Clock signal control method and circuit for open-loop starting circuit

Abstract

The invention provides a clock signal control method for an open-loop starting circuit, and the method comprises the steps: an input voltage monitoring step: monitoring the input voltage of a switching power supply, and outputting a work duration signal according to a monitored input voltage range; an inductive current monitoring step: monitoring the inductive current of the switching power supply, judging whether the inductive current triggers current peak protection or current reverse flow protection or not, and correspondingly outputting protection information; and a self-adaptive duty ratio gradually increasing step: generating second clock signals under different duty ratios, and selectively outputting a third clock signal according to the working duration signal and the protection information, the third clock signal being used for being input to a logic circuit of the open-loop starting circuit. The invention also provides a related control circuit. According to the invention, the blank in the aspect of clock signal control of the open-loop starting circuit is filled up, a power management chip of the switching power supply can be normally started under various working conditions such as large capacitance output and heavy load, and the efficiency is improved and the soft starting time is shortened as much as possible through a method of adaptively adjusting the soft starting time.

Description

technical field [0001] The invention relates to the technical field of a power management chip of a switching power supply, in particular to a clock signal control method of an open-loop startup circuit and a control circuit thereof. Background technique [0002] At present, due to the characteristics of high efficiency and small size, switching power supplies are increasingly in demand in the fields of communications, industrial control, computers, and consumer electronics. During the power-on process of a traditional DC / DC switching power supply, the output voltage rises from zero to the maximum value. Due to the existence of the output filter capacitor in the circuit, it is easy to generate a surge current when the capacitor is charged. At this time, the current passing through the power tube can reach a large level, which is easy to damage the circuit system. In order to prevent the large inrush current from causing damage to the entire system during the startup process...

AI Technical Summary

Problems solved by technology

[0005] When the circuit is started, the output load is heavy, the output capacitor is large, and the output voltage builds up time slowly; if you want to reduce the start-up time under this working condition, there is a risk of not being able to start normally

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