Frequency jitter circuit and frequency jitter generating method

Abstract

The invention provides a frequency jitter circuit, comprising an oscillating circuit, a decoding circuit, a level selecting circuit and a comparator circuit, wherein the oscillating circuit is used for generating a sawtooth signal; an oscillation frequency signal is input into the decoding circuit and controls the decoding circuit to generate a plurality of pulse signals; the pulse signals control the level selecting circuit to generate an output level signal which varies along with variation of a pulse output signal; the comparator circuit is used for comparing the sawtooth signal of the oscillation frequency and the output level signal and generating a frequency jitter signal; and the duty ratio of the frequency jitter signal and the edge of turn-on / turn-off vary along with variation ofthe output level signal. The invention also provides a method for generating frequency jitter. The frequency jitter circuit provided by the invention has the advantages of simple lines and easy realization. Meanwhile, frequency jitter ensures the switching frequency to be in a wide frequency range, ensures the EMI energy measured by EMI equipment to be diffused beyond the bandwidth, reduces the average EMI noises and flattens the energy spectrum density of the EMI noises.

Description

technical field [0001] The invention relates to the field of switching power supplies, in particular to a frequency jitter circuit in an integrated circuit and a method for generating frequency jitter. Background technique [0002] Due to the high-frequency switching of the switching power supply voltage regulator circuit, the circuit generates electromagnetic interference (EMI). EMI noise can be transmitted through the input AC power line, and can also be transmitted through radiation, which will affect other electronic instruments, such as communication tools, The normal work of household appliances, automatic control equipment, etc. [0003] In order to control the electromagnetic interference (EMI), the control standard limits the energy requirements of the radiation, so as to ensure that the normal operation of various instruments will not be affected by mutual interference. In practice, filtering methods are often used to reduce electromagnetic interference, but exter...

AI Technical Summary

Problems solved by technology

In practice, filtering methods are often used to reduce electromagnetic interference, but external capacitors and inductors are required on the chip, which increases the size and cost of the PCB board

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