Abstract: A low drop-out regulator is disclosed. An unregulated DC input terminal receives an input voltage. A pass circuit is coupled between the unregulated DC input terminal and a regulated DC output terminal for supplying a power to the regulated DC output terminal. An amplifying circuit controls the pass circuit for providing a constant voltage or/and a constant current in response to an output voltage or/and an output current.

Abstract: A low dropout (LDO) voltage regulator includes a scaling amplifier for receiving a bandgap voltage, Vbg, and outputting a scaled Vbg. A reference MOSFET device is included for reducing the scaled Vbg by a first voltage Vgs formed across gate and source nodes of the reference MOSFET device. This forms a reduced level of the scaled Vbg. An RC network filters the reduced level of the scaled Vbg and outputs a filtered voltage. An output buffer is included for receiving and increasing the filtered voltage by a second voltage Vgs in order to recover the scaled Vbg. The scaled Vbg is used as the desired regulated voltage output. The second voltage Vgs, which is produced by the output buffer, is equal to the first voltage Vgs, which is produced by the reference MOSFET device.

Abstract: The present invention relates to a low dropout regulator, and more particularly to a low dropout regulator without load capacitor and ESR (equivalent series resistance) designed in response to the discharge curve of a Li-ion battery, includes an input terminal, a reference circuit, a power transfer element, a level regulating device, a regulating circuit, and a first N-type MOSFET. The regulating circuit detects a load change at an output terminal, amplifies the load change, and couples it to the level regulating device. The level regulating device receives and boosts a received signal and transmits the received signal to the power transfer element, so as to achieve the effect of controlling the power of a power supply.

Abstract: A constant-voltage power supply circuit includes a first transistor connected between a power supply terminal and an output terminal. The constant-voltage power supply circuit includes a voltage divider circuit including a first resistor having a first end connected to the output terminal and a second resistor having a first end connected to a second end of the first resistor and a second end connected to ground. The constant-voltage power supply circuit includes an output voltage control amplifier that compares the divided voltage and a reference voltage and controls a voltage of a control terminal of the first transistor. The constant-voltage power supply circuit includes a current-limiting characteristic control circuit that controls the voltage of the control terminal of the first transistor according to the divided voltage and an output current.

Abstract: An apparatus and method are provided for controlling circuit resistance values used for detection of a device in an inline powered system. The system comprises a source device, either a current source or a voltage source, associated with an inline power device. The system also comprises a resistance control circuit comprising a transistor having an emitter, a base and a collector, and a first resistor coupled between the emitter and the collector. In response to the resistance control circuit receiving a relatively low current from the source device, the transistor is configured to be in an off state so that current from the source device flows through the first resistor have a value selected in order to maintain a sufficient resistance during an inline power device detection mode.

Abstract: Provided is a voltage regulator having low current consumption, which is capable of preventing a reverse current from flowing thereto from an output terminal (122), irrespective of a magnitude of a voltage of a VDD terminal (121). The voltage regulator has a circuit configuration in which voltage dividing resistors are not used for a comparator circuit for comparing the voltage of the VDD terminal (121) with a voltage of the output terminal (122), to thereby achieve lower current consumption.

Abstract: A regulator for providing a low dropout voltage at an output node of the regulator is provided. An amplifier has a non-inverting input terminal for receiving an input voltage, an inverting input terminal and an output terminal. A first resistor is coupled between a ground and the inverting input terminal of the amplifier. A second resistor is coupled to the inverting input terminal of the amplifier. A first transistor is coupled between a voltage source and the second resistor. A current source coupled between the voltage source and a gate of the first transistor provides a bias current. A second transistor coupled between the first transistor and a current mirror has a gate coupled to the output terminal of the amplifier. The first and second transistors are different type MOS transistors. The replica unit generates the low dropout voltage according to a voltage of the output terminal of the amplifier.

Abstract: A voltage regulator controls a regulated output voltage (Vout) by feeding it back to a differential input stage (13) receiving a reference voltage (Vref) and applying an output (3) to a control electrode of a follower transistor (M4) that is coupled to an output stage (15) which generates the output voltage (Vout). The output stage operates pull-up (M7B) and pull-down (M5B) transistors in response to a signal (6A) produced by the follower transistor (M4) during normal regulation operation, and provides fast settling of the output voltage by turning on a transient pull-up transistor (M7A) or transient pull-down transistor (M5A) in response to the signal (6A) produced by the follower transistor (M4) during a fast increasing or decreasing transition, respectively, of the load current (IL). A filtering resistor (RFLT) is coupled between the output voltage and a common electrode of the transient pull-up and pull down transistors.

Abstract: Method and apparatus to provide lambda correction of a current foldback circuit using a regulator including a current foldback circuit are disclosed herein.

Abstract: In one embodiment, the current source arrangement comprises a current source (B), that has two output terminals (102, 103) and a control input (101) to be supplied with a control voltage (Vgs) and is set up to provide a current (I) as a function of a voltage (Vds) at the output terminals (102, 103) and the control voltage (Vgs), an operating point adjustment unit (E) that is supplied with an actual value (Vi) proportional to an actual value of the current (I) and is set up to provide the control voltage (Vgs) as a function of the actual value (Vi) and a predetermined target value (Iz) of the current (I), and a comparison unit (A) coupled to the control input (101) of the current source (B) for providing a monitoring signal (100), wherein the monitoring signal (100) is provided as a function of a predetermined limit voltage (VG) and the control voltage (Vgs). A method for operating a current source arrangement is also specified.

Abstract: A three-phase electric motor of a compressor receives first, second, and third phases from a three-phase power supply. A method for protecting the motor includes, using a line break protector, disconnecting the motor from only the first phase in response to a temperature being greater than a predetermined temperature threshold. The method also includes measuring a first current flowing through the line break protector, and determining a current value based on the first current independent of current in the second and third phases. The method further includes disconnecting the motor from the first, second, and third phases in response to the current value being less than or equal to a predetermined threshold.

Abstract: A voltage regulator circuit and a method for operating the voltage regulator circuit are described. In one embodiment, a voltage regulator circuit includes an input terminal to receive an input signal from a power interface, an output terminal to output an output signal using the input signal, an output voltage monitor circuit configured to compare the voltage of the output signal with a predetermined voltage threshold, and a current limit circuit configured to limit current flowing on a path from the input terminal to the output terminal to a transient current limit level. The transient current limit level is lower than a predefined current limit threshold of the power interface. Other embodiments are also described.

Abstract: An amplifier drives the gate of a master source follower and of at least one slave source follower to form a low-dropout (LDO) regulator. Alternatively, a charge pump drives the master source follower to form the regulator. Additional slave source followers may be used in conjunction with the charge pump and the master source follower to improve the regulator performance.

Abstract: A first current corresponding to the drain-to-source voltage of a power MOSFET can pass through an FET; and a second current corresponding to a constant voltage can pass through an FET; a third current corresponding to the difference determined by subtracting the first current from the second current can pass into threshold setting resistors from the connecting point between FETs. Consequently, divided voltages at the connecting points between the threshold setting resistors varies directly with a voltage corresponding to the difference determined by subtracting the drain-to-source voltage of the power MOSFET from the constant voltage.

Abstract: In one embodiment, a method of forming a power supply controller may include configuring the power supply controller to control a pass transistor to form an output current responsively to a control signal and independently of the value of the output voltage until the control signal is less than a deviation from a desired value of the output voltage.

Abstract: An integrated circuit (IC) device is provided that includes at least one internal voltage regulator arranged to receive a voltage supply signal at a first input thereof, receive a control signal at a second input thereof, regulate the received voltage supply signal in accordance with the received control signal, and provide a regulated voltage supply signal at an output thereof. The IC device further includes at least one voltage regulation power control module operably coupled to the second input of the at least one internal voltage regulator and arranged to provide the control signal thereto. The voltage regulation power control module is further arranged to receive at least one IC device conditional indication, and generate the control signal for the at least one internal voltage regulator based at least partly on an available thermal power budget for the IC device corresponding to the at least one IC device conditional indication.

Abstract: A voltage regulator circuit comprises active and standby amplifiers, first and second transistors, and a capacitor. The active amplifier has a negative input connected to a first reference voltage, and the standby amplifier has a negative input connected to a second reference voltage. The first reference voltage is greater than the second reference voltage. The first transistor has a gate connected to an output of the active amplifier and a drain connected to a voltage regulated output, and the second transistor has a gate connected to an output of the standby amplifier and a drain connected to the voltage regulated output. The capacitor is connected between a chip enable signal and the voltage regulated output.

Abstract: An RF switch circuit and method for switching RF signals that may be fabricated using common integrated circuit materials such as silicon, particularly using insulating substrate technologies. The RF switch includes switching and shunting transistor groupings to alternatively couple RF input signals to a common RF node, each controlled by a switching control voltage (SW) or its inverse (SW_), which are approximately symmetrical about ground. The transistor groupings each comprise one or more insulating gate FET transistors connected together in a “stacked” series channel configuration, which increases the breakdown voltage across the series connected transistors and improves RF switch compression. A fully integrated RF switch is described including control logic and a negative voltage generator with the RF switch elements. In one embodiment, the fully integrated RF switch includes an oscillator, a charge pump, CMOS logic circuitry, level-shifting and voltage divider circuits, and an RF buffer circuit.

Abstract: A semiconductor device is disclosed. The semiconductor device includes a switching signal generating circuit formed of a PMOS transistor, a resistor, and inverters which outputs an internal switching signal for switching an operating mode between a first operating mode and a second operating mode when an operating state satisfies a predetermined condition, a mode selection pad to which an external switching signal capable of selecting the first operating mode is input in priority to the internal switching signal, and a switching circuit formed of an OR circuit which switches the operating mode between the first operating mode and the second operating mode based on the external switching signal or the internal switching signal. An output from the switching signal generating circuit is input to the mode selection pad via a trimming fuse.

Abstract: A voltage regulator includes a regulator input connected to a reference voltage; a regulator output that outputs a regulated voltage to an electrical load; a first loop, the first loop configured to receive the reference voltage, the first loop outputting a bias voltage; a second loop, the second loop configured to receive the bias voltage as an input; and a bias voltage capacitor connected to a node between the first loop and the second loop.

Abstract: System and method for reducing power consumption during peak demand period is disclosed. A consumption unit comprises a power limiter. An AC power limiter converts a portion of AC power into heat and generates an output for a temperature sensor. A comparator has one of the inputs as the output of the temperature sensor and another input as a reference generated by a controller. A feedback loop is established by connecting output of the comparator to secondary winding of a power transformer through a switch. A DC power limiter is also disclosed.

Abstract: A voltage regulator includes a driver transistor, a feedback voltage generator, a reference voltage generator, a first differential amplifier, and a differential gain controller. The driver transistor is connected between input and output terminals to conduct a current therethrough according to a control signal applied to a gate terminal thereof. The feedback voltage generator is connected to the output terminal to generate a feedback voltage. The reference voltage generator generates a reference voltage. The first differential amplifier has an output thereof connected to the gate terminal of the driver transistor, and a pair of differential inputs thereof connected to the feedback voltage generator and the reference voltage generator, respectively, to generate the control signal at the output thereof. The differential gain controller is connected to the output of the first differential amplifier to control the differential gain according to a difference between the input and output voltages.

Abstract: A power regulator for converting an input voltage to an output voltage includes an error amplifier, a start-up circuit, and a pass device. The error amplifier is powered by the output voltage and provides a control current according to a difference between a reference signal and a feedback signal indicative of the output voltage. The start-up circuit is powered by the input voltage and provides a start-up current. The pass device receives the input voltage, provides the output voltage at an output terminal of the power regulator, generates an output current flowing through the output terminal according to the start-up current during a start-up duration of the power regulator, and generates the output current through the output terminal according to the control current during a normal operation of the power regulator.

Abstract: A DC voltage converter, comprising: a multi-ratio capacitive converter; a linear voltage regulator in series with the multi-ratio capacitive converter; and a controller; the controller arranged to control the ratio of the multi-ratio capacitive converter dependent upon the voltage difference across the linear voltage regulator.

Abstract: In a low drop out (LDO) regulator and a semiconductor device including the LDO regulator, the LDO regulator regulates a power supply voltage and applies the regulated power supply voltage to a load. The LDO regulator comprises: an output node connected to the load; a pass transistor that applies a power supply voltage to the output node; and a controller that generates a load enable signal enabling the load by delaying a regulator enable signal by a first delay time, and that increases a gate voltage of the pass transistor after receiving the regulator enable signal to thereby reduce a current flowing through the pass transistor.

Abstract: A digital pulse controller uses digital logic to send pulses to a high side and low side switches of a switch-mode power supply converter. The digital logic uses a pulse frequency mode which includes a frequency targeting mode and an ultrasonic mode. The frequency targeting mode dynamically adjusts the size of the pulses in order to achieve a switching frequency within a desired band. The ultrasonic mode is switched into when the frequency of the pulses are at or below a threshold and the time of the pulses reaches a minimum threshold.

Abstract: High bandwidth, low noise switching power supply operating in quasi-resonant mode for filtering switching harmonic noise, while providing a fast control bandwidth and power at high efficiency. The power supply has an LCL tank defining a resonance period Ttank, and a switching circuit regulation loop for turning on its switching circuit for on-time tON commencing at a time based on a state of regulation of the power supply. A switching capacitor current sensor triggers the switching circuit to turn off at the end of the resonance period Ttank, whereupon the switching and output inductors enter a discharging phase for a period not related to resonance period Ttank. “Quasi-resonant” operation, where the power supply is in resonant mode during on time tON and not in resonant mode during off time tOFF ensures that the output inductor filters the switching harmonic noise of the switching circuit.

Abstract: A method and circuits to limit the output load current of a current driven LDO voltage regulator are disclosed. The current through a second pass transistor, being in parallel to a first pass transistor and being a fraction of the current through the first pass transistor is measured and compared with a reference current. In case the current through the second pass transistor is larger than this reference current the current through the gates of both pass devices is reduced and thus the output load current of the voltage regulator is limited.

Abstract: A power supply control device includes a switching regulator, a linear regulator, a switching unit, a consumed current detection unit, a current determination unit, and a power determination unit. The consumed current detection unit detects a consumed current of the regulator serving as a power supply to the load. The current determination unit determines whether or not the consumed current is greater than or equal to a predetermined current. The power determination unit determines whether or not a consumed power of the regulator is greater than or equal to a predetermined power. The switching unit connects the linear regulator to the load when the consumed current is lower than the predetermined current and the consumed power is lower than the predetermined power.

Abstract: A semiconductor circuit device includes a semiconductor circuit including a switching element, a temperature monitoring unit, and a control unit. The temperature monitoring unit detects or estimates a temperature of a component connected to an inside or an outside of the semiconductor circuit. Here, the temperature of the component changes in accordance with a frequency of a current flowing through the component, and the frequency of the current flowing through the component changes in accordance with a switching frequency of the switching element. The control unit adjusts the switching frequency of the switching element such that the temperature of the component is equal to a target temperature.

Abstract: A voltage regulator is configurable to operate in a linear regulator mode or a buck regulator mode. To operate in the buck regulator mode, the voltage regulator is coupled to an inductor. To determine whether an inductor is coupled to voltage regulator, and thus whether the voltage regulator can be configured in the buck regulator mode, a detection circuit determines whether a regulator output of the voltage regulator resists a change in current driven to the regulator output.

Abstract: A voltage generating circuit of semiconductor integrated circuit includes: a voltage controller that detects the level of an external supply voltage and outputs a voltage control signal; a voltage supplier that outputs the external supply voltage or a first internal voltage in response to the voltage control signal; and a first reference voltage generator that is supplied with an output voltage of the voltage supplier and generates a first reference voltage.

Abstract: The present disclosure discloses a low drop-out voltage regulator and an electronic device comprising the same. The present disclosure also discloses a method for converting a power supply voltage to a regulated output voltage. The low drop-out voltage regulator comprises a pass device controllable to convert a power supply voltage to a regulated output voltage; and a controller configured to receive an input signal and to provide a driving signal to the control terminal of the pass device based on the input signal, wherein when the input signal is within a predetermined range, the driving signal turns the pass device ON, and the power supply voltage charges the output voltage; and wherein when the input signal is without the predetermined range, the driving signal turns the pass device OFF, and the power supply voltage stops charging the output voltage.

Abstract: An embodiment of a voltage regulation circuit includes a DC-DC converter configured to control a first current provided from a source to a load via a first output, and a linear regulator configured to control a second current provided from the source to the load via a second output. The voltage regulation circuit further includes a single control loop configured to receive an output voltage across the load and a first reference voltage. The single control loop is further configured to generate a single error signal between the output voltage across the load and the first reference voltage and to control the DC-DC converter and the linear regulator using the single error signal such that when the single error signal is outside of a predetermined range the DC-DC converter provides the first current to the load and the linear regulator provides the second current to the load simultaneously.

Abstract: A low drop-out (LDO) voltage regulation circuit includes first and second internal current paths. The first internal current path is between the input supply voltage and ground and includes the regulator's buffer circuit. The second internal current path is between the input supply voltage and ground and includes the regulator's power transistor. The amount of current flowing through the first internal current path relative to the amount of current flowing through the second internal current path is an increasing function of a current supplied to a load connected to the output supply node. The load regulation of the LDO is improved as the DC gain will not go down at lower load currents. Further, the no load to full load response time is improved as the load pole and power MOS gate pole are actively controlled with respect to output load current.

Abstract: An integrated circuit comprising an adjustable voltage source to allow a plurality of voltage values to be selected; means for measuring a voltage value derived from the adjustable voltage source; and means for configuring the adjustable voltage source to provide a selected voltage value, wherein the selected voltage value is selected based upon a voltage value measured by the means for measuring and a voltage selected by a controller.

Abstract: Various exemplary embodiments relate a system for supplying power. The system may include a power source outputting a source voltage, a regulator connected to the power source, and an extension module connected to the power source. The regulator may output a first voltage when the source voltage is above a minimum threshold, and the extension module may output a second voltage when the source voltage falls below the minimum threshold.

Abstract: Various exemplary embodiments relate a system and method for supplying power. The system may include an input/output port, a regulator, and a clamp. The regulator may supply power to the input/output port in a first mode, sink current from the input/output port in a second mode, and be disabled in a third mode. The clamp may be disabled in the first and second modes, and may limit the voltage at the input/output port below a first value in the third mode.

Abstract: A circuit comprises an inductor, a load, and a controllable switching device arranged in either a first configuration: switchable between the load being bypassed and the inductor energised, and current flowing through the load, and the inductor discharging energy into the load; or, a second configuration: switchable between current being permitted to flow through the load, inductor and controllable switching device in series, energising the inductor, and the current flowing through the load, and the inductor discharging energy into the load. The circuit further comprises control means for controlling the switching device, a load current sensing resistor connected in series with the load, and a demand signal input. Monitoring means is arranged to monitor the demand signal and the voltages across the sense resistors, and generate a monitor signal. The control means is arranged to receive the monitor signal and to switch the switching device in response the monitor signal exceeding a predetermined threshold.

Abstract: A voltage regulator controls a regulated output voltage (Vout) by feeding it back to a differential input stage (13) receiving a reference voltage (Vref) and applying an output (3) to a control electrode of a follower transistor (M4) that is coupled to an output stage (15) which generates the output voltage (Vout). The output stage operates pull-up (M7B) and pull-down (M5B) transistors in response to a signal (6A) produced by the follower transistor (M4) during normal regulation operation, and provides fast settling of the output voltage by turning on a transient pull-up transistor (M7A) or transient pull-down transistor (M5A) in response to the signal (6A) produced by the follower transistor (M4) during a fast increasing or decreasing transition, respectively, of the load current (IL). A filtering resistor (RFLT) is coupled between the output voltage and a common electrode of the transient pull-up and pull down transistors.

Abstract: A power supply uses a power converter to generate a regulated voltage by referencing to a first DC voltage, a low dropout (LDO) regulator to generate an output voltage from the regulated voltage by referencing to a second DC voltage, and a reference voltage generator to dynamically adjust the first DC voltage according to the input voltage and the control voltage of the output transistor of the LDO regulator. The dropout voltage of the LDO regulator can be minimized to maintain the high efficiency of the power supply at different loading or selected output voltages.

Abstract: Embodiments of the present invention provide a voltage regulator. The voltage regulator includes a driving mechanism coupled to an output node (VREG), wherein the driving mechanism is configured to provide current to the output node to sustain a predetermined voltage on the output node. In addition, the voltage regulator includes a boost circuit coupled to the output node, wherein the boost circuit is configured to drive an additional current onto the output node to reduce fluctuations in the output node voltage when a load coupled to the output node requires a transient switching current that is faster than the loop response time of the driving mechanism. Furthermore, the boost circuit is biased using a self-tracking mechanism to provide accurate duration and level of the current to the output node in a transient switching event.

Abstract: A startup circuit for starting up a self-supplied voltage regulator which initiates startup by applying a voltage from a voltage supply to the startup circuit thus causing a voltage at an output node to rise. This rise will start the operation of the differential amplifier of the voltage regulator. When the voltage at the output node has reached the desired final output voltage, the startup circuit disconnects from the voltage regulator. The criterion for switching off the startup circuit is determined by a comparator which compares the output current capability of the voltage regulator with its output current plus the startup current. Inputs to the differential amplifier, such as the reference voltage, derive their power from the output node.

Abstract: An over-current protection device for multiple high-voltage motive devices is provided. The over-current protection device includes a comparison module and a logic operation module. The comparison module receives a plurality of voltages generated from a plurality of operating currents of a plurality of high-voltage motive devices and respectively compares the voltages with at least one reference voltage to generate a plurality of comparison results, wherein the high-voltage motive devices are solenoids, electronic clutches, or a combination of solenoids and electronic clutches. The logic operation module receives the comparison results and generates at least one control signal for a plurality of high-voltage motive device driving circuits according to the comparison results. The high-voltage motive device driving circuits respectively drive the high-voltage motive devices according to the control signal.

Abstract: A motor driving circuit receives a control pulse signal pulse-width modulated according to a target rotational speed, and drives a fan motor. A start pulse signal generating unit generates a start pulse signal having a predetermined duty ratio. A driving unit drives the fan motor by pulse width modulation according to the driving pulse signal received from a control unit. When the duty ratio of the control pulse signal is switched from zero to a nonzero value when the fan motor is in the stopped state, the control unit commences the driving operation for the fan motor. The control unit outputs, as the driving pulse signal, the start pulse signal, in a predetermined start period Ts from the commencement of the driving operation. After the start period elapses, the control unit outputs the control pulse signal as the driving pulse signal.

Abstract: A voltage controlled current source circuit is utilized to clamp the internal compensation node of a low dropout (LDO) regulator with an NMOS output during load transients. The circuit senses a voltage drop of the internal node and mirrors its current to the internal node to hold the internal node voltage when the voltage starts to drop low enough to turn off the output transistor.

Abstract: A power regulator circuit automatically disables an internal pass transistor when a detection circuit detects the presence of an external pass device. The internal pass transistor is made in an integrated circuit along with a detection circuit and a switch for disabling the internal pass transistor. The detection circuit detects a presence of an external pass device external to the integrated circuit. The switch automatically disables the internal pass transistor when the detection circuit detects the presence of the external pass device. The detection circuit has a comparator for comparing a signal on an outside connection of the integrated circuit and a latch to operate the switch. The comparator compares a voltage on an outside connection of the integrated circuit against a reference after power up of the regulator and can delay operation of the comparison until a predetermined time after power up. An integrated circuit can contain the power regulator circuit and the internal pass transistor.

Abstract: The present disclosure provides a management device for a charging circuit and a wireless terminal, which belong to the technical field of management control of a linear charging circuit. The device includes a power supply management module (5), a buck switching voltage converter (1) and a linear charging circuit (2). The power supply management module (5) includes an adjustable Low Dropout (LDO) linear regulator (6) and an Analog-to-Digital Converter (ADC) (4), wherein the output terminal of the adjustable LDO linear regulator (6) is connected with the feedback terminal of the buck switching voltage converter (1) through a first preset resistor (R62). The input terminal of the ADC (4) is connected with the anode of a battery (3). The control terminal of the power supply management module (5) is connected with the control terminal of the linear charging circuit (2). The output terminal of the buck switching voltage converter (1) is connected with the input terminal of the linear charging circuit (2).

Abstract: The present invention discloses an adaptive two-stage voltage regulator and a method for controlling the same. The adaptive two-stage voltage regulator includes: a voltage regulator for converting an input voltage (Vin) to a middle voltage (Vm), wherein Vin?Vin_max; a linear regulator for converting the middle voltage to an output voltage (Vout); and a middle voltage controller for adjusting the middle voltage according to (1) an input voltage indicator and one of (2a) an output voltage indicator and (2b) a predetermined reference signal, such that when Vin?Vout, Vm=Vout+?V and (Vout+?V)<Vin_max.

Abstract: A discharge control device in an electric power conversion system mounted to a motor vehicle turns off a relay in order to instruct an electric power conversion circuit to supply a reactive current into a motor generator, and thereby to decrease a capacitor voltage to a diagnostic voltage. After this process, the discharge control device outputs an emergency discharging instruction signal dis in order to turn on both power switching elements at high voltage side and a low voltage side in the electric power conversion circuit. This makes a short circuit between the electrodes of the capacitor in order to discharge the capacitor, and executes a discharging control to detect whether or not an emergency discharging control is correctly executed and completed. The discharge control device detects whether or not the electric power stored in the capacitor is discharged on the basis of the voltage of a voltage sensor.