Switching-mode power supply having a synchronous rectifier
First Claim
1. A switching-mode power supply for DC-to-DC conversion, comprising:
- (a) DC input means for inputting a DC voltage;
(b) DC output means for outputting a DC voltage;
(c) a converter circuit connected between the DC input means and the DC output means, the converter circuit including an active switch for switching the input DC voltage on and off;
(d) a switch control circuit connected to the active switch of the converter circuit for on/off control thereof;
(e) a synchronous rectifier switch connected between the converter circuit and the DC output means;
(f) a diode connected in parallel with the synchronous rectifier switch;
(g) conduction period detect means for providing a conduction period detect signal indicative of periods of time during which the active switch is held conductive by the switch control circuit;
(h) a capacitor for determination of conducting periods of the synchronous rectifier switch;
(i) a charge/discharge circuit connected to the converter circuit and the capacitor for causing the latter to be charged and discharged according to whether the active switch is conductive or nonconductive; and
(j) a logic network having an input connected to the conduction period detect means, another input connected to the capacitor, and an output connected to the synchronous rectifier switch, for making on/off control of the synchronous rectifier switch according to whether the active switch is conducting or nonconducting and whether the voltage across the capacitor is higher than a predefined voltage or not.
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Accused Products
Abstract
A DC-to-DC converter incorporates a transformer having a primary winding connected to a pair of DC input terminals via an active switch, which turns on and off under the control of a feedback circuit, and a secondary winding connected to a pair of DC output terminals via a synchronous rectifier and a smoothing capacitor. The synchronous rectifier is a parallel connection of a synchronous rectifier switch and a diode. A synchronous rectifier control circuit is connected to the synchronous rectifier switch for causing conduction therethrough while the active switch is off. The synchronous rectifier control circuit comprises a capacitor for determination of the conducting periods of the synchronous rectifier switch, and a logic network for on/off control of the synchronous rectifier switch according to whether the active switch is on or off and whether the capacitor voltage is higher than a predefined threshold or not.
73 Citations
21 Claims
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1. A switching-mode power supply for DC-to-DC conversion, comprising:
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(a) DC input means for inputting a DC voltage; (b) DC output means for outputting a DC voltage; (c) a converter circuit connected between the DC input means and the DC output means, the converter circuit including an active switch for switching the input DC voltage on and off; (d) a switch control circuit connected to the active switch of the converter circuit for on/off control thereof; (e) a synchronous rectifier switch connected between the converter circuit and the DC output means; (f) a diode connected in parallel with the synchronous rectifier switch; (g) conduction period detect means for providing a conduction period detect signal indicative of periods of time during which the active switch is held conductive by the switch control circuit; (h) a capacitor for determination of conducting periods of the synchronous rectifier switch; (i) a charge/discharge circuit connected to the converter circuit and the capacitor for causing the latter to be charged and discharged according to whether the active switch is conductive or nonconductive; and (j) a logic network having an input connected to the conduction period detect means, another input connected to the capacitor, and an output connected to the synchronous rectifier switch, for making on/off control of the synchronous rectifier switch according to whether the active switch is conducting or nonconducting and whether the voltage across the capacitor is higher than a predefined voltage or not. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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Specification