Offset resonance zero volt switching flyback converter
First Claim
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1. A flyback power converter, comprising:
- a power switch and primary winding of a power transformer connected in a series combination, the series combination connected in parallel across first and second input supply nodes;
a secondary winding of the power transformer connected in parallel across a first and a second secondary side node;
a rectifier connected in series between the first secondary side node and a first output node;
an output capacitor connected in parallel across the first output node and a second output node;
an active clamp switch connected in a series combination with an active clamp capacitor at a first common node, the series combination connected in parallel across the primary winding of the power transformer; and
a series combination of a switch and a magnetic energy storage element, the series combination connected in parallel across the primary winding of the power transformer;
wherein the value of said active clamp capacitor is selected so that a zero voltage switching condition is generated across the power switch only in conjunction with operation of said series combination of the switch and the magnetic energy storage element.
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Abstract
A continuous mode flyback converter circuit which includes elements capable of generating a zero volt switching (ZVS) signal across the power switch. The ZVS generating elements include a switched shunt inductance coupled in parallel with active clamp components and connected across the primary winding of the power transformer. The circuit reduces the reverse recovery current through the secondary stage rectifier and the current through the active clamp switch during operation of the converter. The ZVS generating elements may also be used for flyback converters which do not utilize an active clamp.
140 Citations
38 Claims
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1. A flyback power converter, comprising:
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a power switch and primary winding of a power transformer connected in a series combination, the series combination connected in parallel across first and second input supply nodes; a secondary winding of the power transformer connected in parallel across a first and a second secondary side node; a rectifier connected in series between the first secondary side node and a first output node; an output capacitor connected in parallel across the first output node and a second output node; an active clamp switch connected in a series combination with an active clamp capacitor at a first common node, the series combination connected in parallel across the primary winding of the power transformer; and a series combination of a switch and a magnetic energy storage element, the series combination connected in parallel across the primary winding of the power transformer; wherein the value of said active clamp capacitor is selected so that a zero voltage switching condition is generated across the power switch only in conjunction with operation of said series combination of the switch and the magnetic energy storage element.
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2. A flyback converter comprising:
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a power switch and primary winding of a power transformer connected in a series combination, the series combination connected in parallel across first and second input supply nodes; a secondary winding of the power transformer connected in parallel across a first and a second secondary side node; a rectifier connected in series between the first secondary side node and a first output node; an output capacitor connected in parallel across the first output node and a second output node; an active clamp switch connected in a series combination with an active clamp capacitor at a first common node, the series combination connected in parallel across the primary winding of the power transformer; and a series combination of a switch and a magnetic energy storage element, the series combination connected in parallel across the primary winding of the power transformer, the series combination of the switch and the magnetic energy storage element including a second rectifier arranged in series with the switch and magnetic energy storage element and oriented to permit current flow from the primary winding to the magnetic energy storage element in normal operation; wherein the value of said active clamp capacitor is selected so that a zero voltage switching condition is generated across the power switch only in conjunction with operation of said series combination of the switch and the magnetic energy storage element. - View Dependent Claims (3, 4, 5, 6)
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7. A flyback converter, comprising:
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a power switch and primary winding of a power transformer connected in a series combination, the series combination connected in parallel across first and second input supply nodes, wherein the power switch is operable to permit current to flow between a first power switch node and a second power switch node; a capacitive element connected in parallel across the first and second power switch nodes; a secondary winding of the power transformer connected in parallel across a first and a second secondary side node; a rectifier connected in series between the first secondary side node and a first output node; an output capacitor connected in parallel across the first output node and a second output node; an active clamp switch connected in a series combination with an active clamp capacitor at a first common node, the series combination connected in parallel across the primary winding of the power transformer; and a series combination of a switch and a magnetic energy storage element, the series combination connected in parallel across the primary winding of the power transformer; wherein the value of said active clamp capacitor is selected so that a zero voltage switching condition is generated across the power switch only in conjunction with operation of said series combination of the switch and the magnetic energy storage element. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A flyback power converter, comprising:
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a power switch and primary winding of a power transformer connected in a series combination, the series combination connected in parallel across first and second input supply nodes; a secondary winding of the power transformer connected in parallel across a first and a second secondary side node; a rectifier connected in series between the first secondary side node and a first output node; an output capacitor connected in parallel across the first output node and a second output node; a switch connected in a series combination with a first magnetic energy storage element, the series combination connected in parallel across the primary winding of the power transformer; a second magnetic energy storage element coupled to the first magnetic energy storage element, wherein the second magnetic energy storage element is connected across the first and second input supply nodes; and an input capacitor connected in parallel across the first and second input supply nodes. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
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33. A flyback power converter, comprising:
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a power switch and primary winding of a power transformer connected in a series combination, the series combination connected in parallel across first and second input supply nodes; a secondary winding of the power transformer connected in parallel across a first and a second secondary side node; a rectifier connected in series between the first secondary side node and a first output node; an output capacitor connected in parallel across the first output node and a second output node; a switch connected in a series combination with a magnetic energy storage element and a second rectifier, the series combination connected in parallel across the primary winding of the power transformer, the switch and magnetic energy storage element being connected at a common node, and the second rectifier oriented to permit current flow from the primary winding to the switch in normal operation; a third rectifier and an input capacitor connected in a series combination at a second common node, the series combination connected in parallel across the first and second input supply nodes; and a fourth rectifier connected between the first and second common nodes and oriented to permit current flow from the second common node to the first common node in normal operation. - View Dependent Claims (34, 35, 36, 37, 38)
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Specification