Improved PC power supply with in-rush current reduction technique

Abstract

PC power supply unit (PSU) is the device that converts the input AC voltage to the DC voltages needed by the personal computer. Power supplies for computers utilize switching mode technology. Since the introduction of IBM PC/XT there have been about a dozen of different PC standards (such as AT, ATX, SFX, LFX, and so on.) that differ by their form factors, connectors and voltage/current ratings. Currently ATX12V style is the dominant one. Output power of a typical power supply for personal computers is 180 to 450W. PSU over 450W are usually used in servers or industrial PCs. PC power supply system consists of input filter & rectifier stage, main power stage, auxiliary power stage, control stage, and supervisor & protection stage. AC line voltage goes through the input & rectifier stage and it is converted to unregulated DC voltage. This DC voltage is the power source of the main and auxiliary power stage. The main power stage generates main DC output voltages : +5V, ±12V, +3.3V. The auxiliary power stage generates auxiliary or stand-by DC output voltages : +5VSB, +12VSB. The main DC output voltages are regulated DC voltages which results from the feedback operation controlled by control stage. The control stage receives the main output voltages for feedback signal and controls the duty of the primary switches in main power stage. Also, the control stage is connected with the supervisor & protection stage. Supervisor stage communicates with the main board for checking whether the power supply operates normally and orders ON/OFF to control stage for protection condition (UVP, OVP, OCP). In this paper, improved 400W PC power supply based on ATX12V is proposed. The main stage of conventional PC power supplies is hard switching topologies such as RCD forward converter, symmetrical half bridge converter and so on. Therefore, the overall efficiency of power supply is very low : less than 80%. The proposed power supply is asymmetrical half bridge converter which can ac...