Abstract: Methods of operating an induction geyser include drawing current through a resonant tank via a transistor, generating a changing magnetic field around the resonant tank. Owing to the strategic placement of the resonant tank in proximity to a fluid tank, the changing magnetic field envelopes the fluid tank. In a first method, the voltage across the transistor's conduction terminals is monitored, and when this voltage surpasses a predefined threshold, indicating an overvoltage condition, a corrective action is initiated in which a gate driver pulls up a gate drive signal that drives the transistor. In a second method, the current flowing between the transistor's conduction terminals is monitored, and upon detecting an overcurrent condition where the current exceeds a set threshold the gate driver is activated to pull down the gate drive signal. Both methods aim to keep operation of the geyser within desired parameters.

Abstract: An induction cooker includes a rectifying device, a first energy-storage device, a switch device, a second energy-storage device, a heating device and a control device. The capacitance of the second energy-storage device is greater than the capacitance of the first energy-storage device. When the induction cooker is just starting, the control device controls the switch device to be turned off, such that the heating device generates an output current according to an energy of the first energy-storage device. The control device determines whether a pot is on the heating device according to a change state of the output current. When the pot is on the heating device, the control device controls the switch device to be turned on, such that the first and second energy-storage devices are coupled, and the heating device heats the pot according to energies of the first and second energy-storage devices.

Abstract: A cooking apparatus includes: a working coil, an inverter configured to output a resonant current to the working coil, a current detector configured to detect the resonant current and output a detection value corresponding to the resonant current, and a controller. The controller is configured to control the inverter to flow a first resonant current through the working coil, control the inverter to flow, through the working coil, a second resonant current having a frequency different from the first resonant current, and determine, based on a difference between a first detection value for the first resonant current and a second detection value for the second resonant current, whether a target object that is located adjacent to the working coil is a predetermined object.

Abstract: An induction heating apparatus is provided. The induction heating apparatus includes a heating coil configured to heat an object to be heated, a full-bridge type inverter configured to supply power to the heating coil, a capacitor provided between an intermediate node of one arm of the inverter and one end of the heating coil, and a first relay provided between the intermediate node and the other end of the heating coil 30. An intermediate node of the other arm of the inverter and an intermediate point of the heating coil are connected through a first wire. The induction heating apparatus includes a processor configured to open or close the first relay based on an impedance of the object to be heated.

Abstract: An induction heating cooking apparatus includes a plurality of heating coils aligned in at least one row on a flat surface, a plurality of inverter circuits each configured to supply a high-frequency current to the corresponding one of the plurality of heating coils, and a controller configured to control driving of the plurality of inverter circuits. The plurality of heating coils include a first heating coil and a second heating coil that are adjacent to each other. The controller is configured to, when a material forming a heating target loaded on an upper part of the first heating coil is a magnetic material, and a material forming the heating target loaded on an upper part of the second heating coil at least includes a nonmagnetic material, set a frequency of the high-frequency current supplied to the second heating coil higher than a frequency of the high-frequency current supplied to the first heating coil.

Abstract: The present invention relates to a cooking hob (10) comprising at least one cooking area (12) and at least one user interface (14), wherein the cooking area (12) is subdivided into cooking zones, each cooking zone is activatable at a predefined power level and the user interface (14) comprises a position indicator device (18) for indicating a position of at least one cooking vessel on the cooktop.

Abstract: A cooktop appliance apparatus for use in cooking includes a controller for controlling operation of the fan system based on an average power level supplied to a heating system, and based on a temperature measure associated with one or more subsystems. The appliance includes a hardware-implemented safety module having two or more temperature actuated safety circuits. The appliance includes a user interface adapted to receive a user input with respect to operating parameters of the heating system, the user input including a heating control mode and a set temperature. The appliance includes a controller adapted to identify a cooking vessel on an induction cooktop.

Abstract: Induction cooktops and operational methods are provided herein. A method of determining presence of compatible cookware on an induction cooktop can include receiving a request to heat the induction cooktop, controlling at least one switching device to induce a current within an assumed piece of cookware with an induction coil of the induction cooktop, sensing a voltage associated with the at least one switching device, the voltage being proportional to current flowing in the induction coil, determining that the sensed voltage includes one or more voltage spikes above a first threshold, and determining that the assumed piece of cookware is absent when the sensed voltage includes the one or more voltage spikes.

Abstract: Disclosed are an induction heating device and a vessel sensing method of the induction heating device. The induction heating device determines whether a vessel is present in a heating region corresponding to a working coil using two sensing methods. In more detail, the induction heating device determines whether a vessel is present in the heating region by sequentially performing first vessel sensing based on a resonance current value of the working coil and second vessel sensing based on a sensing value obtained by a vessel sensor. It is possible to precisely sense a vessel by applying the two sensing methods as described above.

Abstract: The present invention relates to an induction cooking hob (10) comprising at least one cooking zone (12) including one induction coil (14). The induction cooking hob (10) comprises at least one user interface (22) including at least one display with at least one indicator corresponding with one cooking zone (12, 28, 30, 32). The induction coil (34, 36, 38, 40) is provided for detecting at least one parameter related to the power of the electromagnetic field generated by said induction coil (34, 36, 38, 40). The induction cooking hob (10) comprises a memory for storing a maximum value of the parameter detected by the induction coil (14) of the cooking zone (12) when a cooking pot (26) is arranged upon said cooking zone (12). The indicator corresponding with the cooking zone (12) indicates a signal related to an incorrect position of the cooking pot (26), if the currently detected value of the parameter is lower than the maximum value of said parameter.

Abstract: An induction cooker includes a microcrystal panel and at least three temperature sensors scattered on a bottom surface of the microcrystal panel, and the induction cooker is configured to heat a container to be measured. The method includes: obtaining temperature data collected by the at least three temperature sensors and position data of each temperature sensor relative to the microcrystal panel; obtaining an actual position of the container on the microcrystal panel according to the temperature data and the position data; obtaining a preset temperature curve matching the induction cooker according to the temperature data, and extracting a peak value of the preset temperature curve; and calculating an actual temperature of the container to be measured according to the actual position and the peak value.

Abstract: Provided is an induction cooking apparatus including a heating part including a working coil forming a heating region and configured to heat a container placed in the heating region, an inverter configured to supply a driving voltage to the working coil, a plurality of sensing coils arranged along a circumferential portion of the working coil and sensing the container placed in the heating region, and a controller configured to determine whether to drive the inverter on the basis of information acquired from the plurality of sensing coils.

Abstract: Disclosed herein is a cooking apparatus and a control method thereof. The cooking apparatus includes first and second coils arranged in a first column, third and fourth coils arranged in a second column, a plurality of inverters configured to supply a drive current to the first, second third and fourth coils, a plurality of rectifiers configured to supply direct current (DC) power to the plurality of inverters, a plurality of switches configured to connect each of the plurality of rectifiers to any one of a first external power supply and a second external power supply, and a controller configured to control the plurality of switches wherein the first external power supply supplies power to at least one of the first, second, third, and fourth coils and the second external power supply supplies power to at least one of the first, second, third, and fourth coils.

Abstract: An electrical AC/DC converter arrangement includes: an AC circuit breaker; a rectifier; at least one smoothing capacitor; at least one first isolating relay for electrical isolation; at least one first current sensor; and a control and monitoring unit. An input of the AC circuit breaker forms an AC input of the arrangement. An output of the AC circuit breaker is connected, at least indirectly by a circuit, to an input of the rectifier. The at least one smoothing capacitor connects a first output of the rectifier to a second output of the rectifier. The first output of the rectifier is connected, at least indirectly by a circuit, to an input of the at least one first isolating relay. An output of the at least one first isolating relay forms a first DC output of the arrangement and connects a DC network to at least one first DC load.

Abstract: The present disclosure relates to an induction cooking top comprising a system adapted to modify the control of the presence of the pan on the induction cooking top, upon a command by the user.

Abstract: The invention relates to a method for operating an induction hob (1), the induction hob (1) comprising a power circuit portion (2) with at least one switching element adapted to provide pulsed electric power to an induction coil (3) and a control entity (4) for controlling operating parameters of the switching element, the method comprising the steps of: performing a control loop with control cycles in order to detect coupling changes between the induction coil (3) and a piece of cookware, said control cycles comprising the steps of: o receiving frequency information (fcurr) and power information (Pcurr) at said control entity (4); o calculating at least one relation coefficient (Ds?, Ds?) based on said frequency information (fcurr) and said power information (Pcurr); and o comparing said relation coefficient (Ds?, Ds?) with a relation coefficient boundary, thereby de-riving a comparison result; deciding, based on the comparison result, whether to: o perform a new control cycle of said control loop or whether

Abstract: Systems and methods of quasi-resonant induction heating are provided. In particular, a method for evaluating the resonant frequency of a quasi-resonant induction cooking device can be provided. The method can include generating a startup pulse, receiving multiple feedback pulses from a resonant frequency feedback circuit, measuring a pulse width of each of the feedback pulses, calculating an average pulse width based upon the feedback pulses and determining the resonant frequency based at least in part on the average pulse width and a transfer function.

Abstract: Disclosed herein is a cooking apparatus including a cooking plate, induction heating coils installed under the cooking plate, a vessel sensor configured to detect a cooking vessel while the cooking vessel is placed on the cooking plate, a driving assembly including a driving circuit configured to generate a driving current and distribute the driving current to each of the induction heating coils, and a sub assembly including a vessel sensing circuit configured to determine one or more of the induction heating coils overlapping the cooking vessel based on an output of the vessel sensor. The sub assembly may be separated from the driving assembly.

Abstract: A circuit for driving a cooker includes a sensing unit configured to sense a movement of a user of a cooker. The circuit further includes a contact unit configured to switch a power circuit to which power is supplied from the outside, and perform a closing operation on the basis of a sensing result from the sensing unit to allow power to be supplied to the cooker.

Abstract: In a method for operating a cooking zone of a cook top, wherein the cooking zone is formed by at least two cooking sub-zones and each cooking sub-zone can be heated by at least one heating unit, with the heating units arranged adjacent to each other without overlapping such that a cohesive heatable surface is formed during a joint operation of the cooking sub-zones, detection of an occupancy of a cooking sub-zone by at least one food preparation vessel is activated in a first operating mode and a same electrical power is supplied to all activated cooking sub-zones occupied by a food preparation vessel.

Abstract: The present disclosure generally describes a system that includes a heater, a power converter including a power switch, and a controller. The power converter is in communication with the heater and is operable to apply an adjustable voltage to the heater. The controller is in communication with the power switch to control the voltage output of the power converter based on at least one of a load current and a detected voltage at the heater. The controller operates the power switch to adjust the voltage output of the power converter.

Abstract: Provided is a ripple current generating circuit, which comprises an indicating circuit based on an existing ripple current generating circuit. The indicating circuit comprises a resistor, a capacitor, a diode, and a light-emitting diode (LED). The indicating circuit is formed by connecting the LED and the diode that are reversely connected in parallel first to the resistor in parallel and then to the capacitor in series. The capacitor is low in capacity and serves to block direct current while allowing high frequency to pass. With increasing ESR of a tested capacitor, a high-frequency ripple voltage generated by a high-frequency exciting current across the ESR may rise accordingly. Since the capacitor is capable of allowing high frequency to pass, the LED will emit light when the high-frequency ripple voltage reaches a particular threshold that can be adjusted by adjusting the resistance of the resistor.

Abstract: An electronic induction heat cooking apparatus is provided. The electronic induction heat cooking apparatus includes a rectifier for rectifying an input voltage and outputting a direct current (DC) voltage, a plurality of switching elements for switching the DC voltage output through the rectifier, a cooling fan for cooling the plurality of switching elements, a plurality of heating coils for heating a cooking utensil by controlling the plurality of switching elements, and a controller for controlling the plurality of switching elements according to a plurality of operation modes. In an operation mode for generating maximum heat among the plurality of operation modes, a switching element for generating maximum heat among the plurality of switching elements is arranged closer to the cooling fan than at least one of the other switching elements.

Abstract: When an inverter circuit is driven with a predetermined driving frequency, an amount of current change of an input current or a coil current in a set period is detected, and high frequency power to be supplied from the inverter circuit to a heating coil is adjusted in accordance with the amount of current change.

Abstract: An induction hob has a hob plate, a plurality of induction heating coils arranged under the hob plate and a plurality of sensor coils arranged under the hob plate. The induction heating coils are rectangular, wherein at least two induction heating coils are arranged one behind the other and at least three induction heating coils are arranged one next to the other. Two adjacent induction heating coils form an adjacent region with one another in which the two induction heating coils lie with their adjacent sides. At least one sensor coil is arranged in each adjacent region, wherein precisely a single sensor coil is provided in a spacing direction from the one induction heating coil to the adjacent induction heating coil.

Abstract: The present invention proposes a control circuit and a method of controlling a resonant converter comprising a full-bridge configuration in the following manner: during each half period of a plurality of periods of a resonant current of the resonant converter, starting from an initial state (500) in which a diagonal pair are conductive, turning off (510) a first switch member of the diagonal pair on the basis of the voltage control signal; turning on (520), after the turn-off of the first switch member, a switch member in series connection with the first switch member prior to a zero crossing (E5) of the resonant current; turning off (530), after the turn-off of the first switch member, a second switch member of the diagonal pair prior to the zero crossing (ES); and turning on (540), after the turn-off of the second switch member, a switch member in series connection with the second switch member prior to the zero crossing event of the resonant current.

Abstract: This invention relates to current-fed resonant inverters for electrical power applications to change direct current (DC) into alternating current (AC). One application of the invention is to power supplies for inductive power transfer (IPT) systems. There is provided a resonant inverter including an input for supply of current from a DC power source, a resonant circuit including two coupled inductive elements and a tuning capacitance, the inductive elements being arranged to split current from the power source; a first switching means comprising two switching devices operable in substantially opposite phase to alternately switch current from the power source into the inductive elements; and a second switching means to selectively switch one or more control capacitances into or out of the resonant circuit dependent on a power factor of the resonant circuit.

Abstract: A method for determining the suitability of a cookware for a corresponding induction coil of an induction cooking hob is provided. The method includes detecting current through the induction coil, detecting the phase difference between the voltage and current of the induction coil, and detecting the frequency at the induction coil. The method further includes comparing the detected current with a stored maximum value of the current, comparing the detected phase difference with a stored maximum value of the phase difference, comparing the detected frequency with a stored maximum frequency, calculating the power transfer from the detected current, phase difference and/or frequency, estimating the suitability of the cookware in dependence of the power transfer and at least one of the compared parameters, and outputting at least one optical and/or acoustic signal corresponding with the suitability of the cookware.

Abstract: A method for controlling an induction heating system, particularly an induction heating system of a cooktop on which a cooking utensil with a certain contents is placed for heating/cooking purposes, comprises the steps of carrying out a predetermined number “n” of electrical measurements of a first electrical parameter of the heating system on the basis of a predetermined electrical value of a second electrical parameter, “n” being ?2, repeating the above set of measurements at a predetermined time after the first measurements, and estimating at least one thermal parameter of the heating system, particularly of the contents of the cooking utensil, on the basis of the above set of measurements.

Abstract: A cooktop apparatus, in particular an induction cooktop apparatus, includes a switching unit configured to interrupt and establish current flow from a current supply, a first switching element receiving the current flow during an operating process, a control apparatus, which controls the switching unit during the operating process such that the switching unit interrupts the current supply during a first time interval which has a duration of less than of half a period of the power supply voltage. The control apparatus causes the current supply to be connected during the operating process immediately before and immediately after the first time interval. The first switching element begins switching and ends switching during the first time interval.

Abstract: A system and method for induction cooking using an induction cooking unit, an interface adapted to receive, store, and execute a plurality of instructions of a multistage programmable recipe using the induction cooking unit, a power supply, a controller coupled to said power supply, said interface, and said induction cooking unit.

Abstract: A cooktop device includes at least one heater arrangement, and at least one control unit configured to define in at least one operating mode a number of virtual heating zones with different heat output densities depending on a size of the cookware. The virtual heating zones are formed by adjacently arranged heating elements of the heater arrangement of a number or size sufficient to heat the cookware.

Abstract: A level shifting circuit has an input configured to receive an input signal, wherein the input signal has symmetrical maximum and minimum voltages. The level shifting circuit further includes an output configured to provide an output signal, wherein the output signal has asymmetrical maximum and minimum voltages. The output signal is generated in response to the input signal. The output signal is applied to drive a gate terminal of a SiC MOSFET.

Abstract: A heating apparatus, in particular a hob heating apparatus, with at least one heating connection for at least one heating element and at least one frequency unit. In order to provide a heating apparatus of the generic type with relatively high operational reliability, it is proposed that the heating apparatus comprises a protective unit, which is provided for determining the existence of a conducting path between the frequency unit and the at least one heating connection.

Abstract: A cooker, a method for controlling power of a cooker, and a power control system including the same are provided. A high power cooking device can be used without making an additional power construction work or causing a power circuit breaker installed in an input terminal of a household power source to be opened. Driving power of a burner is controlled or distributed by using a current flowing in a power circuit breaker or an overcurrent breaker installed in a load end, whereby power operation efficiency of an input power source can be enhanced and the input power source cannot be broken.

Abstract: A load control device for controlling power delivered from an AC power source to an electrical load includes a thyristor, a first current path for conducting current through a gate terminal of the thyristor, and a control circuit for controlling the first current path to conduct a pulse of current through the gate terminal to render the thyristor conductive at a firing time during a present half cycle. The first current path is able to conduct at least one other pulse of current through the gate terminal between the firing time, and a second time that occurs before an end of the present half-cycle, but is prevented from conducting pulses of current between the second time and the end of the present half-cycle. The load control device includes a second current path for conducting current through the electrical load if the thyristor becomes and remains non-conductive during the present half-cycle.

Abstract: A control method for a switching power supply circuit, the control method causing a processor to execute a process, the process includes: calculating a differential value between an output voltage of the switching power supply circuit and a target voltage; multiplying the differential value by a first coefficient to calculate a correction value; correcting a first detection value of an output current of the switching power supply circuit, which is detected by a current transformer circuit, based on the correction value, to generate a second detection value; comparing the second detection value with a threshold current value to determine whether or not an overcurrent has occurred; and reducing, when it is determined that the overcurrent has occurred, the output voltage of the switching power supply circuit.

Abstract: The invention relates to a method for determining and regulating the temperature of an article with inductive properties which is heated inductively by means of an induction device, wherein the induction device contains an induction coil, means for producing an induction resonant circuit and a support element arranged above the induction coil and having a first side, which acts as support face for the article, and a second side, which is directed towards the inductive coil. At least one temperature sensor is fitted to the second side. The resonant frequency of the induction resonant circuit is measured via detection means and the temperature of the article is calculated from the measured resonant frequency, wherein the resonant frequency is related to the temperature of the article by virtue of a mathematical function, and the function is determined by determining at least two absolute temperature calibration values of the article at respectively different resonant frequencies.

Abstract: In a method for operating a cooking zone of a cook top, wherein the cooking zone is formed by at least two cooking sub-zones and each cooking sub-zone can be heated by at least one heating unit, with the heating units arranged adjacent to each other without overlapping such that a cohesive heatable surface is formed during a joint operation of the cooking sub-zones, detection of an occupancy of a cooking sub-zone by at least one food preparation vessel is activated in a first operating mode and a same electrical power is supplied to all activated cooking sub-zones occupied by a food preparation vessel.

Abstract: An induction heating apparatus in accordance with the present disclosure includes a coil; an inverter unit configured to have a switching device turned on and off to supply power to the coil; a first controller configured to generate a first threshold current based on information about a coil current flowing in the coil and an input voltage applied to the coil, and generate a clock signal by comparing the coil current with the first threshold current; and a switch driver configured to generate a switch driving signal to turn on or off the switching device of the inverter unit by dividing a frequency of the clock signal.

Abstract: A DC to DC power converter includes a switching circuit and an LC filter configured to reduce parasitic inductance. The LC filter includes an inductor, capacitor, and a coil positioned and oriented relative to and electrically connected with the capacitor. The coil positioned with the capacitor provides the ripple current caused by operation of the switching circuitry to flow through the capacitor and coil with opposite direction. The ripple current flowing through the coil attenuates a magnetic field generated by the capacitor while reducing parasitic inductance of the capacitor.

Abstract: The invention relates to a choke circuit and a bus power supply incorporating same. Such a coil choke circuit includes an inductor connected between a first input terminal and a first output terminal, a boost circuit connected between a second input terminal and a second output terminal for increasing the voltage level that is output by the second output terminal. A switching element is connected in parallel to the boost circuit for bypassing the boost circuit. Additionally, a comparator is connected between the first input terminal and the first output terminal for detecting a potential difference across the inductor; wherein in case the comparator detects a potential difference higher than a threshold, the switching element is controlled to be in an OFF state; and in case the comparator detects a potential difference lower than or equal to the threshold, the switching element is controlled to be in an ON state.

Abstract: An electronic induction heating cooker is provided. The electronic induction heating cooker may include a rectifier that rectifies an input voltage into a direct current (DC) voltage and output the DC voltage, an inverter including first, second and third switches connected in series between a positive power source terminal and a negative power source terminal to generate an alternating current (AC) voltage by switching the DC voltage, a first heater driven by the AC voltage so as to heat a first cooking container, a second heater connected in parallel to the first heater and driven by the AC voltage so as to heat a second cooking container, and a switching controller that generates a switching signal for controlling the first and second heaters in accordance with a set of operating conditions input thereto and adjusts a duty cycle of the switching signal.

Abstract: There is provided a placement position determining part that calculates a rising gradient of an output value of the infrared sensor every after passage of a first predetermined time and performs a placement position determining operation of determining that a placement position of a cooking vessel is improper when the rising gradient is smaller than a first threshold value, and the placement position determining part performs the placement position determining operation after a lapse of a second predetermined time from the start of heating, thereby accurately determining that the cooking vessel is improperly placed on a top plate and preventing overheating of the cooking vessel.

Abstract: An induction heating cooker includes a top plate on which an object to be heated is placed, a plurality of heating coils disposed adjacent to one another below the top plate to generate inductive magnetic fields to heat the object to be heated, a plurality of temperature detectors operable to detect a temperature of the object to be heated; and a controller operable to control operating states of the heating coils based on detection results of the temperature detector, wherein the plurality of temperature detectors are disposed widely below the top plate, and the number of the temperature detectors is less than the number of the heating coils.

Abstract: A hob having at least one inductor, at least one inverter, a switching apparatus and a detection circuit for detection of cooking utensils. The switching apparatus is arranged in a circuit between the inductor and the inverter and switchable between a first switch position in which a connection between the inverter and the inductor is established and a second switch position in which the connection between the inverter and the inductor is interrupted. In order to allow an energy-saving detection mode, the switching apparatus is connected to the detection circuit such that the switching apparatus connects the inductor to the detection circuit when it is in the second switch position.

Abstract: The present disclosure provides systems and methods for protecting switching elements in an induction heating system. A switching power loss associated with a switching element of the induction heating system can be calculated and an operating frequency of the induction heating system can be adjusted based upon the switching power loss. According to one aspect, the switching power loss can be classified into one of a plurality of threat zones based upon the magnitude of the switching power loss and the operating frequency can be adjusted based upon the threat zone into which the switching power loss is classified. According to another aspect, the switching power loss can be calculated based at least in part on a duty cycle of an output signal. The duty cycle of the output signal can provide an indication of the proximity of the operating frequency of the induction heating system to resonance.

Abstract: Provided is an induction heat cooking apparatus. The induction heat cooking apparatus includes a rectifying part rectifying an input voltage to output a DC voltage, an inverter switching the DC voltage outputted through the rectifying part to generate an AC voltage, a first heating part operated by the AC voltage applied from the inverter, a second heating part connected to the first heating part in parallel, the second heating part being operated by the AC voltage applied from the inverter, and a switching signal generation part controlling an operation state of each of the first and second heating parts from the inverter according to an operation mode inputted from the outside. The switching signal generation part includes an inverter driver including a bootstrap circuit.

Abstract: A parallel resonant circuit with excellent distortion and saturation characteristics is provided at low power consumption. A first power-supply voltage is applied to the parallel resonant circuit. In the parallel resonant circuit, a variable resistor includes one or more parallel-connected branches. Each of the branches includes a series circuit of a resistor and a MOS switch. A second power supply supplies power of control signals applied to respective gates of the MOS switches, and supplies back gate voltages to the MOS switches. A power-supply voltage of the second power supply is higher than the first power-supply voltage.

Abstract: Provided is an induction heat cooking apparatus. The induction heat cooking apparatus includes a rectifying part rectifying an input voltage to output a DC voltage, an inverter switching the DC voltage outputted through the rectifying part to generate an AC voltage, a first heating part operated by the AC voltage applied from the inverter, a second heating part connected to the first heating part in parallel, the second heating part being operated by the AC voltage applied from the inverter, and a switching signal generation part controlling an operation state of each of the first and second heating parts from the inverter according to an operation mode inputted from the outside. The switching signal generation part includes a photo coupler.