A control circuit includes: a transistor controller that controls a voltage at a gate terminal of a field effect transistor in accordance with a difference in voltage between a source terminal and a drain terminal of the field effect transistor connected so that a body diode is in a forward direction; and a current controller that reduces an operating current for operating the transistor controller when a load connected via the source terminal of the field effect transistor is light, and increases the operating current when the load is heavy.

A flyback power converter circuit includes: a transformer; a primary side switch, for controlling a primary winding to convert an input voltage to an output voltage and an internal voltage; a primary side control circuit, which is powered by the internal voltage; the primary side control circuit generates a switching signal according to a feedback signal, to operate the primary side switch; a secondary side control circuit, which generates the feedback signal according the output voltage; and a dummy load circuit, which is coupled to the output voltage, wherein when the output voltage drops to or is lower than a predetermined threshold, the dummy load circuit generates a dummy load current, to determine the feedback signal, so that the internal voltage is not undesirably low. When the output voltage exceeds the predetermined threshold, the dummy load circuit adjusts the dummy load current to zero current.

A flyback power converter circuit includes: a transformer; a primary side switch, for controlling a primary winding to convert an input voltage to an output voltage and an internal voltage; a primary side control circuit, which is powered by the internal voltage; the primary side control circuit generates a switching signal according to a feedback signal, to operate the primary side switch; a secondary side control circuit, which generates the feedback signal according the output voltage; and a dummy load circuit, which is coupled to the output voltage, wherein when the output voltage drops to or is lower than a predetermined threshold, the dummy load circuit generates a dummy load current, to determine the feedback signal, so that the internal voltage is not undesirably low. When the output voltage exceeds the predetermined threshold, the dummy load circuit adjusts the dummy load current to zero current.

A switching power supply includes an input terminal and an output terminal, a voltage converter including a first switching circuit configured to serve as a trigger for inputting a voltage from the input terminal and a second switching circuit configured to serve as a trigger for outputting, after the input voltage is converted, the converted voltage from the output terminal 0, a control circuit configured to output a control signal for selectively sequentially driving the first switching circuit and the second switching circuit, and a delay circuit configured to delay, based on the control signal for driving any one of the first switching circuit and the second switching circuit, a subsequent driving timing of the other switching circuit that is not driven to provide a dead time when both the first switching circuit and the second switching circuit are turned off.

A switching power supply includes an input terminal and an output terminal, a voltage converter including a first switching circuit configured to serve as a trigger for inputting a voltage from the input terminal and a second switching circuit configured to serve as a trigger for outputting, after the input voltage is converted, the converted voltage from the output terminal 0, a control circuit configured to output a control signal for selectively sequentially driving the first switching circuit and the second switching circuit, and a delay circuit configured to delay, based on the control signal for driving any one of the first switching circuit and the second switching circuit, a subsequent driving timing of the other switching circuit that is not driven to provide a dead time when both the first switching circuit and the second switching circuit are turned off.

Disclosed is an electronic apparatus including a connector configured to connect the electronic device to an external apparatus; and a power circuit configured to supply power to the connected external apparatus, the power circuit including: a transformer configured to output an output voltage by varying a level of an input voltage; a switching unit comprising a switch configured to perform switching operation for the transformer; a controller configured to control the switching unit to match a level of the output voltage with the external apparatus; and an auxiliary power circuit including an auxiliary winding, and configured to supply power to the controller based on a voltage induced in the auxiliary winding by the output voltage and to decrease the number of turns of the auxiliary winding based on the output voltage having a level greater than or equal to a predetermined value.

Disclosed is an electronic apparatus including a connector configured to connect the electronic device to an external apparatus; and a power circuit configured to supply power to the connected external apparatus, the power circuit including: a transformer configured to output an output voltage by varying a level of an input voltage; a switching unit comprising a switch configured to perform switching operation for the transformer; a controller configured to control the switching unit to match a level of the output voltage with the external apparatus; and an auxiliary power circuit including an auxiliary winding, and configured to supply power to the controller based on a voltage induced in the auxiliary winding by the output voltage and to decrease the number of turns of the auxiliary winding based on the output voltage having a level greater than or equal to a predetermined value.

A power conversion device includes a converter, a first capacitor, and a second capacitor. The first capacitor is connected between a DC positive bus and a DC neutral point bus. The second capacitor is connected between the DC neutral point bus and a DC negative bus. The converter includes a diode rectifier connected between an AC power supply and each of the DC positive bus and the DC negative bus, and a first AC switch electrically connected between the AC power supply and the DC neutral point bus. The power conversion device further includes a first fuse electrically connected between the first AC switch and a connection point between the first and second capacitors.

An AC/DC converter and conversion method are provided, in which an AC input is rectified and shaped by a waveform shaping capacitor. A current source circuit is used to provide the output current to the output load which has a parallel bulk capacitor. The current source circuit is switched on and off with timing which is dependent on the phase of the AC input signal. This enables a relatively high power factor, for example between 0.7 and 0.9, with low cost circuitry with few components.

An object of the invention is to provide a power converter that can be reduced in size. To achieve this, a power converter according to the invention includes: water passages arranged radially from an assumed central axis, each being trapezoid-shaped in cross section; and power modules placed between the water passages such that each of the power modules is sandwiched from both surfaces thereof by the water passages. Each of the power modules has an output terminal and positive and negative terminals on an end face located in a centrifugal direction side with respect to the assumed central axis. Any of the power modules and an adjacent one of the power modules are set in a front-back inverted manner.