IGBT过流保护电路设计

为解决绝缘栅双极性晶体管(IGBT)在实际应用中经常出现的过流击穿问题,在分析了IGBT过流特性和过流检测方法的基础上,根据过流时IGBT集电极电流的大小分别设计了过载保护电路和短路保护电路。过载保护电路在检测到过载时立即关断IGBT,根据不同的过载保护要求可实现持续封锁、固定时间封锁及单周期封锁IGBT的驱动信号;短路保护电路通过检测IGBT通态压降判别短路故障,利用降栅压、软关断和降频综合保护技术降低短路电流并安全关断IGBT。详细阐述了保护电路的保护机制及电路原理,最后对设计的所有保护电路进行了对应的过流保护测试,给出了测试波形图。试验结果表明,IGBT保护电路能及时进行过流检测并准确动作,IGBT在不同的过流情况下都得到了可靠保护。

Design of IGBT over-current protection circuit

In order to solve the over-current breakdown problem of insulated gate bipolar transistor （IGBT） in practical applications, short-circuit protection circuit and overload protection circuits were proposed according to the IGBT＇s collector current, after the analysis of IGBT＇s characteristics and over-current measures. When overload protection circuits detected over-current, it switched off IGBT immediately, IGBT＇s drive signal can be blocked continuously, for fixed time or for a single cycle based on different overload protection requirements; short-circuit protection circuit detected the over-current by measuring IGBT＇s on-state voltage drop, using dropping the grid voltage, soft switch-off and reducing IGBT＇s working frequency the circuit can decrease short-circuit current and switch off IGBT safely. Detailed elaboration of circuits＂ operating mechanism was given. The over-current testing of the all designed protection circuits was done. The waveform graphs were obtained. The experimental results indicate that protection circuits can detect over-current in time and response accurately, IGBT is protected reliably under different over-current conditions.