Power converter, and control circuit and circuit method thereof

Abstract

A power converter, and a control circuit and a circuit method thereof are disclosed. The power converter comprises a clock signal generation circuit, a modulation signal generation circuit, and a logic module which is connected with the clock signal generation circuit and the modulation signal generation circuit and used for generating an on-off control signal according to a working clock signal and a modulation signal, wherein when a ratio between an output voltage and an input voltage is less than a duty ratio corresponding to the working clock signal at a first frequency, the clock signal generation circuit controls the frequency of the working clock signal to be the first frequency, and when the ratio between the output voltage and the input voltage is greater than the duty ratio corresponding to the working clock signal at the first frequency, the clock signal generation circuit controls the frequency of the working clock signal to be a self-adaptive frequency. According to the power converter of the invention, through self-adaptive frequency reduction processing, turn-on time is adaptively prolonged in the case of ensuring certain minimum turn-off time, and the duty ratio ismaximized, thereby expanding the range of a working voltage and improving adjustable dynamic range of the output voltage.

Description

technical field [0001] The present invention relates to the field of switching power supplies, and more specifically, to a power converter and its control circuit and control method. Background technique [0002] With the advancement of circuit electronics technology, switching power supplies continue to develop in the direction of high power density, high efficiency, and high reliability. In switching power supplies of various electronic products, power converters are widely used. Power converters can adopt various topologies, such as BOOST, BUCK, BOOST-BUCK, and flyback topologies. During operation, the power converter uses PWM modulation (Pulse Width Modulation, pulse width modulation) to control the conduction state of the switch tube, thereby controlling the power transmission from the input end to the output end, so as to provide a stable output voltage and / or current. [0003] figure 1 A schematic block diagram of a BUCK converter circuit according to the prior art...

AI Technical Summary

Problems solved by technology

According to the volt-second balance theorem, in the BUCK topology, the duty cycle D of the system operation is equal to the ratio of the output voltage to the input voltage, so when the output voltage of the BUCK converter 100 is close to the input voltage, the duty cycle corresponding to the system operation is greater than CLK contains a duty cycle, but due to the duty cycle limitation of the clock signal CLK, it is difficult for the BUCK converter 100 to work normally

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