Abstract: Methods and systems for ripple suppression in multi-phase buck converters may comprise a buck converter for providing an output voltage with controlled ripple current. The buck converter may include one or more main buck converter stages and one or more suppression buck converter stages coupled with the one or more main buck converter stages. The one or more suppression buck converter stages may provide suppression currents to reduce ripple currents generated in the one or main buck converter stages.

Abstract: Described herein is a spur-free technique for a switching regulator. The switching regulator may self-adaptively reduce the spur of the output voltage without affecting performance of the switching frequency, The switching regulator may track a coil current and may use an active feedback loop to adaptively generate an artificial coil current, which tracks an amplitude of the coil current but having opposite phase. The artificial coil current may then be injected into an output node to cancel the coil current ripple.

Abstract: Electrical converters of the present disclosure feature a boost circuit that is fully integrated with a three phase bridge rectifier to allow for obtaining a pulsed voltage at the rectifier output. Actively switchable semiconductor switches of the boost circuit are controlled by pulse width modulation (PWM) control signals to obtain the pulsed voltage. PWM of this pulsed voltage allows control of two out of three currents at the three input terminals of the rectifier, i.e., the currents at the phase inputs having the highest and the lowest voltage levels of the three phase input voltage.

Abstract: Methods and apparatus for reducing electromagnetic interference (EMI) in power conversion stage line filter are provided herein. The method, for example, includes determining an estimated ripple voltage or estimated ripple current using a predictive model, generating a ripple cancellation signal of opposite polarity to the estimated ripple voltage or ripple current, while compensating for at least one of magnitude or phase distortions in a signal path, and injecting the ripple cancellation signal into a power supply's line filter to reduce a ripple voltage.

Abstract: An active electromagnetic interference (EMI) filter includes a first amplifier and a second amplifier. The first amplifier is configured to sense noise signals on a power conductor. The second amplifier is coupled to the first amplifier and is configured to drive a cancellation signal onto the power conductor. The cancellation signal is to reduce the amplitude of the noise signals sensed by the first amplifier. An output impedance of the second amplifier is lower than an output impedance of the first amplifier.

Abstract: A control circuit of a power converter providing at least a first output voltage and a second output voltage, having: a first loop control circuit, configured to provide a first error amplifying signal based on the first output voltage and a first reference voltage; a second loop control circuit, configured to provide a second error amplifying signal based on the second output voltage and a second reference voltage; a saturation detecting circuit, configured to provide a saturation indicating signal based on the first error amplifying signal and a saturation reference signal; and a first current source circuit, configured to charge an output terminal of the second error amplifier based on the saturation indicating signal.

Abstract: Some apparatus and associated methods relate to a buck-derived switched mode power supply with constant on-time and configured to substantially maintain a steady-state average switch period in a time interval between a start of a load transient and the time when the inductor current returns to a steady state. In an illustrative example, the time interval may include a first and a second predetermined number of cycles after the start of the load transient. The switch period may be modulated, for example, by an amount calculated to supply a change in additional energy demand in the first number of cycles and an opposite amount in the subsequent second number of cycles calculated to maintain the average steady-state switch period over the time interval. In various examples, maintaining average switching period with constant on-time may minimize transient response times without sacrificing stability and without the need for complex compensation networks.

Abstract: Methods and apparatus relate to a minimizing ripple in a polyphase power supply by modulating a voltage pre-regulator output setpoint to minimize ripple performance. In an illustrative example, the modulation may include incrementally adjusting the pre-regulator output setpoint supplied, for example, to a multiphase controller. Some examples may reverse the increment direction in response to determining that the prior incremental adjustment yielded increased ripple. Each phase of the polyphase power supply may include a buck-derived switch-mode power supply connected, for example, to a common output node. Various embodiments may advantageously maximize reduce bulk capacitance requirements for active loads by dynamically seeking a duty cycle of the polyphase power supply with substantially minimal ripple.

Abstract: A ripple suppressor suppresses ripples of a channel current. The ripple suppressor comprises a voltage-controlled current source, a stabilizer, and an auto-calibration circuit. A control voltage at a control node controls the channel current flowing through a path connecting first and second channel nodes. The voltage-controlled current source receives a current-setting signal to generate the control voltage, so as to stabilize the channel current in response to the current-setting signal. The stabilizer at least provides low-pass filtering to generate and stabilize the current-setting signal in response to a first channel voltage at the first channel node. The auto-calibration circuit controls the stabilizer in response to the control voltage, so as to make the control voltage in compliance with a first predetermined condition.

Abstract: A primary side regulated isolation voltage converter. The primary side regulated isolation voltage converter comprises a control module and a ripple control circuit. The control module receives the voltage feedback signal and determines whether the isolation voltage converter operates in a light load state. When the isolation voltage converter operates in a light load state, the ripple control circuit senses the ripple of an output voltage signal to generate a ripple signal, and compare the ripple signal with a ripple threshold. When the ripple signal is larger than the ripple threshold, the isolation voltage converter jumps out the light load state.

Abstract: Aspects of the disclosure provide a circuit. The circuit includes a voltage step up circuit, a voltage control unit, and a complementary voltage generator. The voltage step up circuit is configured to receive a primary supply voltage of a first voltage level and output a secondary supply voltage of a second voltage level that is higher than the first voltage level. The voltage control unit is configured to receive the secondary supply voltage and to output a control voltage having a voltage level in a range from a ground level to the second voltage level. The complementary voltage generator is configured to operate based on the primary supply voltage and to generate a pair of complementary signals in response to the control voltage. The voltage sum of the pair of complementary signals is equivalent to the first voltage level.

Abstract: A system and method for series connecting electronic power devices are disclosed. In one embodiment, a switching device system includes a first upper arm electrically coupled to a first lower arm and a second upper arm electrically coupled to a second lower arm. Each of the arms include a plurality of low voltage sub-modules connected in series and each plurality of low voltage sub-modules includes an auxiliary switching device, a series switching device, and a capacitor. Each plurality of low voltage sub-modules is configured to be sequentially switched using the auxiliary switching device and the series switching device separately in the upper arms and the respective lower arms to control change in voltage over time (dV/dt) while selectively blocking a desired high voltage. Further, a capacitor voltage balancing (sorting or rotating) algorithm may be used to actively balance voltage across each plurality of low voltage sub-modules.

Abstract: Embodiments of the present application provide a power factor correction circuit and a power supply circuit. The power factor correction circuit includes a main correction circuit and a switch module. The main correction circuit includes: a first correction circuit and a second correction circuit that are configured to perform power factor correction on a forward alternating current voltage, and a third correction circuit and a fourth correction circuit that are configured to perform power factor correction on an inverse alternating current voltage. The switch module includes first switch units that are connected in parallel between an input terminal of the first correction circuit and an input terminal of the third correction circuit, and second switch units that are connected in parallel between an input terminal of the second correction circuit and an input terminal of the fourth correction circuit.

Abstract: The present invention discloses a system and a method for controlling PCS voltage and frequency, wherein the system comprises a reference voltage converter, a phase-locked loop, a grid-side voltage converter, a voltage transformer, a first proportional integral controller, a second proportional integral controller, a coordinate converter and a SVPWM generator; a reference voltage converter is connected to an output terminal of a the phase-locked loop, and the output terminal of the phase-locked loop is further connected to a grid-side voltage converter; the grid-side voltage converter is connected to a high-voltage side of an isolating transformer of the electric grid via the voltage transformer; two output terminals of the grid-side voltage converter are respectively connected to the coordinate converter via two proportional integral controllers; an output terminal of the coordinate converter is connected to the SVPWM generator; an output terminal of the SVPWM generator is connected to a power switch of the

Abstract: The step-up converter includes the plurality of converting units, each having the reactor and the semiconductor element part having electronic parts such as the transistor and the diodes. The ECU performs changeover control of increase or decrease of the number of drive phases of the converting units, based on the output condition from the fuel cell, the temperature condition of the reactor, and the temperature condition of the semiconductor element part.

Abstract: Provided are circuits and methods for use with a power supply that provides a main output including a main DC voltage having a first AC voltage ripple, or a main DC current having a first AC current ripple. A ripple cancellation converter provides a second AC voltage ripple connected in series with the main output, such that the first AC voltage ripple is substantially cancelled; or a second AC current ripple connected in parallel with the main output, such that the first AC current ripple is substantially cancelled. As a result, substantially ripple-free DC output power is provided.

Abstract: A voltage regulator includes a pass element having a control input coupled to a control node and operable to generate an output voltage at an output node, a negative feedback amplifier operable to receive a reference voltage and the output voltage and generate a signal at the control node based on a difference between the reference voltage and the output voltage, and a noise cancellation circuit coupled to the control node and the output node and operable to generate a bias current at the control node based on the output voltage.

Abstract: A noise filter can reliably reject an in-phase component included in a differential signal without generating anti-resonance at a target frequency reject and, a transmission device including such a noise filter. Ends of a pair of coils are connected to a pair of transmission lines in the vicinity of the transmitting circuit, and other ends are short-circuited. The coils are magnetically coupled so that the magnetic flux is cancelled regarding the in-phase component that transmits the pair of transmission lines, and the magnetic flux is increased regarding an opposite-phase component that transmits the pair of transmission lines. A series circuit, which includes an inductor and a capacitor connected in series, is connected to the pair of coils and ground. Each value of the pair of coils, the inductor, and the capacitor is set so that a resonance frequency of the in-phase component is a target frequency.

Abstract: This invention provides a current control semiconductor element that can detect a current with high accuracy in a single IC chip by dynamically correcting changes in a gain a and an offset b, and a control device that uses the current control semiconductor element, the current control semiconductor element has a transistor 4, a current-to-voltage conversion circuit 22 and an AD converter 23 on the same semiconductor chip. A reference current generation circuit 6 superimposes a current pulse Ic on a current of a load 2 and changes a voltage digital value to be output from the AD converter. A gain/offset corrector 8 executes signal processing on change in the voltage digital value caused by the reference current generation circuit 6 to dynamically acquire the gain a and the offset b that are used in an equation that indicates a linear relationship between the voltage digital value output from the AD converter 23 and the current digital value of the load.

Abstract: A system and method for digital management and control of power conversion from battery cells. The system utilizes a power management and conversion module that uses a CPU to maintain a high power conversion efficiency over a wide range of loads and to manage charge and discharge operation of the battery cells. The power management and conversion module includes the CPU, a current sense unit, a charge/discharge unit, a DC-to-DC conversion unit, a battery protection unit, a fuel gauge and an internal DC regulation unit. Through intelligent power conversion and charge/discharge operations, a given battery type is given the ability to emulate other battery types by conversion of the output voltage of the battery and adaptation of the charging scheme to suit the battery.

Abstract: A spike-free converter for driving light-emitting diodes includes a closed loop direct current-direct current (dc-dc) converting unit, a switch, a first inductor, and a first diode. The closed loop dc-dc converting unit is used for generating a driving voltage to drive at least one light-emitting diode strings according to a dc voltage, and generating a switch control signal. The switch is used for receiving the switch control signal and being turned on and turned off according to the switch control signal.

Abstract: The disclosure relates to a passive power factor correction circuit. The passive power factor correction circuit comprises: a filtering device being used for decreasing high order harmonic of an input current; a resonance device being coupled to the filtering device for controlling operation time of the input current; and a suppression device being coupled to the resonance device for suppressing ripple of the input current.

Abstract: Provided are circuits and methods for use with a power supply that provides a main output including a main DC voltage having a first AC voltage ripple, or a main DC current having a first AC current ripple. A ripple cancellation converter provides a second AC voltage ripple connected in series with the main output, such that the first AC voltage ripple is substantially cancelled; or a second AC current ripple connected in parallel with the main output, such that the first AC current ripple is substantially cancelled. As a result, substantially ripple-free DC output power is provided.

Abstract: A power supply system has a current source configured to provide an output current, a load supplied by the current source, and a current ripple suppression circuit. The current ripple suppression circuit has a first end and a second end, wherein the first end of the current ripple suppression circuit is coupled to the load, and the second end of the current ripple suppression circuit is coupled to a reference ground; wherein the current ripple suppression circuit is configured to suppress the current ripple in the output current and adaptively adjust the output current of the current source at a predetermined current level.

Abstract: The present invention provides a circuit of reducing electro-magnetic interference for a power converter. The circuit includes an oscillator, a switching voltage divider, and a sample-and-hold circuit. The oscillator has a terminal for receiving a modulation voltage. The modulation voltage is correlated with an input voltage obtained from an input of the power converter. The switching voltage divider is enabled and disabled by a switch to attenuate the input voltage into a sampled voltage in response to a sampling signal. The sample-and-hold circuit receives the sampled voltage to generate the modulation voltage. A switch of the sample-and-hold circuit controlled by a holding signal conducts the sampled voltage to a capacitor of the sample-and-hold circuit to generate the modulation voltage across the capacitor.

Abstract: Provided is a power supply device for an image forming apparatus, the power supply device including: a filter unit filtering alternating current (AC) power from an AC power source; and a converter generating a direct current (DC) power from the filtered AC power, wherein the filter unit includes: a capacitor connected to the AC power source; a discharge device connected to the capacitor and discharging electric charges accumulated in the capacitor; and a switching device switching connection between the capacitor and the discharge device according to a power supply mode of the power supply device.

Abstract: An electronic current transformer (ECT) based on complete self-excitation power supply is provided. The ECT includes an energy-obtaining coil, a rapid voltage-stabilizing circuit and an Analog/Digital (A/D) converting circuit. The output of the energy-obtaining coil is connected with the input of the voltage-stabilizing circuit. The output of the voltage-stabilizing circuit is connected with the control end of the A/D converting circuit. The ECT uses two branch circuits to obtain energy directly from the magnetic field of a bus bar to be measured respectively, synthesizes two output waveforms to fill the wave trough of each other, and reduces the pulse of direct current. In this way, the trough voltage of the synthesized wave is higher than the required stabilizing value of direct voltage and it directly meets the input requirement of the stabilizing module of the voltage-stabilizing circuit. As a result, the ECT can activate the A/D converting circuit rapidly.

Abstract: A method for reducing a ripple, caused by rotational nonuniformity of an internal combustion engine, in the output voltage of a generator which is driven by the internal combustion engine is provided. The generator has a stator winding, a rotor winding, a field controller, associated with the rotor winding, for regulating the output voltage of the generator, and a downstream power converter having controllable switching elements. To reduce the voltage ripple, the output voltage of the generator is regulated on the stator side by appropriately controlling the switching elements of the power converter.

Abstract: A power supply circuit includes a pulse width modulation (PWM) chip, a number of phase circuits, a voltage output end, and a spike suppression circuit. The spike suppression circuit is connected to each of the phase circuits and the voltage output end. The PWM chip controls all of the phase circuits to alternately output power supply voltages according to a predetermined sequence. The spike suppression circuit receives the power supply voltages, and filters out voltage spikes in the power supply voltages, thereby outputting steady voltages to the voltage output end.

Abstract: A power regenerative converter includes: a power conversion unit configured to convert AC power supplied from an AC power supply into DC power and convert DC power into AC power to be supplied as regenerative electric power to the AC power supply supply; an LCL filter including a reactor unit having a plurality of reactors connected in series between the power conversion unit and the AC power supply, and capacitors each having one end connected to a series connection point of the reactors in the reactor unit; a drive control unit for controlling the power conversion unit based on an AC voltage command; and a voltage command compensation unit for calculating a compensation value in accordance with a capacitor voltage being a voltage at the series connection point of the reactors and adding the compensation value to the AC voltage command input to the drive control unit.

Abstract: A power supply circuit to detect whether or not abnormal current is generated in a power factor compensation circuit and forcibly stop an operation of an interleaved power factor compensation circuit controller if abnormal current is generated. The power supply circuit includes a rectifier, a power factor compensation circuit including a plurality of reactors, a plurality of switches and a plurality of current detectors, a power factor compensation circuit controller to control switching of the switches and to control a power factor compensation operation, and a power factor compensation circuit protection circuit to receive the voltages output from the plurality of current detectors and to stop the operation of the power factor compensation circuit controller if at least one of the voltages output from the plurality of current detectors is abnormal. Thus, it is possible to prevent failure of the switches and the current detectors due to abnormal current.

Abstract: A circuit arrangement includes a transformer, having primary windings and secondary windings, and a high voltage capacitor. A first switching circuit couples the high voltage capacitor to the primary windings. A first controller is operatively coupled to the switching circuit. A second switching circuit couples the secondary windings to an output port. A second controller is operatively coupled to the secondary windings. A high voltage generator is provided to charge the high voltage capacitor.

Abstract: Systems and methods described herein provide for high speed power factor correction which can overcome or substantially alleviate the problems associated with changes in the operating conditions of a load or other transient events. The present technology senses the present state conditions of a signal to quickly and accurately determine the presence of an overtone component within the signal. The expected value of the overtone component is then determined based on the sensed state of the signal. Power factor correction is then performed to suppress the overtone utilizing a control signal formed based on the expected value of the overtone. By performing power factor correction based on the expected value, the present technology can provide high speed power factor correction which is not limited by the delay introduced by an adaptive feedback loop.

Abstract: A bi-power motor controlling apparatus, which is electrically connected with a motor, includes a driver IC having a first pin and a second pin. The first and second pins are used to receive a first power and a second power, respectively, from outside. The second power is supplied to the driver IC, and the first power is supplied to the motor for controlling the rotational speed of the motor.

Abstract: An oscillation control part composed of a control switching element and a damping resistance connected in parallel is arranged between an input power supply and a main switching element of a power conversion circuit, and the control switching element and the main switching element have a relationship such as Ron(S2)<E(Rg)×fsw/(D×I2), and the main switching element is turned off and after a current of the main switching element has become zero, the control switching element is turned off to prevent a high-frequency oscillation generated between a parasitic inductance of the circuit and a junction capacitance of the main switching element, with a damping resistance.

Abstract: Systems, methods and devices for power generation systems are described. In particular, embodiments of the invention relate to the architecture of power conditioning systems for use with fuel cells and methods used therein. More particularly, embodiments of the present invention relate to methods and systems usable to reduce ripple currents in fuel cells.

Abstract: A switch controller is disclosed that adaptively controls the operating frequency of a switching power converter in order to improve one-time load response and repetitive dynamic load responses. During a transition from a high load to low load condition, the switch controller clamps the operating frequency of the switching power converter at an intermediate frequency for a period of time before allowing the operating frequency to return to a frequency associated with the low load condition. The clamped frequency is higher than the frequency associated with the low load condition thereby allowing improved response to a subsequent load change to a high load condition. Thus, the system improves dynamic load response without compromising no-load power consumption.

Abstract: A method for selecting the optimum number of phases for a converter is provided, which selects a duty range using an input voltage and an output voltage, obtains ripple values for multiple phases in the duty range, and selects the optimum number of phases using the corresponding ripple values. The method for selecting the optimum number of phases for a converter includes a duty range selection step of selecting a duty range using an input voltage and an output voltage, a ripple value calculation step of obtaining ripple values for multiple phases within the selected duty range, a range ripple selection step of selecting one or more phases in the duty range, and a rated ripple selection step of selecting the phases having the minimum ripple value in a rated duty among the phases selected in the range ripple selection step.

Abstract: The shape of the rising and falling edges of AC output voltage pulses of a PWM frequency converter is controlled by reducing a speed of change, and a height, of the AC output voltage pulse. The PWM frequency converter rectifies the alternating voltage of a supply network into a DC voltage which is filtered. A load bridge having power semiconductor phase switches forms an AC output voltage from the DC voltage for controlling the load. An average speed of voltage change of AC output voltage pulses is set using a phase switch to control at least one power component to be conductive and non-conductive in turn for a period of at least about one microsecond to change a pulse edge of the AC output voltage pulses into at least one micropulse, the width of which is controlled to increase towards a final state of the phase switch.

Abstract: Equipment for vehicle in accordance with the present invention includes: a vehicle-mounted unit which runs with respect to a vehicle body ground on a side of a negative electrode of a battery; an impedance component having an end connected to the vehicle body ground, and another end connected to a circuit ground; a circuit to be controlled which runs with respect to the circuit ground; a control unit which runs with respect to the circuit ground, for controlling the circuit to be controlled and for outputting a communication signal in a digital form which is to be transmitted to the vehicle-mounted unit; and a communication interface circuit which runs with respect to both the vehicle body ground and the circuit ground, for cancelling a potential difference between the vehicle body ground and the circuit ground, and for carrying out bidirectional communications between the vehicle-mounted unit and the control unit.

Abstract: A variable speed drive for an electric motor has an inverter for receiving pulse width modulation controls. The inverter communicates power signals to a poly-phase electrical motor. A resolver communicates signals from the poly-phase motor back to a motor control. The motor control includes a speed control, a field-oriented control, and a pulse width modulation drive for driving the inverter. The resolver is connected to the speed control and to the field-oriented control, and further communicates with a synchronous compensator. The synchronous compensator is configured to drive the harmonic content at a target frequency or frequencies in a selected signal towards zero over time.

Abstract: Methods and apparatus are provided for operation of a voltage source inverter. A method of operating a voltage source inverter having an output with multiple voltage phases having a DC voltage level, the method comprising sensing a low output frequency condition; determining a DC voltage offset responsive to the low output frequency condition; and applying the DC voltage offset when operating the voltage source inverter resulting in a change to the DC voltage level of the multiple voltage phases.

Abstract: Radiofrequency device (30; 30?; 30?; 30??) controlling means for supplying at least one electrical load (14, 14?) and comprising a radiofrequency unit (11) of radiofrequency signals transmitter and/or receiver type and connected by a first conductor (9b) to the AC mains (9), wherein the radiofrequency unit comprises a radiofrequency signal output and/or input (20) connected by an HF link (19) to a first terminal (21) of a tuning circuit (17; 17?) of the radiofrequency device, this tuning circuit being: connected by a second terminal (22) to the first conductor, connected by a third terminal (23) to an electrical ground (GND) of the radiofrequency unit, furnished with means (L1, C1; L2, C3, C4) for blocking the conduction of radiofrequency signals on the first conductor between the second terminal and the third terminal, and traversed between the second terminal and the third terminal by the AC current (I-ACT) flowing in the first conductor and supplying said electrical load.

Abstract: A power supply module having a PFC stage has a hold-up capacitor (34) for continuing output power for a time after an ac power supply (2) stops. The hold-up capacitor is charged by a winding (40) driven magnetically from a first winding (24); the first winding (24) may be the winding used in a boost converter stage, such as commonly used in a PFC stage, or alternatively the winding in an alternative stage such as a flyback converter.

Abstract: An active switching ripple filter system removes ripple currents from a power signal and has a main inverter and an active switching ripple filter inverter whose outputs are combined to form an output power signal.

Abstract: Exemplary embodiments of the present disclosure provide a method and controller for damping multimode electromagnetic oscillations in electric power systems which interconnect a plurality of generators and consumers. The controller for damping such oscillations includes a phasor measurement unit (PMU) and a power oscillation damper (POD) controller. Each oscillating mode signal is damped and then superposed to derive a control signal. A feedback controller is used to feedback the control signal to a power flow control device in the power system.

Abstract: A system for moving an aircraft thrust reverser component includes a power drive unit, a thrust reverser actuator assembly, and a tertiary lock system. The power drive unit is operable to rotate and supply a rotational drive force. The thrust reverser actuator assembly receives the rotational drive force from the power drive unit and moves the thrust reverser component between a stowed position and a deployed position. The tertiary lock system selectively engages and disengages the thrust reverser component and includes a tertiary lock power unit, an electromechanical tertiary lock assembly, and a voltage limiting circuit. The voltage limiting circuit limits the voltage magnitude of a control signal supplied to the tertiary lock assembly to a predetermined value.

Abstract: Systems, methods and devices for power generation systems are described. In particular, embodiments of the invention relate to the architecture of power conditioning systems for use with fuel cells and methods used therein. More particularly, embodiments of the present invention relate to methods and systems usable to reduce ripple currents in fuel cells.

Abstract: A vehicle or other complex system includes at least one switching power converter which generates direct output voltage with inherent ripple. A voltage estimator or simulator estimates the instantaneous output ripple voltage(s) of the converter in the time domain. The estimator is preprogrammed with state equations of the power converter, for generating the estimates of the output ripple voltage of the converter. A comparator compares at least the ripple voltage of the simulator with the actual voltage of the converter, to generate a difference signal. The difference signal is evaluated to identify a fault condition. The fault condition is reported andor switches to a backup converter.

Abstract: In a pulse-width-modulation (PWM) direct current (DC) steady-state output circuit, there are included an electrode switch and a resistor-capacitor (RC) integrating filter. The electronic switch has a signal input end, via which a PWM signal is input, and a high-level end. The RC integrating filter includes at least one RC filtering unit and a first protection unit. There can be (1+n) order(s) of the RC filtering unit(s) with a first-order RC filtering unit connected to the electronic switch and the first protection unit and the RC filtering unit(s) at the rest order(s), if any, being sequentially connected to the first-order RC filtering unit one by one. When the electronic switch has signals input thereto, the RC integrating filter makes feedback compensation to enable output of a steady-state DC level.