A PC Off-Line Supply

This chapter illustrates the design of a 220 W PC switching power supply and examines all steps necessary to create working designs. A typical universal input power supply is graphically presented. It has a power switch, a fuse, an RFI filter, an NTC inrush current limit thermistor, a full wave bridge rectifier, and a filter capacitor. A schematic diagram of the DC-DC converter is also presented. The chapter focuses on the designs of capacitor, transformer, and inductor. When the target internal temperature of the supply is quite high a electrolytic capacitors are designed, these capacitors are about 60 times larger than the required capacitance, in order to meet all of the requirements of these special capacitors in return involves various steps, such as calculating required capacitance of the input supply, designing the bootstrap power supply, and choosing the value of the current sense from the data sheet.