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US 7,116,562 B2Granted
Synchronous rectification switching power supply
AssigneeCosel Co., Ltd.
InventorsMakoto Takashima, Yoshimichi Hirokawa
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AssigneeCosel Co., Ltd.
InventorsMakoto Takashima, Yoshimichi Hirokawa
Estimating the term…
A fly-back type synchronous rectifying switching power supply device in which a rectifying element is turned off before the main switch is turned on even when the on-time of a main switch element is lengthened due to sudden variation of a load. The synchronous rectifying switching power supply device is equipped with a synchronous rectifying element connected to a secondary winding of a transformer in series and driving means including an auxiliary winding for turning on the synchronous rectifying element complementarily with a main switch element between output terminals. A transistor serving as interrupting means for turning off the synchronous rectifying element is provided between the gate and source of the synchronous rectifying element. An off-timing at which the synchronous rectifying element is turned off by the interrupting means is set within a timing range which corresponds to a fixed time after the main switch element is turned on and also is as near as a fixed driving period of the main switch element.
A fly-back type synchronous rectifying switching power supply device comprising a primary winding of a transformer and a main switch element connected to each other in series between input terminals and which has a control circuit for subjecting the main switch element to PWM control within a fixed period, a synchronous rectifying element connected to a secondary winding of the transformer in series between output terminals, and driving means for turning on the synchronous rectifying element complementarily with the switching element, a different power supply source charged by a pulse voltage occurring at the secondary winding of the transformer through a switching operation of the main switch element, and interrupting means disposed between the gate and source of the synchronous rectifying element and which turns off the synchronous rectifying element, wherein an off-timing at which the interrupting means turns off the synchronous rectifying element is set to a timing which corresponds to a fixed time set by current from the different power source after the switch element is turned on and is within a range which is as near as a fixed driving period of the switch element.
A fly-back type synchronous rectifying switching power supply device comprising a primary winding of a transformer and a main switch element connected to each other in series between input terminals and which has a control circuit for subjecting the main switch element to PWM control within a fixed period, a synchronous rectifying element connected to a secondary winding of the transformer in series between output terminals, and driving means for turning on the synchronous rectifying element complementarily with the switching element, a different power supply source charged by a pulse voltage occurring at the secondary winding of the transformer through a switching operation of the main switch element, interrupting means disposed between the gate and source of the synchronous rectifying element and which turns off the synchronous rectifying element, and a control element for comparing the output voltage of the different power source with the output voltage of the output terminal of the switching power supply device, and controlling the interrupting means to turn off the synchronous rectifying element when the output voltage of the different power source is reduced to a fixed value or less.
Dependencies are inferred from the claim text.