用于降压型DC-DC转换器的短路保护电路设计

Design of Short-Circuit Protection Circuits for Buck DC-DC Converters

设计了一套用于降压型DC-DC转换器的隔断触发模式短路保护方案。除了具有基本的峰值限流功能,该方案还能使转换器在输出短路时触发周期性的休眠与软启动。通过对软启动信号的控制,将短路下的休眠时间设计为软启动时间的2倍。在软启动被触发时,当电感电流峰值达到限流门限时,转换器开关频率将降低到原来的四分之一,较好地控制了电感峰值电流。采用0.5μm BCD工艺进行仿真,结果表明,当峰值限流为3.6A时,平均输出短路电流仅1.06A,低于传统的逐周期降频限流方案。

A hiccup mode short-circuit protection method was proposed for buck DC-DC converters. Except for the basic peak current limiting function, this method could also make converters enter sleep mode and soft start periodically once the output was shorted. Through the control of soft start signal, the sleep time was designed twice times to soft start time. Under output shorted condition, when inductor peak current reached the current limiting threshold, the switching frequency of converter was reduced to a quarter of the original ones. Therefore, inductor peak current was well controlled. Based on 0. 5 /-m BCD process, the simulation results showed that the output average short-circuit current was 1.06 A with 3.6 A of peak current limiting, which was much lower than the traditional cycle-by-cycle frequency reducing and current limiting ways.