A protection and attenuation circuit for sensitive AC loads is described. The circuit provides AC power protection and attenuation utilizing high-efficiency switch-mode techniques to attenuate an AC power signal by incorporating a bidirectional, transistorized switch driven from a pulse width modulation signal, PWM. The circuit monitors characteristics of the AC power signal driving a known load and characteristics of the load or other elements and determines the duty cycle of the pulse width modulated signal, PWM, based upon the duration and amplitude of the over-voltage, over-current, over-limit or other event.

A protection and attenuation circuit for sensitive AC loads is described. The circuit provides AC power protection and attenuation utilizing high-efficiency switch-mode techniques to attenuate an AC power signal by incorporating a bidirectional, transistorized switch driven from a pulse width modulation signal, PWM. The circuit monitors characteristics of the AC power signal driving a known load and characteristics of the load or other elements and determines the duty cycle of the pulse width modulated signal, PWM, based upon the duration and amplitude of the over-voltage, over-current, over-limit or other event.

A liquid heater is described including a chamber for receiving a liquid, a pair of electrodes located within the chamber for applying electric current to the liquid, input terminals for connection to a power supply, a plurality of bi-directional switches for connecting the electrodes to the input terminals, and a control unit for controlling the switches. The power supply supplies an alternating voltage having a frequency no greater than 60 Hz, and the control unit controls the switches such that the electrodes are energised with an alternating voltage having a frequency no less than 150 kHz.

A load control device for controlling the power delivered from an AC power source to an electrical load includes a thyristor, a gate coupling circuit for conducting a gate current through a gate of the thyristor, and a control circuit for controlling the gate coupling circuit to conduct the gate current through a first current path to render the thyristor conductive at a firing time during a half cycle. The gate coupling circuit is able to conduct the gate current through the first current path again after the firing time, but the gate current is not able to be conducted through the gate from a transition time before the end of the half-cycle until approximately the end of the half-cycle. The load current is able to be conducted through a second current path to the electrical load after the transition time until approximately the end of the half-cycle.

A load control device for controlling the power delivered from an AC power source to an electrical load includes a thyristor, a gate coupling circuit for conducting a gate current through a gate of the thyristor, and a control circuit for controlling the gate coupling circuit to conduct the gate current through a first current path to render the thyristor conductive at a firing time during a half cycle. The gate coupling circuit is able to conduct the gate current through the first current path again after the firing time, but the gate current is not able to be conducted through the gate from a transition time before the end of the half-cycle until approximately the end of the half-cycle. The load current is able to be conducted through a second current path to the electrical load after the transition time until approximately the end of the half-cycle.

Aspects of the invention overcome a monolithic approach to conventional low-frequency LPTs by using a high-frequency solid-state alternating current ac/ac modular powerconversion approach. Embodiments of the invention enable the ability to incorporate new technologies without in all cases redoing a LPT design from scratch. Furthermore, given that LPTs are for the long term, aspects of the invention ensure that they are durable, efficient, and fault tolerant with overloading capability.

Aspects of the invention overcome a monolithic approach to conventional low-frequency LPTs by using a high-frequency solid-state alternating current ac/ac modular powerconversion approach. Embodiments of the invention enable the ability to incorporate new technologies without in all cases redoing a LPT design from scratch. Furthermore, given that LPTs are for the long term, aspects of the invention ensure that they are durable, efficient, and fault tolerant with overloading capability.

Controller and method for a power converter. For example, a controller for a power converter includes: a feedback detector configured to receive a feedback voltage, sample the feedback voltage, and generate a sampled voltage based at least in part on the feedback voltage, the sampled voltage being associated with one or more fluctuations in magnitude; a resistor selector configured to receive the sampled voltage and generate one or more control signals based at least in part on the one or more fluctuations associated with the sampled voltage; a variable resistor network configured to receive the one or more control signals, determine a network resistance based at least in part on the one or more control signals, and output a compensation voltage based at least in part on the network resistance; and a voltage generator connected to the variable resistor network and configured to receive the compensation voltage.

A switched mode power converter is provided herein and comprises a cycloconverter comprising a plurality of switches, wherein each switch of the plurality of switches is a native four quadrant bi-directional switch with a common drift region configured to allow current flow in a first direction from a first source terminal to second source terminal and in a second direction from the second source terminal to the first direction.

A switched mode power converter is provided herein and comprises a cycloconverter comprising a plurality of switches, wherein each switch of the plurality of switches is a native four quadrant bi-directional switch with a common drift region configured to allow current flow in a first direction from a first source terminal to second source terminal and in a second direction from the second source terminal to the first direction.