Feedback type power source supplier and its control method

Abstract

The power supplier is composed of transformer, primary switching circuit and secondary switching circuit. Primary switching circuit is connected to primary side of the transformer, and secondary switching circuit is connected to secondary side of the transformer. Switching circuit consists of control circuit and switching modules. Control circuit maintains switching module at fixed voltage, and makes inversely proportional change between value of resistance of switching module and output current of transformer. Thus, when current output from secondary side of transformer is changed in inverted triangle waveform, value of resistance of switching module approaches infinity in time of current being as zero. Thus, switching module enters into cut-off state automatically, making power supplier work smoothly.

Description

technical field [0001] The present invention relates to a flyback power supply and its control method, in particular to a power supply that utilizes a switch assembly to switch between off and on. Background technique [0002] Such as Figure 1A Shown is a circuit device of a known flyback switching power supply. Wherein S1 may be a switch component such as a transistor, a thyristor or a metal-oxide-semiconductor field-effect transistor, which has a function of on / off controlled by a small signal. When D1 is turned on, it will produce a voltage drop ranging from 0.4V to 1.5V. This is the characteristic of a diode. Therefore, when the output voltage Vo is low, low efficiency often occurs, the power consumption of diode D1 is too large, and a large area of ​​heat dissipation is required. film etc. For example, when Vo is 5VDC, the voltage drop of D1 is 0.4V, the reverse withstand voltage of D1 is 30VDC, and the output of the power supply is 50w (5v / 10A), so the power consump...

AI Technical Summary

Problems solved by technology

The converter has the effect of DC blocking, so it is necessary to increase the circuit to restore the DC level, which will greatly reduce the accuracy of the converter as the current detection side

[0006] (2) The accuracy of the current detection side must be quite accurate, otherwise the switching power supply is either easy to burn out, or the efficiency that can be improved is not high

Replacing D1 with S2 becomes an expensive and unstable project for two reasons

[0007] Therefore, it can be seen from the above that the above-mentioned known flyback power supply obviously has inconvenience and disadvantages in actual use and needs to be improved.

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