Method and circuit for inhibiting switching converter EMI with chaos using PMW chip

Abstract

The invention provides a method and a circuit for inhibiting switching converter EMI with chaos using a PMW chip. In the method, a chaotic signal provided by a chaos generating circuit is utilized to regulate the charge-discharge time of a peripheral clock circuit of the PWM chip and change the working frequency of the PWM chip along with the amplitude of the chaotic signal, thus changing the frequency of the drive signal output by the PWM chip, reallocating the energy originally centralized at the frequency multiplication harmonic wave of the switching signal frequency of the switching converter in a wider frequency band, and achieving inhibition of the switching converter EMI. The circuit for realizing the method comprises the chaos generating circuit, a modulation degree control circuit and the peripheral clock circuit of the PWM chip, wherein, the chaotic signal generated from the chaos generating circuit is sent to the modulation degree control circuit, and then the modulation degree control circuit changes the variation range of a switching frequency through regulating the strength of the chaotic signal. The invention has the advantages of good EMI inhabitation effect, low cost, strong applicability and easy popularization.

Description

technical field [0001] The invention provides a method and a circuit for realizing chaos suppression EMI directly on the existing PWM control chip of the switching converter. Background technique [0002] In order to obtain a smaller volume, the switching frequency of switching power supplies using pulse width modulation (PWM) technology has been continuously increased (tens of KHz to several MHz). The existing experimental analysis shows that the peak value of the electromagnetic interference of the switching converter used in the switching power supply is mainly concentrated at the multiplier of the switching frequency. Since it is a discrete spectrum with the switching frequency as the fundamental wave, these harmonic components pass through the transmission line and the space electromagnetic field. Outward propagation, resulting in conduction and radiation interference problems, not only seriously pollute the surrounding electromagnetic environment, but also cause electr...

AI Technical Summary

Problems solved by technology

[0004] The research work on the electromagnetic compatibility of switching power supplies is still in its infancy. The measures to suppress the electromagnetic interference of power electronic converters mainly include: 1) Increase the input filtering and shielding technology. The disadvantage of this method is that the production is complicated and the power electronic conversion The cost and volume of the switching power supply are limited, and the application with strict requirements on the area and volume of the switching power supply is limited

2) Add Snubbers circuit on the high-frequency switch (MOSFET and secondary rectifier diode) to reduce dv / dt and di / dt, the disadvantage is that the high-frequency switching loss is increased

3) Reduce the area of ​​the high-frequency current loop by improving the PCB design. The disadvantage is that the layout of the original components in the actual product must be considered and rich experience is required.

None of the above methods has fundamentally solved the EMI problem of the switching converter. The research on the characteristics of electromagnetic interference shows that if the EMI energy can be distributed as evenly as possible in the frequency domain, the spectrum peak value of the electromagnetic interference can be reduced, and the switching converter Electromagnetic interference is suppressed

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