why.
Thank you very much for your help!
I have done the design of the Driver stage folllowing the application notes from IR:
http://www.irf.com/technical-info/appnotes/an-1144.pdf
My problem is that HO and LO outputs are kept low all time and I could not find the reason. The timing capacitor of the Over-current protection is continously charging and discharging all time, going from the high threshold to the low threshold, but I can assure that the current limits are not exceeded, since I am using a laboratory power supply that can deliver a maximum of 3A and the limit is set to more than 7A. But anyway, the driver, as far as I can see, never starts. So that is why I think that the problem may be due to the bootstraping circuit, even though I can't say exactly why.
Thank you very much for your help!
