Switching power supply
AssigneeDensei-Lambda Kabushiki Kaisha
InventorNobutaka Uesono
Life of this patent
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Abstract
A switching power supply which includes a sychronous rectifier circuit that performs sychronous rectification with a main switching element by using rectifying switching elements. When a current begins to flow into the rectifying switching element 6, the rectifying switching element 6 builds up rapidly by the voltage induced in the auxiliary winding 21 of low impedance. Accordingly, the rectifying switching element 6 turns on rapidly at a point showing an approximately maximum current so that the ON-state resistance of the rectifying switching element 6 can be smaller. The voltage induced in the auxiliary winding 21 is fed directly as a drive signal of the rectifying switching element 6 so that the drive signal is not influenced by an output voltage.
Claims18
A switching power supply including a rectifying switching element used as a rectifier element, connected to a secondary winding of a transformer, which comprises a synchronous rectifier circuit, comprising:
- a current transformer for detecting current flowing through said rectifying switching element;
- an auxiliary winding, wound in said transformer, said auxiliary winding having a lower impedance than that of said current transformer;
- a drive circuit for feeding a voltage generated in said auxiliary winding to said rectifying switching element as an “on” signal to build up sharply the rectifying switching element;
- and
- a turn-off circuit for turning off said rectifying switching element before the current flowing through said rectifying switching element turns reverse by a detection signal generated in a secondary winding of said current transformer.
A switching power supply having a main switching element, a choke coil charging or discharging energy corresponding to on or off of the main switching element and a rectifying switching element which turns on when said choke coil discharges energy, wherein said switching regulator comprises a synchronous rectifier circuit comprising:
- a drive winding wound in said choke coil;
- a current transformer detecting current flowing through said rectifying switching element;
- a drive circuit which feeds a voltage induced in said drive winding to said rectifying switching element as an “on” signal when said choke coil discharges energy to thereby build up the rectifying switching element;
- and
- a turn-off circuit which turns off said rectifying switching element by a detection signal induced in the secondary winding of said current transformer.
Dependencies are inferred from the claim text.