Low-power consumption feedback circuit for control chip of AC-DC switching power supply

Abstract

The invention relates to a low-power consumption feedback circuit for a control chip of an AC-DC switching power supply. The feedback circuit comprises a resistor divider; a current limiting resistor for controlling the output current of the feedback end of the chip is connected in the resistor divider in series; a parallel branch consisting of a bleeder resistor and a bleeder switch which are connected in series is arranged on the current limiting resistor; the bleeder switch is controlled by a comparator; and a comparison signal is obtained from comparing a resonant signal with a reference voltage. In the invention, the resistance of the current limiting resistor is increased to reduce the output current of the feedback end of the control chip in an idle state, so as to reduce no-load loss. The resonant detection signal is skillfully multiplexed to indirectly detect an output voltage VO so as to cause the feedback end of the control chip to bleed when the VO shoots down, thereby preventing the response speed reduction of the control chip, which is caused by only increasing the current limiting resistor. By using the invention,the problem of large idle loss of the power is solved,and the feedback circuit has the advantages of simple circuit structure and low cost and is convneient to be integrated.

Description

technical field [0001] The invention relates to a control chip of an AC-DC switching power supply, in particular to a low-power feedback circuit of the control chip of an AC-DC switching power supply. Background technique [0002] The existing flyback AC-DC switching power supply such as figure 2 As shown, it mainly includes a transformer 30, an output voltage sampling circuit 60, a control chip 10, a switching tube 20 and a quasi-resonant signal detection circuit 80. The transformer 30 is used to isolate input and output, and the control chip 10 is based on the load (ie The change of the output terminal voltage) controls the input voltage V accordingly by adjusting the duty cycle of the switch tube 20 conducting in The energy transferred from the primary side of the transformer to the secondary side in each cycle, so that the output voltage V O Follow the set value and keep unchanged, meanwhile, the control chip 10 also controls the conduction of the switch tube 20 at the...

AI Technical Summary

Problems solved by technology

This compromise setting fails to solve the problem of large power supply no-load loss, and the resulting loss generally exceeds 15mW, which still occupies a considerable share of the power system’s standby no-load power consumption.

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