Onkyo Corporation

Onkyo & Pioneer Technology Corporation

Kazuki Yamamoto

A switching power supply includes a first switching element connected between a primary winding of a transformer for the switching power supply and the ground, a shunt regulator serving as an output voltage detection circuit configured to detect an output voltage on a secondary winding side of the transformer, a photocoupler configured to transmit the output voltage to a control circuit, a second switching element configured to receive a stop signal for stopping operation of the switching power supply, and a photocoupler drive circuit configured such that when the second switching element has received the stop signal, power output from a low-frequency transformer power supply or the switching power supply is supplied to the photocoupler, and the stop signal is transmitted to the control circuit via the photocoupler.

Power supply system with photocoupler drive circuit

To provide a protection circuit that can reduce output voltage that is output from a switching power supply greatly when temperature rises. A protection circuit includes a comparator that supplies detection current based on voltage Vsens that a temperature sensor outputs in case that voltage Vsens that the temperature sensor outputs exceeds voltage Vref of predetermined potential, a control circuit that supplies control current that the control circuit increases detection current that the comparator supplies exponentially, and a constant voltage circuit reduces output voltage Vout that is output from a switching power supply based on control current that the control circuit supplies.

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Osaka, Japan

Kazuki Yamamoto