Frequency Modulation Switching Power Supply Based on Frequency Divider Oscillator

Abstract

A switching power supply for realizing frequency modulation based on a frequency division oscillator relates to a switching power supply circuit. It includes: a working circuit provided with an energy storage element, which switches between charge and discharge modes under the action of a pulse modulation signal; a control circuit, which is used for a reference voltage, a voltage feedback signal, a current detection signal and a clock signal Generate a pulse modulation signal; the control circuit includes an error amplifier for obtaining an error amplification signal; the clock signal generator includes a clock frequency division unit that generates a plurality of clock signals with different frequencies under the action of a reference clock source; The selection unit selects one of the multiple clock signals to output to the control circuit under the action of the error amplifier signal. The present invention generates a plurality of clock signals with a set frequency through a frequency division oscillator, and selects a clock signal with a set frequency to output to the control circuit within a set time through an error amplification signal, so that the cycle is stable and the ripple of the output voltage is reduced. Wave.

Description

technical field [0001] The invention relates to the field of electronic technology, in particular to a switching power supply circuit. Background technique [0002] The power supplies used by modern electronic equipment are roughly divided into two categories: linear regulated power supply and switching regulated power supply. The linear regulated power supply is that its adjustment tube works in the amplification area. This kind of regulated power supply will not introduce additional interference, but its volume is relatively small. Large, the power mainly depends on the transformer and power tube, and the conversion efficiency is low; compared with the linear regulated power supply, the switching power supply has the characteristics of small power consumption, small size, and wide voltage regulation range. The switching power supply uses modern power electronics technology, and the control The time ratio of switching devices to turn on and off to maintain a stable output v...

AI Technical Summary

Problems solved by technology

[0002] The power supplies used by modern electronic equipment are roughly divided into two categories: linear regulated power supply and switching regulated power supply. The linear regulated power supply is that its adjustment tube works in the amplification area. This kind of regulated power supply will not introduce additional interference, but its volume is relatively small. Large, the power mainly depends on the transformer and power tube, and the conversion efficiency is low; compared with the linear regulated power supply, the switching power supply has the characteristics of small power consumption, small size, and wide voltage regulation range. The switching power supply uses modern power electronics technology, and the control The time ratio of switching devices to turn on and off to maintain a stable output voltage. Pulse frequency modulation is usually used in switching power supplies to improve light load efficiency. Switching power converters operating in power-saving mode are used under light load current conditions. Pulse frequency modulation mode, use pulse width modulation mode under heavier load current conditions

However, because the control method of pulse frequency modulation is not easy, it is not as widely used in switching power supply circuits as pulse width modulation

In the prior art, in order to improve circuit efficiency under light load or standby conditions, a low power consumption mode is set, also known as: Skip Cycle Mode (Skip Cycle Mode), when the circuit is under light load or standby conditions, control PWM The controller sends out pulse signals intermittently to improve the efficiency of light load and standby by reducing the number of switching times and increasing the duty cycle at a constant frequency. The waveform of the pulse modulation signal PFM1 in skip cycle control mode is shown figure 1 As shown, however, this method will cause higher output ripple, and the control method is not ideal

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