Principle of single-phase full-bridge PWM rectifier circuit with high power factor

In the process of electronic circuit design, how to continuously improve the power factor has always been a problem that many developers have been studying. PWM rectifier circuit is a rectifier circuit that uses PWM control, which can effectively improve the power factor of the circuit. This article will explain the working principle of the single-phase full-bridge PWM rectifier circuit, hoping to provide convenience for power supply novices.

figure 1

As shown in Figure 1, the comparison method of triangular wave and sine signal is used to perform SPWM control on V1~V4 in the circuit. In this way, an SPWM wave uAB can be generated at the AC input terminal AB of the bridge. uAB contains the fundamental component with the same frequency and proportional amplitude as the sine signal wave, as well as high-frequency harmonics related to the triangular wave carrier, and does not contain low-order harmonics.

Due to the filtering effect of Ls , the harmonic voltage only causes a small pulsation in is. When the frequency of the sine signal wave is the same as the power supply frequency, is is also a sine wave with the same power supply frequency. When us is constant, the amplitude and phase of is are only determined by the amplitude of the fundamental wave uABf in uAB and its phase difference with us. By changing the amplitude and phase of uABf, is and us can be made in phase or out of phase, is can be ahead of us by 90°, or the phase difference between is and us can be made to be the required angle.

Working principle of PWM rectifier circuit

Figure 3 Further explanation of the working principle of the single-phase full-bridge PWM rectifier circuit

In rectification state:

When us > 0, (V2, VD4, VD1, Ls) and (V3, VD1, VD4, Ls) respectively form two boost chopper circuits, taking (V2, VD4, VD1, Ls) as an example.

When V2 is on, us stores energy to Ls through V2 and VD4.

When V2 is turned off, the energy stored in Ls charges C through VD1 and VD4.

When us < 0, (V1, VD3, VD2, Ls) and (V4, VD2, VD3, Ls) respectively form two boost chopper circuits.

This article explains the working principle of the single-phase half-bridge PWM rectifier circuit and determines multiple values ​​under the rectifier state. I hope that after reading this article, power supply novices can fully understand the working principle of the single-phase half-bridge PWM rectifier circuit.