Switching power supply and multi-threshold switching circuit thereof

Abstract

The invention is applicable to the technical field of switching power supplies, and provides a switching power supply and a multi-threshold switching circuit thereof. The multi-threshold switching circuit is characterized in that a sampling voltage judgment module is used for dividing voltage outputted by a power supply circuit, comparing the voltage with a first reference voltage, a second reference voltage and a third reference voltage outputted by a reference voltage generating module and outputting corresponding control signals to a voltage-controlled oscillation module according to comparison results; the voltage-controlled oscillation module is used for generating pulse signals with specific duty ratio according to a fourth reference voltage and a fifth reference voltage which are outputted by the reference voltage generating module and the control signals; and a power switch is used for high-frequency on-off switching with a corresponding frequency according to the pulse signals to enable a transformer to perform storage and release of electricity energy correspondingly, so that output voltage of the transformer is periodically modulated to achieve stable contact voltage output. The switching power supply is further simplified structurally by the aid of the multi-threshold switching circuit, and cost is reduced.

Description

technical field [0001] The invention belongs to the technical field of switching power supplies, and in particular relates to a switching power supply and a multi-threshold switching circuit thereof. Background technique [0002] At present, with the continuous development and updating of switching power supply technology, switching power supply has the advantages of high efficiency, small size and low cost, so it has been widely used in various electronic devices. Especially in power supplies such as mobile phone chargers or adapters or standby power supplies, switching power supplies generally only need to have a constant voltage output function. [0003] In order to achieve constant voltage output in power supplies such as mobile phone chargers or adapters, the existing technology provides a primary-side feedback flyback switching power supply, which needs to sample the conduction current of the switch tube, and through the independent internal controller After the pin s...

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Problems solved by technology

[0004] The purpose of the present invention is to provide a multi-threshold switching circuit for a switching power supply, which aims to solve the problems of poor stability and reliability of the switching power supply system, complex circuit structure and high cost in the prior art

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