Switching Power Converter Synchronous Rectification Circuit

Abstract

The invention discloses a synchronous rectifying circuit for a switching power supply converter. The synchronous rectifying circuit comprises a transformer, a synchronous sorting output circuit and a control circuit, wherein the synchronous sorting output circuit is connected with a primary coil winding of the transformer; the control circuit is connected between a secondary coil winding of the transformer and a power supply load; the control circuit is at least formed by connecting a switch tube, a first chip and a second chip; after the first chip is connected with the second chip, the first chip and the second chip are connected to the positive end of the secondary coil winding, and connected between the input end and the control end of the switch tube; the output end of the switch tube is connected with the negative end of the secondary coil winding; and a branch, which is connected with the output end of the switch tube, of the second chip is provided with a one-way conducting original piece, so that reverse current generated by the secondary coil winding in a sensing way is prevented from flowing into the second chip through the branch.

Description

technical field [0001] The invention relates to the field of a switching power supply circuit, in particular to a synchronous rectification circuit of a switching power supply converter which partially limits the excessive temperature rise of components. Background technique [0002] figure 1 It is a synchronous rectification circuit of a switching power supply converter in the prior art, including a transformer T1, a synchronous finishing output circuit 11 connected to the primary coil winding L1 of the transformer T1, a secondary coil winding L2 connected to the transformer and a power load A first control circuit 21 between R10 and a second control circuit 22 connected between the secondary winding L3 of the transformer and the power load R10. The internal structures of the first control circuit 21 and the second control circuit 22 are the same, for example, the first control circuit 21 is used for a specific description, including a MOSFET switch tube Q5, a first chip U...

AI Technical Summary

Problems solved by technology

The reason for the reverse current on this loop is caused by the long reverse recovery time of the first triode Q1 (equivalent diode D3) inside the second control chip U2. The reverse current of this loop is related to the power supply load and working If the operating frequency is higher and the power supply load is heavier, the reverse current of this branch will be larger (the reverse recovery time is a characteristic parameter of the diode, and the longer the reverse recovery time can lead to the diode's The greater the reverse current), this current causes the second control chip U2 to heat up seriously and the temperature to rise by more than 65 degrees (similarly, it will also affect the second control chip U4 of the second control circuit 22 to heat up seriously and the temperature to rise by 65 degrees above), thus affecting the operation of the switching power converter to a certain extent and reducing the service life of the product

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