A welding-type power supply includes a controller, a preregulator, a preregulator bus, and an output converter. The controller has a preregulator control output and an output converter control output. The preregulator receives a range of inputs voltages as a power input, and receives the preregulator control output as a control input, and provides a preregulator power output signal. The preregulator includes a plurality of stacked boost circuits. The preregulator bus receives the preregulator output signal. The output converter receives the preregulator bus as a power signal and receives the output converter control output as a control input. The output converter provides a welding type power output, and includes at least one stacked inverter circuit.

A switching power supply apparatus includes a PFM control circuit that outputs a clock signal Set such that a switching frequency of a switching element varies in accordance with a load state. The clock signal Set determines a turn-on timing of the switching element. A reference value of a current flowing through the switching element determines a turn-off timing of the switching element. A modulation signal is applied to the turn-off timing of the switching element to modulate one of a peak value of a drain current flowing through the switching element and an on-time of the switching element. Input control is performed separately on the clock signal Set and the modulation signal. Accordingly, even when the clock signal Set and the modulation signal contribute to each other to offset each other, modulation effects are not cancelled.

A wireless power transfer apparatus has a resonant circuit electrically coupled to a power converter. The resonant circuit includes a magnetic coupler L.sub.pt for magnetic coupling with a second apparatus. A controller associated with the power converter is configured to vary a relative phase of operation of the power converter with respect to the second apparatus, the phase being varied to at least partially compensate for variations in a resonant frequency of the resonant circuit.

A secondary controller drives a light emitting element of a photocoupler such that a detection voltage V.sub.OUTS corresponding to an output voltage V.sub.OUT generated in an output capacitor C approximates to a reference voltage V.sub.REF. A primary controller controls a switching transistor M according to a feedback signal V.sub.FB. A protection circuit is activated and drives the light emitting element of the photocoupler when detecting an abnormal state. An auxiliary power supply circuit includes a power supply capacitor C provided separately from the output capacitor C and supplies a power supply voltage V.sub.CC to the protection circuit and an anode of the light emitting element of the photocoupler.

In a push-pull type DC/DC converter capable of operating primary side switching elements alternately, a switching operation section turns on a primary side switching element having a high priority after a mode (d) as a normal state is transferred to a mode (d) as an inverse state during a circulation period when a load current is circulated into the secondary side rectifier elements when all of the primary side switching elements are turned off. To turn on the primary side switching element having a high priority after occurrence of the state transition to the inverse state can reduce a voltage immediately after supplying of electric power to the primary side switching elements with using exciting current and without adding any additional component.

A switching power supply apparatus includes a PFM control circuit that outputs a clock signal Set such that a switching frequency of a switching element varies in accordance with a load state. The clock signal Set determines a turn-on timing of the switching element. A reference value of a current flowing through the switching element determines a turn-off timing of the switching element. A modulation signal is applied to the turn-off timing of the switching element to modulate one of a peak value of a drain current flowing through the switching element and an on-time of the switching element. Input control is performed separately on the clock signal Set and the modulation signal. Accordingly, even when the clock signal Set and the modulation signal contribute to each other to offset each other, modulation effects are not cancelled.

A secondary controller drives a light emitting element of a photocoupler such that a detection voltage V.sub.OUTS corresponding to an output voltage V.sub.OUT generated in an output capacitor C approximates to a reference voltage V.sub.REF. A primary controller controls a switching transistor M according to a feedback signal V.sub.FB. A protection circuit is activated and drives the light emitting element of the photocoupler when detecting an abnormal state. An auxiliary power supply circuit includes a power supply capacitor C provided separately from the output capacitor C and supplies a power supply voltage V.sub.CC to the protection circuit and an anode of the light emitting element of the photocoupler.

An object of the present invention is to provide a charging apparatus having high efficiency of charging a battery by inputting an alternating current voltage. A charging apparatus that charges a direct current battery includes a step-down converter unit to which a direct current voltage from a power supply is input and that converts the direct current voltage, and when a voltage of the direct current battery is between a predetermined first voltage smaller than a charge completion voltage of the direct current battery and the charge completion voltage, a variable voltage that increases from the first voltage to the charge completion voltage in accordance with charging of the direct current battery is input to the step-down converter unit.

A welding-type power supply includes a controller, a preregulator, a preregulator bus, and an output converter. The controller has a preregulator control output and an output converter control output. The preregulator receives a range of inputs voltages as a power input, and receives the preregulator control output as a control input, and provides a preregulator power output signal. The preregulator includes a plurality of stacked boost circuits. The preregulator bus receives the preregulator output signal. The output converter receives the preregulator bus as a power signal and receives the output converter control output as a control input. The output converter provides a welding type power output, and includes at least one stacked inverter circuit.

A welding-type power supply includes a controller, a preregulator, a preregulator bus, and an output converter. The controller has a preregulator control output and an output converter control output. The preregulator receives a range of inputs voltages as a power input, and receives the preregulator control output as a control input, and provides a preregulator power output signal. The preregulator includes a plurality of stacked boost circuits. The preregulator bus receives the preregulator output signal. The output converter receives the preregulator bus as a power signal and receives the output converter control output as a control input. The output converter provides a welding type power output, and includes at least one stacked inverter circuit.