Abstract: A sound and music playback device includes: an output amplifier; a power supply circuit that supplies electric power to the output amplifier; and an output signal level judging circuit; wherein an output voltage value of the power supply circuit is changed based on a level of a sound and music signal to be outputted.

Abstract: A switching power supply circuit for generating an output voltage at an output node based on an input voltage at an input node includes a reference voltage generating circuit configured to generate a reference voltage such that during an initial start-up period of the reference voltage a voltage rise rate of the reference voltage within a first predetermined period from a start point of the initial start-up period and a voltage rise rate thereof within a second predetermined period immediately preceding an end point of the initial start-up period are smaller than a voltage rise rate thereof in a period between the first predetermined period and the second predetermined period, a coil disposed between the input output nodes, and a switch circuit configured to switch on and off to control current through the coil in response to comparison between the reference voltage and a voltage proportional to the output voltage.

Abstract: An output circuit including an input terminal; an output terminal; a PMOS transistor connected with a positive side of a power voltage and the output terminal; a NMOS transistor connected with a negative side of the power supply voltage and the output terminal; a first inverter, to which a gate voltage of the PMOS transistor is input and which exhibits hysteresis in threshold voltage; and a second inverter, to which a gate voltage of the NMOS transistor is input and which exhibits hysteresis in threshold voltage, wherein an OR logic signal of the input signal and a signal obtained by inverting an output signal from the second inverter is input to a gate of the PMOS transistor, and an AND logic signal of the input signal and a signal obtained by inverting an output signal from the first inverter is input to a gate of the NMOS transistor.

Abstract: A switching power supply circuit for generating an output voltage at an output node based on an input voltage at an input node includes a reference voltage generating circuit configured to generate a reference voltage such that during an initial start-up period of the reference voltage a voltage rise rate of the reference voltage within a first predetermined period from a start point of the initial start-up period and a voltage rise rate thereof within a second predetermined period immediately preceding an end point of the initial start-up period are smaller than a voltage rise rate thereof in a period between the first predetermined period and the second predetermined period, a coil disposed between the input output nodes, and a switch circuit configured to switch on and off to control current through the coil in response to comparison between the reference voltage and a voltage proportional to the output voltage.

Abstract: An electric power supply circuit includes a first switching element that turns on or off according to an external signal; an inductor capacitor circuit provided between the power supply and the load that charges or discharges electric power provided by the power supply according to the on or off state of the first switching element; a rectifier diode provided between the first switching element and the ground; a second switching element provided in parallel with the rectifier diode that turns on or off synchronously with the first switching element; and a depletion transistor that detects a direction of a current flowing through the inductor capacitor circuit based on a voltage detected across the second switching element to generate a detection result, and causes the second switching element to turn on or off according to the detection result.

Abstract: This patent specification describes a switching regulator which includes a step-up/step-down unit configured to generate an output voltage by stepping up or down an input voltage in accordance with a control signal, and a control unit configured to cause the step-up/step-down unit to perform the step-up or step-down operation.

Abstract: A power supply device includes a step-up circuit configured to supply a driving voltage to a load, a comparison circuit configured to compare an output voltage from the load with a reference voltage, and a control circuit configured to control the step-up circuit based on a comparison result generated by the comparison circuit. The step-up circuit includes multiple operation modes each outputting a given voltage not lower than a power source voltage. The control circuit controls the step-up circuit to operate in one of the multiple operation modes. The control circuit maintains a current operation mode of the step-up circuit until the output voltage from the load decrease to below the reference voltage and, when the output voltage from the load is less than the reference voltage, switches the operation mode to another operation mode to output a voltage higher than a voltage output in the current operation mode.

Abstract: An output circuit including an input terminal; an output terminal; a PMOS transistor connected with a positive side of a power voltage and the output terminal; a NMOS transistor connected with a negative side of the power supply voltage and the output terminal; a first inverter, to which a gate voltage of the PMOS transistor is input and which exhibits hysteresis in threshold voltage; and a second inverter, to which a gate voltage of the NMOS transistor is input and which exhibits hysteresis in threshold voltage, wherein an OR logic signal of the input signal and a signal obtained by inverting an output signal from the second inverter is input to a gate of the PMOS transistor, and an AND logic signal of the input signal and a signal obtained by inverting an output signal from the first inverter is input to a gate of the NMOS transistor.

Abstract: A power supply device includes a step-up circuit configured to supply a driving voltage to a load, a comparison circuit configured to compare an output voltage from the load with a reference voltage, and a control circuit configured to control the step-up circuit based on a comparison result generated by the comparison circuit. The step-up circuit includes multiple operation modes each outputting a given voltage not lower than a power source voltage. The control circuit controls the step-up circuit to operate in one of the multiple operation modes. The control circuit maintains a current operation mode of the step-up circuit until the output voltage from the load decrease to below the reference voltage and, when the output voltage from the load is less than the reference voltage, switches the operation mode to another operation mode to output a voltage higher than a voltage output in the current operation mode.

Abstract: An electric power supply circuit includes a first switching element that turns on or off according to an external signal; an inductor capacitor circuit provided between the power supply and the load that charges or discharges electric power provided by the power supply according to the on or off state of the first switching element; a rectifier diode provided between the first switching element and the ground; a second switching element provided in parallel with the rectifier diode that turns on or off synchronously with the first switching element; and a depression transistor that detects a direction of a current flowing through the inductor capacitor circuit based on a voltage detected across the second switching element to generate a detection result, and causes the second switching element to turn on or off according to the detection result.

Abstract: This patent specification describes a switching regulator which includes a step-up/step-down unit configured to generate an output voltage by stepping up or down an input voltage in accordance with a control signal, and a control unit configured to cause the step-up/step-down unit to perform the step-up or step-down operation.