Fuji Electric Co., Ltd.

Masahiro Motonobu

Kouichi Ueki

Yasuo Kobayashi

Koichi Ueki

The present invention provides a snubber circuit for a switching power supply that generates rectified direct current power from an inductive load cyclically connected and disconnected by two switching means fed by a direct current power supply. To reduce turn-on and turn-off loss of the switching means and increase switching frequency by reducing power loss in the snubber circuit, the snubber circuit according to the present invention absorbs counter-electromotive force generated during turn-off of the switching means. Turn-on loss of the switching means is reduced because a current from the switching means does not flow through the snubber circuit when the switching means are turned on. Power consumption in the snubber circuit is reduced and energy is efficiently utilized, because energy, stored in the snubber circuit in association with counter-electromotive force absorption from the inductive load when the switching means are turned off, is regenerated during subsequent turned-off period and turning-on action of the switching means. Additionally, transient voltage spikes are not applied to the switching means during turn-off because the counter-electromotive force is more quickly absorbed in comparison to prior art circuits.

Snubber circuit for switching power supply

In a switching power supply, electric current is supplied through a switching device to a load located away from the switching power supply. The electric current at the load is detected by a remote detecting device at remote detecting terminals. The remote detecting device includes a differential amplifier and a comparator connected to an output terminal of the differential amplifier. The comparator compares an output voltage of the differential amplifier with a reference voltage and outputs an alarm signal when the output voltage of the differential amplifier is lower than the reference voltage. A control device is connected to the switching device, the output terminal of the remote detecting device and a first reference voltage supply device. The control device changes ON-OFF duty ratio of the switching device by comparing the output voltage of the differential amplifier with the first reference voltage to control an output voltage of the switching device at a predetermined value. A first overvoltage protecting device is connected to the control device for protecting the load from overvoltage by monitoring the output of the switching device.

Growing community of inventors

Kanagawa, Japan

Masahiro Motonobu