in order to understand the lamp's negative incremental impedance of characteristics and analyze the stability of ballast / lamp system clearly, the low-frequency ballast system stability with closed loop are analyzed based on the hid lamp frequency-domain model in chapter ii 为了更好地理解灯的负阻特性并分析电子镇流器系统的稳定性问题,论文第二章着重从灯的频域模型出发分析了闭环控制下的低频方波电子镇流器系统的稳定性问题。