Abstract: A switching power supply device includes a switching transistor, a sense resistor, a transformer, an optocoupler, and a current limiting feedback circuit. The switching transistor is controlled to be turned on and turned off. The sense resistor is configured to generate a sense voltage when the switching transistor is turned-on. The transformer includes a primary winding to which an input voltage is applied when the switching transistor is turned-on, a secondary winding is configured to supply an output voltage to a load, and an auxiliary winding that is configured to detect the output voltage. The optocoupler is configured to generate first and second optocoupler currents corresponding to the output voltage. The current limiting feedback circuit is configured to generate first, second, and third feedback currents using a voltage of the auxiliary winding, the first, second, and third feedback currents being in inverse proportion to the output voltage.

Abstract: A switching power supply device includes a switching transistor that is controlled to be turned on and turned off, a sense resistor that is configured to generate a sense voltage when the switching transistor is turned-on, a transformer including a primary winding to which an input voltage is applied when the switching transistor is turned-on, a secondary winding that is configured to supply an output voltage to a load, and an auxiliary winding that is configured to detect the output voltage, an optocoupler that is configured to generate first and second optocoupler currents corresponding to the output voltage, and a current limiting feedback circuit that is configured to generate first, second, and third feedback currents using a voltage of the auxiliary winding, the first, second, and third feedback currents being in inverse proportion to the output voltage.

Abstract: A switching power supply device includes a switching transistor, a sense resistor connected to the switching transistor in series and on which a sense voltage generates when the switching transistor is turned on, a transformer including a first winding to which an input voltage is applied when the switching transistor is turned on and a second winding connected to a load, an optocoupler in which an optocoupler current is generated based on an output voltage on the second winding side, a load power detection circuit that generates a load power signal in accordance with a turn-on period of the switching transistor, a turn-on period control circuit, a turn-off period control circuit, and an SRFF circuit.

Abstract: A switching power supply device includes a switching transistor, a sense resistor connected to the switching transistor in series and on which a sense voltage generates when the switching transistor is turned on, a transformer including a first winding to which an input voltage is applied when the switching transistor is turned on and a second winding connected to a load, an optocoupler in which an optocoupler current is generated based on an output voltage on the second winding side, a load power detection circuit that generates a load power signal in accordance with a turn-on period of the switching transistor, a turn-on period control circuit, a turn-off period control circuit, and an SRFF circuit.

Abstract: An amplifier circuit has a simple circuit architecture that enables a push-pull output function while exhibiting low power consumption. The amplifier circuit includes a first transconductance amplifier to which an output of a two-input differential amplifier and a first bias voltage are input. An output of the first transconductance amplifier is connected to another input and an output of a second transconductance amplifier, which has one input thereof connected to an output of the first transconductance amplifier and a gate of a first output transistor. The output of the differential amplifier is connected to a gate of a second output transistor, which has the polarity opposite to the polarity of the first output transistor. Drains of the first and the second output transistors are connected to each other thus constituting a push-pull output.

Abstract: An amplifier circuit has a simple circuit architecture that enables a push-pull output function while exhibiting low power consumption. The amplifier circuit includes a first transconductance amplifier to which an output of a two-input differential amplifier and a first bias voltage are input. An output of the first transconductance amplifier is connected to another input and an output of a second transconductance amplifier, which has one input thereof connected to an output of the first transconductance amplifier and a gate of a first output transistor. The output of the differential amplifier is connected to a gate of a second output transistor, which has the polarity opposite to the polarity of the first output transistor. Drains of the first and the second output transistors are connected to each other thus constituting a push-pull output.

Abstract: An overcurrent detection circuit detects an overcurrent in a current path accurately and sensitively. The overcurrent detection circuit includes a first resistance element connected between first input and output terminals of the current path; a second resistance element connected to the first input terminal; a differential amplifying device connected to the first output terminal and the second resistance element; and a proportional-current output device connected to the second resistance element in series and to an output terminal of the differential amplifying device. The proportional-current output device receives an output signal from the differential amplifying device to output a proportional current with a magnitude proportional to a current flowing through the first resistance element.