Abstract: A DC-DC converter of a synchronous rectifier type, a control circuit thereof and control method thereof, facilitates detecting and interrupting negative inductor current IL with low power consumption, high accuracy and a simple configuration and facilitates improving the efficiency under a light load. An ON-period decision circuit determines whether an ON-period of the synchronous rectifier switch is too long or too short. An ON-period adjustment circuit generates a signal for adjusting the ON-period, during which the synchronous rectifier switch is ON, based on the decision of the ON-period decision part. A delay circuit adjusts the length of the delay, from the time when a signal changing the ON and OFF states of the synchronous rectifier switch changes to ON, to the time when the synchronous rectifier switch is forcibly turned off based on the adjusting signal.

Abstract: A synchronous switch uses body-control switches to control the polarity of the parasitic device, which can be used to reduce power consumption by the parasitic device in accordance with various operating conditions. A charge-supplying device (such as a capacitor) is coupled in series between the bulk node (of the synchronous switch) and a power node (such as Vout or ground). The charge-supplying device provides power to the bulk node of the switch during reverse recovery of the parasitic device to minimize recombination time. Minimizing recombination time allows the polarity of the parasitic device to be switched more quickly (especially under low operating voltage and/or heavy load conditions), which converses more power.

Abstract: A power supply includes a first switch to establish a first path to charge an output of the power supply by a voltage source, a second switch to establish a second path to discharge the output, and a third switch connected between the output and a capacitor. When to discharge the output, the third switch is turned on before the second switch turns on, to transfer a portion of energy on the output to the capacitor. When to charge the output, the third switch is turned on before the first switch turns on, to transfer a portion of the energy on the capacitor to the output.

Abstract: A switch-mode synchronous boost voltage regulator is disclosed that includes a boost voltage regulator and an active current modulator. The active current modulator detects a negative current flowing through the high-side switch during a light load condition. When the negative current is detected, the active current modulator is operable to maintain the high-side switch “on” in a linear mode and to limit the negative current to a predetermined current level.

Abstract: A power control system includes a switching power converter and a power factor correction (PFC) and output voltage controller. The PFC and output voltage controller provides a control signal to a switch to control power factor correction and regulate output voltage of the switching power converter. During a single period of the control signal, the PFC and output voltage controller determines the line input voltage, the output voltage, or both using a single feedback signal received from the switching power converter. The feedback signal is received from a switch node located between an inductor and the switch. The PFC and output voltage controller determines either the line input voltage or the output voltage, whichever was not determined from the feedback signal, using a second feedback signal received from either a PFC stage or a driver stage of the switching power converter.

Abstract: Circuit and method for controlling a high bridge circuit with increased efficiency is disclosed. Circuitry is provided outputting gating signals to a high side driver and a low side driver responsive to a time varying input signal. A frequency measurement circuit determines a high speed mode when the input signal is at a frequency above a threshold, and the gating signal to the high side driver is inhibited. When the input signal frequency is below the threshold, the low side driver and the high side driver gating signals switch alternately. In an exemplary implementation, the frequency measurement circuit is provided as two counters outputting signals to a decision circuit which controls the half bridge circuit. Methods are provided for efficiently providing gating signals to the drivers of a half bridge circuit based upon the frequency of the input signal.

Abstract: A circuit provides a voltage reference using very low power. It can also be used as a shut regulator for a quiescent current as low as 1.5 ?A. It includes a transconductance amplifier, a gain stage, and a power transistor. One embodiment of this invention utilizes a work function difference between p+ gate and n+ gate to generate a predetermined reference voltage. In another embodiment of this invention, the predetermined reference voltage can be pre-adjusted using gate materials with different work functions.

Abstract: A synchronous switching voltage regulator circuit is provided. After the first PWM pulse or at the end of a soft-start, a gradual transition is made from asynchronous rectification to fully synchronous rectification. The gradual transition to synchronous rectification is made by gradually increasing the time that the synchronous switch is enabled to be on.

Abstract: A torque control circuit includes a motor driving circuit, a motor operating current detection circuit, a reference voltage generation circuit, a maximum motor current setting circuit, a torque setting circuit, an information output circuit, a regulated-voltage power supply circuit, a motor operating temperature detection circuit, and a control circuit. The control circuit includes an integrated circuit to carry out functions of reading information detection sources, processing, and instruction for execution of torque control and output terminals of the reference voltage generation circuit, the maximum motor current setting circuit, the motor operating temperature detection circuit, and the motor impedance torque setting circuit are respectively connected to corresponding input terminals of the integrated circuit to carry out desired control of torque supplied to the impact tool.

Abstract: A method and apparatus for supplying a voltage in an information handling system. A modulated voltage signal output circuit linked to an amplitude control element. The amplitude control element linked to a voltage output circuit, the output circuit including one or more electrical energy-storage elements to receive an electrical current. The voltage output circuit having one or more electronic switches to alter the current passing to the energy-storage element(s) to provide a modulated voltage output.

Abstract: A system comprises a load and a voltage regulator. The voltage regulator is configured to select a gate drive signal from among a plurality of input voltages. The voltage regulator is configured to use the selected gate drive signal to turn on a power transistor to produce a regulated voltage for the load.

Abstract: A method to generate a substantially DC output having a voltage level different than a DC input, constituted of receiving a feedback signal representing at least one of the voltage level and the current level of the generated substantially DC output; relatively emphasizing the high frequency portion of the feedback signal; controlling the buck function of a cascaded buck-boost converter with a first switching signal having a first duty cycle, the first duty cycle being a first function of the received feedback signal responsive to said relatively emphasized high frequency portion; and controlling the boost function with a second switching signal having a second duty cycle, the second duty cycle being a second function of the received feedback signal, wherein the first switching signal and the second switching signal are continuously enabled to facilitate a continuous conduction mode.

Abstract: A controller (1) comprises a comparator (10) which compares an input signal (Vo) with a reference signal (Vr) to obtain an error signal (ER). An integrator (11) applies an integrating action on the error signal (ER) to obtain a control signal (ICO). The integrator (11) allows influencing the integrating action. A copy circuit (81) supplies a copy control signal (ICOC) being proportional to the control signal (ICO). A determination circuit (85) determines whether the copy control signal (ICOC) reaches a limit value (IMIN, IMAX). An influencing circuit (83) influences the integrating action to limit the control signal (ICO) when the copy control signal (ICOC) reaches the limit value (IMIN, IMAX).

Abstract: The invention relates to a driver device for a load (11), particularly an LED/OLED unit (12; 20, 22), comprising a shunting switch (30) parallel to the load, a control unit (14, 26) for controlling the shunting switch (30), an energy storage element (40) adapted to supply energy to at least the control unit (14, 26), and a recharge control circuitry (46) arranged in series with the energy storage element (40), the series connection of energy storage element (40) and recharge control circuitry (46) being provided parallel to the shunting switch (30), wherein said control unit (14, 26) is adapted to activate said recharge control circuitry (46) and to switch said shunting switch (30) off, when said energy storage element (40) is to be recharged. The invention also relates to a method of driving a load (11).

Abstract: A feed controller adopted to be included in a battery drive type device, the feed controller adopted to supply power to a predetermined load from a battery holder that obtains rated electromotive force from plural rated number of batteries having predetermined specification and connected in series while held by the battery holder, the feed controller includes: an outer casing attached to the battery holder in place of one of the plural batteries and having shape and size appropriate for being held by the battery holder; a converter unit disposed within the outer casing to receive voltage corresponding to the sum of the electromotive forces from the other batteries when the outer casing is held by the battery holder in place of the one battery and convert the supplied voltage to output voltage corresponding to the rated electromotive force; a switch unit inserted into a feed path for supplying the output from the converter unit to the predetermined load to open and close the feed path according to a feed contr

Abstract: A switching regulator for inputting a power source, supplying output power to an external circuit, and adjusting the output voltage to a target voltage, the switching regulator has a switching regulator circuit having first and second transistors, a feedback circuit that receives the output voltage, and outputs a control pulse signal at a frequency in accordance with the received output voltage; a PLL circuit unit having a PLL circuit, and a first control signal generating circuit that outputs the first control signal for controlling the first transistor; and a drive circuit that outputs a second control signal that controls the second transistor; and a control circuit that monitors the period of the PLL output pulse and the control pulse signal, and controls the ON and OFF timing of the second transistor when a difference of monitored periods.

Abstract: The synchronous rectifier MOSFET in a Buck or boost DC/DC converter is operated as a current source rather than being turned off, thereby reducing undesirable losses in efficiency, the generation of unwanted electrical and radiated noise, and numerous other potential problems, particularly when the converter is operating in a light-load condition.

Abstract: A voltage converter having four switches Q1, Q2, Q3, Q4, connected in series and operated in pairs in a complementary fashion. An input voltage is provided across the four switches. A middle capacitor is connected in parallel with two middle switches Q2, Q3. Voltage output is provided across switches Q3 and Q4 (i.e. at a midpoint of the four switches). Series-connected output capacitors can be connected in parallel with the set of four switches. The middle capacitor alone or in combination with parallel connected capacitors, when connected to the input voltage or output terminals functions as a capacitive voltage divider for voltage conversion and/or regulation with extremely high efficiency and which can provide either step-down or step-up function. Also, an output inductor can be provided as a perfecting feature to further increase efficiency. Alternatively, two of the four switches can be replaced with rectifying diodes.

Abstract: Converters that employ synchronous rectification, such as DC/DC converters, are disclosed. These converters can control their synchronous rectifiers to selectively block or pass a negative current from flowing in their output lines. Also disclosed are converters which can operate as slaves based on timing signals from other daisy-chained converters. Open-loop synchronous rectifier driving circuitry is further disclosed to allow converters to operate independently of any timing information from their output stages.

Abstract: A digital circuit implementing pulse width modulation controls power delivered in what one can model as a second order or higher order system. An exemplary control plant could embody a step-down switch mode power supply providing a precise sequence of voltages or currents to any of a variety of loads such as the core voltage of a semiconductor unique compared to its input/output ring voltage. One of several algorithms produce a specific predetermined sequence of pulses of varying width such that the voltage maintains maximally flat characteristics while the current delivered to the load from the system plant varies within a range bounded only by inductive element continuous conduction at the low power extreme and non-saturation of the inductor core at the high power extreme.

Abstract: A circuit arrangement for regulating the current in an on-board electric power supply system of a vehicle, with a controllable damping resistance, an energy accumulator and an electronic control unit. The damping resistance is adjustable to satisfy a control condition, such that generator current flowing through the control unit can be compensated by a counter-current originating from the energy accumulator and flowing through the damping resistance, having regard to a specified current limit value. In a method for controlling the circuit arrangement, generator current flowing through the control unit is compensated by a counter-current originating from the energy accumulator and flowing through the damping resistance, and the damping resistance is controlled, in such a manner, that a predetermined current limit value is taken into account.

Abstract: In general, in one aspect, the disclosure describes a voltage regulator (VR) that includes a first amplifier receiving a first reference voltage and a feedback voltage as inputs. A second amplifier receiving a second reference voltage and an output of the first amplifier as inputs. A drive component (e.g., transistor(s)) coupled to the second amplifier to drive current to an output based on an output of the second amplifier. A shunt component (e.g., transistor(s)) coupled to the first amplifier to shunt current from the output based on the output of the first amplifier. Current variations in the shunt component are controlled.

Abstract: Many power converters operate with an input voltage that has a normal range of voltage that is quite narrow, for example, commercial ac voltage or from a regulated upstream power converter. To accommodate transient and abnormal conditions, power converters are often designed for a wide range of input voltage, which seriously compromises their efficiency at nominal voltage. This invention teaches a power converter that is optimized for the normal operating voltage range. A variable dc-dc transformer and a buck derived modulator are used in series. The buck circuit is most efficient at high duty cycles, and for normal input voltage, the buck converter may be saturated at 100 percent duty cycle. The duty cycle of the buck converter is reduced to accommodate over voltage transients. Efficiency is compromised, but the duration is short, so that is acceptable. For normal and under voltage conditions, the effective turns ratio of the variable dc-dc transformer is modulated to effect control.

Abstract: The present invention discloses a switching regulator, which comprises: a first and a second transistors electrically connected with each other; a pulse width modulation control circuit for turning ON and OFF the first transistor and turning ON the second transistor; and a current source control circuit for controlling the second transistor so that the second transistor becomes a current source, wherein the second transistor has only two states: ON and low current, and wherein when the first transistor is ON, the second transistor is in the low current state; and when the first transistor is OFF, the second transistor is ON or in the low current state.

Abstract: The method of the invention in one aspect involves electronic power control by varying the amplitude of an electrical power supply voltage, independent of frequency, whereby the output frequency will always be the same as the input frequency. An electrical circuit apparatus for accomplishing this function in a specific embodiment is also disclosed herein. The specific circuitry of this aspect of the invention uses eight solid state switches, such as IGBT's, eight diodes, an inductor, input and output filters and novel controlling circuitry. The controller apparatus and methods of the invention may be used to implement all otherwise conventional converter types, buck, boost, and inverting (and duals of these) versions to obtain different regulating characteristics, including galvanic isolation of the output from the input.

Abstract: A power generating circuit includes a rectifying module and a tuning module. The rectifying module is operably coupled to convert a radio frequency (RF) signal into a voltage. The tuning module is operably coupled to tune the rectifying module in accordance with the RF signal.

Abstract: A two-wire load control device, such as a dimmer, is operable to control the amount of power delivered to an electrical load, such as a magnetic low-voltage (MLV) load, and comprises a bidirectional semiconductor switch, a timing circuit, a trigger circuit having a variable voltage threshold, and a clamp circuit. When a timing voltage signal of the timing circuit exceeds an initial magnitude of the variable voltage threshold, the trigger circuit is operable to render the semiconductor switch conductive, reduce the timing voltage signal to a predetermined magnitude less than the initial magnitude, and to increase the variable voltage threshold to a second magnitude greater than the first magnitude. The clamp circuit limits the magnitude of the timing voltage signal to a clamp magnitude between the initial magnitude and the second magnitude, thereby preventing the timing voltage signal from exceeding the second magnitude.

Abstract: A circuit provides a voltage reference using very low power. It can also be used as a shut regulator for a quiescent current as low as 1.5 ?A. It includes a transconductance amplifier, a gain stage, and a power transistor. One embodiment of this invention utilizes a work function difference between p+ gate and n+ gate to generate a predetermined reference voltage. In another embodiment of this invention, the predetermined reference voltage can be pre-adjusted using gate materials with different work functions.

Abstract: A clamp circuit comprises a first transistor, a second transistor and a voltage-dividing circuit. The first transistor has a source terminal connected to a reference voltage, and has a drain terminal grounded through a current source. The second transistor has a gate terminal connected to the gate and drain terminals of the first transistor, and has a drain terminal grounded. The voltage-dividing circuit is connected to an input voltage end, an output voltage end and a source terminal of the second transistor for providing a clamping voltage.

Abstract: An electronic power unit includes first and second MOS transistors and a digital control circuit. The first MOS transistor applies a voltage to the load. The second MOS transistor remains on while the first MOS transistor remains off and rectifies the current flowing in the load. The digital control circuit turns on the first transistor upon lapse of a first time interval from the time the second MOS transistor is turned off. The digital control circuit turns on the second MOS transistor upon lapse of a second time interval from the time the first MOS transistor is turned off. The digital control circuit controls the on-period of the first MOS transistor so that the voltage applied to the load is constant in a discontinuous conduction mode. The digital control circuit determines, while the voltage applied to the load is constant, an optimal value of the first time from the duty.

Abstract: A modular power distribution system comprises a chassis; and a backplane including a power input, and a plurality of module connection locations. A plurality of modules are mounted in the chassis, each module mounted to one of the module connection locations. Each module includes: (i) an OR-ing diode; (ii) a circuit protection device; (iii) a microprocessor controlling the circuit protection device; and (iv) a power output connection location. A circuit option switch is located on each module for setting the current limits for each module. A control module is provided connected to the backplane.

Abstract: A power converter includes an inductor, first through fourth switches, and a control device. The first switch is coupled between a first end of the inductor and ground, the second switch is coupled between an input end and a second end of the inductor, the third switch is coupled between the first end of the inductor and a first output end, and the fourth switch is coupled between the second end of the inductor and a second output end. The control device charges the inductor by turning on the first and second switches. Based on output voltages of the first and second output ends, the control device determines whether the first and second output ends are to be charged or discharged. The second and third switches are turned on for charging the first output end, or the first and fourth switches are turned on for discharging the second output end.

Abstract: A power converter has simple coupled inductor circuit process the power and drive the semiconductor switch perfectly to reduce the power loss and eliminate the needs of high circuit complexity controller, improve the conversion efficiency and reduce the component counts to reach low cost and high reliability at one time.

Abstract: A power supply for providing an internal supply voltage, the power supply including a current source configured to provide an internal supply voltage directly from its output, and a high speed internal supply voltage shunt, which is coupled to the current source output.

Abstract: A system and method for a bridgeless power supply is disclosed. The bridgeless power supply includes a digital control module that controls a first switch, a second switch, and a transistor, thereby the bridgeless power supply rectifies an alternating current (AC) variable input voltage and regulates a direct current (DC) output voltage. The digital control module applies a first and second control signal to the first and second switches thereby rectifying and regulating the AC variable input voltage. Additionally, the digital control module provides a high frequency and constant duty cycle third control signal to the transistor in series with an output transformer of the bridgeless power supply device, to assure primary-to-secondary isolation.

Abstract: A synchronous rectifying type switching regulator control circuit has a first reference voltage circuit that receives a soft start signal from a soft start circuit and outputs a first reference voltage. An error amplifying circuit amplifies a difference of the first reference voltage and a divided voltage from a voltage dividing circuit and outputs an error voltage Verr. A first comparing circuit compares a triangular wave from an oscillator with the error voltage Verr and outputs an output pulse Vcomp. A second comparing circuit compares a second reference voltage from a second reference voltage circuit with the error voltage Verr and outputs a voltage ERRcomp. A logic circuit receives the soft start signal, the output pulse Vcomp, and the voltage ERRcomp and outputs a voltage Vcomp2. The logic circuit outputs the output pulse Vcomp when the error voltage Verr is higher than the second reference voltage during a soft start period.

Abstract: A power supply circuit comprising a charge storage capacitor having a first capacitor terminal adapted to provide a power supply voltage of the power supply and a second capacitor terminal coupled to a circuit common; a first switching device having a first switching terminal adapted to be connected to a voltage source, a second switching terminal operatively coupled to the first capacitor terminal of the charge storage capacitor, and a control terminal, the first switching device characterized by a control terminal switching threshold voltage, the first switching device adapted to conduct a charging current from the first switching terminal to the second switching terminal and into the charge storage capacitor; a control circuit controlling an on/off operation of the first switching device whereby the first switching device is operable to turn on when the magnitude of the voltage of the voltage source is below a predetermined level and turn off when the magnitude of the voltage of the voltage source is above

Abstract: The present invention discloses an anti-ringing switching regulator, comprising a variable resistor, a transistor, and an inductor electrically connected to a common node, in which the variable resistor is electrically connected with an input voltage, the transistor is electrically connected to ground, and the inductor is electrically connected to an output terminal, whereby the input voltage is converted and transmitted to the output terminal according to the resistance variation of the variable resistor and the switching of the transistor.

Abstract: In an embodiment of the present invention there is provided a device for providing a control voltage that is substantially equivalent to a reference voltage used by a power supply. The device includes a first electronic circuit that is arranged to be connected to a ground via a resistor and to produce a supplementary voltage that is dependant on a resistance of the resistor. The device also includes a second electronic circuit that is arranged to present a resistance to a current in order to provide the control voltage and to receive an output voltage of the power supply and the supplementary voltage to effect the current.

Abstract: According to the present invention, a semiconductor device is provided wherein a stepdown-type DC-DC converter includes a first off detection circuit, a second off detection circuit, a capacitor, a capacitor, a diode, inverters, an inductor, a first level shift circuit, a second level shift circuit, a third level shift circuit, a 2-input NAND circuit, a 2-input NAND circuit, a high-side N-channel power MOS transistor and a low-side N-channel power MOS transistor. The first off detection circuit and the second off detection circuit reduce fall times of the gates of the N-channel power MOS transistors, thereby reducing dead time.

Abstract: A synchronous rectification switching regulator includes a reverse current prevention circuit unit that detects a symptom of a reverse current flowing in a direction from an output terminal to a second switching element or a generation of the reverse current based on a voltage of a connecting portion for connecting the second switching element with a third switching element. The reverse current prevention circuit unit turns off the third switching element to interrupt the reverse current when the reverse current prevention circuit unit detects the symptom or the generation of the reverse current.

Abstract: A power supply step-down circuit is adapted to a semiconductor integrated circuit having a first operation mode and a second operation mode having a smaller current consumption than the first operation mode. The power supply step-down circuit includes a first step-down circuit activated only during the first operation mode to step down an input power supply voltage to an output voltage, a second step-down circuit provided integrally with the first step-down circuit and activated only during the second operation mode to step down the input power supply voltage to an output voltage, an output terminal to output the output voltage of one of the first and second step-down circuits that is activated, and an output circuit to maintain the output voltage that is output from the output terminal lower than the input power supply voltage for a first predetermined time when an operation mode makes a transition from the first operation mode to the second operation mode.

Abstract: A light emitting component can include a substrate, a light emitting device supported by the substrate, wherein the light-emitting device has first and second terminals, and a switching element supported by the substrate and having first and second terminals electrically connected to the first and second terminals of the light-emitting device, respectively. The switching element is configured to, at least in part, divert at least some current away from the light emitting device when the switching element is in a closed state. An electrical connection between the first terminal of the switching element and the first terminal of the light emitting device can have a length of less than 5 cm (e.g., less than 2 cm, less than 1 cm, less than 5 mm, less than 1 mm). A current regulator may be supported by a second substrate and can supply current to the light emitting device.

Abstract: A power control system includes a power reduction module operable to reduce power to a connected load, a switching module operable to selectively transfer power directly to the load or to the power reduction module, a harmonic reduction module connected to an output of the power reduction module for reducing signal harmonics from power transferred to the load, a controller linked to the switching module to provide control signals, a resistor coupled between the switching module and the power reduction module, and a resistor voltage monitor coupled between the switching module and the resistor, wherein the resistor voltage monitor measures a voltage across the resistor and sends voltage measurement data to the controller. A method for a power control system to reduce power consumption of a load is also disclosed.

Abstract: The method of the invention in one aspect involves electronic power control by varying the amplitude of an electrical power supply voltage, independent of frequency, whereby the output frequency will always be the same as the input frequency. An electrical circuit apparatus for accomplishing this function in a specific embodiment is also disclosed herein. The specific circuitry of this aspect of the invention uses eight solid state switches, such as IGBT's, eight diodes, an inductor, input and output filters and novel controlling circuitry. The controller apparatus and methods of the invention may be used to implement all otherwise conventional converter types, buck, boost, and inverting (and duals of these) versions to obtain different regulating characteristics, including galvanic isolation of the output from the input.

Abstract: An adjustable shunt regulator comprises an operational amplifier, a transistor having a base terminal operatively connected to the output of the operational amplifier, a diode operatively connected in parallel with the transistor, and a voltage reference connected to the inverting input of the operational amplifier. The operational amplifier provides an output signal at the output thereof that corresponds to a difference between an input signal applied to the non-inverting input and the voltage reference. The output signal controls a voltage between the collector and emitter. A current source is operatively connected to the inverting input of the operational amplifier, and a capacitor is operatively connected to the inverting input of the operational amplifier in parallel with voltage reference. Upon a start-up condition of the shunt regulator, the capacitor is charged by current supplied by the current source causing the voltage reference to be limited to a charge voltage of the capacitor.

Abstract: A buck or boost converter, which includes a first inductor, a controlled switch, a main diode, and an output capacitor, also includes a snubber circuit to reduce losses. The snubber circuit includes a second inductor in a path in series with the switch and main diode of the converter, a series-connected resistor and diode connected directly in parallel with the second inductor, and a capacitance in parallel with the main diode and which can be constituted partly or entirely by parasitic capacitance of the main diode.

Abstract: A pair of upper and lower semiconductor switching elements can switch between the conductive state and the non-conductive state when control voltages vary. A controller controls the levels of the control voltages to alternately turn on the upper and lower semiconductor switching elements. The controller controls the absolute value of the second control voltage of the lower semiconductor switching element so as to reach a mean voltage before and after the time of transition between the conductive state and the non-conductive state of the upper semiconductor switching element. The mean voltage is lower than the absolute value of a threshold voltage and higher than a reference voltage.

Abstract: A supply power can be fed in at a circuit arrangement for supplying power to, and clocking, clocked loads. The circuit arrangement provides a clock signal at a frequency and a supply voltage, the frequency and/or the supply voltage being able to be controlled by the circuit arrangement in such a manner that a power tapped off at the output and the supply power fed in are in a predefined relationship.

Abstract: A dropper type regulator of the invention, in which a semiconductor device is connected in series between a DC power supply and a voltage output terminal, extracts a second voltage from the first voltage of the DC power supply; when the driving voltage of the semiconductor device is detected as being larger than a preset first threshold value, the voltage difference occurring between the input and output terminals of the semiconductor device is detected, and when this voltage difference is detected as being larger than a second threshold value, an overload protection circuit performs overload protection.