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PFC circuit

A circuit and main circuit technology, applied in the direction of electrical components, sustainable manufacturing/processing, output power conversion devices, etc., can solve problems such as electromagnetic interference

Active Publication Date: 2015-10-21
INVENTRONICS HANGZHOU
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] However, when the harmonic compensation circuit works, it is easy to cause the input current Iin of the PFC circuit to oscillate near the zero crossing of the input voltage Vin, such as figure 2 As shown, causing serious EMI (Electromagnetic Interference, electromagnetic interference) problems

Method used

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Embodiment Construction

[0084] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

[0085] The invention provides a PFC circuit, which is applied to a switching power supply to solve the EMI problem existing in the prior art.

[0086] Specifically, such as image 3 As shown, the PFC circuit includes: a PFC main circuit 101, a PFC control circuit 102, a harmonic compensation circuit 103 and a zero-crossing compensation circuit 104; wherein:

[0087] The input end of the zero-crossing compensation circuit 104 is connected to the switching tube...

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Abstract

The invention discloses a PFC circuit. A harmonic signal Vx is generated and outputted after through a harmonic compensation circuit sampling the current of a filter capacitor; a zero-crossing compensation signal is generated and outputted through peak value holding of a current sampling signal in a switch tube in the PFC main circuit by a zero-compensation circuit; a sampling signal is superposed with a first signal V1 which is generated through the PFC control circuit sampling the current of the switch tube to obtain a comparison reference value for comparing with a difference value of a second signal V2 and the harmonic signal Vx or comparing with the second signal V2 after superposition with the harmonic signal Vx to generate and output a control signal for the switch tube; due to the action of the over-crossing compensation signal, the real current signal which is inputted into the switch tube of the comparison circuit is weakened, which enables the conduction time of every cycle of the switch tube is shortened when the input voltage of the PFC circuit is close to zero, reduces the input current value of the PFC circuit when the zero is approached, and greatly inhibits the EMI problem caused by current oscillation.

Description

technical field [0001] The invention relates to the technical field of switching power supplies, in particular to a PFC circuit. Background technique [0002] A traditional PFC circuit includes: a PFC main circuit and a PFC control circuit. In the prior art, in order to reduce the high-frequency pollution of the switching power supply to the power grid, a filter capacitor (such as figure 1 In the first capacitor C1 and the second capacitor C2); but due to the existence of the filter capacitor, the input current contains harmonic components, so that the phase of the total input current Iin will lead the input voltage Vin, thereby reducing the PF value or increasing the THD; In the prior art, in order to reduce the THD and increase the PF value, a harmonic compensation circuit is usually added to the PFC circuit of the switching power supply, such as figure 1 shown. [0003] However, when the harmonic compensation circuit works, it is easy to cause the input current Iin of ...

Claims

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Application Information

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IPC IPC(8): H02M1/44
CPCY02P80/10
Inventor 罗世伟
Owner INVENTRONICS HANGZHOU