Relaxation oscillator with frequency dithering

Abstract

The invention discloses a relaxation oscillator with the frequency jittering function. The relaxation oscillator mainly solves the problem that an existing switching power source is relatively concentrated in energy of electromagnetic interference and has great influences on a power source system. The relaxation oscillator comprises an RC charge-discharge network (201), a first comparator (202), a second comparator (203), an RS trigger (204) and a frequency jittering control module (205). After a sawtooth voltage generated by the RC charge-discharge network (201) is compared with two threshold voltages through the two comparators, the sawtooth voltage is output to the RS trigger (204) to generate square signals with variable frequencies, charging or discharging of the RC charge-discharge network (201) is fed back and controlled by the square signals, the square signals simultaneously serve as clock signals to periodically change the charge-discharge capacitance in the RC charge-discharge network (201) through the frequency jittering control module (205), the frequencies of the output square signals are changed in a linear mode, and therefore the energy of the electromagnetic interference is dispersed. According to the relaxation oscillator, influences of the electromagnetic interference in a switching power source can be effectively reduced, and the relaxation oscillator can be used for management class chips of the switching power source.

Description

technical field [0001] The invention belongs to the technical field of electronic circuits, and relates to an analog integrated circuit, in particular to a relaxation oscillator, which can reduce electromagnetic interference brought by a switching power supply system. technical background [0002] From radio and television transmitters and receivers, oscilloscopes, signal generators, to digital frequency meters and other electronic devices, oscillators are used. Basic components, it is a very important module in the power chip. Especially in the field of switching power supply, the oscillator circuit is its core functional component, which has a great influence on the signal processing performance of the circuit. Among them, the relaxation oscillator in the oscillator is widely used in switching power management chips. [0003] The relaxation oscillator is usually realized by charging and discharging a given time constant capacitor between two set high and low threshold vo...

AI Technical Summary

Problems solved by technology

It can be seen from this process that the square wave signal V output by the relaxation oscillator OSC The frequency of the oscillator is controlled by the charge and discharge capacitance and the charge and discharge current. Since the charge capacitance and charge and discharge current of the relaxation oscillator will not change after design, the oscillation frequency will also be fixed, so that the energy of the electromagnetic interference noise will be concentrated. So that the switching power supply system will be subject to greater electromagnetic interference, reducing the stability of the switching power supply system

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