A switch voltage regulation circuit and method with a frequency limiting function

Abstract

A switching regulator with frequency limitation comprises a switch, a current sensing circuit, a voltage feedback circuit, a control circuit and a frequency limitation circuit. The current sensing circuit senses the current flowing through the switch and generating a current sensing signal representative of it. The voltage feedback circuit senses the output signal of the switching regulator and generates a feedback signal accordingly. The control circuit compares the current sensing signal with the feedback signal and turns off the switch based on the comparison result. The frequency limitation circuit is electrically coupled to the control circuit to limit the switching frequency of the switch.

Description

technical field [0001] The invention relates to a switching voltage stabilizing circuit, in particular to a switching voltage stabilizing circuit and a method with a frequency limiting function. Background technique [0002] Many electronic devices today require DC voltage to be powered, and this DC supply voltage usually comes from an adapter. The adapter obtains AC voltage from the wall socket (grid), converts the AC voltage into an uncontrolled DC voltage through a rectifier bridge, and converts the uncontrolled DC voltage into the required DC power supply voltage through a switching power supply. [0003] Switching power supplies usually use transformers or inductors as energy storage elements. For example, a transformer is used as an energy storage element in a flyback converter. A switch is electrically coupled to the primary side of the transformer, and the control circuit controls the switch to be turned on and off, so that energy is alternately stored or transmitte...

AI Technical Summary

Problems solved by technology

Switching at high frequency in the switching power supply will cause serious electromagnetic interference (EMI), which not only reduces the quality of the power grid, but also affects the normal operation of electronic equipment connected to or near the switching power supply, and even affects radio waves and televisions. signal interference

For this reason, countries have established strict standards for EMI generated by switching power supplies. These EMI standards, such as EN55022, usually have lower limit values ​​in the high frequency band and higher limit values ​​in the low frequency band, so too high switching frequency will cause Switching power supply is difficult to pass EMI test

In addition, the higher the switching frequency, the greater the switching loss, which is not conducive to the improvement of the efficiency of switching power supply

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