介绍一种采用半桥电路的开关电源，其输入电压为交流220V±20％，输出电压为直流4～16V，最大电流40A，工作频率50kHz。重点介绍了该电源的设计思想，工作原理及特点。-Introduction of a half-bridge circuit using the switching power supply, the input voltage for AC 220V ± 20, output voltage of DC 4 ~ 16V, maximum current 40A, operating frequency of 50kHz. Focuses on the design of the power of thought, working principle and characteristics.