Control circuit for voltage dropping type power factor corrector

Abstract

The invention discloses a control circuit for a voltage dropping type power factor corrector, which is used for controlling a voltage dropping converter to realize the power factor correction function. Inductance current critical intermittent control of changed on-time is performed on a Buck circuit through the control circuit to ensure that the on-time of a switching tube rises in the power frequency period along with increase of input voltage; and the critical intermittent working mode of inductance current in the Buck circuit is controlled, and when the inductance current is greater than zero, the junction capacitance of the switching tube and inductance are resonated, and the switching tube is connected when the voltage resonance of the junction capacitance reaches the volley bottom. The control circuit for the voltage dropping type power factor corrector has the characteristics of ensuring high power factors in the whole input voltage range, and meeting the harmonic requirements of IEC 61000-3-2 Class C, Class D, along with high efficiency.

Description

technical field [0001] The invention relates to a control circuit of a step-down power factor corrector, in particular to a step-down power factor correction circuit with high efficiency and low input current harmonics. Background technique [0002] Due to the presence of non-linear components and energy storage components in most electrical equipment at present, the input AC current waveform will be severely distorted, and the input power factor of the grid side is very low. In order to meet the harmonic requirements of the international standard IEC61000-3-2, A power factor correction (power factor correction, PFC) circuit must be added to these electric devices. Traditional active power factor correction circuits generally use a boost (Boost) topology, because the Boost topology is easy to control, simple to drive, and can perform switching operations during the entire power frequency cycle, and the power factor of the input current can be close to 1. The advantages. Ho...

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Problems solved by technology

However, the peak value of the current in the first control mode is very large, which increases the conduction loss of the semiconductor device and affects the efficiency.

The second control method can realize the current waveform close to the sine wave by rationally designing the slope of the compensation ramp wave, and its circuit system structure diagram is as follows figure 1 as shown, figure 2 is the input voltage and current waveform of the circuit, where i L is the current waveform of the Buck inductor, i avg It is the waveform of the input average current. It can be seen from the figure that the current is in a continuous working state near the peak voltage, which will cause reverse recovery loss of the diode, and the power factor of the input current is difficult to maintain above 0.9 in the full voltage input range.

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