A motor driving device includes: a converter that converts AC power into DC power; a DC link capacitor provided for the DC link; an inverter that converts DC power into AC power for a motor; an initial charging circuit that charges the DC link capacitor; a potential difference determination unit that determines a potential difference between both ends of the initial charging circuit; a direct current detecting unit that detects direct current supplied to the initial charging circuit; an alternating current detecting unit that detects alternating current supplied to a motor; and an abnormality determination unit that determines that abnormal heat generation occurs in the initial charging circuit when the alternating current detecting unit detects alternating current and the direct current detecting unit detects direct current, in a case in which a potential difference occurs between both of the ends of the initial charging circuit.

A protection circuit includes a pre-charge rectifying circuit, a pre-charge resistor, a varistor, a switch, a main rectifying circuit, a bulk capacitor, and a control circuit. The pre-charge rectifying circuit is connected with an AC power source. The pre-charge resistor and the varistor are connected between the pre-charge rectifying circuit and the switch. The switch is further connected with a first node. The main rectifying circuit is connected between the AC power source and the first node. The bulk capacitor and the control circuit are connected between the first node and a ground terminal. The control circuit generates a first control signal to control the switch. The control circuit further generates a control signal set to control the main rectifying circuit.

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 bulk capacitor circuit for an AC input AC/DC Switching Mode Power Supply, such as an AC/DC adapter/charger without active power factor correction, is provided, comprising a plurality of bulk capacitors having different voltage ratings, and driver and control circuitry comprising AC input voltage sensing and comparator circuitry, which enables selective connection of one or more of the plurality of bulk capacitors, responsive to a sensed AC input voltage range. A startup circuit provides power to the driver circuit initially, so that the AC input voltage can be determined before power-up and enabling of the DC/DC converter. This solution provides for a reduction in capacitor volume, with associated improvement in the power density of an isolated AC/DC power supply, while the startup circuit ensures that an appropriate bulk capacitance is connected at startup for low line AC input, to maintain the ripple voltage in an appropriate range for reliable operation.

In some implementations, a device that powers a load includes a first terminal to couple with an alternating current (AC) power source, a second terminal to couple with the AC power source, and a full bridge rectifier arranged to receive power from the AC power source and provide direct current (DC) power between a positive node and a negative node. The device includes a first capacitor coupled in series between the full bridge rectifier and the first terminal or the second terminal, a load coupled between the positive node and negative node of the rectifier, and a second capacitor coupled between the positive node and negative node of the rectifier, in parallel with the load.

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.

A DC power-supply device that suppresses an excessive inrush current, can prevent breakage of elements and burnout of circuits, and converts alternating current from a three-phase AC power supply into direct current to supply it to a load, includes a rectifier circuit having a reactor connected to input or output side thereof and rectifying the alternating current from the three-phase AC power supply; first and second capacitors and connected in series between output terminals to the load; a charging unit selectively charges one or both of the first and second capacitors; and a control unit controlling the charging unit. When charging of the first and second capacitors is started, the control unit reduces the on-duty ratio, and then, until the on-duty ratio during a normal operation is reached, the control unit executes control such that the on-duty ratio is gradually increased as a predetermined time period is passed.

Disclosed are an inverter circuit, and air conditioner and refrigerator using the same. The inverter circuit includes a rectifier configured to rectify an input Alternating-Current (AC) voltage into a Direct-Current (DC) voltage; a smoothing portion configured to smoothen the DC voltage output from the rectifier; an inverter connected to a load, and configured to convert the DC voltage smoothened by the smoothing portion into an AC voltage, and to output the AC voltage to the load; and a suppressor installed between the rectifier and the smoothing portion, and configured to suppress an overvoltage or overcurrent of a DC link to which the DC voltage from the smoothing portion is applied.

An inrush current suppression device is an inrush current suppression device that suppresses an inrush current flowing from a DC power supply through a mechanical switch, and includes: a first capacitor having one end connected to a positive terminal of the DC power supply through the mechanical switch; a semiconductor switching element connected to the other end of the first capacitor and a negative terminal of DC power supply between the other end of the first capacitor and the negative terminal of the DC power supply; a resistance element connected in parallel to the semiconductor switching element; and a control circuit for controlling the semiconductor switching element. The control circuit has a first output port, and controls ON time and OFF time of the semiconductor switching element by outputting a PWM signal from the first output port to the semiconductor switching element after the mechanical switch is closed.