A Convertible Conduction Mode Pfc Circuit Design

In recent years, more and more electric equipments connect to power supply. So, harmonic pollution of power supply becomes serious. Power Factor Correction is an effective technique for improving this problem. With the stricter quality requirement of electric equipment, this technique has been widely applied.According to the requirement of the projection, a boost PFC circuit is designed based on UMC 0.6μm BCD process. The chip could change the control mode between discontinuous conduction mode to critical conduction mode. It could produce 400V output voltage with the input voltage range from 85Vac to 255Vac over -25℃to 125℃. The largest power factor nearly comes to 1 (over 0.99), the minimum THD is 3% and the efficiency is larger than 90%. It is suitable for electronic light ballast, AC adapters and power supply equipments.In this thesis, basic principles and some key points of a boost active power factor correction were given firstly. Then, the whole chip diagram according to the design specification and the whole chip operational principle were introduced. Based on the whole chip function requirements, sub-block design and simulation were completed, including current sensing, oscillator, power factor correction modulation, control logic and drive and the sub-block circuits were simulated in different supply voltages and temperature. At last, the whole chip function simulation and typical performance characteristics simulation were presented. The simulation results indicate that the converter has achieved the design specification and it could change the control mode. The power factor is 0.9961, the THD is 3.8% and the efficiency is 93.36% when the ac peak input voltage is 160V. In the conclusion of this thesis, the research value of this circuit was pointed out, but it was suggested that corner simulation and post-layout simulation should be indispensable.This thesis is a production of circuit principles and simulation practice. Based on the circuit principle analysis, the author simulated the sub-block circuits and the whole chip circuit by applying the EDA tool HSPICE. The simulation results indicate that the converter has achieved the design specification. Furthermore, the circuit principle analysis has been verified.