power conversion system

Abstract

The invention provides a power conversion system, which comprises a transformer, a bipolar transistor BJT and a pulse width modulation control chip PWM IC; after the power conversion system enters a closed loop state, in the PWM IC, a first control signal and a second control signal are generated on the basis of current detection voltage representing current flowing through a primary winding of the transformer and output representation voltage representing DC output voltage; on and off of a first power switch and a second power switch are controlled on the basis of the first control signal and on and off of a third power switch are controlled on the basis of the second control signal; and when the first power switch and the second power switch are changed into an off state from an on state, but the third power switch is in the off state, the PWM IC controls the BJT to be in the on state, so that DC input voltage obtained through rectifying and filtering AC input voltage charges a capacitor connected to a second terminal of the PWM IC through the primary winding of the transformer, the BJT, a first terminal of the PWM IC and a diode, connected between the first terminal and the second terminal, in the PWM IC.

Description

technical field [0001] The present invention relates to the field of circuits, and more specifically relates to a power conversion system. Background technique [0002] figure 1 is a circuit diagram of a conventional flyback alternating current (AC)-direct current (DC) power conversion system. Such as figure 1 As shown, the traditional AC-DC power conversion system converts AC input voltage to DC output voltage as follows: [0003] The AC input voltage is filtered and rectified by an electromagnetic interference (EMI) filter and a rectifier (including a rectifier bridge composed of four diodes and a bulk capacitor (bulk capacitor)), and then becomes a DC input voltage VIN; the DC input voltage VIN passes through a starting resistor Rst Charge the capacitor C1 connected between the VDD terminal of the pulse width modulation control chip (PWM IC) and the reference ground; when the voltage on the capacitor C1 (that is, the voltage at the VDD terminal) is higher than the PWM ...

AI Technical Summary

Problems solved by technology

[0005] exist figure 1 After the power conversion system shown enters the closed-loop state, the auxiliary winding Naux of the transformer T1 supplies power to the PWM IC through the diode D2 and the capacitor C1. The disadvantage of this power supply method is that the auxiliary winding Naux of the transformer T1 and the diode D2 connected to it need to be additionally added. Increases the complexity of the transformer and thus increases the system cost

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