Frequency jitter device and switching power supply

Abstract

The invention discloses a frequency jitter device and a switching power supply, and relates to the technical field of switching power supplies. The frequency jitter device comprises an oscillator circuit and a frequency jitter circuit. Wherein the oscillator circuit comprises a first current source, a first switching circuit and a first charging and discharging circuit; the first switching circuit controls the first current source to charge the first charging and discharging circuit and controls the first charging and discharging circuit to discharge at a constant current so as to generate a clock signal; the frequency jitter circuit comprises a frequency dividing circuit, a second switching circuit and a second charging and discharging circuit; the frequency dividing circuit carries out frequency halving on the clock signal and outputs a frequency dividing signal to control the second switching circuit; and the second switching circuit controls the second charging and discharging circuit to charge and discharge according to the frequency division signal to realize frequency jitter. Therefore, frequency jitter can be simply realized, peak current and harmonic waves generated by the capacitor/inductor can be well eliminated, and EMI (Electro-Magnetic Interference) can be effectively reduced.

Description

technical field [0001] The invention relates to the technical field of switching power supplies, in particular to a frequency shaking device and a switching power supply. Background technique [0002] Switching power supply plays a vital role in electronic design. As the input of any chip, the stability of its working state will affect the working stability of the whole system. [0003] The switching power supply system usually adopts the control method of pulse width modulation (PWM, Pulse Width Modulation), and the switching frequency is continuously increasing. Its high-frequency switching waveform contains a large number of harmonic components. Spikes, voltage changes in capacitance and parasitic capacitances cause electric fields to form higher current spikes. [0004] Spikes often contain huge harmonic components, which propagate outward through transmission lines and space electromagnetic fields, causing conduction and radiation interference (EMI interference). Such ...

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Problems solved by technology

[0007] In view of this, a frequency dithering device and a switching power supply provided by the embodiment of the present invention can solve the problem that the current frequency dithering circuit design is too complicated, and the peak current and its harmonics generated by the capacitor / inductance cannot be effectively eliminated, and the EMI cannot be effectively reduced. interference problem

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