关键词:功率因数校正,整流器,UC3854
The design of power factor correction
Abstract:PFC (Power Factor Correction) is an effective method to reduce harmonic currents in power grids. The principle of traditional active power factor correction (APFC) are introduced, the paper anylyses the current impact and the ripple noise problems owing to the diode reverse recovery abo and ut PFC main circuit which is in practical applications. A single-phase Boost power factor corrector with centrally tapped inductor is designed. Using the average current model,UC3854 controls the state of the switching transistor in the circuit by outputting a series of PWM (Pulse Width Modulation) signals, By this mean, it readjusts input current and output voltage to synchronization , thus fulfilling power factor Correction.
Compared with the main circuit of traditional PFC, only several windings are added on magnetic ring and tapped, which effectively suppresses the impact current, reduces the ripple noise and improves the reliability of PFC main circuit. Problems of cusp distortion, output voltage shifting and output voltage regulation with heavy load are analyzed and solutions are given respectively. At the same time, protecting circuit for pins of UC3854 and current amplifier clamping circuit to limit the output voltage swing are designed. The simulation and experiment show that, the proposed PFC design is rational, reliable and compatible with popular PFC control circuit, while its power factor reaches 0.999.
Key word: power factor correction, rectifier,UC3854