Abstract: A high efficiency, high power factor, low voltage power converter includes a dual active bridge converter (DABC) having transformer-coupled primary-side and secondary-side bridge connections of switching devices and providing two output voltages. One output voltage drives a resonant boost converter coupled in series between an ac rectifier for rectifying an ac line voltage and the DABC. The boost converter, which is controlled by frequency modulation, boosts a dc bus voltage above the peak line voltage, thereby providing a high power factor. The other output is a low dc voltage which is regulated by controlling the phase shift between the voltages respectively produced by the primary-side and secondary-side connections of switching devices of the DABC. Advantageously, the leakage inductance of the DABC transformer coupling the primary and secondary sides of the DABC is efficiently used for energy transfer therebetween such that an output filter inductor is not needed.

Abstract: A capacitance multiplier/regulator (FIG. 1) stores charge at high voltage across a capacitor (22,32), and capacitance-multiplies current to a load (100) by step-down transformers (26,36), controlled switches (24,34), and rectifiers (28,38). The switch pairs (24a,24b;34a,34b) each switch in antiphase, but the switching phase between the pairs is controlled (FIG. 5) in a feedback manner to controllably generate a voltage across a transformer primary winding (14.sub.p), which couples a feedback-controlled alternating voltage across secondary winding (14.sub.s). The alternating voltage is added to the unregulated voltage by a rectifier (18,20), so the bus voltage is controllably greater than the unregulated input voltage. The feedback controls either the bus voltage or the load voltage. Stress on the switches is reduced by preventing capacitor recharge during a load pulse.

Abstract: A power supply for a thruster for space applications (e.g., an arcjet thruster) comprises a series/parallel resonant converter wherein the load quality (Q) factor of the resonant tank circuit inherently varies with arc voltage so as to accommodate changes in arc voltage from initiation thereof through steady-state operation. Effectively, the resonant tank circuit acts as a ballast by matching the arc during initiation thereof through steady-state operation. Furthermore, the resonant converter operates in a soft-switching, low-voltage switched mode so as to maximize efficiency.

Abstract: A distributed power system for providing multiple output voltages, including pulsed voltages, to a solid-state phased-array radar transmit/receive module, for example, includes: an energy-storage capacitor for coupling to an input dc power source and for storing substantial energy at high voltage for supplying pulsed voltages at low voltage; at least one capacitance-multiplying converter, including first and second transformers with multiple secondary windings, for producing positive and negative voltages on buses internal to a power module; and a plurality of series regulators to obtain multiple positive and negative load voltages, including pulsed voltages, from the positive and negative bus voltages. Substantial energy storage is achieved within the power module; and, if even more energy storage is desired, an additional external energy-storage capacitor can be coupled to the input power leads, thereby being coupled in parallel with the energy-storage capacitor.

Abstract: A power supply system for thrusters (e.g., arcjet thrusters) in a spacecraft system comprises lightweight, redundant power supplies that share the power distribution function to the thrusters. Each power supply comprises a plurality of parallel-connected power supply subunits of which the combined power output capability exceeds the required maximum power demand by at least one subunit capacity for each arcjet thruster in the system. Each power supply subunit comprises a lightweight, high-frequency, soft-switching power supply. For arcjet systems comprising arcjet thrusters that do not operate simultaneously, relays are employed to switch between thrusters.

Abstract: A starting circuit for providing a high-voltage pulse for igniting an arc in an arcjet thruster includes a resonant capacitor for storage of the energy required to generate the high-voltage pulse. The capacitor is resonantly switched with a small resonant inductor which, in turn, resonates with a high-voltage cable capacitance, generating a high-voltage pulse via a step-up transformer to the arcjet thruster for igniting the arc. Advantageously, the transformer turns ratio is minimized, thus minimizing the required transformer size and weight; and the high-voltage pulse is isolated from the arcjet power supply semiconductor devices.

Abstract: A gate driver circuit for a converter which requires an approximately 50% duty cycle to drive two power switching devices (e.g., in many interleaved, push-pull and bridge converters) includes a single transformer secondary winding coupled between the gates of the two devices. The transformer is reset every half-cycle by driving each device in the forward, or positive, direction only. Advantageously, the result is an approximately 50% reduction in gate drive power as compared with conventional schemes requiring a negative gate drive voltage for turn-off.

Abstract: A method and system for controlling a dual output power converter of the type having a pair of input terminals connectable to a source of rectified AC power of variable voltage amplitude, a boosting circuit including a secondary winding of a boost transformer operatively coupled in circuit with the pair of input terminals for providing a boosted voltage onto a DC power bus, and a full-bridge inverter including at least one controllable switching device serially connected in each leg of the inverter. The inverter has an input connected to the DC bus and a pair of output terminals connected to respective ends of a primary winding of an output transformer, at least one of the pair of output terminals being connected in circuit with the primary winding of the boost transformer.

Abstract: A distributed power system for supplying pulsed loads, such as radar loads, includes a relatively high-voltage, energy-storage capacitor coupled in parallel between an input dc power source and a capacitance-multiplying converter. The pulse energy is stored in the energy-storage capacitor and is coupled to the load via low-leakage inductance transformer action. As a result, the size of the energy-storage capacitor is reduced, while maintaining a high bandwidth for supplying fast-rising pulsed loads.

Abstract: A resonant converter, including a transformer for separating a high-voltage (primary) side from a relatively low-voltage (secondary) side, has at least one synchronous rectifier and an auxiliary sense winding coupled to the gate thereof. The input capacitances of the synchronous rectifiers are reflected to the primary side and the secondary side by the square of the ratio of the number of auxiliary sense winding turns to the number of primary andsecondary winding turns, respectively, thereby reducing the required size of the discrete resonant capacitor. In one embodiment, a gate bias voltage approximately equal to the device threshold voltage is applied to the gate of the synchronous rectifiers. The auxiliary sense windings are etched into a conductive film pattern of the secondary windings. The auxiliary sense windings provide nearly identical secondary and gate drive voltages so that the synchronous rectifiers are gated substantially at the zero-voltage crossings of the secondary winding voltages.

Abstract: A voltage-doubler rectifier includes an ac fullbridge diode rectifier and a dc-to-dc converter having two output boost circuits. One of the output boost circuits is coupled between the rectifier and a dc link, and the other output boost circuit is coupled, with opposite polarity, between the rectifier and the circuit common. Two series-connected filter capacitors are also coupled between the dc link and the circuit common. In a preferred embodiment, the two output boost circuits each comprise either a series, parallel, or combination series/parallel resonant circuit and a rectifier. A switch is coupled between the junction joining one pair of diodes of the rectifier and the junction joining the two filter capacitors. For a relatively high ac line voltage, the switch is open, and the circuit operates in a low boost mode. For a relatively low ac line voltage, the switch is closed, and the circuit operates in a high boost, or voltage-doubling, mode.

Abstract: An off-line switching power supply includes an ac rectifier and a dual-output switching converter having one output coupled between the ac rectifier and the input to the dual-output converter in order to provide a high power factor, the other output of the dual-output switching converter providing a dc voltage as the power supply output. The outputs of the dual-output converter are fully decoupled so as to allow independent control of the ac input current and the power supply output voltage. In a preferred embodiment, a full-wave ac rectifier bridge is coupled in series with the second output of the power converter via an input resonant boosting converter. A full-bridge dc-to-ac converter is coupled between the dc link and ground for providing an ac signal to excite the boosting converter and for providing another ac voltage through a transformer to an output rectifier to generate a regulated dc output voltage.

Abstract: A power distribution system for supplying power to a plurality of point-to-load power supplies includes a plurality of bulk power supplies, each having a separate respective power distribution bus coupled at the output thereof. Each power distribution bus is coupled to each point-of-load power supply through an OR gate such that if one or more of the bulk power supplies fails, or if a fault occurs on one or more of the power distribution buses, then the point-of-load power supplies are unaffected because they continue to receive power from the other bulk power supplies via the respective OR gates. Furthermore, if a power distribution bus becomes short-circuited to ground, the current therein is limited electronically by the respective bulk power supply. Hence, the power distribution buses are protected against overcurrent without the need for a multitude of dc circuit breakers.

Abstract: A power supply includes a dc-to-dc converter with an integral boost power supply for maintaining the effective converter input voltage within a predetermined steady-state range, even if the input voltage to the power supply exhibits substantial voltage transients. In one preferred embodiment, the boost power supply comprises a boost transformer and a rectifier, and the converter comprises two parallel-coupled resonant converter modules, each including either a half-bridge or full-bridge connection of switching devices and a resonant circuit. The primary winding of the boost transformer is coupled between the junctions joining the switching devices of the resonant converter bridges. When the power supply input voltage is outside the steady-state voltage range, the boost power supply is activated by phase shift control of the voltage across the primary winding of the boost transformer.

Abstract: A single-ended, resonant power converter includes an input filter having at least one primary winding and multiple auxiliary, or secondary, windings. A regulated input DC voltage is transformed directly to the auxiliary windings. The voltages across the auxiliary windings are respectively rectified and filtered to provide multiple, auxiliary, regulated output voltages which are independent of the main output voltage and converter switching frequency.

Abstract: A high efficiency gate driver circuit for driving a power switching device of a high frequency converter includes a series resonant circuit for making resonant transfers of energy between the input capacitance of the power switching device and a storage capacitor to achieve substantially lossless gate switching. An ac switch couples the resonant circuit to the junction between upper and lower switching devices connected in a half-bridge configuration. The upper and lower switches of the half-bridge function to maintain the power switching device in either an ON-state or an OFF-state, respectively, depending on the transfer of energy being made. Timing circuitry ensures proper gating of the switching devices relative to operation of the ac switch.

Abstract: A high efficiency gate driver circuit for driving a power switching device of a high frequency power converter utilizes a series resonant circuit to reduce or substantially eliminate turn-on switching losses. The resonant circuit comprises the input capacitance of the power switching device and an inductance connected in series between the upper and lower switching devices of a half-bridge driver circuit. During device turn-on, the input capacitance resonates up to a voltage level approximately twice that of the gate drive power supply, and turn-on is substantially lossless. The input capacitance is prevented from discharging back to the supply by a Schottky diode connected in series between the supply and the upper switching device of the half-bridge. During device turn-off, the input capacitance discharges through the lower switching device.

Abstract: A control circuit for a full bridge switching converter including power FET switching devices. The control circuit including a gate driver with a voltage sensor circuit which senses the precise instant to gate the power FET on in order to achieve substantially lossless switching by the converter.

Abstract: A synchronous rectifier is able to operate at higher frequencies and provides an output having lower noise than prior art FET synchronous rectifier system by using field effect switching devices which contain only one conductivity type of semiconductor material and connecting a high speed, low charge storage diode in parallel. Schottky diodes are preferred whereby there is no junction diode in the structure. Conventional FETs may be used when paralleled with a Schottky diode which prevents the FET's parasitic internal diode from becoming conductive.

Abstract: A circuit for "resetting" snubbers in a series resonant bridge inverter maintains lossless snubber action during light-load and no-load inverter operation and during operation near resonance. Series resonant circuit operation is controlled to be above the resonant frequency to ensure operation at a lagging power factor. The snubber-resetting operation is facilitated by a relatively small inductor connected across the output terminals of the series resonant inverter.