PWM/PFM dual mode automatically-switched step-down DC-DC converter

Abstract

The invention discloses a PWM / PFM dual mode automatically-switched step-down DC-DC converter, comprising a conversion circuit and a control circuit, wherein the control circuit comprises an output voltage sampling circuit, a PWM control module, a control logic module and a driving module; two output ends of the driving module are connected with the control end of a main switch tube and the control end of a freewheeling switch tube; the PWM control module comprises an error amplifier, a comparator, an oscillator and a sawtooth wave generation circuit; the first input end of the error amplifier is connected with the output end of the output voltage sampling circuit, and the second input end of the error amplifier is connected with the reference voltage; the first input end of the comparator is connected with the output end of the error amplifier, and the second input end of the comparator is connected with the output end of the sawtooth wave generation circuit; the output end of the comparator is connected with the first input end of the control logic module, and the output end of the oscillator is connected with the second input end of the control logic module; and the output end of the control logic module is connected with the input end of the driving module. In summary, the PWM / PFM dual mode automatically-switched step-down DC-DC converter disclosed by the invention determines the switching points by using the delay of the comparator, and is simple in structure and small in occupied chip area.

Description

[0001] [Technical Field] [0002] The present invention relates to a DC-DC converter, in particular to a step-down DC-DC converter with PWM / PFM dual-mode automatic switching. [0003] [Background technique] [0004] The DC-DC converter is a voltage converter that effectively outputs a fixed voltage after converting the input voltage. DC-DC converters are divided into three categories: step-up DC / DC converters, step-down DC / DC converters, and buck-boost DC / DC converters. Three types of control can be used according to requirements. The PWM control type has high efficiency and good output voltage ripple and noise. Even if the PFM control type is used for a long time, especially when the load is small, it has the advantage of low power consumption. PWM / PFM conversion type implements PFM control at light load, and automatically switches to PWM control at heavy load. [0005] Southeast University Du Fei's master's degree thesis "Analysis and Design of PWM / PFM Switching Step-Down DC-DC C...

AI Technical Summary

Problems solved by technology

[0007] The traditional PWM / PFM dual-mode step-down DC-DC converter adopts a complex mode switching circuit structure, which usually involves complex current detection circuits, PWM / PFM mode detection circuits, and two-mode control circuits and mode selection circuits. The PWM / PFM dual-mode step-down DC-DC converter has the disadvantages of high circuit complexity and large chip area occupation

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