Cosel Co., Ltd.

Kazuhiro Horii

A switching power supply apparatus is configured of, as a primary-side circuit, a synchronous rectification step-up/down chopper circuit including a main switching element (), a commutation element (), a choke coil (), and a buffer capacitor (). As a secondary-side circuit, to a secondary winding provided to the choke coil, a series circuit including a rectifying element and an output capacitor is connected. An inductance of the choke coil is set to have a predetermined value so that a choke coil current IL flowing through the choke coil flows in both of a positive direction and a negative direction across zero in one cycle of switching when an output current is equal to or smaller than a maximum output current. A switching control circuit performs control of complementarily turning the main switching element and the commutation element ON/OFF in a switching cycle by providing a deadtime, thereby performing soft switching.

Switching power supply apparatus capable of achieving soft switching operation

A switching power source device includes current control pulse generating means configured of a target value setting module, which outputs a changeable value which is a predetermined target value relating to a control of an output current, a computing module, which carries out a computing process relating to the control of the output current based on the target value, and outputs a computation result, and a pulse generating module, which generates a current control pulse voltage for controlling the output current based on the computation result. The switching power source device includes a current detecting circuit, which detects the output current or a current flowing in a switching element TR, and a current limit signal generating circuit which, when the detected current exceeds a reference value set based on the output of the current control pulse generating means, outputs a current limit signal for limiting the current. A drive pulse generating circuit, on the current limit signal being output, operates in such a way that an on-duty of a drive pulse stops widening, or becomes narrower.

Switching power source device and drive method thereof

A switching power supply device has a synchronized rectifying element that turns on and off complementarily with a main oscillation element that is connected in series with an input power supply, and a parasitic diode that is connected to the two ends of the synchronized rectifying element in a direction enabling current supply toward a smoothing circuit. The device has a control circuit that generates a control pulse according to which a time delay is set for turning on the main oscillation element after a certain period of time elapses after the synchronized rectifying element is turned off, and that drives the main oscillation element and the synchronized rectifying element. An auxiliary rectification circuit has a series circuit formed by an auxiliary switch element and an auxiliary capacitor driven by the control circuit (PW) and which is provided between the two ends of the parasitic diode.

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Toyama, Japan

Kazuhiro Horii