Switching power supply circuit
AssigneeFujitsu Limited
InventorNaoki Takahashi
Life of this patent
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Abstract
The present invention relates to a synchronous rectifying type power supply circuit as a switching power supply having a control circuit including a rectifying FET for synchronous rectifying operation in the secondary side of a transformer. A commutating FET can be structured by providing a switching control circuit that is connected to a tertiary coil provided to the transformer to conduct ON/OFF operation of the rectifying FET and commutating FET.
Claims14
A switching power supply circuit in a synchronous rectification type power supply circuit having of a rectifying FET for synchronous rectifying operation in a secondary side of a transformer and a control circuit including a commutating FET, said switching power supply circuit comprising:
- a switching control circuit that is connected with a tertiary coil provided in said transformer to assure the ON/OFF operations of said rectifying FET and said commutating FET.
A power supply circuit having a transformer, a switching FET coupled to a primary side of said transformer, and a rectifying FET couple to a secondary side of said transformer, said power supply circuit comprising:
- a tertiary coil one end coupled to a gate of said rectifying FET,
- a control FET having its gate coupled to said one end of said tertiary coil and its source coupled to a second end of said tertiary coil,
- a commutating FET having its drain coupled to one end of said secondary coil and a source coupled to a second end of said secondary coil and a gate coupled to a drain of said control FET, and
- a switching control circuit for ensuring the ON/OFF operation of the rectifying FET and commutating FET.
A flyback power supply circuit having a transformer, a switching FET coupled to a primary side of said transformer, and a rectifying FET couple to a secondary side of said transformer, said flyback power supply circuit comprising:
- a tertiary coil one end coupled to a gate of said rectifying FET,
- a first control FET having its gate coupled to a second end of said tertiary coil and coupled between a gate and source of said rectifying FET,
- a second control FET coupled between said source of said rectifying FET and said gate of the first control FET, and
- a capacitor coupled between a drain and source of said second control FET.
Dependencies are inferred from the claim text.