Abstract: A switching array includes a plurality of switching elements electrically coupled to each other, each switching element being configured to be switched between conducting and non-conducting states. The switching array also includes at least one parasitic minimizing circuitry electrically coupled to the plurality of switching elements and configured to provide near zero electrical voltage and current across and through each of the plurality of switching elements during switching of the plurality of switching elements between the conducting and non-conducting states.

Abstract: A system is presented. The system includes detection circuitry configured to detect occurrence of a zero crossing of an alternating source voltage or an alternating load current. The system also includes switching circuitry coupled to the detection circuitry and comprising a micro-electromechanical system switch. Additionally, the system includes control circuitry coupled to the detection circuitry and the switching circuitry and configured to perform arc-less switching of the micro-electromechanical system switch responsive to a detected zero crossing of an alternating source voltage or alternating load current.

Abstract: An ultra compact ring topology puts the output terminals of solid state switches physically at the center of a circuit with the switches surrounded by voltage busses. The switches are symmetrically arranged around the output bus, the voltage busses are filtered (decoupled) to ground using symmetrically positioned filter components, and lead lengths to and from the switches are minimized. Switch driver circuits are closely integrated with each switch and positioned as close as possible, each to its associated switch, and arranged symmetrically. Switches may be at cryogenic temperatures and busses and lead connectors may be superconductive.

Abstract: Switching losses and conduction losses are isolated by networks which are partially cryogenic and partially at room temperature. Switching losses are independent of temperature. Advantageously the switching losses are taken in a snubber network at room temperature and conduction losses are incurred at cryogenic temperatures, where majority carrier devices like MOSFETs operate with ultra low on-state resistance and corresponding low conduction losses. Low loss leads carry current efficiently from the cryogenic environment to room temperature without adversely affecting refrigeration. Switch and snubber network may both operate cryogenically.

Abstract: A surge suppression module is provided for connection to a wall receptacle and interconnection with other modules. Each module includes a top portion rotatably connected to a bottom portion. A male electrical plug extends from a top surface, and a female plug from a bottom surface. The top and bottom surfaces of the top and bottom portions, respectively, form opposing top and bottom surfaces of the module when the module is in an in-line orientation with an in-line axis through the module passing through the female and male plugs. The top and bottom portions are rotatable about an axis of rotation angled at 45.degree. to the in-line axis, and rotate from the in-line orientation to a wall mounting orientation, wherein the male plug extends from a side of the module and is perpendicular to in-line axis. Surge suppression and filtering circuitry is carried within the bottom portion along with connectors for connection of electrical equipment used with the surge suppression module.

Abstract: An uninterruptible power supply (UPS) system includes a control and display module operational with a UPS when carried by a housing of the UPS and when remote from the housing. An orientation sensing switch carried by the module senses a horizontal or vertical position of the module and provides a signal to a module processor for providing performance diagnostics of the UPS in a horizontal or vertical format as appropriate. The UPS system housing includes support arms extendable from the housing for providing added stability to the housing when in a vertical position. The control and display processor receives manual input from user buttons on the module and communicates with a UPS processor carried by the housing. The UPS includes a battery positioned within the housing for access by removal of a front housing panel for avoiding movement of the UPS system during replacement of batteries.

Abstract: An amplification device is provided for driving a gradient coil in an MR system, wherein the gradient coil is required to generate a rapidly changing gradient magnetic field during a first time period, and a substantially constant field during an immediately following second time period. The device includes a adjustable bus, for providing first and second voltage levels, and a switching or PWM amplifier. A switch is coupled between the bus and the switching amplifier for applying the first voltage to the amplifier during the first time period, and the second voltage to the amplifier during the second time period. The switching amplifier comprises an inverter for generating a PWM voltage in response to its input, and an LC filter for converting the PWM wave into a DC voltage. The switching amplifier generates a substantially higher coil driving voltage during the first period, in response to the first voltage level, than during the second period in response to the second voltage level.

Abstract: Power is transferred from a stationary power supply to a rotational gantry in a computer tomography (CT) system through a rotary transformer arranged in a ring configuration with an inner diameter that is sufficiently large to receive a patient. The rotary transformer has a toroidal rotor core and a toroidal stator core arranged either concentrically with an air gap extending radially therebetween or side-by-side with an air gap extending axially therebetween. A resonant inverter provides ac power to the rotary transformer which, in turn, drives a high-voltage tank circuit coupled to a x-ray tube, the tank circuit and x-ray tube being mounted on a rotational gantry. Advantageously, this is a contactless power transfer system which eliminates conventional brush and slip ring arrangements and moreover avoids the need for mounting the inverter to rotate with the CT gantry.

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 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 gradient amplifier for use in magnetic resonance imaging equipment employs a low voltage DC power supply connected in series between a pair of higher voltage DC power supplies, the latter supplies serving to provide increased power for rapid gradient switching and the former supply providing correction current to produce the desired voltage output. The high voltage DC power supplies preferably comprise multiple DC units which can be combined to provide finer steps of control prior to correction by the lower voltage supply. The low voltage DC power supply preferably comprise one or more linear amplifiers connected in series, or one or more switchmode amplifiers connected in series. The DC power supplies are controlled in an open loop manner from a gradient signal that designates the desired current for the gradient coil and the amplifiers are operated in a closed loop responding to to a feedback signal from the gradient coil.

Abstract: A gradient current speed-up circuit, for use in a higher-speed NMR imaging system having an associated gradient coil, has a gradient power amplifier receiving an input analog signal controlling amplifier output current, and a transformer having a primary winding and a pair of secondary windings connected in series with the amplifier output and the coil. Semiconductor switching elements selectively connect the primary winding between first and second potential sources, and are turned on and off in selected patterns to cause a current to be suddenly applied to, and removed from, flow through the associated gradient coil; the amplifier output current is changed with the gradient coil current lags behind an amplitude commanded by a master input signal.

Abstract: A series resonant inverter is controlled to maintain a substantially constant gain and a substantially constant bandwidth, thereby ensuring stable operation under all operating conditions. A load compensating gain control circuit generates a unique gain or attenuation factor for each unique set of output load conditions. To maintain constant gain, inverter gain for each set of operating conditions is multiplied by the corresponding gain or attenuation factor. Bandwidth is increased (or decreased) and maintained constant to ensure stable operation.

Abstract: A gradient current speed-up circuit, for use in a higher-speed NMR imaging system with a gradient power amplifier and an associated gradient coil, has an energy-storage element, with an inductance typically between 5 and 20 times the inductance of the associated gradient coil. A plurality of semiconductor switching elements receive the current output of the energy-storage element; and the associated gradient coil is connected between selected ones of these semiconductors devices. The semiconductor devices are turned on and off in selected patterns, to cause the energy-storage element current to be suddenly applied to and removed from flow through the associated gradient coil.

Abstract: A series resonant inverter is controlled to provide a substantially constant output voltage to a load. The control utilizes a combination of optimal control methods and phase modulation to enable time optimal responses to changes in state of the system. State determinants (including resonant capacitor voltage, resonant inductor current, source voltage, and output load voltage) are continuously monitored, and an optimal control signal is generated therefrom. When operating within the operable frequency range of the inverter's controllable switch means, frequency is varied to maintain proper operation. When operating at an extremity of the operable frequency range, phase modulation is employed.

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.

Abstract: A resonant inverter is operated in a manner to provide a substantially constant output voltage to a load. The inverter is controlled using either a frequency control mode or a phase shift control mode. In the frequency control mode, a constant output voltage is maintained through frequency variation of the rectangular wave signal applied to the resonant circuit of the inverter. In the phase shift control mode, constant output voltage is maintained by phase shifting one component signal of the rectangular wave signal relative to another component signal thereof while maintaining constant the frequency of both component signals. Mode switching occurs automatically at the extremities of the operating frequency range of controllable switch means in the resonant inverter.

Abstract: Improved control of a resonant inverter upon enablement from a disabled state is achieved by restricting, to a frequency remote from resonance, the rectangular wave signal applied to the resonant circuit immediately subsequent to enablement, and by controllably sweeping the rectangular wave signal frequency toward resonance until a desired output voltage or current is reached. Closed loop variation of the rectangular wave signal frequency applied to the resonant circuit is employed to maintain a constant output voltage or current once the desired value is reached.

Abstract: A series resonant inverter is controlled to provide a substantially constant output voltage to a load. The control utilizes a combination of optimal control methods and phase modulation to enable time optimal responses to changes in state of the system. State determinants (including resonant capacitor voltage, resonant inductor current, source voltage, and output load voltage) are continuously monitored, and an optimal control signal is generated therefrom. When operating within the operable frequency range of the inverter's controllable switch means, frequency is varied to maintain proper operation. When operating at an extremity of the operable frequency range, phase modulation is employed.