A device includes a transformer configured to supply a pre-charge voltage to a capacitor and a converter configured for coupling to the transformer and responsive to an increasing modulation index. The modulation index increases for a time quanta after the capacitor becomes substantially fully charged and the pre-charge voltage is substantially constant during the time quanta.

A bidirectional switch for the control of power from an AC source to a load is described. The approach uses power MOSFETs in a bidirectional switch subcircuit configuration having an optically coupled, electrically floating control circuit that self-biases the switches into the “on” state and uses an optically coupled control element to force the switches into the “off” state. The time constant of the control circuit is fast enough to allow phase control as well as on-off control. A boost circuit is included to ensure that the control voltage exceeds a threshold voltage of the MOSFETs to force an off state. A plurality of subcircuits can be easily cascaded to provide improved performance.

A frequency converter with a rectifier on an input side and a backup capacitor arranged downstream of the rectifier. Input-side phases of the rectifier feed the backup capacitor via multiple half-bridges of the rectifier. The input-side phases are connected to grid-side phases of a multiphase supply grid via a pre-circuit. Each grid-side phase is connected to an input-side phase within the pre-circuit via a phase capacitor. Each grid-side phase is additionally directly connected to another input-side phase within the pre-circuit via a switch and the grid-side phases are short-circuited with the input-side phases when the switches are closed. Each phase capacitor connects two grid-side phases or two input-side phases together. The frequency converter has a control apparatus which keeps the switches open when pre-charging the backup capacitor and closes the switches when a specified charge state of the backup capacitor is reached.

A frequency converter includes a rectifier on an input side and a support capacitor downstream of the rectifier. Input-side phases of the rectifier feed the backup capacitor via multiple half-bridges of the rectifier. The half-bridges have active switching elements and the rectifier is designed as a recovery rectifier. The input-side phases are connected to grid-side phases of a multiphase supply grid via an upstream circuit. Each grid-side phase is connected to one of the input-side phases within the upstream circuit via a respective phase capacitor. A control facility controls the active switching elements when a first charge state of the support capacitor is reached and input-side phase voltages are applied to the input-side phases via the active switching elements. Voltages running in the opposite direction to the grid-side phase voltages are applied to the grid-side phases to which the input-side phases are connected via the phase capacitors.

A load control device for controlling power delivered from an alternating-current power source to an electrical load may comprise a controllably conductive device, a control circuit, and an overcurrent protection circuit that is configured to be disabled when the controllably conductive device is non-conductive. The control circuit may be configured to control the controllably conductive device to be non-conductive at the beginning of each half-cycle of the AC power source and to render the controllably conductive device conductive at a firing time during each half-cycle (e.g., using a forward phase-control dimming technique). The overcurrent protection circuit may be configured to render the controllably conductive device non-conductive in the event of an overcurrent condition in the controllably conductive device. The overcurrent protection circuit may be disabled when the controllably conductive device is non-conductive and enabled after the firing time when the controllably conductive device is rendered conductive during each half-cycle.

An AC/DC converter receives an AC voltage at a first terminal and a second terminal. A rectifying bridge has a first input terminal coupled via a resistive element to the first terminal and a second input terminal connected to the second terminal, with output terminals of the rectifying bridge coupled to third and fourth terminals of the converter for generating a DC voltage. A first controllable rectifying thyristor couples the first terminal to the third terminal and a second controllable rectifying thyristor couples the fourth terminal to the first terminal. The resistive element functions as an inrush protection device during a first phase when the thyristors are turned off. In a second phase, the thyristors are selectively actuated.

The present disclosure relates to a method and apparatus for charging and discharging. The apparatus includes: an AC power terminal, including first to third nodes, and a first center line node, and being configured to receive input an AC input or send an AC output; a power conversion stage, including fourth to sixth nodes, and a second center line node; a first bus capacitor and a second bus capacitor both coupled to the second center line node, the first center line node being coupled to the second center line node; a first switch set; a second switch set; a control module, coupled to the first switch set, the second switch set, the AC power terminal, and the power conversion stage.

A frequency converter with a rectifier on an input side and a backup capacitor arranged downstream of the rectifier. Input-side phases of the rectifier feed the backup capacitor via multiple half-bridges of the rectifier. The input-side phases are connected to grid-side phases of a multiphase supply grid via a pre-circuit. Each grid-side phase is connected to an input-side phase within the pre-circuit via a phase capacitor. Each grid-side phase is additionally directly connected to another input-side phase within the pre-circuit via a switch and the grid-side phases are short-circuited with the input-side phases when the switches are closed. Each phase capacitor connects two grid-side phases or two input-side phases together. The frequency converter has a control apparatus which keeps the switches open when pre-charging the backup capacitor and closes the switches when a specified charge state of the backup capacitor is reached.

An apparatus and methods to reduce current transient during power mode transfer in uninterruptible power supply (UPS). The disclosure provides a zero-cross detection based phase width modulated (PWM) element (E3). The element (E3) is configured to delay activation of a PWM modulator, by delaying a PWM start command for a first delay time (T.sub.dz), wherein the first delay time is the time between receiving a static switch command to the time when a positive sequence component of a phase load current crosses zero. The element (E3) is further configured to delay the activation of the PWM modulator for a second delay time (T.sub.di) after the end of the first delay time (T.sub.dz), by delaying the PWM start command for the second delay time, wherein the second delay time is based on a power factor of load connected to the UPS.

In accordance with some embodiments of the present invention, a wireless power receiver that ramps an ASK impedance is presented. A method of amplitude shift key (ASK) modulation in a wireless power receiver includes initiating transition of an ASK impedance from a first state to a second state, the ASK impedance being coupled to a resonant circuit that includes a wireless power receive coil that receives a time-varying magnetic field; transitioning the ASK impedance from the first state to the second state according to the transition over a plurality of switching cycles of the time-varying magnetic field; and holding the second state.