An overvoltage protection circuit is provided which is connected between a rectifier circuit and a load including an input capacitor element connected to both ends of the load. The overvoltage protection circuit includes a semiconductor switch connected between the rectifier circuit and the load, and a control circuit controls the semiconductor switch. When the rectified voltage exceeds a predetermined value, the control circuit turns off the semiconductor switch, and detects a voltage potential difference between both ends of the semiconductor switch, and then, for an interval when the voltage potential difference is zero or a predetermined minute value, the control circuit generates a control voltage for turning on the semiconductor switch, and outputs the control voltage to a control terminal of the semiconductor switch. The overvoltage protection circuit includes a current change circuit that gradually changes a current flowing through the semiconductor switch.

A circuit for converting DC to AC power or AC to DC power comprises a storage capacitor, boost and buck inductors and switching elements. The switches are controlled to steer current to and from the storage capacitor to cancel DC input ripple or to provide near unity power factor AC input. The capacitor is alternately charged to high positive or negative voltages with an average DC bias near zero. The circuit is configured to deliver high-efficiency power in applications including industrial equipment, home appliances, mobility devices and electric vehicle applications.

To enable in a circuit arrangement (8) with a transformer with center tap the voltage measurement on the secondary side simply and safely, it is provided that at least two series-connected resistors (R3, R4) are connected between the two outer connections (A1, A2) of the secondary side of the transformer (T) to form a measurement point (P) between the two resistors (R3, R4), and a voltage measurement unit (V) is provided to measure the voltage (U.sub.P) between the measurement point (P) and the second output pole (13), which corresponds to the output voltage (U.sub.A).

A circuit for converting DC to AC power or AC to DC power comprises a storage capacitor, boost and buck inductors and switching elements. The switches are controlled to steer current to and from the storage capacitor to cancel DC input ripple or to provide near unity power factor AC input. The capacitor is alternately charged to high positive or negative voltages with an average DC bias near zero. The circuit is configured to deliver high-efficiency power in applications including industrial equipment, home appliances, mobility devices and electric vehicle applications.

A circuit for converting DC to AC power or AC to DC power comprises a storage capacitor, boost and buck inductors and switching elements. The switches are controlled to steer current to and from the storage capacitor to cancel DC input ripple or to provide near unity power factor AC input. The capacitor is alternately charged to high positive or negative voltages with an average DC bias near zero. The circuit is configured to deliver high-efficiency power in applications including industrial equipment, home appliances, mobility devices and electric vehicle applications.

A method and apparatus for modulating a load by means of control command obtained by varying conduction angle of AC voltage is provided. Under normal operation, conduction angle of AC is approximate to 180 degrees. When a state change command of the load is to be executed, the angle of conduction angle is changed by a conduction angle modulation circuit of control end. After a conduction angle detection circuit of the load end detects the conduction angle, a control unit decodes the information of the conduction angle, and controls the load to perform a corresponding operation. The method and apparatus do not need to add an extra control wiring for the load, and may use the conduction angle of an AC power supply to effectively perform multifunctional modulations on the load with existing power lines, and the defect of a low power commonly found in a traditional dimmer is overcome.

A current converter apparatus includes a multi-phase current converter having current-converter modules for each phase that are electrically connected to one another and arranged in a current-converter cabinet. Each current-converter module has at least one semiconductor component arranged on a heat sink and includes just two semiconductor components connected to each other and connected to be controlled by a control component. The current-converter modules in the current-converter cabinet are arranged so that the current-converter modules of each current-converter phase form a horizontal row of modules arranged one beside the other and the rows are arranged vertically one above the other.

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.

A circuit for converting DC to AC power or AC to DC power comprises a storage capacitor, boost and buck inductors and switching elements. The switches are controlled to steer current to and from the storage capacitor to cancel DC input ripple or to provide near unity power factor AC input. The capacitor is alternately charged to high positive or negative voltages with an average DC bias near zero. The circuit is configured to deliver high-efficiency power in applications including industrial equipment, home appliances, mobility devices and electric vehicle applications.

The present description concerns a circuit for converting from a first alternating voltage to a second voltage. The circuit includes: a first thyristor; a first control circuit of the first thyristor; a power factor correction circuit comprising a coil; and a first circuit configured to convert a third voltage into a fourth DC voltage. The third voltage corresponds to a difference between a potential at a first node connected to an output node of the coil and a reference potential. The fourth DC voltage is configured to supply the first control circuit of the first thyristor, and is referenced with respect to the same reference potential as the third voltage.