A circuit, method and switching power supply for eliminating noise of pfm switching power supply

A switching power supply and charging circuit technology, applied in the direction of converting irreversible AC power input to DC power output, etc., can solve the problems of audio noise, switching power supply entering the audio range, etc., to avoid audio noise, eliminate the effect of switching power supply noise

Active Publication Date: 2016-08-10
BCD (SHANGHAI) MICRO ELECTRONICS LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] In view of this, the present invention provides a switching power supply noise reduction protection circuit, method and switching power supply to overcome the problem in the prior art that when the operating frequency of the system is lower than a certain preset value, the switching power supply enters the audio frequency range and produces audio noise problem

Method used

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  • A circuit, method and switching power supply for eliminating noise of pfm switching power supply
  • A circuit, method and switching power supply for eliminating noise of pfm switching power supply
  • A circuit, method and switching power supply for eliminating noise of pfm switching power supply

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Embodiment 1

[0032] Please refer to the attached figure 1 , is a linear relationship diagram between the switching power supply operating frequency and the load current.

[0033] The present invention provides a circuit for eliminating noise of a switching power supply, comprising: a first charging circuit, a first frequency detection circuit and a control circuit; the first charging circuit includes a first capacitor;

[0034] The first frequency detection circuit is used to compare the voltage value on the first capacitor with the size of the first reference voltage, and hold the compared signal according to the synchronization signal of the PFM switching power supply, and output the first logic level to said control circuit;

[0035] The control circuit is connected to the frequency detection circuit, and is used for controlling the peak current of the switching power supply to jump from the first mode to the second mode according to the first logic level. It effectively solves the pr...

Embodiment 2

[0043] The inventor considers that there are various peak current states of the switching power supply, so on the basis of the first embodiment, the present invention also provides a second frequency detection circuit, such as Figure 4 As shown, the second frequency detection circuit is used to compare the magnitude of the input voltage with the second reference voltage, and when the input voltage is greater than the second reference voltage, the second frequency detection circuit generates a second logic voltage level to the control circuit.

[0044] Specifically, the second frequency detection circuit includes: a second voltage comparator comp2 and a second flip-flop 8 . Wherein, the non-inverting input terminal of the second voltage comparator comp2 receives the second reference voltage Vref3, the inverting input terminal of the second voltage comparator comp2 receives the input voltage VIN, and the second voltage comparator The output terminal of comp2 is connected to on...

Embodiment 3

[0058] In addition, this embodiment provides a method for eliminating switching power supply noise, which is characterized in that it includes:

[0059] Comparing the operating frequency of the switching power supply to be detected with the size of the first preset frequency, when the operating frequency is less than the first preset frequency, controlling the peak current of the switching power supply to jump from the first mode to the second mode, avoiding produced audio noise.

[0060] Preferably, it also includes:

[0061] Comparing the operating frequency of the switching power supply to be detected with the second preset frequency, when the operating frequency is greater than the second preset frequency, controlling the peak current of the switching power supply to jump from the second mode to the third mode.

[0062] Preferably, it also includes:

[0063] The operating frequency of the switching power supply is detected by using the first charging circuit described in...

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PUM

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Abstract

The invention provides a method for eliminating PFM switch power source noise. The working frequency of a switch power source to be detected is compared with first preset frequency, when the working frequency is smaller than the first preset frequency, a peak current of the switch power source is controlled to jump and be changed from a first mode to a second mode, and thus the occurrence of voice frequency noise is avoided. In addition, the invention further provides a specific circuit for the realization of the method for eliminating the PFM switch power source noise. According to the fact that a working frequency domain of the switch power source and load currents are in a linear relation, through the fact that the size of input voltages and a preset voltage are detected, the detection and the comparison of the working frequency are achieved, and the problems that in the prior art, when the working efficiency of a system is lower than a certain preset value, the switch power source enters a voice frequency range, and the voice frequency noise is generated are effectively solved.

Description

technical field [0001] The invention relates to the field of switching power supplies, and more specifically relates to a circuit, a method and a switching power supply for eliminating the noise of a switching power supply by PFM. Background technique [0002] With the rapid development of the electronic information industry, switching power supplies are widely used in computers, electrical equipment, instruments, LED lighting, medical equipment, military equipment and other fields. Usually, a switching power supply converts an external alternating current (such as mains 220V, 380V, etc.) into a stable direct current to supply the load. [0003] There are many types of switching power supplies, and the switching power supply based on the flyback topology is introduced here, which mainly includes: control chips, transformers, power switch tubes, etc. Among them, the control chip controls the conduction of the power switch tube. When the power switch tube is turned on, the re...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02M7/04
Inventor 高超张美玲陈超
Owner BCD (SHANGHAI) MICRO ELECTRONICS LTD
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