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pfm constant current control circuit applied in ac-dc converter

A technology of constant current control circuit and converter, which is applied in the direction of output power conversion device, conversion of AC power input to DC power output, electrical components, etc., which can solve the problems of high overall cost and complex system, so as to improve cost performance and simplify Peripheral circuits, system cost reduction effect

Inactive Publication Date: 2011-12-21
XIDIAN UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

For the whole system, adding the optocoupler and the secondary loop control circuit not only makes the system more complicated, but also the overall cost is higher

Method used

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  • pfm constant current control circuit applied in ac-dc converter
  • pfm constant current control circuit applied in ac-dc converter
  • pfm constant current control circuit applied in ac-dc converter

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Embodiment Construction

[0023] The present invention will be described in further detail below with reference to the accompanying drawings.

[0024] refer to figure 1 , The present invention includes a first voltage / current conversion circuit 1, a voltage sampling and holding circuit 2, a second voltage / current conversion circuit 3, a first current subtraction circuit 4, and a second current subtraction circuit 5. Among them: the first voltage / current conversion circuit 1 converts the voltage V generated by the AC-DC converter reference module REF1 It is converted into two currents through two resistors, and then the two currents are subtracted to obtain the current I 1 Input to the first current subtraction circuit 4; the voltage sampling and holding circuit 2 is connected to the resistance voltage dividing terminal FB of the auxiliary winding of the external flyback converter, and after the switch tube is turned off for 2.5 μS, the signal of the resistance voltage dividing terminal FB is started t...

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Abstract

The invention discloses a PFM constant-current control circuit applied in AC-DC converters, which mainly solves the problem that: since constant current in the prior art needs a photocoupler and a secondary loop control circuit, the application circuit is complex, and the cost is high. The PFM constant-current control circuit comprises a first voltage / current conversion circuit, a voltage sampling and retaining circuit, a second voltage / current conversion circuit, a first current subtraction circuit and a second current subtraction circuit. The voltage sampling and retaining circuit samples the change of output voltage by means of the feedback of a resistor voltage-dividing end of an auxiliary winding of a flyback converter, the voltage / current conversion circuits and the current subtraction circuits are utilized to convert the sampled voltage change of the resistor voltage-dividing end into current change, the current, the output magnitude of which is in direct proportion to the frequency of an oscillator, is used as the working current of the oscillator of an AC-DC converter, and when the load is changed, the magnitude of input power is regulated in order to realize constant current. The PFM constant-current control circuit can simplify application circuits and reduce the system cost, and can be used in the designs of constant-current constant-voltage AC-DC converters.

Description

technical field [0001] The invention belongs to the technical field of electronic components, relates to an analog integrated circuit, and can be used for constant current control in a flyback structure constant current constant voltage AC-DC converter. Background technique [0002] With the wide application of various electronic products, the requirements for power modules are getting higher and higher. The power module usually provides constant voltage or constant current for other devices to ensure their normal operation. For example, the CPU needs a constant voltage; the LED needs a constant current, and the charging of a lithium battery requires a constant current first and then a constant voltage. AC-DC switching power supply converter is a circuit that uses semiconductor power devices as switches to convert alternating current into direct current, and uses automatic control closed-loop to stabilize its output during conversion. It can meet the high efficiency and low...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M7/217H02M1/36
Inventor 叶强来新泉呙陈宇王松林何惠森
Owner XIDIAN UNIV
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