A switching unit of an embodiment includes a first switching element of normally-on type, a second switching element of normally-off type having a non-reference potential side conductive terminal connected to a reference potential side conductive terminal of the first switching element, a series capacitor connected between a conduction control terminal of the first switching element and a conduction control terminal of the second switching element, and a diode having an anode connected to the conduction control terminal of the first switching element and a cathode connected to a common junction of the first switching element and the second switching element.

A DC-to-DC converter includes a first switching circuit, a second switching circuit, a transformer positioned between an AC side of the first switching circuit and an AC side of the second switching circuit, an inductance element positioned between the transformer and at least one of the AC side of the first switching circuit and the AC side of the second switching circuit, and control circuitry that operates the first switching circuit and the second switching circuit. The control circuitry sets a predetermined operation ratio of the first switching circuit and the second switching circuit to each other, and adjusts, based on the predetermined operation ratio, a first operation period of the first switching circuit and a second operation period of the second switching circuit.

The invention relates to a switched-mode power supply (14) for supplying the components of a photovoltaic system (1) with a constant DC output voltage (U.sub.a), comprising connections (15) for connecting to the photovoltaic modules (2) of the photovoltaic system (1) for providing a DC input voltage (U.sub.e), a DC/DC voltage converter (16) comprising at least one switch (17), a transformer (18), a control device (22) for controlling the at least one switch (17) at a switching frequency (f.sub.s) for obtaining the desired DC output voltage (U.sub.a), an output equalizing voltage (23) and connections (24) for providing the DC output voltage, as well as the inverter (4) and a string monitoring assembly (3) of a photovoltaic system (1). In order to obtain a DC output voltage (U.sub.a) with the losses as low as possible for a very wide range of DC input voltages (U.sub.e) between 200 V and 1500 V, the DC/DC voltage converter (16) is formed by a combination of flyback and forward converters having two serially arranged switches (17, 17′). Said switches (17, 17′) are connected to the control device (22) which is designed such that the control of the DC output voltage (U.sub.a) occurs such that the switches (17, 17′) are switched in accordance with the flow on the primary side passing through the primary winding (20) of the transformer (18).

Electrical power distribution systems and methods of operating electrical power distribution systems are provided. One electrical power distribution system comprises: an electrical power storage unit; a transformer; a first bidirectional converter circuit connected between the electrical power storage unit and a first winding of the transformer; a first DC bus; a second DC bus; a second bidirectional converter circuit connected between the first DC bus and a second winding of the transformer; a third bidirectional converter circuit connected between the second DC bus and a third winding of the transformer; and a controller connected for control of the first, second and third converter circuits to distribute electrical power between the electrical power storage unit, the first DC bus and the second DC bus.

In a DC/DC converter that performs zero-voltage switching, capacitors are connected respectively in parallel to first and second MOSFETs that are included in an inverter unit in the primary-side of a transformer, and an inductor is connected to an AC output line. In a range of a current being more than a predetermined value, a control circuit controls the inverter unit using a PWM control with a fixed dead time, and in a light load range where the current is equal to or less than the predetermined value, the control unit changes the control to a PFM control and decreases a frequency so that the dead time becomes longer as the current decreases, to thereby keep a duty ratio without change.

A device can include a first circuit configured to be exposed to a first environment, the first circuit comprising one or more first transfer inductors, and a second circuit isolated from the first circuit and configured to be exposed to a second environment, the second circuit comprising one or more second transfer inductors. The second environment can be a harsh environment. The first circuit and the second circuit can be wirelessly coupled via the one or more first transfer inductors and the one or more second transfer inductors to allow transfer of power and/or signals between the first circuit and the second circuit.

Circuits that provide an auxiliary power supply on the secondary side of an isolated switched-mode power converter are described. Such an auxiliary supply may be used to provide power to a secondary side controller or to other circuitry in the secondary side of the power converter. During at least a start-up phase of the power converter, the secondary side auxiliary power supply is supplied power by use of a self-starting primary side driver that operates autonomously until the secondary side controller is fully operational. Circuits and methods for such a self-starting primary side driver are provided. The techniques disclosed provide for a secondary side auxiliary power supply that uses minimal additional circuitry.

As an object of reducing a noise resulted from the mutual influences between circuit-configuring components, a DC-DC converter includes a high voltage circuit section that is electrically connected to a transformer, a low voltage circuit section that is electrically connected to the transformer, a housing in which the high voltage circuit section and the low voltage circuit section are accommodated, a control circuit board that controls the driving of the low voltage circuit section, and a frame that supports the control circuit board. The frame is arranged on a position facing a bottom surface of the housing while crossing the low voltage circuit section. The housing includes a first wall that separates a first space in which the high voltage circuit section is accommodated and a second space in which circuit components configuring the low voltage circuit section are accommodated. The frame forms a second wall that protrudes toward a direction approaching a leading end of the first wall.

An AC-DC conversion circuit includes an input rectifier circuit, a primary side input filtering capacitor, a primary side inverter circuit, a drive circuit, an isolation transformer, a secondary side rectifier circuit, a secondary side capacitors, and a control circuit connected between the secondary side output filtering capacitor and the drive circuit, where the drive circuit is connected to the primary side inverter circuit. The primary side inverter circuit and the primary side input filtering capacitor form a loop, so as to form a clamping resonant circuit. Inverter switching transistors operate in a zero voltage switching (ZVS) state. The secondary side rectifier circuit has two operation modes including a forward operation mode and a flyback operation mode. Each of the first and the second inverter switching transistors in the primary side inverter circuit is used as an inverter switching transistor or a clamping switching transistor according to an operation period.

A power supply circuit includes a power amplifier that receives a direct current (DC) voltage from a first power source. A control signal applied to the power amplifier causes the power amplifier to convert the DC voltage to an alternating current (AC) output signal. The AC output signal is applied to a transformer that includes a first winding, a second winding, and a third winding. The first winding receives the AC output signal and the second winding receives an output current that varies in accordance with the AC output signal to apply current to a load. A rectifier includes a plurality of diodes configured to rectify a voltage across the third winding and clamp the voltage at the load. Return power from the third winding may be returned to the first power source.