Reciprocating converter
First Claim
1. A method of operating a power converter, comprising the steps of:
- (a.) ramping up current in a first direction through a primary winding of a transformer;
(b.) opening a first switch which is in series with said primary winding, to obstruct current through said primary winding and thereby drive current through a secondary winding of said transformer which is inductively coupled to said primary winding;
(c.) closing a second switch which is in series with said secondary winding, to permit said secondary winding to pass current in a first direction to charge up an output capacitor;
(d.) holding said second switch closed for long enough so that current in said secondary winding becomes zero, and thereafter said output capacitor drives current through said secondary winding in a second direction which is opposite to said first direction;
(e.) opening said second switch while said secondary winding is passing current in said second direction, to thereby drive current through said primary winding in a second direction which is opposite to said first direction while said first switch remains open;
whereby said step (e.) recovers energy stored on the parasitic capacitance of said first switch.
3 Assignments
0 Petitions
Accused Products
Abstract
A power converter which transfers energy from an output circuit coupled to a secondary winding of a power transformer to an input circuit coupled to a primary winding of the power transformer in order to reduce the power loss and electromagnetic interference (EMI) originating from a primary switch. The reciprocating action of the converter is accomplished by placing the series switched path of a secondary switch in parallel with a diode in the output circuit. A control circuit is coupled to the primary switch and the secondary switch which allows the inherent capacitance of each switch to discharge before turning on the respective switch, thereby reducing the EMI and power losses occurring at these switches. The control circuit includes feedback and feedforward voltage control of the switching duty cycle. The control circuit varies the energy transferred from the output circuit to the input circuit according to changes in the accumulated charge on the primary switch.
184 Citations
23 Claims
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1. A method of operating a power converter, comprising the steps of:
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(a.) ramping up current in a first direction through a primary winding of a transformer; (b.) opening a first switch which is in series with said primary winding, to obstruct current through said primary winding and thereby drive current through a secondary winding of said transformer which is inductively coupled to said primary winding; (c.) closing a second switch which is in series with said secondary winding, to permit said secondary winding to pass current in a first direction to charge up an output capacitor; (d.) holding said second switch closed for long enough so that current in said secondary winding becomes zero, and thereafter said output capacitor drives current through said secondary winding in a second direction which is opposite to said first direction; (e.) opening said second switch while said secondary winding is passing current in said second direction, to thereby drive current through said primary winding in a second direction which is opposite to said first direction while said first switch remains open; whereby said step (e.) recovers energy stored on the parasitic capacitance of said first switch. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A power converter circuit comprising:
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a transformer having primary and secondary windings inductively coupled together; a first switching transistor connected to increase current in a first sense through said primary winding when said transistor is on, and to obstruct current through said primary winding when said transistor is off; an output capacitor having a first terminal operatively connected to a first terminal of said secondary winding, and a second terminal operatively connected to a second terminal of said secondary winding through a second switching transistor; and control circuitry connected to turn on said second transistor during at least some times when said first transistor is off, and to keep said second transistor continuously on thereafter until the direction of current flowing therethrough has reversed, and thereafter to turn off said second transistor to thereby drive current through said primary winding in a second sense which is opposite to said first sense while said first transistor remains off; whereby energy stored on the parasitic capacitance of said first switch is recovered. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. A computer system comprising:
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a user input device; a microprocessor operatively connected to detect inputs from said input device; memory which is read/write accessible by said microprocessor; a display operatively connected to display data generated by said microprocessor; a power connection for drawing power from AC mains, and a power supply connected to said power connection;
wherein said power supply comprisesa transformer having primary and secondary windings inductively coupled together; a first switching transistor connected to increase current in a first sense through said primary winding when said transistor is on, and to obstruct current through said primary winding when said transistor is off; an output capacitor having a first terminal operatively connected to a first terminal of said secondary winding, and a second terminal operatively connected to a second terminal of said secondary winding through a second switching transistor; and control circuitry connected to turn on said second transistor during at least some times when said first transistor is off, and to keep said second transistor continuously on thereafter until the direction of current flowing therethrough has reversed, and thereafter to shut off said second transistor to drive current through said primary winding in a second sense which is opposite to said first sense while said first transistor remains off; whereby energy stored on the parasitic capacitance of said first switch is recovered. - View Dependent Claims (18, 19, 20, 21, 22, 23)
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Specification