Synchronous rectifier circuit capable of preventing flow-through current
AssigneeFunai Electric Co., Ltd.
InventorsHitoshi Miyamoto, Takashi Jinnouchi
Life of this patent
Estimating the term…
Abstract
A synchronous rectifier circuit (DC-DC converter) includes a CR integration circuit and a discharge circuit. The CR integration circuit outputs a voltage that varies at delayed timing as compared with a voltage induced in a secondary-side main winding. The discharge circuit discharges a gate voltage of a rectifier transistor as a result of conduction of a discharge transistor in response to the output voltage from the CR integration circuit. According to such a configuration, the rectifier transistor is turned off earlier than the timing of switching of polarity of voltages induced in the secondary-side main winding and a secondary-side auxiliary winding in response to turn-on of a primary-side transistor.
Claims1
A synchronous rectifier circuit, comprising:
- first and second input terminals;
- first and second output terminals;
- a transformer including first and second nodes, a primary-side main winding, provided between said first and second input terminals, a secondary-side main winding provided between said second output terminal and said first node, and a secondary-side auxiliary winding provided between said first and second nodes and wound in a direction identical to a direction of winding of said secondary-side main winding;
- a first switching element provided between said first and second input terminals and connected in series to said primary-side main winding;
- a second switching element for rectification provided between said first node and said first output terminal, said second switching element having a control electrode for receiving a voltage of said second node generated by switching of said first switching element or a voltage obtained by dividing the voltage of said second node and being turned on in response to the voltage of said second node;
- a delay circuit for receiving a voltage of said first node generated by switching of said first switching element;
- and outputting a voltage that varies at delayed timing as compared with the voltage of said first node;
- and
- a third switching element provided between the control electrode of said second switching element and said second output terminal, said third switching element having a control electrode for receiving the output voltage from said delay circuit and being turned on in response to the output voltage from said delay circuit,
- said second switching element being turned off in response to turn-on of said third switching element,
- said delay circuit includes a capacitive element and a Zener diode,
- said capacitive element and said Zener diode are provided in series between said second output terminal and said first node in this order, and
- a connection node of said capacitive element and said Zener diode is connected to the control electrode of said third switching element.
Dependencies are inferred from the claim text.