Abstract: A light emitting element drive device includes a driving circuit that supplies a variable drive current to a light emitting unit having one or more light emitting elements so that the light emitting unit can emit light, a drive reference voltage generation circuit that generates a drive reference voltage defining the upper limit value of the drive current and supplies the same to the driving circuit, and a specific external terminal capable of connecting to an external resistor. The drive reference voltage generation circuit operates selectively in a first mode to generate the drive reference voltage regardless of the state of the specific external terminal, or a second mode to generate the drive reference voltage in accordance with a second mode current through the specific external terminal.

Abstract: A display device may include a display panel, a backlight unit including a plurality of blocks for providing light to the display panel, each of the plurality of blocks comprising a plurality of light emitting diodes (LEDs), and a controller configured to obtain backlight control information and to activate a duty ratio control function for controlling a duty ratio and current flowing in a block during a cycle of one frame, when a low current condition is satisfied based on the obtained backlight control information.

Abstract: A non-isolated buck converter generates an output voltage by stepping down an input voltage obtained by subjecting an alternating-current voltage to full-wave rectification and smoothing, by using a step-down circuit including a switching element, an inductor, and a freewheeling diode. The switching element is disposed between a first terminal and a second terminal. A semiconductor device in charge of switching control operates with a potential at the second terminal as a reference. A control circuit provided in the semiconductor device includes a protecting circuit capable of referring to an evaluation voltage corresponding to a voltage between the first terminal and the second terminal at a sampling timing at which a predetermined period of time has passed from turning off of the switching element, and performing a protecting operation that fixes the switching element to an off state on the basis of the evaluation voltage.

Abstract: A power supply system includes a rectifier configured to rectify an input signal to generate a rectified signal having a single polarity, a converter configured to generate a drive signal for powering a light source, and a ripple control system including a voltage-controlled resistor (VCR) coupled to a secondary-side of the converter and configured to dynamically adjust a resistance of the VCR to compensate for ripples in the drive signal.

Abstract: A lighting apparatus includes a light source, a driver module, a light passing cover, a main housing and a manual switch module. The light source includes a LED module. The driver module converts an external power source to a driving current supplied to the LED module. The main housing includes a light source holder for disposing the light source, a driver holder for disposing the driver module, and a light passing holder for disposing the light passing cover for a light of the LED module emitting through the light passing cover. The manual switch module is attached to an external side of main housing. The manual switch module includes a switch housing, a circuit board and a manual switch.

Abstract: An apparatus that physically and electrically attaches to an existing AC electrical switch, and controls the power to the electrical load via outputs from the existing electrical switch or from wireless commands from a remote controller.

Abstract: The present invention provides a self-adaptive dimming driving system, configured to work with a light-emitting diode (LED) power port, the self-adaptive dimming driving system comprising: a driving circuit, a forward bias voltage detection circuit, and a controller. The driving circuit is connected to the LED power port. The forward bias voltage detection circuit is connected between the LED power port and the driving circuit, Wherein the forward bias voltage detection circuit comprises a test current output module and a voltage feedback module, the test current output module is configured to output a test current to the LED power port, and the voltage feedback module is configured to output a detection signal according to a voltage parameter of the LED power port. The controller receives the detection signal, obtains a barrier potential parameter of an LED lamp according to the detection signal, and switches a power output mode of the driving circuit according to the barrier potential parameter.

Abstract: A synchronous control system of light bulbs includes a rectifier unit connected to a live line and a neutral line of an external power supply, a sampling unit connected to the rectifier unit or the external power supply to count a number of changes in a cycle and obtain a cycle length of the alternating current or a control signal pulse, so as to provide a synchronization signal and acquire a control signal input by an external controller, a control unit for receiving the synchronization signal and control the synchronization signal and/or control signal output by the sampling unit, an MCU power supply unit respectively connected to the rectifier unit and the control unit to supply power to the control unit, and LED assembly including one or more LED units which is respectively connected to the rectifier unit and the control unit and controlled by the control unit.

Abstract: System controller and method for a lighting system. The system controller includes a first controller terminal configured to receive a first signal, and a second controller terminal configured to output a second signal to a diver component. The driver component is configured to receive a first current and provide one or more drive currents to one or more light emitting diodes in response to the second signal. Additionally, the system controller is configured to process information associated with the first signal, determine a first time period for the first signal to increase from a first threshold to a second threshold, and determine a second time period for the first signal to decrease from the second threshold to the first threshold.

Abstract: A method of controlling a power supply in a multi-input power supply system includes retrieving a prior input state flag from a memory of the multi-input power supply system, determining a first dimmer input of the multi-input power supply system based on the prior input state flag, determining whether the first dimmer input is currently valid, and in response to determining that the first dimmer input is not valid, determining whether a second dimmer input of the multi-input power supply system is currently valid, and in response to determining that the second dimmer input is valid, controlling the power supply based on a second input signal received through the second dimmer input.

Abstract: The invention provides a dimmable lamp, which is used in combination with a dimmable device outputting a dimming signal with polarity. The dimmable lamp comprises: a light emitting device for emitting light; a dimming drive module for controlling the work of the light emitting device being electrically connected with the light emitting device; a polarity conversion unit for selectively converting the polarity of the dimming signal being electrically connected to the dimmer; a signal processing unit used for processing the dimming signal being connected with the polarity conversion unit and the dimming drive module respectively to control the dimming drive module according to the dimming signal. The dimming function of the dimmable lamp can be normally realized when the dimming signal are connected at any polarity.

Abstract: An LED driver includes a power input configured to receive an input power; a dimmer switch input configured to receive a brightness input; and a power supply coupled to the power input and the dimmer switch input, the power supply having a plurality of selectable transfer functions and a currently selected transfer function of the plurality of selectable transfer functions, the power supply being configured to generate an output power from the input power, the output power having a level based on a value of the brightness input and the currently selected transfer function.

Abstract: A line protection device includes a current sensor, a digital filter circuit, a switch control circuit, and a non-volatile memory circuit. The current sensor is adapted to a sense a value of electric current through the electric line. The digital filter circuit is adapted to perform digital filtering of the value of electric current. The switch control circuit is adapted to control a switch to interrupt flow of the electric current through the electric line depending on the digitally filtered value of the electric current. The non-volatile memory circuit is adapted to store a state of the digital filter circuit.

Abstract: A method is provided. The method comprises: booting a system; determining if the system has properly booted; if the system has properly booted, then initiating communications with the at least one DC-DC voltage converter system that is configured to power at least one remote radio head; determining if communications have been established with the at least one DC-DC voltage converter system; and if communications have been established, then supplying a higher voltage from the system.

Abstract: An illumination system, comprising: a light fixture including a driver coupled to a light source; a dimmer switch; and a dimmer switch interface, including: (i) a transformer having a first winding that is magnetically coupled to a second winding, the first winding being electrically coupled to the dimmer switch, and the second winding being electrically coupled to the driver of the light fixture, and (ii) a current source configured to power the transformer with an intermittent alternating current when the current source is energized.

Abstract: There is provided a white light source approximating sunlight and being capable of reproducing a subtle difference in sunlight which changes depending on times and locations, and provided a white light source system of a lighting system or the like. The white light source includes a light source unit. Light which is emitted from the light source unit is a chromaticity point on a CIE chromaticity diagram and has a correlated color temperature corresponding to a chromaticity point including a deviation of ?0.005 or more to +0.005 or less with respect to a black body radiation locus, and satisfies a formula: ?0.2?[(P (?)×V (?))/(P (?max1)×V (?max1))?(B (?)×V (?))/(B (?max2)×V (?max2))]?+0.2.

Abstract: The disclosure is directed to a circuit that may detect a single short in a chain of loads, such as light emitting diodes (LEDs). The circuit may drive either multiple LED chains or a single LED chain to determine whether one, or more, of the LEDs in the LED chain is no longer working because of a short. The circuit determines whether the LED chain voltage satisfies a threshold based on a single LED voltage drop. Therefore, the same circuit may be used for applications regardless of the number of LEDs in an LED chain. Additionally, the circuit, according to the techniques of this disclosure may use may use no output pins, other than those used to deliver current to LED chains, regardless of the number of LED chains that the circuit drives.

Abstract: A daylight portable lamp for inspecting painted surfaces, in particular during paint repair work on motor vehicles, has a setting device for setting the light intensity. The setting device has an operating element that can be adjusted between a minimum position and a maximum position, the light intensity being set to a minimum in the minimum position and the light intensity being set to a maximum in the maximum position. When the operating element is arranged in the vicinity of the minimum or maximum position returns automatically to the relevant minimum or maximum position on the basis of a spring restoring force. The operating element can be arranged infinitely variably in at least one transitional adjusting region between the minimum and maximum position without the operating element returning automatically to the minimum or maximum position, so that in the transitional adjusting region the light intensity can be set infinitely variably by the operating element.

Abstract: An electrical load controller includes an electrical switching device and an actuator assembly having at least one user actuator for use in turning power on and off to the load and for use in adjustably controlling the level of power to the load. A frame attached to the actuator includes an integrally formed backlightable indicator region having an outer continuous solid surface. Light from an illumination assembly related to the level of power to the load is directable onto a portion of an inner surface of the backlightable indicator region, transmittable through the backlightable region from the inner surface to the outer surface, emittable from a portion of the outer surface, and observable by the user.

Abstract: A Near Field Communication (NFC) tag placed inside a light fixture is provided with information by using a commissioning device such as a smartphone or other dedicated tool. For example, in one implementation, a light fixture in a smart lighting control system can be provided with a microcontroller that has access to the memory of a NFC tag. A commissioning device or tool with GPS and NFC capabilities obtains and writes GPS coordinates to the memory of the NFC tag. After the fixture is connected to the network, the smart system can then access the written GPS coordinates from the memory in the NFC tag. Based on this information, a user with access to the microcontroller (e.g., via computer network) can view the map of fixtures based on the obtained coordinates.

Abstract: An illumination device and method are provided for controlling light emitting diodes (LEDs). The LEDs (specifically, the LED loads) are controlled, e.g., brightness and color of the LED loads, independent of a phase-cut dimmer applied to the AC mains feeding a DC power supply. The power supply is active dependent upon the duration of a conduction angle supplied from the dimmer. The power supply, however, produces drive currents that are independent from the conduction angle by using a two-stage power supply and a relatively slow and fast control loops that are controlled through a microprocessor based control circuit. Parameters stored in the control circuit are drawn by the microprocessor to control the two-stage power supply to produce the drive currents independent and decoupled from the conduction angle yet dependent on the controller parameters.

Abstract: In one aspect, an integrated circuit (IC) is configured to receive an input signal. The IC includes a boost switch driver configured to provide a switching operation to a boost converter to drive a string of light emitting diodes (LEDs), a current sink driver connected to a current source and configured to provide a current signal to the string of LEDs, and a delay module configured to delay the current signal to the string of LEDs with respect to the input signal.

Abstract: An LED drive circuit includes a rectification circuit configured to rectify an alternating-current voltage that is input via a dimmer circuit, a delay circuit having a switch, and a light emitting unit including an LED array including LEDs connected in series, wherein the delay circuit turns on the switch when a predetermined time elapses after the alternating-current current is input, and the rectification circuit and the LED array are directly connected when the switch is on.

Abstract: A dimmer switch includes an air-gap switch for coupling to a power source, a power semiconductor switch electronically controlling power to a load connected in series with the air-gap switch, a dimmer module connected to the power semiconductor switch for coupling to the load to deliver an adjustable level of power to the load, and a dimmer actuator. The dimmer actuator is movable between an operational position and a disconnected position wherein the dimmer actuator is configured to act as a single control mechanism for selectively engaging either the dimmer module to adjust the level of power delivered to the load when in the operational position or the air-gap switch when in the disconnected position.

Abstract: An electronic device may be provided with display circuitry that includes a display timing controller, a backlight driver, a light source, and other associated backlight structures. The backlight control circuitry may generate a control signal having an adjustable duty cycle to the backlight driver. The backlight driver may include a boost converter, a current driver, and backlight control circuitry. The current driver may only be activated when the control signal is high. The backlight control circuitry may output an enable signal to the boost converter. The backlight control circuitry may activate the boost converter a predetermined amount of time before each rising clock edge in the control signal by asserting the enable signal for a longer period of time than when the control signal is high. The control signal and the enable signal may be deasserted at around the same times.

Abstract: A controller for a power converter includes an edge detection circuit and a drive circuit. The edge detection circuit includes a comparator, a count module, and an edge checking module. The comparator is coupled to output a compare signal in response to comparing an input sense signal and a count signal. The input sense signal is representative of an input voltage of the power converter. The count module is coupled to adjust the count signal to track the input sense signal in response to receiving the compare signal. The edge checking module is coupled to output at least one edge signal in response to the compare signal. The drive circuit is coupled to output a drive signal in response to the at least one edge signal. The drive signal is for controlling a switch coupled to regulate an output of the power converter.

Abstract: The present invention provides a light emitting device driver circuit and a control circuit and a control method thereof. The light emitting device driver circuit is used for driving a light emitting device circuit according to a rectified dimming signal. The light emitting device driver circuit includes a power stage circuit and a control circuit. The control circuit includes a pulse width modulation (PWM) circuit, a current limit (CL) circuit, and a determination circuit. The CL circuit generates a CL signal according to a current sense signal and a predetermined CL threshold. The determination circuit is coupled to the PWM circuit and the CL circuit, for generating an operation signal according to a PWM signal and the CL signal. The power stage circuit maintains an absolute level of an AC dimming current not lower than a holding current in an ON phase period.

Abstract: A TRIAC low voltage dimming control system for effectively controlling the dimming of low voltage lighting using a TRIAC dimmer. The TRIAC low voltage dimming control system generally includes a TRIAC analyzer that applies a test voltage to a TRIAC dimmer and measures the amount of time required for the TRIAC dimmer to conduct electricity. Utilizing the measured time for the TRIAC dimmer to conduct electricity, the TRIAC analyzer is able to calculate an approximate state of the TRIAC dimmer and provide a corresponding level of DC electrical power to a DC load.

Abstract: An LED driving apparatus includes a rectifier bridge generating a DC bus voltage, a bus capacitor coupled between the output terminal of the rectifier bridge and a reference ground, a voltage sensing circuit generating a voltage sensing signal indicative of the DC bus voltage, a bleeding circuit providing a bleeding current for the bus capacitor, a switching converter configured to convert the DC bus voltage into a driving signal to drive an LED, a dimming mode detector detecting whether the LED driving apparatus is coupled to a leading edge dimmer or a trailing edge dimmer based on the voltage sensing signal, and a bleeding control circuit generating a control signal to control the bleeding circuit based on the voltage sensing signal, the leading edge dimming mode signal and the trailing edge dimming mode signal.

Abstract: A switching converter detects when a dimmer circuit supplying power to the switching converter changes from a conducting state to a nonconducting state or from a nonconducting state to a conducting state; an equivalent input resistance of the switching converter is changed to a first, higher value when the dimmer circuit is in the conducting state and to a second, lower value when the dimmer circuit is in the nonconducting state, thereby drawing a minimum current from the dimmer circuit while the dimmer circuit is in the nonconducting state.

Abstract: The invention relates to a dimmable LED light source comprising:—a rectifier having rectifier input terminals for connection to respective output terminals of a phase cut dimmer of the trailing edge type, input terminals of the phase cut dimmer being connected to the mains supply, and having rectifier output terminals,—a first bleeder circuit connecting the rectifier output terminals, —a series arrangement comprising a unidirectional element and a capacitive means connecting the rectifier output terminals, —a converter circuit, having input terminals coupled to respective sides of the capacitive means and output terminals coupled to a LED load, for generating a current through the LED load, in dependence on a dim signal, out of a voltage present across the capacitive means, —a dim circuit for generating a dim signal as a function of the adjusted phase angle of the phase cut dimmer and for supplying the dim signal to a dim input of the converter circuit, the dim circuit comprising: —gradient detection circuitr

Abstract: Various exemplary embodiments relate to a current driver for controlling a current source controlled by an alternating current (AC) signal, including: a current sensor configured to measure an output current from the current source; a threshold detector configured to detect when the measured current is below a threshold value; and a controller configured to control the current source using a duty cycle of the AC signal when the measured current is below the threshold.

Abstract: Disclosed herein is a power supply device. The power supply device includes a conversion unit converting an applied voltage into a predetermined level, a switching unit performing an opening operation or a closing operation to control a current flowing in the conversion unit, a sensing unit sensing an occurrence of overcurrent when a voltage applied to the switching unit is equal to or larger than a reference voltage set in advance, and a control unit performing a protection operation when the overcurrent is sensed again within a protection time set in advance after a predetermined time is delayed from the time at which the overcurrent is sensed, so that malfunction due to noise is prevented.

Abstract: A method for ignition of a ceramic high intensity discharge (HID) lamp. The method includes applying to the electrodes multiple pre-ignition voltage pulses of sufficiently short duration to avoid igniting the HID lamp. The pre-ignition voltage pulses heat the electrodes prior to ignition to avoid arcing in the bores of the capillaries surrounding the electrodes. The ignition circuit is configured subsequent to application of the pre-ignition voltage pulses to apply an ignition pulse to ignite the HID lamp.

Abstract: To maintain the shape of the projection on the electrodes of the tip end for a long time to extend the lifetime of a discharge lamp, a lighting device lighting a high pressure discharge lamp supplies alternating current such that an alternating current with a basic frequency at the time of the steady state lighting selected from a range between 60 and 1000 Hz and a low frequency of a half cycle with a frequency lower than the basic frequency are generated alternatingly. The alternating current is supplied such that the waveform with one polarity of the low frequency appears consecutively at least twice. It is also possible for the alternately generated low frequency to be lower than the basic frequency in a range from 5 to 200 Hz, and for the interval during which the basic frequency is supplied to be gradually increased and decreased at specified times.

Abstract: It is an object of the present invention to provide a lighting circuit for and a lighting method of a high-pressure discharge lamp whereby remarkable reduction in illuminance maintaining rate can be avoided by reducing variation in inter-electrode distance in the beginning of usage without modulating a lighting frequency. The object can be achieved by a lighting circuit configured to light a high-pressure discharge lamp by supplying an alternating lamp current, which includes at least one pulse current superimposed on the former half of each half period of a base lamp current and at least two pulse currents and superimposed on the latter half of each half period, to the high-pressure discharge lamp.

Abstract: In one embodiment, a method of controlling dimming can include: (i) generating a dimming signal according to a DC input voltage signal; (ii) generating a voltage average value signal from the dimming signal; (iii) determining whether the dimming signal is in a positive half cycle or a negative half cycle; (iv) comparing the voltage average value signal against an output current feedback signal to generate a first comparison signal, and output a driving signal according to the first comparison signal when the dimming signal is in the positive half cycle; and (v) comparing the voltage average value signal against the output current feedback signal to generate a second comparison signal, and output the driving signal according to the second comparison signal when the dimming signal is in the negative half cycle.

Abstract: The inventive subject matter provides a circuit and a method for efficiently operating a lighting device, such as a light-emitting diode and a fluorescent lamp. In one aspect of the invention, the circuit includes an oscillator that generates a series of current pulses at a frequency that is at least 50,000 Hz and that corresponds to a resonant frequency of the circuit including the lighting device. The series of pulses is operated at a low duty cycle of no more than 15%. The lighting device has a manufacturer's specification for current consumption and power consumption for a specified luminosity. The circuit provides a current to the lighting device at no more than 1/500 of the manufacturer's specification to produce at least the specified luminosity. The lighting device also operates within the circuit at no more than 50% of the manufacturer's specification to produce the specified luminosity.

Abstract: A system and method for controlling the dimming of a lighting element, or other electrical load, that uses a timer synchronized to the AC waveform is disclosed. The timer is set up to repeatedly count at a rate equal to twice the frequency of the AC waveform. An output from the timer logic is asserted when the timer value exceeds a predetermined value, stored in a compare register. This output is connected to the gate of a triac, which controls the passage of current from the AC power source to the electrical load. A capture register is used to determine the temporal relationship between the restart of the timer and the AC waveform. This system and method reduces the real time requirements of an associated processing unit, and improves consistency, thereby reducing flicker.

Abstract: An apparatus for supplying power includes a power input, an output driver operable to transfer power from the power input to a load output, an output driver control switch operable to control a current from the power input through the output driver, a pulse generator operable to generate a pulse signal to control the output driver control switch, and a stealer switch operable to disable the pulse signal.

Abstract: A power-supply device includes a rectifying unit configured to rectify a phase-controlled AC voltage; a current limiting unit including a current limiting resistor, which limits an input current flowing from the rectifying unit at rise of a rectified voltage outputted from the rectifying unit; and an adjustment unit configured to cause the current limiting unit to limit the input current flowing from the rectifying unit until a predetermined time period has elapsed after an input of the AC voltage to the rectifying unit is started.

Abstract: A luminary dimming system having a three terminal dimming unit. The dimming unit includes a power controller and a receiver and is responsive to dimming directives received by the receiver. The power controller controls a buck switch and a freewheel switch in a manner that allows reduction of alternating current voltages. Such voltage reduction is accomplished in a manner that preserves the waveform of the source voltage and the power factor exhibited by the luminary.

Abstract: A circuit for driving a light emitting diode (LED) comprises: an alternating voltage power supply, comprising a triac dimmer having a firing angle and output terminals that provide power to the LED; a zero crossing detector that detects a polarity change of the alternating voltage provided by the alternating voltage power supply and provides a zero crossing output signal indicative of the zero crossing; a timer triggered by the zero crossing output signal that generates a timer output signal during a time period of the timer; and LED power circuitry that reduces current to the light emitting diode based upon timing characteristics of the timer output signal.

Abstract: The present disclosure provides a variable energy lamp control circuit, including a power supply management circuit, an alternating current detection and high-frequency signal transmission circuit, a manual switch, a high-frequency signal receiving circuit, a delay circuit working power input control circuit, a work delay circuit, an alternating current sensing circuit, a control signal conversion circuit, and a driving circuit. The control signal conversion circuit is configured for controlling on and off of the variable energy lamp via the driving circuit according to a first control signal outputted from a first control signal output terminal of the alternating current detection and high-frequency signal transmission circuit, a second control signal outputted from an output terminal of the alternating current sensing circuit, and a third control signal outputted form a third control signal output terminal of the work delay circuit.

Abstract: It is an object of the present invention to provide a lighting circuit for and a lighting method of a high-pressure discharge lamp whereby remarkable reduction in illuminance maintaining rate can be avoided by reducing variation in inter-electrode distance in the beginning of usage without modulating a lighting frequency. The object can be achieved by a lighting circuit configured to light a high-pressure discharge lamp by supplying an alternating lamp current, which includes at least one pulse current superimposed on the former half of each half period of a base lamp current and at least two pulse currents and superimposed on the latter half of each half period, to the high-pressure discharge lamp.

Abstract: A liquid crystal display (LCD) includes a backlight driving module. The backlight driving module includes a boost circuit, a control chip, and a ferrite bead. The boost circuit includes a metal-oxide-semiconductor-field-effect transistor (MOSFET). The control chip includes a pulse width modulation (PWM) input pin and provides PWM signals to turn on and turn off the MOSFET. One end of the ferrite bead is connected to the PWM input pin, and another end is connected to the gate of the MOSFET.

Abstract: A lighting device formed of a FIPEL panel driven by electrical connection. For example, a frequency generator can create a frequency that creates a light output having any frequency in the spectrum. The light emitting panel can be flexible, and can be coded along a curved surface, such as the inner surface of a light bulb.

Abstract: An LED driver includes a transformer, current control loop and current adjustment circuit. The primary side of the transformer transfers energy to the secondary side of the transformer responsive to an input signal. The secondary side delivers output current to one or more LEDs at a magnitude corresponding to the amount of energy transferred to the secondary side. The current control loop controls current in the primary side so that the output current equals a reference current signal. The current adjustment circuit injects a current adjustment signal into the current control loop responsive to a phase-cut signal which removes a portion of the input signal. The current control loop also decreases the current in the primary side responsive to the current adjustment signal so that a brightness of each LED connected to the secondary side is decreased by an amount corresponding to the magnitude of the current adjustment signal.

Abstract: An impedance matching device includes an input port connected to a high-frequency power supply, an output port connected to a load, an impedance variable circuit, a T-parameter memory for storing sets of T-parameters in a manner such that each of the sets of T-parameters is related to a corresponding one of adjustable impedance values of the device, an input voltage detector for detecting a forward wave voltage and a reflected wave voltage at the input port, and a p-p value calculator for computation of a p-p value of a high-frequency voltage at the output port. The computation of the p-p value of the high-frequency voltage is performed by using the forward wave voltage and the reflected wave voltage detected at the input port and also using one set of the T-parameters stored in the T-parameter memory.

Abstract: A light source device includes a discharge lamp having a light emitting case and a pair of electrodes, a drive device, a voltage detector, and a time measurement device, the drive device alternately repeats a first alternating current supply interval and a second alternating current supply interval, measures a period of the first and the second alternating current supply interval with the time measurement device, performs a change from the first alternating current supply interval to the second alternating current supply interval when the period of the first alternating current supply interval reaches a predetermined period A, and performs a change from the second alternating current supply interval to the first alternating current supply interval when the period of the second alternating current supply interval reaches a predetermined period B, or when an absolute value of an inter-electrode voltage of the pair of electrodes reaches a threshold value.