Adaptive frequency spreading circuit of switching power supply and adaptive frequency spreading method

Abstract

The invention provides an adaptive frequency spreading circuit of a switching power supply and an adaptive frequency spreading method. The adaptive frequency spreading method comprises the steps thatan oscillator module for generating an oscillation signal turns on a power switch tube at a rising edge of the oscillation signal; a slope compensation module generates a slope compensation signal, performs slope compensation at the rising edge of the oscillation signal when working at a low duty cycle state and turns off the slope compensation when the power switch tube is turned off; the slope compensation module performs slope compensation at the rising edge of the oscillation signal when working at a high duty cycle state and turns off the slope compensation when the turn-on time of the power switch tube exceeds the set time; and a pulse width modulation module turns off the power switch tube when the sum of an inductance sampling signal and the slope compensation signal is greater than a set value. The adaptive frequency spreading circuit has a function of providing the oscillation frequency signal, and also has the functions of automatically controlling the superposition of slopecompensation current when working at a high duty cycle or even a duty cycle of 100% and adaptively spreading the frequency at the same time through a plurality of newly added feedback signals inside.

Description

technical field [0001] The invention relates to the field of electronic circuits, in particular to a switching power supply adaptive spread spectrum circuit and an adaptive spread spectrum method thereof. Background technique [0002] The step-down DC converter (Buck) using the peak current control mode is currently the most widely used step-down topology control mode, which is used to convert a high DC voltage into a stable lower DC voltage. The circuit adopts The fixed clock is turned on and the peak current is turned off. That is, every time the rising edge of the oscillator comes, the switch tube is turned on, and the inductor current starts to rise. When the inductor current rises to the design value, the relevant comparator is triggered, the switch tube is turned off, the freewheeling tube is turned on, and the inductor current starts to drop; When the next rising edge of the oscillator comes, the switch tube is turned on again, and the above process is repeated. When...

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Problems solved by technology

[0016] In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide a switching power supply adaptive spread spectrum circuit and its adaptive spread spectrum method, which is used to solve the problem that the DC switching power supply converter in the prior art cannot work at 100 In the % duty cycle working mode, the output fluctuation becomes larger, etc.

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