Constant-current and constant-voltage fly-back converter based on primary side feedback

Abstract

The invention discloses a constant-current and constant-voltage fly-back converter based on primary side feedback. The constant-current and constant-voltage fly-back converter comprises a rectifying bridge, an inverted U-shaped filter, a transformer, an auxiliary power supply circuit, a constant-current and constant-voltage controller and a switch tube, wherein the transformer consists of a primary winding, a secondary winding and an auxiliary winding; the constant-current and constant-voltage controller comprises a constant-voltage module, a frequency generator, a constant-current module, a joint gate, an RS trigger and a driving module; the output end of the constant-voltage module and the first and second output ends of the constant-current module are connected with three input ends of the joint gate; the input end of the constant-current module is connected with the emitting electrode of the switch tube, and is used for sampling a current signal of the primary winding; the output end of the joint gate is connected with the R end of the RS trigger, and is used for transmitting a switch-off signal generated by the joint gate to the R end of the RS trigger; the switch-on signal of the frequency generator is output to the S end of the RS trigger; the RS trigger is used for receiving the switch-on signal and the switch-off signal to generate a modulating signal; and the Q end of the RS trigger is connected with the input end of the driving module.

Description

technical field [0001] The invention relates to the field of integrated circuits. More specifically, the present invention relates to a constant current and constant voltage flyback converter based on primary side feedback. Background technique [0002] In recent years, handheld personal communication terminals (such as mobile phones) have developed rapidly. Its related charger market develops accordingly. The flyback converter is widely used in this field due to its own cost and performance advantages. Various constant-current and constant-voltage controllers using primary-side feedback are widely accepted and applied because of their simple peripheral structure and low cost. [0003] The existing constant current and constant voltage controller with primary side feedback and the built flyback converter, such as figure 1 shown. Including, rectifier bridge 170, Π-type filter 171, absorption circuit 172, transformer 173 (primary winding 180, secondary winding 181, auxili...

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Problems solved by technology

Then, within a period of time, because the controller fed back by the primary side cannot detect the output voltage information, the output voltage will continue to drop

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