Switching power supply apparatus
View Patent ↗A switching power supply apparatus of the present disclosure is a device connection state detection circuit that detects a connection state in a load device connection terminal in a power supply system having the load device connection terminal. The device connection state detection circuit includes a transformer, a switching element, a pulse generator, and a waveform detection circuit. The waveform detection circuit detects a voltage or a current generated in a primary winding wire or a secondary winding wire of the transformer in accordance with operation of a pulse signal, compares the detected voltage or current with a preset reference value, and outputs an output signal in accordance with a comparison result, to an OFF terminal.
1. A switching power supply apparatus comprising:
a second switching element to which an input voltage is supplied;
an output terminal connected to a load device;
an input/output conversion circuit that converts the input voltage switched by the second switching element into an output voltage, and outputs the converted output voltage to the output terminal;
a switching control circuit that controls switching operation of the second switching element, and has an off mode for stopping the switching operation in accordance with a signal input to an OFF terminal;
a first rectifier circuit connected between the input/output conversion circuit and the output terminal;
a transformer having a secondary winding wire whose first end is connected to a first terminal of the output terminal through a second rectifier circuit;
a first switching element connected to a primary winding wire of the transformer;
a pulse generator that supplies a pulse signal to a gate terminal of the first switching element; and
a waveform detection circuit that detects a voltage or a current generated in the primary winding wire or the secondary winding wire of the transformer in accordance with operation of the pulse signal, compares the detected voltage or current with a preset reference value, and outputs an output signal in accordance with a comparison result to the OFF terminal.
2. The switching power supply apparatus according to claim 1 , wherein the waveform detection circuit is connected to the primary winding wire of the transformer, detects a voltage or a current generated in the primary winding wire of the transformer, compares the detected voltage or current with the preset reference value, and outputs an output signal in accordance a comparison result to the OFF terminal.
3. The switching power supply apparatus according to claim 1 ,
wherein the waveform detection circuit includes:
a waveform detection circuit transmitter connected to the secondary winding wire of the transformer, and including a light-emitting diode of a photocoupler; and
a waveform detection circuit receiver connected to the OFF terminal, and including a phototransistor of the photocoupler, and
wherein the waveform detection circuit transmitter detects a voltage or a current of the secondary winding wire of the transformer, compares the detected voltage or current with the preset reference value, and outputs an output signal in accordance with the comparison result, from the waveform detection circuit receiver to the OFF terminal.
4. The switching power supply apparatus according any one of claim 1 to claim 3 , wherein a second end of the secondary winding wire of the transformer is connected to a second terminal of the output terminal.
5. The switching power supply apparatus according any one of claim 1 to claim 3 , wherein a second end of the secondary winding wire of the transformer is connected to a connecting point of the input/output conversion circuit and the first rectifier circuit.
6. The switching power supply apparatus according to claim 1 , wherein the first rectifier circuit is a diode.
7. The switching power supply apparatus according any one of claim 1 to claim. 3 , wherein the first rectifier circuit is formed of a transistor, and the transistor is controlled to interrupt when power consumed by the load device is smaller than a preset power reference value.
8. The switching power supply apparatus according any one of claim 1 to claim 3 , wherein operation of the pulse generator oscillates only in the off mode.
9. The switching power supply apparatus according to claim 1 , wherein an oscillation frequency of the pulse generator is equal to or lower than a commercial frequency.
10. The switching power supply apparatus according any one of claim 1 to claim 3 , further comprising a protective circuit that stops the switching operation of the second switching element when the switching power supply apparatus is abnormal, and controls the switching control circuit so as not to be in the off mode.