Control circuit in power factor correction circuit

Abstract

The invention provides a control circuit in a power factor correction circuit. The control circuit comprises an output feedback module, a waveform generating module, a control signal generating module and a drive control module, wherein the output feedback module is used for sampling output electric parameters of the power factor correction circuit PFC, comparing the sampled output electric parameters with a preset value, and outputting a feedback signal Vf according to the compared result; the waveform generating module is used for generating a second signal I2 associated with current of a filter capacitor which is in parallel connected to an input end and / or an output end of a rectifying bridge; the control signal generating module is used for outputting a control signal according to the feedback signal Vf output by the output feedback module and the second signal I2; and the drive control module is used for driving a main switch tube according to the control signal output by the control signal generating module, and controlling switch-on time of the main switch tube. And therefore, phase difference of Iin and Vin due to phase difference caused by the filter capacitor is eliminated.

Description

technical field [0001] The invention relates to the technical field of power factor correction, in particular to a control circuit in a power factor correction circuit. Background technique [0002] In a two-stage circuit or a single-stage power factor correction (PFC, Power Factor Correction) circuit, the control circuit usually adopts the following method: when the main switch of the PFC circuit is turned on, the constant current source charges a capacitor, and the capacitance of the capacitor The voltage starts to increase from zero, and when it increases to be equal to the feedback signal at the PFC output end, the main switching tube of the PFC circuit is controlled to be turned off. In the steady state, within one cycle of the input voltage of the PFC circuit, the amplitude of the feedback signal at the PFC output terminal is relatively unchanged, therefore, within one cycle of the input voltage of the PFC circuit, the conduction time of the main switch is also constan...

AI Technical Summary

Problems solved by technology

This will cause the input current Iin (of the AC input) and the input voltage Vin to have a phase difference in the entire circuit

This is because the input current Iin (of the AC input terminal) of the entire circuit is the sum of the current on the filter capacitor and the input current of the PFC circuit, and the phase of the current on the filter capacitor is 90 degrees ahead of the input voltage, that is, due to the filter capacitor Existence, the phase of the input current Iin is ahead of the phase of the input voltage Vin, so that the phase of the input current Iin and the phase of the input voltage Vin are inconsistent, resulting in a decrease in the power factor of the power supply and an increase in harmonic content

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