CMOS PWM D类音频功率放大器的过流保护电路

基于Class-D音频功率放大器的应用,采用失调比较器及单边迟滞技术,提出了一种过流保护电路,其核心为两个CMOS失调比较器。整个电路基于CSMC0.5μmCMOS工艺的BSIM3V3Spice典型模型,采用Hspice对比较器的特性进行了仿真。失调比较器的直流开环增益约为95dB,失调电压分别为0.25V和0.286V。仿真和测试结果显示,当音频放大器输出短路或输出短接电源时,过流保护电路都能正常启动,保证音频放大器不会受到损坏,能完全满足D类音频放大器的设计要求。过流保护电路有效面积为291μm×59.5μm。

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.