分立式非隔离型降压开关稳压电源的设计

Design of discrete non-isolated buck switching regulated power supply

为实现电源从交流220V输入电压到低压直流的转换,设计一种基于分立式元器件的BUCK降压电路。利用比较器输出端高低电平的反馈,实现比较器输入端电平切换,产生幅度较大的三角波。三角波与直流可调参考电平比较产生占空比可变的脉冲宽度调制(PWM)驱动信号。电源采用电容自举的方式克服MOSFET高压侧驱动问题,利用推挽电路驱动开关管的开通和关断,对直流电压进行斩波,实现15V降压输出。同时设计欠压保护电路、过流保护和电压反馈电路提高电源工作时的可靠性。经实际调试该电源负载调整率为1.8%,平均效率为90.4%,负载能力为1A。

Based on discrete components,this paper designs a BUCK circuit in order to achieve the conversion of power supply from AC 220 Vinput voltage to low DC voltage.The feedback of the high and low level of the comparator output is used to realize the voltage changing of the input terminal of the comparator so that the circuit can produce triangular wave.Triangular wave is compared with DC adjustable reference voltage to produce PWM signal.Power supply adopts the way of capacitance bootstrapping to overcome the problem of driving the high side of MOSFET.The push-pull circuit is used to drive MOSFET,and the DC voltage is chopped to achieve 15 Vvoltage output.Meanwhile,under-voltage protection,over-current protection and voltage feedback circuit are designed to improve the reliability of power supply.By the actual debugging,power supply load regulation is 1.8%,the average efficiency is 90.4%,and the load capacity is 1 A.