Frequency dithering circuit and frequency dithering method as well as application thereof in switch power supply

Abstract

The invention provides a frequency dithering circuit and a frequency dithering method. The frequency dithering circuit comprises an oscillatory circuit, a decoding circuit and a delay circuit, wherein the oscillatory circuit generates an oscillatory frequency output signal; the oscillatory frequency output signal controls the decoding circuit to generate a plurality of pulse output signals; and the delay circuit generates a frequency dithering output signal when the oscillatory frequency output signal passes by the delay circuit; the frequency dithering output signal delays for a period of time compared with the oscillatory frequency output signal; and the pulse output signals control the delay time of the oscillatory frequency output signal. The invention applied in a switch power supply can reduce the EMI average noise of the switch power supply and has energy spectrum density planarization.

Description

technical field

[0001] The invention relates to the field of switching power supplies, in particular to frequency jitter technology in integrated circuits. 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 electromagnetic interference (EMI), control standards for radiated energy are stipulated to ensure that various instruments will not affect normal work due to mutual interference. In practice, filtering is often used to reduce electromagnetic interference, but this method requires external capacitors and inductors on the chip, which increases the size and cos...

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