A control method and circuit for a switching power supply to realize a super-audio light-load working mode

Abstract

A control method and circuit for a switching power supply to realize a super-audio light-load working mode, belonging to the technical field of switching power supply chip design. The control method proposed by the present invention detects the switching frequency of the switching power supply and compares it with the upper threshold frequency and the lower threshold frequency respectively, and performs digital control according to the comparison result to generate a digital code word, wherein the upper threshold frequency>lower threshold frequency>audio frequency; when judging When the current switching frequency is higher than the upper threshold frequency, the negative current of the inductor in the switching power supply is reduced through digital control, and when it is determined that the current switching frequency is lower than the lower threshold frequency, the negative current of the inductor in the switching power supply is increased to achieve switching frequency locking. Between the upper threshold frequency and the lower threshold frequency, and at the same time ensure that the steady state value of the output center will not change within this load range. The digital control method proposed by the invention not only ensures the efficiency, but also does not need complex compensation, and can also ensure stable output.

Description

technical field [0001] The invention belongs to the technical field of switching power supply chip design, and relates to a control method and a realization circuit for a switching power supply to realize a super-audio light-load working mode. Background technique [0002] Switching power supply is widely used in the field of power supply because of its high-efficiency characteristics, but when its load becomes lighter, in order to continue to ensure switching conversion efficiency, it is generally selected to enter the spread spectrum mode. In the spread spectrum mode, the switching frequency is reduced to reduce the switching itself. loss. When the switching frequency of the switching power supply is further reduced, the switching frequency will enter the audio range. In some applications, the noise of the switching power supply in these audio ranges will be heard by the human ear (the human ear can hear vibrations in the frequency range of 20Hz~20KHz), resulting in Unwan...

AI Technical Summary

Problems solved by technology

Although this method is efficient, it is not compatible with peripheral devices ( image 3 In the output capacitance Cout, inductance L) and the input and output voltage ( image 3 There is a great correlation between the input voltage Vin and the output voltage Vout). In order to meet the application scenarios of various peripheral devices and voltage ranges, the compensation needs to be more complicated, so the hardware overhead is very large

At the same time, due to the loop gain in the analog circuit, the control loop will cause the output voltage to rise after locking the frequency, which is unacceptable for some applications, such as battery charging.

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