High efficiency resonant switching converters
First Claim
1. A DC to DC flyback converter for supplying power derived from an input voltage source to one or more output terminals, comprising:
- a first transformer which isolates the one or more output terminals from the input voltage source, said transformer having a primary winding;
a first semiconductor switch that, when ON, electrically couples said primary winding with the input voltage source;
a resonant capacitor;
a second semiconductor switch that, when ON, electrically couples said resonant capacitor with said primary winding; and
control circuitry having means for alternately turning said first switch ON and OFF according to a first selected duty cycle and means for alternately turning said second switch ON and OFF according to a second selected duty cycle, wherein said second duty cycle is selected such that said second switch is turned ON only so long as required to discharge said resonant capacitor.
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Accused Products
Abstract
Resonant DC to DC power converter topologies include a PWM-controlled flyback converter having a single transformer and a primary side resonant subcircuit that is optimally controlled to minimize reverse recovery losses. A second transformer may be added wherein the primary windings are connected in series, the first transformer having substantially greater inductance than the second transformer to more efficiently transfer energy over a wide range of output load conditions. A combined forward-flyback resonant converter utilizing a load-side buck loop for increased power delivery performance and start-up circuitry for initial power connection of the converter to a voltage source utilizing a hysteresis protection circuit are also disclosed.
168 Citations
24 Claims
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1. A DC to DC flyback converter for supplying power derived from an input voltage source to one or more output terminals, comprising:
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a first transformer which isolates the one or more output terminals from the input voltage source, said transformer having a primary winding; a first semiconductor switch that, when ON, electrically couples said primary winding with the input voltage source; a resonant capacitor; a second semiconductor switch that, when ON, electrically couples said resonant capacitor with said primary winding; and control circuitry having means for alternately turning said first switch ON and OFF according to a first selected duty cycle and means for alternately turning said second switch ON and OFF according to a second selected duty cycle, wherein said second duty cycle is selected such that said second switch is turned ON only so long as required to discharge said resonant capacitor. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A DC to DC flyback converter for supplying power derived from an input voltage source to one or more output terminals, comprising:
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a transformer which isolates the one or more output terminals from the input voltage source, said transformer having a primary winding; a first semiconductor switch that, when ON, electrically couples said primary winding with the input voltage source; a resonant capacitor; a second semiconductor switch that, when ON, electrically couples said resonant capacitor with said primary winding; and control circuitry having means for alternately turning said first switch ON for a period of time TON and OFF for a period of time TOFF, respectively, and means for alternately turning said second switch ON for a period of time TD2 and OFF for a period of time TD3, respectively, wherein each second switch ON time period TD2 commences after a time delay TD1 following each instance said first switch is turned ON, and wherein said time period TD2 is limited to the time required to discharge said resonant capacitor.
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9. A method for controlling a DC to DC flyback converter, said converter comprising a transformer having a primary winding, a first semiconductor switch operated by a first voltage control signal according to a first duty cycle, said first switch, when ON, electrically coupling said primary winding with an input voltage, a resonant capacitor, and a second semiconductor switch operated by a second voltage control signal according to a second duty cycle, said second switch, when ON, electrically coupling said primary winding with said resonant capacitor, comprising the steps of:
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selecting said first duty cycle so that said first switch is alternately turned ON for a period of time TON and OFF for a period of time TOFF, respectively; and selecting said second duty cycle so that said second switch is alternately turned ON for a period of time TD2 and OFF for a period of time TD3, respectively, wherein each second switch ON time period TD2 commences after a time delay TD1 following each instance said first switch is turned ON, and wherein said time period TD2 is limited to the time required to discharge said resonant capacitor. - View Dependent Claims (10)
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11. A DC to DC flyback converter for supplying power derived from an input voltage source to one or more output terminals, comprising:
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a first transformer having a primary winding; and a second transformer having a primary winding, said first transformer primary winding provided in series with said second transformer primary winding, said first transformer having substantially greater inductance than said second transformer. - View Dependent Claims (12, 13)
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14. A DC to DC flyback converter for supplying power derived from an input voltage source to one or more output voltage terminals over a wide range of output load levels, comprising:
magnetic energy transfer means for isolating the one or more output voltage terminals from the input voltage source, said magnetic energy transfer means having an effective variable inductance. - View Dependent Claims (15, 16)
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17. A DC to DC power converter for supplying power derived from an input voltage source to an output voltage terminal, comprising:
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a transformer which isolates the output voltage terminal from the input voltage source, said transformer having a primary winding, a flyback-secondary winding and a forward-secondary winding, respectively; a load-side inductor electrically coupled in series with said forward-secondary winding; and a load-side storage capacitor electrically coupled with said flyback-secondary winding, said inductor and capacitor connected in parallel across said output voltage terminal. - View Dependent Claims (18, 19)
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20. Start-up circuitry for connecting a voltage supply for the control circuitry of a power converter to a voltage source, comprising:
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means including a first semiconductor switch to connect the voltage supply to the voltage source upon initial start-up of the power converter; means including a second semiconductor switch and a comparator to maintain said connection until the voltage supply is charged to a first voltage level and then discontinuing said connection until the voltage of said voltage supply drops below a second voltage level, said first voltage level being greater than said second voltage level, wherein said second switch is controlled by an output signal from said comparator and said first switch is controlled by said second switch. - View Dependent Claims (21, 22, 23)
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24. A DC to DC flyback converter for supplying power to one or more output terminals from an input voltage source, comprising:
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a first transformer which isolates the one or more output terminals from the input voltage source, said transformer having a primary winding; a first semiconductor switch that, when ON, electrically couples said primary winding with the input voltage source; a resonant capacitor; a second semiconductor switch that, when ON, electrically couples said resonant capacitor with said primary winding; control circuitry having means for alternately turning said first switch ON and OFF according to a first selected duty cycle and means for alternately turning said second switch ON and OFF according to a second selected duty cycle, wherein said second duty cycle is selected such that said second switch is turned ON only so long as required to discharge said resonant capacitor; and start-up circuitry having means including a first semiconductor switch to connect a voltage supply for said control circuitry to the input voltage, said connection being maintained from start-up by means including a second semiconductor switch and a comparator until said voltage supply is charged by the input voltage to a first selected voltage level and then discontinued until said voltage supply drops below a second selected voltage level, wherein said second switch is controlled by an output signal from said comparator and said first switch is controlled by said second switch.
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Specification