Control circuit of power factor correcting circuit

Abstract

A control circuit in a power factor correction (PFC) circuit comprises: a multiplier (300), used for multiplying a voltage sampling signal (Vs) by a feedback signal (Vf), and outputting a first signal (I1); and a waveform generating module (400), used for generating a second signal (I2) related to a filter capacitor (C1, C2) connected in parallel to an input end and / or an output end of a rectifier bridge. A control signal for controlling a state of a main switch transistor (S1) is generated by using the first signal, the second signal, and a current sampling signal (Is) of the main switch transistor in the PFC circuit. By controlling ON or OFF of the main switch transistor, a phase of a sum of an input current (Ip) and a total filter current (Ic) of the PFC circuit, that is, a phase of an input current (Iin) on an alternating current side, is same as a phase of an input voltage (Vin), thereby eliminating the difference between the phase of the input current and the phase of the input voltage occurring due to a phase difference caused by the filter capacitor.

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 output voltage of the sampling rectifier bridge is usually multiplied by the feedback signal at the output of the PFC, and the product is used as the reference signal of the switching tube current in the PFC. [0003] In this way, the input current of the PFC circuit can follow the change of the input voltage, so that the input current Iin (of the AC input terminal) in the entire circuit has the same phase as the input voltage Vin. Such as figure 1 As shown, the figure is a schematic diagram of the same phase of the input current Iin (of the AC input terminal) and the input voltage Vin in the prior art. [0004] However, in order to reduce high-frequency pollution to the...

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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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