Abstract: In an embodiment, a semiconductor device is disclosed that comprises a multiplexer. The multiplexer is configured to receive signals from each of a plurality of transmission coils of a wireless power transmitter as inputs and to output an output signal based at least in part on one of the signals. The semiconductor device further comprises an attenuator connected to the multiplexer that is configured to adjust a voltage of the output signal. The attenuator comprises a variable resistance. The semiconductor device further comprises a plurality of pull down circuits each corresponding to one of the transmission coils. The pull down circuits are configured to selectively clamp the signals received from the corresponding transmission coils to ground.

Abstract: A power system comprises a power source, a transmission line coupled to the power source through a circuit breaker, a shunt reactor coupled to the transmission line, and a current transformer connected in series with the shunt reactor. A method for controlling the circuit breaker of the power system comprises processing an output signal of the current transformer to obtain the voltage on the transmission line by determining a time derivative of a current sensed by the current transformer. The method further comprises performing, by at least one control or protection device, a control or protection operation (e.g., auto-reclosing) based on the determined time derivative of the current sensed by the current transformer.

Abstract: An electronic device includes a power transmitting circuit configured to transmit power to a wireless power receiver, a communication circuit configured to perform communication with the wireless power receiver, and a control circuit configured to control the power transmitting circuit to apply first power to a coil of the power transmitting circuit, control the power transmitting circuit to stop applying the first power and to prevent power from being applied to the coil during a first period, identify a first Q-factor during the first period, control the power transmitting circuit to apply, to the coil, a second power based on a calibration operation for identifying at least one parameter used for identifying a power loss during power transmission, control the power transmitting circuit to stop applying the second power and to prevent power from being applied to the coil during a second period, identify a second Q-factor during the second period, and identify a validity of the at least one parameter based o

Abstract: A system for charging a battery includes an adapter, and a charger coupled to receive power from the adapter, and to provide a charging current to the battery. The charger includes a power stage with a charge pump to provide the charging current, and a feedback circuit to provide a feedback signal to the adapter. The power stage can be one of: an adjustable current source with voltage clamp, and an adjustable voltage source with current clamp. The charge pump can be implemented as a voltage divider, so that an input adapter current is multiplied by a pre-defined divider ratio to provide the charging current. The charge pump can be one of: single-phase; and multi-phase.

Abstract: In certain aspects, an apparatus includes a power detector coupled between a power amplifier and an antenna, and a voltage detector coupled between the power amplifier and the antenna. The apparatus also includes a phase shifter coupled to the power detector, and a load measurement circuit coupled to the power detector, the voltage detector, and the phase shifter.

Abstract: Devices, systems, and methods for measurement of parameters of electric power transmission lines can improve electric power usage, while wireless circuitry can provide communication from field-located devices. Connection to draw electrical power from the transmission line can be distinct from connection to sense line parameters.

Abstract: The present disclosure relates to a capacitor bank controller that automatically determines the size of a capacitor bank using wireless current sensors. The capacitor bank controller determines a first capacitor bank size estimate using voltage and current measurements from when the capacitor bank is open and when the capacitor bank is closed a first time. The capacitor bank controller determines a second capacitor bank size estimate by using voltage measurements and current measurements from when the capacitor bank is open and when the capacitor bank is closed a second time. The capacitor bank controller determines a filtered capacitor bank size estimate based on the first capacitor bank estimate and the second capacitor bank estimate and controls operation of the capacitor bank based on the filtered capacitor bank size estimate.

Abstract: The invention concerns a wireless power transfer arrangement (1) including a primary side (2) and a secondary side (3) where the primary side includes an input stage (5) for converting an input power to an AC primary output and a primary resonator (6) for receiving the AC primary output and inducing a magnetic field (9) for wireless power transfer through an air gap (8). The secondary side (3) includes a secondary resonator (10) for converting the power received through the magnetic field (9) to an AC secondary output and an output stage (11) for converting the AC secondary output to a DC secondary output. A controller (15) is adapted to control independently of each other a frequency of the AC primary output to be at a resonance frequency of the resonators and the power transferred from the primary side (2) to the secondary side (3) by controlling the voltage or the current of the AC primary output.

Abstract: A power delivery system may include a power converter configured to electrically couple to a power source and further configured to supply electrical energy to one or more loads electrically coupled to an output of the power converter and control circuitry configured to determine whether a voltage node in the power delivery system has fallen below a warning threshold voltage, determine whether the voltage node has fallen below a critical threshold voltage, wherein the critical threshold voltage is lesser than the warning threshold voltage, in response to a voltage of the voltage node falling below the warning threshold voltage, decrease a maximum current drawn by the power converter from a first current level to a second current level, and in response to a voltage of the voltage node falling below the critical threshold voltage, decrease a maximum current drawn by the power converter from the second current level to a third current level.

Abstract: A battery control system includes a battery comprising: first and second terminals; third and fourth terminals; a plurality of individually housed batteries; and a plurality of switches configured to connect ones of the batteries to and from ones of the first, second, third, and fourth terminals. A mode module is configured to set a mode of operation based on at least one of a plurality of present operating parameters. A switch control module is configured to control the plurality of switches based on the mode of operation.

Abstract: A battery (10) for an electric vehicle comprises a plurality of battery cells (11), where a first group (12) comprises a plurality of battery cells (11) connected to each other in parallel, a second group (13) comprises a plurality of battery cells (11) connected to each other in parallel, and the first group (12) and the second group (13) are connected with each other in series forming a first line (14) of battery cells (11). The battery (10) further comprises a first terminal (16) which is configured to be connected with an electric machine (30) and with a power net (31) of the electric vehicle, and a second terminal (17) which is configured to be connected with a reference potential (32). The battery (10) is configured to supply the electric machine (30) and the power net (31) of the electric vehicle with power, and the electric machine (30) and the power net (31) are supplied with the same voltage level by the battery (10).

Abstract: Some embodiments are directed to a method for detecting harmonic pollution in an electrical distribution network carrying a three-phase current, including a step of measuring the voltages and strengths of the current, for each of said phases, at a counting point of the network; a step of calculating a first quaternion impedance corresponding to the fundamental frequency of the current; a step of calculating at least one second quaternion impedance corresponding to a harmonic frequency of the current, these impedances being calculated by converting the voltages and strengths in a two-dimensional frame of reference defined according to an angle that is dependent on said frequency in order to provide a system of two vectors of three quantities, ud, uq, uo and id, iq, io, respectively.

Abstract: Within electrical test equipment systems comparator bridges are employed to provide the required dynamic range, accuracy, and flexibility. However, whilst bridge based measurement configurations remove many of the issues associated with making measurements at accuracies of sub-parts, a part, or few parts per million they still require, in many instances, that a null point be determined where the bridge is balanced. However, this becomes increasingly difficult within electrically noisy environments, with modern digital multimeters, and where the desired measurement point within the electrical system is physically difficult to access particularly when improved accuracy in calibration, standards, and measurements on circuits and components means measurement systems must operate at 50 parts per billion (ppb) and below.

Abstract: A voltage reactive power control device includes a bus voltage fluctuation extracting unit that extracts a bus voltage fluctuation from a voltage of a secondary-side bus, an RE component extracting unit that extracts a fluctuation component due to renewable energy power generation from the bus voltage fluctuation, a creating unit that creates a reactive power command value for suppressing the fluctuation component based on the bus voltage fluctuation component due to the renewable energy power generation extracted by the RE component extracting unit, and a control unit that executes the reactive power control on a battery system based on the reactive power command value. The RE component extracting unit extracts the fluctuation component due to the renewable energy power generation by eliminating the fluctuation components other than the fluctuation component due to the renewable energy power generation from the bus voltage fluctuation.

Abstract: A method for optimizing consumption of reactive power in an electrical network includes a system for monitoring and adjusting electrical power supply, the system including an electrical generator, electrical loads, a power compensation system, an electric transmission line, an electro-digital processor and a remote-readable meter. The method further includes: measuring the dataset of the electrical loads via at least one remote-readable meter; collecting the dataset of the electrical loads and transmitting it to the electro-digital processor in order to establish data curves; calculating a power factor of the electrical loads; enabling reactive power compensation by setting the type and configuration of the compensation systems to be installed, when the calculated power factor has a value lower than or equal to a predefined threshold value; and compensating for reactive power by actuating the installed compensation systems.

Abstract: A method of controlling a tunable passive component in a pulse width modulation controlled switched mode power supply (SMPS) having a power input and an output with tunable passive component power filter. The method includes operably connecting and supplying power relative to a circuit ground to a DC bus, converting a voltage on the DC bus to an output voltage by operating a first switching device and a second switching device at a selected frequency, and filtering the output voltage with a tunable output filter, the tunable output filter including a tunable passive component responsive to a control function circuit configured to automatically tune the tunable passive component value based on a voltage associated with operation of the power supply to maintain resonance of the tunable output filter at about the selected frequency.

Abstract: A power factor correction circuit corrects a filter current flowing through a filter capacitor asymmetrically based on a peak of an input voltage by controlling a switching operation of a power switch, thereby correcting distortion of an input current.

Abstract: The present invention provides a resonant wireless power transmitter circuit, including: a load circuit, a power conversion circuit which is coupled between an input power supply and the load circuit, and a phase detection and control circuit. The power conversion circuit includes plural power switches and a current sensing device. The plural power switches operate with an operating frequency to convert the input power supply to an output power for driving the load circuit, wherein the load circuit has a load current. The load current has a load current phase difference from the switching frequency. The phase detection and control circuit detects a voltage difference between the current inflow terminal and the current outflow terminal of the current sensing device within a dead time in which the plural power switches are not conductive. The voltage difference corresponds to the load current phase difference.

Abstract: Methods are provided for assessing reliability of a power system of a utility company. At least one main overview display is obtained. Violation markers are displayed on the one main overview display. A monitored elements tab is updated with a list of monitored elements.

Abstract: Some embodiments include apparatuses having a resistive memory device and methods to apply a combination of voltage stepping current stepping and pulse width stepping during an operation of changing a resistance of a memory cell of the resistive memory device. The apparatuses also include a write termination circuit to limit drive current provided to a memory cell of the resistive memory device during a particular time of an operation performed on the memory cell. The apparatuses further include a programmable variable resistor and resistor control circuit that operate during sensing operation of the memory device.

Abstract: Apparatus, systems, methods, and related computer program products for managing demand-response programs and events. The systems disclosed include an energy management system in operation with an intelligent, network-connected thermostat located at a structure. The thermostat controls an HVAC system to cool the structure using a demand response event implementation profile over the demand response event period. The thermostat can also receive a requested change to the setpoint temperatures defined by the demand response event implementation profile and access a determination of an impact on energy shifting that would result if the requested change is incorporated into the demand response event implementation profile. This determination can be communicated to the energy consumer.

Abstract: A power feeding coil unit for wireless power transmission including a base portion with bottom having an opening on an upper end, a magnetic body having a plurality of magnetic plates disposed on a bottom surface of the base portion, a power feeding coil formed by winding a conductive wire on the magnetic body, a cover portion covering the opening of the base portion, and a rib extending from the base portion toward the cover portion between the plurality of magnetic plates and between the wires of the conductive wires, wherein, a distance between the rib and the cover portion is smaller than a distance between the power feeding coil and the cover portion.

Abstract: A series compensation device suitable to double-circuit lines is disclosed. The device includes one series transformer and one converter. One converter and dual-circuit transmission lines are respectively connected to three windings of one series transformer. In the solution provided in the present application, the device can be independently installed in a power transmission system to be used as a static synchronous series compensator, and can also be used as a component of a unified power flow controller, a convertible static compensator, an interline power flow controller and a unified power quality conditioner to be connected to a power transmission system device in series. The device can save the capacity of a converter, improve the application efficiency of the series compensation device, and reduce the cost and area occupation.

Abstract: A method, apparatus, system and computer program is provided for optimizing and controlling volt-amperes reactive on an electrical control system. System-level and local-level measurements are determined and analyzed to prioritize and optimize which VAR adjusters are adjusted.

Abstract: A control device, which is applied to a flyback converter including an auxiliary switch, includes: an on-time setter, configured to set an on-time threshold according to a reference value and an output voltage of the flyback converter; and an on-time controller, configured to output a control signal to turn on the auxiliary switch, and turn off the auxiliary switch when on-time of the auxiliary switch reaches the on-time threshold. According to the present disclosure, it is able to achieve zero voltage switching of a primary-side switch of the flyback converter with variable outputs.

Abstract: A system includes a power source and a memory to store an event that is predicted to occur, an action to be performed by the power source to increase efficiency of the power source during the stored event, and a mis-prediction counter indicating a count of mis-predictions. The system further includes an ECU designed to predict that the stored event will occur and to control the power source to take the action when the stored event is predicted to occur. The ECU is further designed to update the mis-prediction counter and to adjust at least one of the stored event that is predicted to occur, the stored action to be performed by the power source, or a prediction horizon of the prediction when the mis-prediction counter reaches or exceeds a threshold quantity of mis-predictions to increase efficiency of the power source during a subsequent prediction of the stored event.

Abstract: A method of critical peak pricing (CPP) demand response (DR) event implementation includes performing an initial CPP participant selection assessment. The method includes generating an initial CPP participant selection and an estimated CPP curtailment based on the initial CPP participant selection assessment. The method includes calculating a reduced day-ahead demand. The method includes evaluating the reduced day-ahead demand. The method includes submitting an energy bid to a market server. The method includes forecasting a revised real time price. The method includes performing a final CPP participation selection assessment. The method may include generating a final CPP participant selection to include the CPP participants having accumulated individual participant revenue effects up to the reduced day-ahead demand. The method includes communicating CPP event notifications to each of the CPP participants in the final CPP participant selection.

Abstract: A method and system for detecting whether the position of a user's hand gripping a mobile communication device chassis affects an external antenna is provided. A sectioned metal band about a periphery of a mobile communication device has a radiating antenna in at least one metal section. The radiating antenna section is bounded on both sides by electrically floating metal sections. Each of the electrically floating metal sections is bounded on the side distal from the antenna section by a ground metal section. Each metal section separated from an adjacent metal section by an insulating gap. Embodiments measure a differential capacitance between the antenna section and the floating metal section and measure a single and capacitance between the floating metal section and the grounded section to determine whether a user's hand is bridging one or more of the insulating gaps.

Abstract: A power source device has: a storage unit configured to receive a generated power and store as a storage power; a boost unit configured to generate, from a storage power supplied from the storage unit, a boosted power having a higher voltage than a voltage of the storage power, and supply the boosted power to a load; and a voltage detection unit configured to output a boost operation permission signal permitting a boost operation of the boost unit to the boost unit when the storage voltage of the boost unit increases to become a voltage equal to or higher than a minimum operation voltage of the boost unit. The boost unit is configured to start the boost operation by the storage power supplied from the storage unit and operates on the boosted power generated by the boost operation as an operation power source when the boost operation permission signal is output from the voltage detection unit.

Abstract: A regenerative direct current (DC) load includes an input circuit, an output circuit, a low pass filter circuit, and a current regulating circuit. The input circuit is configured to receive electrical power. The output circuit is configured to provide electrical power. The low pass filter circuit is electrically coupled to the output in series. The current regulating circuit is configured to regulate a current of the electrical power. The current regulating circuit is electrically coupled to the input. The current regulating circuit includes a first switch, and a first control circuit. The first switch is electrically coupled between the input circuit and ground. The first control circuit is configured to sense the current and adjust a cycle duration and/or duty cycle of the first switch based upon the sensed current.

Abstract: An image processing device that is capable of executing a job by working together with a server, having: an application that establishes a connection that enables a communication with the server, and establishes periodic communications with the server at predetermined time intervals to maintain the connection; a periodic communication managing part that manages the periodic communication with the server by the application; and a power controller that includes a timer that measures a time elapsed after the application establishes the periodic communication, the power controller starting again a power supply to the application when the timer measures the time interval after the power supply to the application is stopped if a predetermined condition is met. The periodic communication managing part enables the application to establish the periodic communication with the server and resets the measured time before the power supply to the application is stopped by the power controller.

Abstract: Methods and systems for stabilizing a power system include receiving a set point for a power system that includes the compensation circuitry controlled by the control system. A firing angle for the power system is set based at least in part on the set point. An angle between a generator terminal of a generator of the power system and a bus of the power system is calculated. A determination is made whether the angle is within a threshold value of the firing angle. When the angle is not within the threshold value of the firing angle, compensation circuitry is engaged to stabilize the power system.

Abstract: A method for energy management is described. In one embodiment, an aspect of a dwelling is monitored. The monitored aspect of the dwelling is compared to an energy policy to determine a deviation of the monitored aspect of the dwelling from a setting of the energy policy. A notification is sent to an occupant, the notification comprising the deviation of the monitored aspect of the dwelling from the setting of the energy policy.

Abstract: A method and a device for suppressing a common-mode voltage of an inverter AC cable relative to ground are provided. A control unit generates a control signal according to a voltage of the AC side of the inverter. A switch unit connects or disconnects the discharge unit with ground or reference ground in response to the control signal. A discharge unit discharges the common-mode voltage of the inverter AC cable relative to ground when the switch unit is turned on. Therefore, during maintenance of the inverter when the AC switch is turned off, the common-mode voltage of the AC cable relative to ground can be discharged without using the isolated sampling solution in the conventional technology which has a high implementation cost and has a high requirement on the insulation class of the components, thereby avoiding the risk of electric shock to the maintenance technician.

Abstract: A voltage drop protection apparatus is provided. The voltage drop protection apparatus includes a power source, a controller electrically connected with the power source and configured to control electronic device by using a power supplied from the power source, a transmission capacitor electrically connected with the power source and configured to accumulate a transmission power to be used when transmitting either one of an electromagnetic wave and a sound wave, and a voltage detector configured to detect a value of voltage applied from the power source toward the electronic device. When the voltage value detected by the voltage detector is lower than a predetermined threshold, the transmission capacitor applies the voltage at least to the controller.

Abstract: A combined power supply and charging method includes controlling switching from a motor power supply mode to an energy storage charging mode on an electrical network and vice versa, and compensating for magnetic fields during the energy storage charging mode in order to limit or eliminate movements of a rotor of the motor.

Abstract: A wireless power supply system includes a power transmission device having a power transmission coil and a power receiving device having a power receiving coil. The power receiving device calculates a first efficiency based on a transmission power command value and the electric power supplied to the battery. The power transmission device calculates a second efficiency based on a phase difference between a voltage and a current supplied to the power transmission coil. The power transmission device controls electric power supplied to the power transmission coil according to the transmission power command value, and regulate the electric power supplied to the power transmission coil when the first efficiency falls to a predetermined first threshold efficiency or less or when the second efficiency falls to a predetermined second threshold efficiency or less.

Abstract: An inverter device applies an excitation current to an excitation winding of a step-up transformer through a switching element, and outputs an output voltage with an alternating-current half-wave waveform from an output winding of the step-up transformer. The inverter device includes: an input-voltage detecting unit that detects a state of the input voltage, as a voltage; a current detecting unit that converts a current flowing through the switching element into a voltage to detects the current; and a comparing unit that compares a detected current value detected by the current detecting unit with a detected input voltage value detected by the input-voltage detecting unit, and detects a high-current period in which the detected current value exceeds the detected input voltage value. Based on information indicating the high-current period detected by the comparing unit, the control circuit adjusts a period in which the switching element is turned on.

Abstract: Methods and systems for power management include determining a voltage level of a grid; if the voltage level is below a lower voltage threshold, setting power outputs for one or more distributed generators on the grid to maximum; and if the voltage level is above the lower voltage threshold and below an upper voltage threshold, determining power outputs for one or more distributed generators on the grid using sensitivity-based distributed Q compensation.

Abstract: A control circuit for power system sub-synchronous oscillation dampening is described. The control circuit is configured to provide low impedance at sub-synchronous frequencies and high impedance at the fundamental frequency. The control circuit includes an input configured to receive a direct voltage value and a quadrature voltage value. Both the direct voltage value and the quadrature voltage value are based on a three-phase voltage. At least one controller configured to determine a direct current value and a quadrature current value based at least in part on the direct voltage value and the quadrature voltage value is included. The control circuit also includes an output configured to send the direct current value and the quadrature current value as feed forward signals to a control loop for the three-phase voltage.

Abstract: The autonomous charging management system for electric vehicles utilizes a voltage feedback control structure that compares the system voltage at the point of charging against a reference, while also taking into account the EV battery state of charge (SOC). A proportional control structure reduces the EV charging as the system voltage approaches the reference. Moreover, the control structure does not require any communication between the EV and the utility.

Abstract: A method for compensating an inductance imbalance in a three-phase alternating current electrical system is provided. An inductance imbalance is determined in the three-phase electrical system, an induction compensation device is selected based on the determination and thereafter applied within the three-phase electrical system. The induction compensation device is applied onto a power cable within the electrical system. A three-phase electrical system wherein an inductance imbalance is addressed with an inductance compensation device is further provided. A wind turbine generator comprising such a three-phase AC electrical system.

Abstract: In one aspect, a switching power converter is described that includes a transformer, a switch, and a controller that generates a control signal to turn on and turn off the switch. For each alternating current (AC) half-cycle of an input voltage, the controller determines a minimum value of a signal representing an on-time of the power converter, compares the determined minimum value with a threshold value that is used to determine whether the switching power converter operates in a constant on-time mode or in a constant power mode, and adjusts the threshold value based on a result of the comparison. The controller further generates the control signal to operate the switching power converter in a constant power mode during a first time period of the AC half-cycle, the first time period representing a duration where the threshold value is larger than an instantaneous value of the first signal.

Abstract: The present invention relates to a rectifier circuit with a three-phase rectifier arrangement (1) of semiconductor valves (2), preferably a bridge rectifier circuit of diodes, wherein the rectifier arrangement (1) comprises a three-phase mains input (3) and a DC output (4), and at least one of the three phases (U, V, W) at the mains input (3) is connected to a first pole connection (A) of a three-pole circuit (5) for diverting an injection current (ih3) into the three-pole circuit (5).

Abstract: A method for controlling a pilot signal (Ps) to a WPPT with an adjustable coil ratio, wherein the primary side of the transformer is connected to a plurality of WTGs and a variable reactive compensation load, the method comprising the steps of receiving an actual primary-side voltage (VMV), receiving an actual primary-side current (IQMV), estimating a line drop voltage (DV) on the basis of the compensation current (IQC) and the actual primary-side current (IQMV), forming a voltage error (Verr) as the sum of a rated voltage value (VR) and the estimated line drop voltage (DV) minus the actual primary-side voltage (VMV), namely: Verr=VR+DV VMV, and updating the pilot signal (Ps) in accordance with the voltage error (Verr).

Abstract: A reactive power compensator for a three-phase network having first, second and third phases includes an assembly of capacitors and electromechanical contactors electrically connected to the capacitors. Each contactor includes at least one upstream and one downstream power terminal. An electric current circulates between the upstream and downstream power terminals when the contactors are closed. A first contactor is connected to the first phase and a second contactor is connected to the third phase. The voltage between the upstream and downstream power terminals of at least one electromechanical contactor is measured so that the electromechanical contactors can be controlled according to a control algorithm. The control algorithm includes the closure of a contactor for a substantially zero voltage between the upstream and downstream power terminals thereof, and the opening a contactor for a substantially minimum power value of the capacitors to which the contactor is connected.

Abstract: Apparatus for controlling the excitation current of a variable frequency generator (VFG) including means to create a voltage-regulated DC link using PMG power and frequency information, the latter being the image of the VFG mechanical input speed. A step-down voltage-controlled chopper is inserted between the passive rectifier stage and the excitation current control chopper. The control law of this voltage-controlled source is such that when the mechanical input speed of the VFG increases, its output (controlled DC-link voltage) decreases non-linearly, leading to DC link voltage varying from V (engine at idle) to V/2 (engine at take-off speed). The DC voltage becomes inverse-proportional to input mechanical speed.

Abstract: A method and apparatus for LCL resonant converter control utilizing Asymmetric Voltage Cancellation is described. The methods to determine the optimal trajectory of the control variables are discussed. Practical implementations of sensing load parameters are included. Simple PI, PID and fuzzy logic controllers are included with AVC for achieving good transient response characteristics with output current regulation.

Abstract: In general, according to an embodiment, a power conversion apparatus includes a first inverter, second inverter and a cooler. The first inverter includes a plurality of semiconductor devices connected together in parallel per phase. In the second inverter, the number of parallel-connected semiconductor devices are two or more per phase, the semiconductor devices are connected together in parallel and the number of parallel-connected semiconductor devices in the second inverter is fewer than that in the first inverter per phase. The semiconductor devices in the first inverter are installed in an area of a cooling surface of the cooler positioned over a first channel. The semiconductor devices in the second inverter are installed in an area of the cooling surface positioned over the second channel.

Abstract: A display device includes a plurality of pixels and a power supply controller that includes a first power supply source unit supplying a high power supply voltage, and a second power supply source unit supplying a low power supply voltage. The high power supply voltage is different from the low power supply voltage. The power supply controller connects one of the first and second power supply source units to the plurality of the pixels. The one of the first and second power supply source units is switched to another of the first and second power supply source units at a switching time, at which the one of the first and second power supply source units stops operation.