D类音频功放过流保护电路的设计

Design of Overcurrent and Short Circuit Protection Circuit for Class-D Power Amplifier

本文设计了一种D类音频功放的过流保护电路。通过和功率管同类型,缩小尺寸的采样管监测流过功率管电流的大小,因此在高侧功率管和低侧功率管过流时,使用一个基准电压值和一个比较器就可以完成过流检测及保护功能,有效降低了过流保护电路的功耗和版图面积。栅驱动电路通过一个自举电容不仅为高侧功率管及采样管的开启提供足够的驱动电压,还为过流保护电路提供选择控制信号,交替检测高低侧功率管的过流情况。过流保护电路采用耐高压结构,保证D类音频功放大功率输出时正常工作。

In this paper, an overcurrent protection circuit for class D audio power amplifier is designed. The sampling tube with the same type and reduced size as the power tube monitors the current flowing through the power tube.Therefore, when the high side power tube and the low side power tube are overcurrent, the overcurrent detection and protection functions can be completed by using a reference voltage value and a comparator, which effectively reduces the power consumption and layout area of the overcurrent protection circuit. Through a bootstrap capacitor, the gate driving circuit not only provides sufficient driving voltage for the opening of the high side power tube and sampling tube, but also provides a selection control signal for the overcurrent protection circuit to alternately detect the overcurrent of the high and low side power tubes. The overcurrent protection circuit adopts high-voltage resistant structure to ensure the normal operation of class D audio power amplifier at high power output.