Switching power supply and no-load control circuit and no-load control method thereof

Abstract

The invention discloses a switching power supply and a no-load control circuit and a no-load control method thereof. The switching power supply comprises a switching circuit for providing an electric signal for a load. The no-load control circuit comprises a no-load detection circuit and a reloading detection circuit, wherein the no-load detection circuit is electrically coupled to the load and is used for judging whether the switching power supply enters a no-load state or not and generating a no-load signal; the reloading detection circuit is used for outputting a current to the load after the no-load state is detected by the no-load detection circuit and comparing voltages at both ends of the load with a third threshold value so as to detect whether the load is switched in and generatea reloading signal; and the switching circuit is closed when the no-load state is detected by the no-load detection circuit and is recovered to normally work when the load is detected to be switched in by the reloading detection circuit.

Description

technical field [0001] Embodiments of the present invention relate to a switching power supply, in particular, to a switching power supply and its no-load control circuit and control method. Background technique [0002] With the increasing importance of energy efficiency and environmental protection, people have higher and higher expectations for the standby efficiency of switching power supplies. Customers require power supply manufacturers to provide power supply products that can meet green energy standards such as BLUE ANGEL, ENERGY STAR, and ENERGY 2000. In order to meet these standards, many new technologies have emerged, such as pulse skipping mode, burst mode and off time modulation. The main idea of ​​these new technologies is to allow the switching power supply to switch at a lower switching frequency when it is under light load (very small load current) or no load (the load current is zero or approximately zero, or the load is disconnected from the output of the ...

AI Technical Summary

Problems solved by technology

However, the selection of the sense resistor value is a problem

If the resistance value of the sensing resistor is too large, the power loss will be too large under heavy load conditions, thereby reducing the efficiency of the switching power supply; if the resistance value of the sensing resistor is too small, the sensing resistor double The voltage signal at the terminal will be too small, easily disturbed and unable to accurately reflect the load current

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