Method and circuit for correcting power factor

Abstract

This invention discloses a power factor rectify method and its circuit characterized in reducing the loss of reverse recovery current by the following way: after finishing the reverse recovery, at the time when the reverse recovery energy stored in an auxiliary inductance is transferred to the first energy storage capacitance, the first and second energy storage capacitances also input a portion of energy in proportion to Vin from the input voltage. The said energy volume should make the continuous current completely transfer to the first branch when the current is at the sine wave peak valueto ensure the action of the current buffer to reduce loss to the utmost. When commercial power voltage crosses zero about, Vin reaches zero, the energy storage capacitance stores only the reverse recovery energy.

Description

Technical field: [0001] The invention relates to a power factor correction (PFC) method and circuit, which is used in switching power supply equipment input by commercial power such as communication power supply and uninterruptible power supply (UPS), to reduce input current harmonics and improve power factor. Background technique: [0002] Power factor correction circuit (PFC) is widely used in switching power supply equipment such as communication power supply, UPS and other mains input, so as to make the input current meet the relevant harmonic standard requirements of IEC, and at the same time make the power factor approximately 1. [0003] Such as figure 1 As shown, the traditional power factor correction circuit works as follows: [0004] Input voltage (V IN ) is the rectified voltage of the mains sine wave voltage; its waveform is the absolute value waveform of the sine wave voltage; [0005] ①By controlling the opening and closing of the power switch S1, the input...

AI Technical Summary

Problems solved by technology

However, increasing energy storage will bring the following negative effects: When the mains voltage is near the zero crossing point, the circuit works in DCM (discontinuous current control) mode, and there are several switching cycles in this mode, when S1 is turned off Within a certain time, the energy stored on the capacitor Cb may not be fully transferred to the output capacitor, thus forming an accumulation, causing the voltage on the capacitor Cb to pump up. The greater the energy of the voltage buffer, the greater the voltage pumping range on the capacitor Cb. As a result, a large voltage peak stress is caused on the freewheeling diode, which increases the withstand voltage requirements for the freewheeling diode, and a diode with a higher voltage rating is selected, thereby increasing the diode loss

Images