An over-current protection circuit for CMOS PWM class-D audio power amplifier applications

This paper puts forward an over current protection circuit for CMOS class-D audio power amplifier applications. The core of this circuit is two offset comparators using unilateral hysteresis. The experimental results show that the open loop gain of the comparators is about 95 dB and the offset voltages are 0.25 V and 0.286 V respectively under the condition of CSMC 0.5 μm CMOS process. The over current protection circuit will start up when the output short to power supply voltage or short to ground voltage. So the audio power amplifier can not be damaged and the circuit completely meets the design of class-D audio power amplifier. The active area of the over current protection circuit is about 291 μm × 59.5 μm. The measured results shows that the proposed over current protection circuit can operate accurately when the output short to power supply voltage or short to ground voltage.