Abstract: A power supply circuit relating to the present invention comprises a differential amplifier for feeding out a voltage as a control voltage in accordance with a difference between a feedback voltage commensurate with an output voltage and a reference voltage, an output current control element for feeding out an output current in accordance with the control voltage fed thereto from the differential amplifier, an output line by way of which the output current is supplied to a load, a feedback line by way of which a voltage on the output line is fed back as the feedback voltage to the differential amplifier, the feedback line connected to the output line, and a clamping circuit for maintaining the control voltage so as not drop below a predetermined value.

Abstract: A power supply circuit relating to the present invention comprises a differential amplifier for feeding out a voltage as a control voltage in accordance with a difference between a feedback voltage commensurate with an output voltage and a reference voltage, an output current control element for feeding out an output current in accordance with the control voltage fed thereto from the differential amplifier, an output line by way of which the output current is supplied to a load, a feedback line by way of which a voltage on the output line is fed back as the feedback voltage to the differential amplifier, the feedback line connected to the output line, and a sink current generating circuit, connected between the feedback line and ground, for generating a sink current by which the control voltage fed to the output current control element is raised to a predetermined value.

Abstract: A switching power supply unit generates a pulse signal having a duty factor based on the voltage associated with the difference between a reference voltage and the output voltage of the unit, and the voltage associated with the current flowing through a smoothing coil. Upon receipt of the pulse signal and a light-load determination signal, a delay-control unit of the power supply unit outputs as an instruction signal supplied to the switching circuit the pulse signal as it is when the light-load determination signal indicates that the load is not light, but otherwise outputs the pulse signal after delaying and widening the pulse width thereof. Thus, when the load is light, the switching power supply unit may hold its switching frequency substantially low and constant without rendering the frequency bursting discontinuously.

Abstract: In a power supply apparatus that is so configured as to produce from an input voltage an output voltage Vo within a predetermined permissible variation range, the output voltage Vo is so controlled as to decrease within the permissible variation range as the output current Io increases.

Abstract: A constant voltage generating circuit has a reference voltage generating circuit of which the output voltage is controlled to be a constant voltage when the output voltage has risen, with an increase in the input supply voltage, to reach a predetermined voltage and that outputs the constant voltage as a reference voltage, a first transistor that turns on when the output voltage reaches the predetermined voltage to control the constant voltage output from the reference voltage generating circuit, a second transistor that is so connected that, when the first transistor turns on, a current proportional to the current flowing through the first transistor flows through the second transistor, and a signal output circuit that detects the current flowing through the second transistor to output a detection signal indicating that the constant voltage is being output.

Abstract: In a semiconductor integrated circuit device, a reference voltage is connected to one input terminal of an amplifier, and the voltage appearing on the output side is divided by a plurality of resistors and is negatively fed back to the other input terminal of the amplifier to control the output voltage. Here, according to an input code fed to the semiconductor integrated circuit device, switching devices are turned on or off correspondingly to vary how the resistors are connected and thereby control the voltage division factor. Thus, the output voltage is set according to the input code.

Abstract: A DC/DC converter produces from an input voltage a desired output voltage by first finding the error voltage between the output voltage and a first reference voltage and then controlling the output current according to the differential voltage between the error voltage and a second reference voltage. Used as the first reference voltage is whichever of a variable reference voltage and a first constant reference voltage is lower, and used as the second reference voltage is whichever of the variable reference voltage and a second constant reference voltage is lower. With this circuit configuration, an overshoot or undershoot in the output voltage can be prevented or reduced.

Abstract: A switching device driving apparatus has a driver for controlling, according to an input signal, the on/off states of a pair of field-effect transistors connected in series between a first supply voltage and a second supply voltage lower than the first supply voltage, and a detector for detecting the on/off states of body diodes attached respectively to the field-effect transistors. Only after either of the body diodes is detected being on are the field-effect transistors respectively turned on to produce an output corresponding to the input signal. This makes it possible to securely prevent the two FETs from being turned on simultaneously independently of their characteristics and type.

Abstract: The power supply unit is provided with a power supply circuit adapted to generate an output voltage in accord with an instruction voltage, an output condenser Co connected to the output end of the power supply circuit, and an auxiliary output voltage setting circuit adapted to compare the instruction voltage and the output voltage and to cause the output condenser to discharge its electric charge when the instruction voltage becomes lower than the output voltage. Because of the auxiliary output voltage setting circuit, the power supply circuit quickly generates an output voltage in accord with the instruction voltage if the instruction voltage is lowered.

Abstract: A switching power supply unit generates a pulse signal having a duty factor based on the voltage associated with the difference between a reference voltage and the output voltage of the unit, and the voltage associated with the current flowing through a smoothing coil. Upon receipt of the pulse signal and a light-load determination signal, a delay-control unit of the power supply unit outputs as an instruction signal supplied to the switching circuit the pulse signal as it is when the light-load determination signal indicates that the load is not light, but otherwise outputs the pulse signal after delaying and widening the pulse width thereof. Thus, when the load is light, the switching power supply unit may hold its switching frequency substantially low and constant without rendering the frequency bursting discontinuously.

Abstract: In a semiconductor integrated circuit device, a reference voltage is connected to one input terminal of an amplifier, and the voltage appearing on the output side is divided by a plurality of resistors and is negatively fed back to the other input terminal of the amplifier to control the output voltage. Here, according to an input code fed to the semiconductor integrated circuit device, switching devices are turned on or off correspondingly to vary how the resistors are connected and thereby control the voltage division factor. Thus, the output voltage is set according to the input code.

Abstract: In a multiphase DC/DC converter having a plurality of DC/DC converters, to prevent faults in the circuit and the circuit elements constituting it even when the balance of current limiting operation among the individual DC/DC converters is disturbed due to individual and temperature-related variations in the characteristics of the circuit elements, the output currents of the individual DC/DC converters are detected and added together, and are limited individually so that their sum does not exceed a predetermined level of current.

Abstract: To a plurality of terminals are connected, one to one, a plurality of current mirror circuits each having a first load portion through which a first current flows when an overvoltage is applied and a second load portion through which a second current proportional to the first current flows. The first load portion of the current mirror circuit connected to one of the plurality of terminals is shared as the first load portions of the current mirror circuits connected to the others of the plurality of terminals. The shared first load portion includes an overvoltage protection circuit. The second load portions of the current mirror circuits connected to the plurality of terminals each include an overvoltage detection circuit for detecting the second current.

Abstract: A constant voltage generating circuit has a reference voltage generating circuit of which the output voltage is controlled to be a constant voltage when the output voltage has risen, with an increase in the input supply voltage, to reach a predetermined voltage and that outputs the constant voltage as a reference voltage, a first transistor that turns on when the output voltage reaches the predetermined voltage to control the constant voltage output from the reference voltage generating circuit, a second transistor that is so connected that, when the first transistor turns on, a current proportional to the current flowing through the first transistor flows through the second transistor, and a signal output circuit that detects the current flowing through the second transistor to output a detection signal indicating that the constant voltage is being output.

Abstract: A power supply device has a reference voltage generator for generating a reference voltage, a monitor voltage generator for generating a monitor voltage that varies according to an output voltage, an output controller for producing the output voltage from an input voltage in such a way that the monitor voltage is kept equal to the reference voltage and then supplying the output voltage to a load, and a reference voltage adjuster for varying the reference voltage according to the monitor voltage. This makes it possible to reduce, with a simple configuration, variation in the output voltage resulting from variation in the power source or the load.