Switching power supply and its control method

Abstract

A switching power supply and a control method therefor. The switching power supply comprises: a switching circuit (1), a controller (2), a driver (3) and a four-order low pass filter (4), wherein the four-order low pass filter has a negative coupling property; the switching circuit receives an input voltage, and outputs the input voltage into the four-order low pass filter; the four-order low pass filter outputs a first output voltage and a second output voltage into the controller; the controller receives a reference voltage, generates a modulation pulse based on the first output voltage, the second output voltage and the reference voltage, and outputs the modulation pulse into the driver; and the driver outputs the modulation pulse to the switching circuit so as to control the switching circuit by means of the modulation pulse. By means of a four-order low pass filter having a negative coupling property, ripples of an output voltage can be reduced.

Description

technical field [0001] Embodiments of the present invention relate to the field of electronic technology, in particular to a switching power supply and a control method thereof. Background technique [0002] With the rapid development of electronic technology, the relationship between electronic equipment and people's work and life is becoming increasingly close, and electronic equipment cannot do without a reliable power supply. However, a switching power supply is a high-frequency power conversion device used to convert the input voltage into a stable voltage required by the user, and the switching power supply is widely used in almost all electronic equipment due to its small size, light weight and high efficiency. , Therefore, the design of switching power supply has attracted much attention. [0003] Such as figure 1 As shown in (a), the switching power supply includes a first MOS (Metal Oxid Semiconductor, metal oxide semiconductor) transistor Q 1 , the second MOS t...

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Problems solved by technology

[0005] There are at least the following problems in the above technical solutions: since the cut-off frequency of the second-order low-pass filter or the fourth-order low-pass filter is relatively low, the attenuation of the input voltage by the second-order low-pass filter or the fourth-order low-pass filter is relatively small , and then during the discharge of the second-order low-pass filter or the fourth-order low-pass filter, it will lead to a higher ripple of the output voltage, where the ripple refers to the AC component superimposed on the stable amount of the DC output voltage

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