Power factor correction circuit and control circuit and control method thereof

Abstract

The invention discloses a power factor correction circuit and a control circuit and control method of the power factor correction circuit. The PFC circuit comprises a switch circuit comprising a main switch, an analog-to-digital conversion unit, a digital-to-analog conversion unit, a comparing circuit, a calculation control unit and a pulse generating unit, wherein the analog-to-digital conversion unit generates a sampling signal according to an input voltage, an input current and an output voltage; the digital-to-analog conversion unit provides a shutdown current reference signal; the comparing circuit generates a comparing signal according to the shutdown current reference signal and the input current; the calculation control unit provides starting delay time, expected switch-on time duration and a digital shutdown current referent signal according to the sampling signal; the pulse generating unit is coupled to the comparing circuit and the calculation control unit, the switch-on time of the main switch is controlled according to the comparing signal and a switch-on delay signal, and the switch-off time of the main switch is controlled according to the expected switch-on time duration. Calculation of the circuit is convenient to perform, and the circuit is easy to obtain and higher in efficiency and power factor in light loads compared with a traditional continuous current mode control method.

Description

technical field

[0001] The embodiment of the present invention relates to a control circuit of a power supply, in particular to a power factor correction circuit, a control circuit and a control method thereof. Background technique

[0002] Power Factor Correction (PFC) circuits are widely used in power conversion systems to correct the phase of current and improve power factor. figure 1 A schematic diagram of a waveform of PFC control is shown. As shown in the figure, the input voltage Vin is in the shape of steamed buns, and the input voltage is generally obtained by rectifying the sinusoidal AC signal of the mains. In order to realize PFC control, it is necessary to control the waveform of the input current Iin to follow the waveform of the input voltage Vin, so that the phase of the input current Iin is consistent with the input voltage Vin. Generally, a higher input voltage Vin corresponds to a lower average input current Iin_avg. In the switch-mode PFC circuit, the ...

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