A dimmer is provided for controlling power to a load, the dimmer having a ground leakage power supply deriving power from a connection of the dimmer to ground. The power supply may be a switching-mode power supply that can be the sole or primary power supply to power operation of the dimmer, including operation of the controller.

An improved method for zero-voltage switching (ZVS) of a voltage-fed half-bridge using a variable dead band is provided. The duration of the dead band is determined dynamically and is precisely long enough to ensure the absence of shoot-through events while also minimizing or eliminating switching losses and reverse conduction losses. The method generally includes: (a) calculating the equivalent capacitance as seen by the current source charging the midpoint of the half-bridge; (b) calculating the ZVS charge requirement based on the link voltage and the equivalent capacitance; (c) calculating the charge delivered by the current source over time during a dead band vector, equating the result to the ZVS charge requirement, and solving for the ZVS time requirement at each commutation point over the switching cycle; and (d) updating the dead bands for each commutation of each half-bridge in the switched-mode power converter.

A soft switching resonant converter is disclosed. The converter includes a power switch operable to connect and disconnect a DC link rail node and an output node. A resonant capacitor is coupled with the power switch. An auxiliary leg is coupled with a DC link midpoint node and the output node. An active damper is coupled in series with the resonant capacitor and the output node and is controllable to provide a first resistance of the active damper in a first state and a second resistance of the active damper in a second state, the first resistance having a lower magnitude than the second resistance. A driver controls the damper switch to provide a first resistance during the soft switching operation of the power switch and a second resistance after the soft switching operation of the power switch.

A control method for regulating the switching frequency of a resonant converter having an input terminal to receive an input voltage and an output terminal to output an output voltage. The control method is sensing the input voltage and adjusting the switching frequency based on the comparison of the input voltage with a reference threshold voltage. When the input voltage is less than the reference threshold voltage, the switching frequency is adjusted to decrease, and when the input voltage is higher than the reference threshold voltage, the switching frequency is adjusted to increase.

A power transmission unit for controlling a flow of electric energy between two AC power units is provided. The power transmission unit comprises a main transformer having a first winding and a second winding as well as a switchable auxiliary AC unit for applying a tunable auxiliary AC voltage across an auxiliary AC side of the auxiliary AC unit. The auxiliary AC side is connected in series with the first winding of the main transformer to form a series connection. Further, a power conversion unit comprising the power transmission unit and two AC power units as well as a method for controlling a flow of electric energy by using such a power conversion unit are provided.

A conversion circuit is disclosed. In the conversion circuit, an input terminal includes a positive direct current bus terminal and a negative direct current bus terminal, and an output terminal includes an alternating current output end; a first switch unit includes a flying clamping capacitor and a first converter bridge arm; a second switch unit includes a second converter bridge arm; an output end of the first switch unit and the second switch unit is connected to the alternating current output end; and the first switch unit and the second switch unit are connected to a control module, and switch under control of the control module, so that the conversion circuit converts between a direct current voltage and an alternating current voltage, to output a required alternating current voltage.

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.

A ZVS (zero voltage switching) control circuit for controlling a flyback power converter includes: a primary side controller circuit, for generating a switching signal to control a primary side switch; and a secondary side controller circuit, for generating a synchronous rectifier (SR) control signal to control a synchronous rectifier switch. The SR control signal includes an SR-control pulse and a ZVS pulse. The primary side controller circuit determines a trigger timing point of the switching signal according to a first waveform characteristic of a ringing signal, to control the primary side switch to be ON. The secondary side controller circuit determines a trigger timing point of the ZVS pulse according to a second waveform characteristic of the ringing signal, to control the synchronous rectifier switch to be ON for a predetermined ZVS time period, thereby achieving zero voltage switching of the primary side switch.

An exemplary embodiment of the present invention is a wireless power transmission circuit that provides power to a load of variable resistance with an alternating current (AC) power source induced at a secondary coil in a secondary side of the circuit by a primary coil in a primary side of the said circuit. The wireless power transmission circuit includes a switch-controlled capacitor (SCC) and a semi-active rectifier (SAR). The SCC connects to the AC power source. The SCC includes a first capacitor connected in parallel with two electrically controllable switches in series. The SAR connects to output of the SCC for rectifying the output of the SCC, wherein the SAR comprises a bridge circuit that includes two electrically controllable switches. A control angle of the SCC and a conduction angle of the SAR are regulated to provide a load impedance that matches the impedance of the coils.

A method and a control circuit for driving an electronic switch coupled to an inductor in a power converter in successive drive cycles each including an on-time and an off-time are disclosed. Driving the electronic switch includes: measuring an inductor voltage during the on-time in a drive cycle in order to obtain a first measurement value; measuring the inductor voltage during the off-time in a drive cycle in order to obtain a second measurement value; obtaining a first voltage measurement signal that is dependent on a sum of the first measurement value and the second measurement value; and adjusting the on-time in a successive drive cycle dependent on a feedback signal and the first voltage measurement signal.