A voltage converter includes a circuit formed by a parallel association, connected between first and second nodes, of a first branch and a second branch. The first branch includes a first controlled rectifying element having a first impedance. The second branch includes a resistor associated in series with a second rectifying element having a second impedance substantially equal to the first impedance. The second rectifying element may, for example, be a triac having its gate coupled to receive a signal from an intermediate node in the series association of the second branch. Alternatively, the second rectifying element may be a thyristor having its gate coupled to receive a signal at the anode of the thyristor.

In response to a problem wherein a voltage of a capacitor of a power conversion device decreases when a voltage of an alternating current power supply is restored after once decreasing, the voltage of the capacitor drops below a maximum value of the voltage of the alternating current power supply when power is restored, and an inrush current occurs, the power conversion device, provided between an alternating current power supply and a load, is such that a decrease in an input voltage or an input current of a power converting unit is detected, a change in the voltage of the capacitor is predicted, and operations of the power converting unit are caused to stop before the voltage of the capacitor drops to or below the maximum value of the voltage of the alternating current power supply, thereby restricting an occurrence of an inrush current.

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.

A pre-charging circuit is provided, including a first switch, a second switch, a diode, a first current-limiting apparatus, a capacitor, and an inverter unit. One end of the pre-charging circuit is connected to a power grid. After the first current-limiting apparatus, the first switch, and the diode are connected in series, one end of a line formed by the series connection is connected to one terminal of the capacitor, the other end of the line is connected to a first-phase alternating current of the power grid, and the other terminal of the capacitor is connected to a second-phase alternating current of the power grid via the inverter unit and the second switch successively.

In a switching power supply device, a control circuit controls a first thyristor, a second thyristor, and a switching element according to an input voltage. The control circuit maintains the first thyristor in an on state while maintaining the second thyristor and the switching element in an off state in a first period in which the absolute amplitude value is equal to or less than a first threshold value within the latter half of a first half-cycle of the input voltage at startup, and maintains the second thyristor in an on state while maintaining the first thyristor and the switching element in an off state in a second period in which the absolute amplitude value is equal to or less than a second threshold value within the latter half of a second half-cycle of the input voltage at startup. The second half-cycle is the half-cycle following the first half-cycle.

Disclosed are a power stabilization circuit and a display device to which the power stabilization circuit is applied. The power stabilization circuit includes a thermistor provided on a first path through which an input power is supplied, to limit an inrush current of the power, a relay that provides a second path through which the power is supplied without passing through the thermistor, to allow the power to be transferred through the second path instead of the first path when a current is supplied, and a switching circuit that is switched to supply the current generated from the input power to the relay when an activation signal for activating at least one of a display and a backlight of the display is received.

A precharge system for precharging a DC bus circuit includes a first input, first and second circuit branches, and a controller, where the first circuit branch includes a first contactor between the first input and an AC to DC converter, the second circuit branch has: a disconnect switch coupled to the first input; a variable frequency drive (VFD) with an AC input coupled to the disconnect switch; an inductor coupled to an AC output of the VFD; and a second contactor coupled to the inductor. The precharge VFD provides precise control of the precharge operation such as charging time, current limiting, short-circuit and ground fault protection, monitoring DC Bus capacitance and verifies the health of the shared DC bus circuit through startup diagnostic. The controller opens the first contactor and closes the second contactor and the disconnect switch in a first mode to precharge the DC bus circuit using the VFD, and in a second mode, the controller closes the first contactor and opens the second contactor and the disconnect switch.

A power converter arrangement includes a semiconductor switch system with a controllable switch. A capacitor unit includes a capacitor having a capacitance value, the capacitor unit being operatively connected to the semiconductor switch system. A conductor arrangement includes a conductor adapted to conduct an electric current between the capacitor unit and the semiconductor switch system. The conductor has a resistance and an inductance. A resonant circuit is formed by the resistance, the inductance and the capacitance, and the power converter arrangement includes at least one attenuating element for attenuating an electrical ringing in the resonant circuit. The attenuating element is conductively isolated from the resonant circuit. The attenuating element includes ferromagnetic material, and the attenuating element is magnetically coupled to the conductor such that variations in the electric current intensity of the conductor induces eddy currents within the attenuating element.

A device for resolving common-mode voltage interference is applied to a power supply system including a power converter and a switch mechanism. Each phase of an output end of the power converter is connected to a downstream circuit by using the switch mechanism. The switch mechanism includes a first switch and a second switch. The device includes a controller and a passive component. Two ends of the first switch in at least one phase of the output end of the power converter are connected in parallel to the passive component, and the controller controls the second switch to be turned on, and when a voltage difference between the two ends of the first switch is less than a preset voltage, controls the first switch to be turned on. In this manner, the switch mechanism is protected, thereby prolonging a service life of the switch mechanism.

The present disclosure provides a three-phase AC/DC converter aiming for low input current harmonic. The converter includes an input stage for receiving a three-phase AC input voltage, an output stage for at least one load, and one or more switching conversion stages, each stage including a plurality of half bridge modules. The switches in each module operate with a substantially fixed 50% duty cycle and are connected in a specific pattern to couple a DC-link and a neutral node of the input voltage. The AC/DC converter further includes one or more controllers adapted to vary the switching frequency of the switches in the switching conversion stages based on at least one of load voltage, load current, input voltage, and DC-link voltage. The converter can also include one or more decoupling stages, such as, inductive components adapted to decouple the output stage from the switching conversion stages.