Cryogenically-cooled switching circuit
First Claim
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1. A power conversion system comprising:
- a switching circuit having an input terminal for supplying power to said circuit and an output terminal coupled to a load which receives power from said circuit, said circuit comprising;
cryogenically cooled first and second switching devices, each switching device comprising an intrinsic drain-to-source commutating diode capable of conveying an inductive current component from the load;
a controller, which controls a deadtime period between switching of the first switching device and the second switching device, the controller providing a first control signal to turn-on the first switching device in a first time interval following turn-off of the second switching device, such that an inductive current component flows through the first switching device rather than through the intrinsic drain-to-source diode associated with the first switching device, said controller including a sensing circuit for sensing said inductive current component for generating said first control signal; and
a refrigeration unit for cryogenically cooling at least said switching devices.
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Abstract
An electronic power conversion circuit includes cryogenically cooled MOSFET power switching devices arranged in a switch-mode configuration and responsive to control signals for reducing capacitive discharge and commutation losses in the circuit by controlling the period between switch-on and switch-off time (i.e., “deadtime”) of the MOSFET devices. When one of the MOSFET devices of the circuit is switched off, the opposing MOSFET, after the short deadtime period, is switched on to serve as a commutating device rather, than the opposing MOSFET'"'"'s intrinsic drain-source diode. The power conversion circuit may include a half-bridge circuit or combinations thereof.
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Citations
29 Claims
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1. A power conversion system comprising:
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a switching circuit having an input terminal for supplying power to said circuit and an output terminal coupled to a load which receives power from said circuit, said circuit comprising;
cryogenically cooled first and second switching devices, each switching device comprising an intrinsic drain-to-source commutating diode capable of conveying an inductive current component from the load;
a controller, which controls a deadtime period between switching of the first switching device and the second switching device, the controller providing a first control signal to turn-on the first switching device in a first time interval following turn-off of the second switching device, such that an inductive current component flows through the first switching device rather than through the intrinsic drain-to-source diode associated with the first switching device, said controller including a sensing circuit for sensing said inductive current component for generating said first control signal; and
a refrigeration unit for cryogenically cooling at least said switching devices. - View Dependent Claims (2, 3, 4)
sample-and-hold circuitry which samples the inductive current component with the sensing circuit; and
a clock oscillator, responsive to a control signal from the sample-and-hold circuitry, for generating a feedback signal;
a timing generator which, in response to a pulsewidth modulated signal and the feedback signal, generates the first control signal and a second control signal.
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5. A method of reducing the switching losses of a cryogenically-cooled switching circuit comprising first and second switching devices connected to a load circuit having an inductive component, each of said switching devices comprising an intrinsic drain-to-source commutating diode, said method comprising the steps of:
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controlling a deadtime period between switching of the first switching device and the second switching device by;
applying to the first switching device when in a turned-on state, a first control signal to turn-off said first switching device;
applying, in the deadtime period following turn-off of said first switching device, a second control signal to turn-on said second switching device to convey an inductive current component from the load circuit through said second switching device rather than through said intrinsic drain-to-source commutating diode associated with said second switching device; and
generating said second control signal in response to a sensed value of the inductive current component. - View Dependent Claims (6, 7)
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8. A switching circuit having an input terminal for supplying power to said circuit and an output terminal coupled to a load receiving power from said circuit, comprising:
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a pair of switching devices including a cryogenically cooled first switching device and a cryogenically cooled second switching device, each switching device comprising an intrinsic drain-to-source commutating diode capable of conveying an inductive current component from the load; and
a controller, which controls a deadtime period between switching of the first switching device and the second switching device, the controller providing a first control signal to turn-on the first switching device in a first deadtime period following turn-off of the second switching device, such that an inductive current component flows through the first switching device rather than through the intrinsic drain-to-source diode associated with the first switching device, said controller including a sensing circuit for sensing said inductive current component for generating said first control signal, the controller including sample-and-hold circuitry which samples the inductive current component with the sensing circuit;
a clock oscillator, responsive to a control signal from the sample-and-hold circuitry, for generating a feedback signal; and
a timing generator which, in response to a pulsewidth modulated signal and the feedback signal, generates the first control signal and a second control signal.
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9. A half-bridge switching circuit having an input terminal for supplying power to said circuit and an output terminal coupled to a load receiving power from said circuit, comprising:
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a pair of switching devices including a cryogenically cooled first switching device and a cryogenically cooled second switching device, the pair of switching devices being configured as a half-bridge circuit, each switching device comprising an intrinsic drain-to-source commutating diode capable of conveying an inductive current component from the load; and
a controller, which controls a deadtime period between switching of the first switching device and the second switching device, the controller providing a first control signal to turn-on the first switching device in a first deadtime period following turn-off of the second switching device, such that an inductive current component flows through the first switching device rather than through the intrinsic drain-to-source diode associated with the first switching device, said controller including a sensing circuit for sensing said inductive current component for generating said first control signal. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. A full-bridge switching circuit having an input terminal for supplying power to said circuit and an output terminal coupled to a load receiving power from said circuit, comprising:
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a first pair of switching devices including a cryogenically cooled first switching device and a cryogenically cooled second switching device, the first pair of switching devices being configured as a half-bridge circuit, each switching device including an intrinsic drain-to-source commutating diode capable of conveying an inductive current component from the load;
a second pair of switching devices including a cryogenically cooled third switching device and a cryogenically cooled fourth switching device, the second pair of switching devices being configured as a half-bridge circuit, each switching device including an intrinsic drain-to-source commutating diode capable of conveying the inductive current component from the load, the first, second, third and fourth switching devices being configured as a full-bridge circuit; and
a controller controlling a deadtime period between switching of the first, second, third and fourth switching devices, the controller providing a first control signal to turn-on the first switching device and the third switching device in a first deadtime period following turn-off of the second switching device and the fourth switching device, such that an inductive current component flows through the first switching device and the third switching device rather than through the intrinsic drain-to-source diode associated with the first switching device and the third switching device. - View Dependent Claims (17, 18, 19, 20, 21, 22)
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23. A polyphase switching circuit having an input terminal for supplying power to said circuit and an output terminal coupled to a load receiving power from said circuit, comprising:
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a plurality of pairs of switching devices configured as a polyphase switching circuit having an input terminal, each of the pair of switching devices having an intrinsic drain-to-source commutating diode capable of conveying the inductive current component from the load, said polyphase switching circuit having a set of terminals for receiving a plurality of alternating current signals having a differential phase shift relationship with respect to each other, a controller controlling a deadtime period between switching of the switching devices, the controller providing a first control signal to turn-on a first one of the pair of switching devices in a first deadtime period following turn-off of a second one of the pair of switching devices, such that an inductive current component flows through the first one of the pair of switching devices rather than through the intrinsic drain-to-source diode associated with the first one of the switching devices. - View Dependent Claims (24, 25, 26, 27, 28, 29)
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Specification