Power supply circuit and control method thereof

Abstract

The invention provides a power supply circuit and a control method thereof. In the power supply circuit, two output capacitors connected in series are arranged between a positive electrode and a negative electrode of the direct current side of a bridge type rectification unit, and a controllable semiconductor switch circuit is arranged between one of a zero line and a live line of the alternating current side of the bridge type rectification unit and a connection point of the two output capacitors; an input voltage mean value sampling comparison circuit and an input voltage change rate comparison circuit output a mean value comparison result and a change rate comparison result respectively; a control unit controls the on-off state of the controllable semiconductor switch circuit according to a mean value comparison result and a change rate comparison result, so that the power supply circuit is equivalently converted into a voltage doubling rectifying circuit when the mean value and the change rate of the input voltage of the power supply circuit are lower than corresponding threshold values, and when the average value or the change rate of the input voltage is higher than a corresponding threshold value, the bridge rectifier circuit is equivalently converted into a bridge rectifier circuit; therefore, automatic switching of the rectification mode of the power supply circuit is realized, and the phenomenon of failure and explosion caused by overvoltage due to forgetting or mistakenly shifting a switch by a user is avoided.

Description

technical field [0001] The invention belongs to the technical field of power electronics, and more specifically, relates to a power supply circuit and a control method thereof. Background technique [0002] In the existing AC input rectification mode switchable power supply circuit, a bridge rectification circuit, a switch, and two electrolytic capacitors in series are generally used to realize the following rectification mode switching function, such as figure 1 Shown: When the power supply circuit is in the voltage doubler rectification mode, the maximum value of the rectified output voltage is about twice the peak voltage of the power grid; When the circuit is in bridge rectification mode, the maximum output voltage after rectification is about the peak voltage of the power grid, such as Among them, Uac is the effective value of the voltage between the AC input line AC-L and AC-N; Udc is the maximum value of the voltage between the rectified positive DC voltage VDC and...

AI Technical Summary

Problems solved by technology

However, the terminal user is not professional in the operation of the switch inside the device, and often forgets or dials the wrong switch. Therefore, it often causes the power supply to be connected to the input high-voltage AC when the switch S1 is closed, that is, in the voltage doubler rectification mode. The nominal voltage is 220-240Vac; at this time, electrolytic capacitors (such as figure 1 Shown C1 and C2) will fail and explode due to overpressure, resulting in economic losses and reputation losses for customers and equipment manufacturers, as well as a series of safety hazards

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