DESCRIPTION
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`Title of Invention
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`POWER CONVERSION DEVICE
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`Technical Field
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`[0001] The present disclosure relates to a power conversion apparatus.
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`Background Art
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`[0002]
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`Ina power conversion apparatus configured to convert AC powerinto DC power, such
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`10
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`as one used in a chargerorthe like, a capacitor for voltage smoothing is precharged by utilizing
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`athyristor. For example, Patent Literature (hereinafter, referred to as “PTL”) 1 uses a thyristor
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`as a rectifier device, and discloses a configuration in which a thyristor is fired in accordance
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`with a difference value between a voltage of AC powerand a voltage charged to a capacitor.
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`[0003]
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`Incidentally, when a malfunction occurs in which a voltage value of AC powerat the
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`15
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`time of starting firing of a thyristor deviates from an assumed voltage value (hereinafter, the
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`malfunction will be referred to as “erroneous firing”), an excessive inrush current may be
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`generated to affect a circuit and/or the like of a power conversion apparatus in a case wherethe
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`difference value described above is large. Accordingly, for example, PTL 2 discloses a
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`configuration for preventing the erroneous firing described above by detecting a pulse-shaped
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`20
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`voltage drop or an instantaneousvoltage decline in an input voltage.
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`Citation List
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`Patent Literature
`
`[0004]
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`

`

`PTL 1
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`Japanese Patent No. 4337032
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`PTL 2
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`Japanese Patent Application Laid-Open No. H08-275532
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`Summary of Invention
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`Technical Problem
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`[0005] However, in a case where a frequency of AC powerhasfluctuated, the erroneousfiring
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`described above mayeasily occur since voltage values of the AC power before and after the
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`10
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`fluctuation at a timing of firing a thyristor diverge from each other.
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`The configuration
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`described in PTL 2 does not take a fluctuation in a frequency of AC powerinto consideration so
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`that there is a certain limit as a configuration for preventing erroneousfiring ofa thyristor.
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`[0006] An object of the present disclosure is to provide a power conversion apparatus capable
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`of preventing erroneousfiring of a thyristor.
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`15
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`Solution to Problem
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`[0007]
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`A power conversion apparatus according to the present disclosure is a power
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`conversion apparatus that converts AC power into DC power, the power conversion apparatus
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`including:
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`20
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`a rectifier including a thyristor;
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`a capacitor provided at a stage subsequentto the rectifier; and
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`a controller that controls firing of the thyristor, wherein
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`the controller causes powerto be supplied to the capacitor by performingthefiring of the
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`thyristor after a predetermined time from when a voltage of the AC powerhasreached a zero-
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`

`

`cross point, and sets the predetermined time short every time the firing of the thyristor is
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`performed,
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`the predetermined time being determined in accordance with a predetermined
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`frequency of the AC power, the zero-cross point being where the voltage of the AC poweris
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`zero, and
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`in a case where a frequency of the AC power has fluctuated from the predetermined
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`frequency, the controller performs control such that the firing of the thyristor is not performed
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`after the predetermined time determined in accordance with the predetermined frequency.
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`AdvantageousEffects of Invention
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`10
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`[0008] According to the present disclosure, it is possible to prevent erroneous firing of a
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`thyristor.
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`Brief Description of Drawings
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`[0009]
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`15
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`FIG.
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`1
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`illustrates a power conversion apparatus according to an embodiment of the
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`present disclosure;
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`FIG.2 is a time chart for describing thyristor firing control;
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`FIG. 3 is a time chart for describing an example in whichathyristorfiring timing deviates;
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`FIG.4A is a diagram for describing voltage ranges set for each predetermined timing;
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`20
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`FIG. 4B is a diagram for describing an example of determination of a frequency
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`fluctuation of AC power;
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`FIG.5 is a flowchart illustrating an example of operation of the thyristor firing control in
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`the power conversion apparatus;
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`FIG.6 illustrates a voltage waveform of the AC power when a sudden voltage fluctuation
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`

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`occurs; and
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`FIG. 7 illustrates a power conversion apparatus according to a variation of the
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`embodiment.
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`Description of Embodiments
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`[0010] Hereinafter, an embodiment of the present disclosure will be described in detail based
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`on the accompanying drawings.
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`FIG. 1 illustrates power conversion apparatus 100 according
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`to the embodimentof the present disclosure.
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`[0011] As illustrated in FIG. 1, power conversion apparatus 100 is a charger which is
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`10
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`connected to external AC power supply 10, and which charges battery 20 by converting AC
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`powersupplied from external AC powersupply 10 into DC power. Battery 20 is, for example,
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`a battery mounted on a vehicle such as an electric car and a hybrid vehicle.
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`[0012] Power conversion apparatus 100 includesrectifier 110, voltage detector 120, power
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`factor corrector 130, DC/DC converter 140, and controller 150.
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`15
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`[0013] Rectifier 110 includes a bridge circuit formed offirst thyristor 111, second thyristor
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`112,first diode 113, and second diode 114.
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`[0014] First thyristor 111 includes an anode connected to a positive electrode of external AC
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`power supply 10, and a cathode connected to input wiring 130A of powerfactor corrector 130.
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`Further, first thyristor 111 includes a gate connected to controller 150.
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`20
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`[0015]
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`Second thyristor 112 includes an anode connected to ground wiring 130B of power
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`factor corrector 130, and a cathode connected to the positive electrode of external AC power
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`supply 10.
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`Second thyristor 112 includes a gate connected to controller 150.
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`[0016] First diode 113 includes an anode connected to a negative electrode of external AC
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`powersupply 10, and a cathode connected to input wiring 130A of powerfactor corrector 130.
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`

`

`[0017]
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`Second diode 114 includes an anode connected to ground wiring 130B of power factor
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`corrector 130, and a cathode connected to the negative electrode of external AC powersupply
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`10.
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`[0018]
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`Controller 150 controls firing of first
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`thyristor 111 and second thyristor 112.
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`Specifically, controller 150 adjusts conduction states of first thyristor 111 and second thyristor
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`112 by applying a voltage to each gate of first thyristor 111 and second thyristor 112. First
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`thyristor 111 and second thyristor 112 are fired, and thereby rectifier 110 converts AC power
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`output from external AC powersupply 10 into DC powerbyfull-waverectification, and outputs
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`the DC power to powerfactor corrector 130. Control of rectifier 110 will be describedlater.
`
`10
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`[0019] Voltage detector 120 is a voltage sensor configured to detect a voltage value of AC
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`powerinputto rectifier 110, and is provided at a stage precedingrectifier 110.
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`[0020]
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`Powerfactor corrector 130 is a powerfactor correction circuit configured to correct the
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`power factor of DC powerinput from rectifier 110. Power factor corrector 130 includescoil
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`131, switching device 132, diode 133, and capacitor 134.
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`15
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`[0021] Coil 131 is provided in input wiring 130A. Coil 131 includes one end connected to
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`an output terminal on a side of the cathode offirst thyristor 111 of rectifier 110, and the other
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`end connected to the anode of diode 133.
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`[0022]
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`Switching device 132 is a field effect transistor, and is provided between input wiring
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`130A and ground wiring 130B.
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`Specifically, switching device 132 includes a drain connected
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`20
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`to the other end of coil 131 in input wiring 130A and to the anode of diode 133, and a source
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`connected to ground wiring 130B of power factor corrector 130.
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`Switching device 132
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`includes a gate connected to controller 150.
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`[0023] Diode 133 is provided in input wiring 130A. Diode 133 includes an anode connected
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`to the other end of coil 131, and a cathode connected to DC/DC converter 140.
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`

`

`[0024] Capacitor 134 is provided at a stage subsequent to diode 133.
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`Specifically, capacitor
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`134 includes one end connected to the cathode of diode 133, and the other end connected to a
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`ground of powerfactor corrector 130. Thus, an electric charge corresponding to the output of
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`powerfactor corrector 130 is charged to capacitor 134, and DC poweroutput from power factor
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`corrector 130 is smoothed.
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`[0025] DC/DC converter 140is a circuit configured to convert DC power output from power
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`factor corrector 130 into DC powerthat can be charged to battery 20, and is connectedat a stage
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`subsequent to power factor corrector 130. Controller 150 controls a switching device (not
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`illustrated) mounted on DC/DC converter 140.
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`Thus, DC power converted by DC/DC
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`10
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`converter 140 is output to battery 20 to charge battery 20.
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`[0026] Controller 150 includes a central processing unit (CPU) (notillustrated), a read only
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`memory (ROM)(not illustrated), a random access memory (RAM)(notillustrated), and an
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`input/output circuit (not illustrated). Controller 150 is configured to control, in addition to
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`powerfactor corrector 130 and DC/DC converter 140, firing of first thyristor 111 and second
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`15
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`thyristor 112, based on a preset program. Notethat, in the following description, first thyristor
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`111 and second thyristor 112 are simply referred to as “thyristor” in a case where they are not
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`particularly distinguished.
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`[0027]
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`Controller 150 controls an amount of DC power output from rectifier 110 by
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`controlling firing of the thyristor.
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`Specifically, in a case where a voltage is precharged to
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`20
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`capacitor 134, controller 150 adjusts a firing timing of the thyristor in accordance with a voltage
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`value of capacitor 134 such that the voltage value increases stepwise.
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`[0028] The reason for this will be described below.
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`To cause power factor corrector 130 of power conversion apparatus 100 to operate
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`normally, it is necessary to perform precharging such that a voltage value of capacitor 134
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`

`

`becomes a desired voltage value. However, in a case where capacitor 134 is not sufficiently
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`charged, a difference between a voltage value of capacitor 134 and a voltage value of AC power
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`becomes excessive. Asa result, an excessive inrush current may occur dueto the difference to
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`affect a peripheral circuit.
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`[0029] Accordingly, controller 150 adjusts a firing timing of the thyristor such that the voltage
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`value of capacitor 134 increases stepwise.
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`[0030]
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`In more detail, controller 150 performs firing of one offirst thyristor 111 and second
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`thyristor 112 for a fixed term after a predetermined time from when a voltage value of AC power
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`output from external AC powersupply 10 has reached a zero-cross point where the voltage value
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`10
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`of the AC poweris zero. First thyristor 111 1s fired when the voltage value of the AC poweris
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`a positive value.
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`Second thyristor 112 is fired when the voltage value of the AC poweris a
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`negative value.
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`[0031]
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`The predetermined time is a time determined in accordance with a predetermined
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`frequency and is, for example, a time equivalent to a time less than a half period of the
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`15
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`predetermined frequency. The predetermined frequency is a frequency of AC powerandis,
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`for example, a frequency identified by controller 150 based on a voltage value of the AC power
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`detected by voltage detector 120.
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`[0032] Then, controller 150 sets the predetermined time short every time the firing of one of
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`first thyristor 111 and second thyristor 112 is performed.
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`Thyristor firing control will be
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`20
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`described in detail with reference to FIG.2.
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`[0033]
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`Asillustrated in FIG.2, the firing of the thyristoris started at time TT1 after the output
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`of AC powerhas been started and a predetermined time (a predetermined timefor first firing)
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`has elapsed from time T1 serving as the zero-cross point.
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`Since the voltage value of the AC
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`power from time T1 to time T2is a positive value, first thyristor 111 1s fired at time TT1. At
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`

`

`this time, the voltage value of capacitor 134 is set to zero. Note that, time T2 is a time when a
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`time equivalent to a half period of the AC powerhaselapsed from time T1.
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`[0034] The predetermined timeforthefirst firing is a time equivalent to from a phase angle
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`of the AC power of 0° (equivalent to a point corresponding to time T1) to a phase angle of the
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`AC power(time TT1) slightly smaller than a phase angle of the AC power of 180° (a point
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`corresponding to time T2). The predetermined timefor the first firing is a time such that an
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`inrush current generated due to a voltage value equivalent to a voltage value of the AC power
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`whenthe predetermined time has elapsed becomes such a value that does not affect a peripheral
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`circuit, and is appropriately set by an experimentor the like.
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`10
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`[0035] Whenthefirst firing is started, a current based on a difference between a voltage value
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`of the AC powerat the time of starting the first firing and a voltage value of capacitor 134
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`(hereinafter, the current will be referred to as “precharge current’) flows, and thereby an electric
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`charge equivalent to the precharge current is charged to capacitor 134. Thus, the voltage value
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`of capacitor 134 increases to a voltage value correspondingto the electric charge.
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`Since the
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`15
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`voltage of the AC power decreases between time TT1 and time T2 and the voltage value of
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`capacitor 134 does not increase any further, first thyristor 111 automatically stops and the
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`precharge currentalso stops.
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`[0036] Note that, a voltage is applied to the gate offirst thyristor 111 for a fixed term (a term
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`from time TT1 to a time slightly past time T2) by controller 150 (see “gate voltage of first
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`20
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`thyristor” in FIG.2).
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`[0037] After the AC powerhas reached the zero-cross point at time T2, the firing of the
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`thyristor is started at time TT2 after a predetermined time (a predetermined time for second
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`firing) has elapsed from time T2.
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`Since the voltage value of the AC power from time T2 to
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`time T3 is a negative value, second thyristor 112 is fired at time TT2. Note that, time T3 is a
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`

`

`time when the time equivalent to the half period of the AC powerhaselapsed from time T2.
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`[0038] The predetermined time for the secondfiring is a time shorter than the predetermined
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`time for the first firing. The predetermined time for the secondfiring is a time such that an
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`inrush current generated due to a voltage value equivalent to a difference value between a
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`voltage value of the AC power whenthe predetermined time has elapsed and a voltage value of
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`capacitor 134 becomessuch a value that doesnot affect a peripheral circuit, and is appropriately
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`set by an experimentorthelike.
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`[0039] Whenthe secondfiring is started, a precharge current based on a difference between a
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`voltage value of the AC powerat the time of starting the second firing and a voltage value of
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`10
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`capacitor 134 flows, and thereby an electric charge equivalent to the precharge current is charged
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`to capacitor 134.
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`Thus, the voltage value of capacitor 134 increases to a voltage value
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`corresponding to the electric charge.
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`Since the voltage of the AC power decreases between
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`time TT2 and time T3 and the voltage value of capacitor 134 does not increase any further,
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`second thyristor 112 automatically stops and the precharge currentalso stops.
`
`15
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`[0040]
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`In this way, the firing of the thyristor is repeatedly performed, and thereby the voltage
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`value of capacitor 134 gradually increases.
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`Then, at n-th (where n is an arbitrary natural
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`number)firing, the firing is performed at time TTn when a predetermined time has elapsed from
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`time Tn of the zero-cross point, and thereby the voltage value of capacitor 134 reaches a desired
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`value.
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`20
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`[0041] Thereafter, the gate of first thyristor 111 and the gate of second thyristor 112 are in a
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`state in which a voltage is always applied thereto, and operations of power factor corrector 130
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`and DC/DC converter 140 are started.
`
`[0042]
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`Further,
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`in a case where a frequency of the AC power has fluctuated from the
`
`predetermined frequency, controller 150 controls such that the firing of the thyristor is not
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`

`

`performed after the predetermined time from when the zero-cross point has been reached.
`
`[0043]
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`Asillustrated in FIG. 3, there is a case where a frequency of AC power output from
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`external AC powersupply 10 fluctuates.
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`Thesolid line in FIG. 3 indicates an example in which
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`the frequency of the AC powerin a secondperiod (after time T3) is smaller than the frequency
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`of the AC powerinafirst period (from time T1 to time T3). The broken line in FIG.3 indicates
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`an example in which the frequency of the AC powerin the second period has not fluctuated from
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`the frequency of the AC powerin thefirst period.
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`[0044] For example, in a case where the frequency of the AC powerhas fluctuated such that
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`the frequency of the AC powerin the second period becomes smaller than the frequency of the
`
`10
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`AC powerin the first period, third firing is performed based on a predetermined time for the
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`third firing set in accordance with predetermined times for firing in the first period(first firing
`
`and secondfiring). That is, the firing of first thyristor 111 is started at time TT3 when the
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`predetermined timefor the third firing has elapsed from time T3 that is the zero-cross point of
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`the AC powerin the second period.
`
`15
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`[0045] Accordingly, when the frequency of the AC powerhasfluctuated, a malfunction occurs
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`in which difference value D between a voltage value at time TT3 at the timeofstarting the firing
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`in a case where the frequency of the AC power has notfluctuated (see the broken line) and a
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`voltage value at time TT3 in a case where the frequency of the AC powerhasfluctuated (see the
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`solid line) becomes large (hereinafter, the malfunction will be referred to as “erroneousfiring”).
`
`20
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`Whendifference value D described above becomeslarge dueto the erroneousfiring, a difference
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`value between a voltage value of capacitor 134 and a voltage value of the AC powerat the time
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`of starting the firing may become excessive, and further an excessive inrush current may occur.
`
`[0046]
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`Inthe present embodiment, however, controller 150 controls such that the firing of the
`
`thyristor is not performed after the predetermined time in a case where the frequency of the AC
`
`10
`
`

`

`powerhasfluctuated from the predetermined frequency so that the thyristor is not fired at time
`
`TT3. Asaresult, it is possible to prevent an inrush current from being generated due to a
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`fluctuation in the frequency of the AC power. Note that, FIG.3 illustrates an example in which
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`the firing of first thyristor 111 is not performed at time TT3 since the voltage value of the AC
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`powerrelating to the third firing is positive.
`
`[0047]
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`Specifically, controller 150 determines whether the frequency of the AC power has
`
`fluctuated from the predetermined frequency by detecting a voltage waveform of the AC power
`
`until a predetermined time elapses from whenthe zero-cross point has been reached.
`
`[0048]
`
`In more detail, controller 150 sets respectively voltage ranges of a plurality of voltage
`
`10
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`values for each predetermined timing within one period of the AC powerin accordance with the
`
`predetermined frequency. The respective voltage values are, for example, voltage values of
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`the AC power within a period before that of a current time, and are stored in a storage (not
`
`illustrated).
`
`The predetermined timing is a timing determined in accordance with the
`
`frequency of the AC powerand is 1 ms, for example.
`
`15
`
`[0049]
`
`For example, a voltage value to be compared with a voltage value of the voltage
`
`waveform after time T3 in FIG.3 is that of the voltage waveform of one period from time T1 to
`
`time T3. A voltage value of the voltage waveform from time T1 to time T3 is detected by
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`voltage detector 120 for each predetermined timing, and is stored in the storage or the like for
`
`each predetermined timing. Note that, the voltage waveform to be compared may be the
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`20
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`voltage waveform of one period further before that of time T1.
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`[0050]
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`Then, controller 150 reads voltage values corresponding to each timing from the
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`storage, and sets voltage ranges of the voltage values.
`
`[0051]
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`Specifically, as illustrated in FIG. 4A, controller 150 sets voltage ranges of respective
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`voltage values of AC power for each predetermined timing during a predetermined time.
`
`FIG.
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`11
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`

`

`4Aillustrates an example in which voltage ranges v1, v2, v3, v4, v5, v6, v7, v8, v9, and v10 are
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`set at respective timings of times m1, m2, m3, m4, m5, m6, m7, m8, m9, and m10.
`
`[0052]
`
`In acase wherea voltage value of the AC power does not deviate from at least one of
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`the voltage ranges set at a timing corresponding to the voltage value, controller 150 determines
`
`that the frequency of the AC powerhasnotfluctuated from the predetermined frequency.
`
`Ina
`
`case where a voltage value of the AC powerdeviates from at least one of the voltage range set
`
`at a timing corresponding to the voltage value, controller 150 determines that the frequency of
`
`the AC powerhasfluctuated from the predetermined frequency.
`
`[0053] For example, in an example illustrated in FIG. 4B, the voltage of the AC powerat time
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`10
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`m1 (see the solid line) is within voltage range v1 set by a voltage of the AC powerin a period
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`before that of time m1 (see the broken line), controller 150 determines that the frequency ofthe
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`AC powerhasnotfluctuated from the predetermined frequency at time m1.
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`[0054] On the other hand, since the voltage of the AC powerat time m3, for example, is outside
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`voltage range v3 set by a voltage of the AC powerin a period before that of time m3, controller
`
`15
`
`150 determines that the frequency of the AC power has fluctuated from the predetermined
`
`frequency at time m3.
`
`[0055]
`
`Inacase where the frequency of the AC powerhasfluctuated from the predetermined
`
`frequency, controller 150 does not control the firing of the thyristor during a predetermined
`
`period (for example, three periods). Then, controller 150 resumesthe control of the firing of
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`20
`
`the thyristor after the predeterminedperiod.
`
`[0056]
`
`In this way, in a case wherethe frequency of the AC powerhasfluctuated,it is possible
`
`to resume the control of the firing of the thyristor after waiting for the frequency of the AC
`
`powerto return to normal by the predetermined period having elapsed.
`
`[0057] Note that, the predetermined period may be configured to fluctuate in accordance with
`
`12
`
`

`

`an amountof fluctuation in the frequency of the AC power. For example, the predetermined
`
`period may be configured to be longer as an amount offluctuation in the frequency of the AC
`
`poweris larger.
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`Thus,it is possible to ensure a lot of time for the frequency of the AC power
`
`to return to normal.
`
`[0058]
`
`Further, when the control of the firing of the thyristor is resumed, the voltage value of
`
`capacitor 134 may fluctuate due to an electric discharge or the like. Accordingly, controller
`
`150 may be configured to resume the control of the firing of the thyristor after setting the
`
`predetermined time described above in accordance with the voltage value of capacitor 134.
`
`[0059]
`
`Thus,it is possible to control the firing of the thyristor in view of a fluctuation in the
`
`10
`
`voltage value of capacitor 134 after resumingthe firing of the thyristor. Note that, the voltage
`
`value of capacitor 134 may be detected by a voltage detector (notillustrated).
`
`[0060] Note that, all the voltage ranges at the respective timesare set as the same range in FIG.
`
`4A orthe like, but may be set as different ranges depending on the times. For example, when
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`voltage rangesare set such that the voltage ranges becomenarroweras closer to a time when the
`
`15
`
`firing of the thyristor is started, it is possible to prevent an excessive current from flowing at the
`
`time of erroneousfiring, and to improve the accuracy of control of the firing of the thyristor.
`
`[0061] An example of operation of the thyristor firing control in power conversion apparatus
`
`100 configured as described above will be described.
`
`FIG. 5 is a flowchart illustrating the
`
`example of operation of the thyristor firing control in power conversion apparatus 100. The
`
`20
`
`processing in FIG. 5 is executed, for example, (1) after the input of AC powerfrom external AC
`
`powersupply 10 to power conversion apparatus 100is started, (2) after the firing of the thyristor
`
`is started, and (3) aftera firing stop counter to be describedlater is set.
`
`Further, the processing
`
`in FIG. 5 is repeatedly performeduntil the voltage value of capacitor 134 reachesa desired value.
`
`[0062] Asillustrated in FIG. 5, controller 150 determines whetherthe voltage of the AC power
`
`13
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`

`

`has reached the zero-cross point (step S101). Asa result of the determination, in a case where
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`the voltage of the AC powerhasnot reached the zero-cross point (step $101, NO), the processing
`
`of step $101 is repeated.
`
`[0063]
`
`In a case where the voltage of the AC power has reached the zero-cross point (step
`
`$101, YES), on the other hand, controller 150 determines whetherthefiring stop counter is at 0
`
`(step $102). The firing stop counteris set in accordance with the predetermined period when
`
`the firing of the thyristor is not performed in step $112 to be describedlater.
`
`[0064] As aresult of the determination, in a case wherethe firing stop counteris not at 0 (step
`
`$102, NO), controller 150 decrements the firing stop counter (step $103). After step $103,
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`10
`
`this control ends.
`
`[0065]
`
`In a case wherethe firing stop counter is at 0 (step $102, YES), on the other hand,
`
`controller 150 causes the voltage value of the AC powerin the last period to be stored in the
`
`storage or the like (notillustrated) (step $104).
`
`[0066] Next, controller 150 sets the predetermined time in accordance with the number of
`
`15
`
`firing (step S105). Controller 150 calculates a prediction voltage value of the AC powerat a
`
`current time (step $106). Then, controller 150 calculates an upper limit value and a lowerlimit
`
`value of the prediction voltage value (step $107).
`
`Further, controller 150 acquires an actual
`
`measurementvalue of the voltage of the AC powerat the current time (step $108).
`
`[0067] Next, controller 150 determines whether the actual measurement value is within a
`
`20
`
`range between the upper limit value and the lowerlimit value (step $109). As a result of the
`
`determination, in a case where the actual measurement value is within the range between the
`
`upperlimit value and the lowerlimit value (step S109, YES), controller 150 determines whether
`
`the predetermined time has elapsed from a time whenthe zero-cross point has been reached in
`
`step $101 (step S110).
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`14
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`

`

`[0068] As aresult of the determination, in a case where the predetermined time hasnot elapsed
`
`(step S110, NO), the processing returns to step $106.
`
`In a case where the predetermined time
`
`has elapsed (step S110, YES), on the other hand, controller 150 starts the firing of the thyristor
`
`(step $111).
`
`[0069]
`
`Inacase wherethe actual measurementvalueis not within the range between the upper
`
`limit value and the lower limit value in the determination of step S109 (step S109, NO),
`
`controller 150 sets the firing stop counter to a predetermined value (for example, 3) without
`
`performing the firing of the thyristor (step $112). After step S111 or step $112, this control
`
`ends.
`
`10
`
`[0070] According to the present embodiment configured as described above,the firing of the
`
`thyristor 1s not performed in a case where the frequency of the AC powerhasfluctuated so that
`
`it is possible to prevent erroneousfiring of the thyristor, and further to suppress generation of an
`
`excessive inrush current generated dueto the erroneousfiring.
`
`[0071]
`
`Further, even in a case where the frequency of the AC powerhasnotfluctuated and the
`
`15
`
`voltage of the AC powerhas suddenly fluctuated as illustrated in FIG. 6, a voltage value of the
`
`AC powerat a timing at which the voltage has fluctuated deviates from a voltage range at the
`
`timing. The example illustrated in FIG. 6 is an example in which a voltage value of the AC
`
`powerdeviates from voltage range v2. Thus, when a voltage value of the AC powerdeviates
`
`from a voltage range, the voltage value may diverge from a voltage value that is assumed when
`
`20
`
`performing the firing, and erroneousfiring may be performed.
`
`[0072] However, the present embodimentis capable of detecting a voltage fluctuation of AC
`
`powereven in such a case, and is therefore capable of preventing erroneousfiring from being
`
`performed due to a voltage fluctuation of AC power.
`
`[0073] Note that, although rectifier 110 including a thyristor is provided at a stage preceding
`
`15
`
`

`

`powerfactor corrector 130 in the embodiment described above, the present disclosure is not
`
`limited thereto. For example, as illustrated in FIG. 7, rectifier 135 including a thyristor may
`
`be provided in powerfactor corrector 130.
`
`[0074] Power conversion apparatus 100 illustrated in FIG. 7 includes voltage detector 120,
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`powerfactor corrector 130, DC/DC converter 140, and controller 150. Voltage detector 120
`
`and DC/DC converter 140 are the sameasin the configuration illustrated in FIG. 1.
`
`[0075] Power factor corrector 130 includes coil 131, capacitor 134, and rectifier 135. Coil
`
`131 includes one end connected to a positive electrode of external AC powersupply 10, and the
`
`other end connected to rectifier 135. Capacitor 134 includes one end connected to output
`
`10
`
`wiring 130C of power factor corrector 130, and the other end connected to ground wiring 130D
`
`of powerfactor corrector 130.
`
`[0076] Rectifier 135 includes a bridge circuit formedoffirst thyristor 135A, second thyristor
`
`135B, first switching device 135C, and second switching device 135D.
`
`[0077] First thyristor 135A includes an anode connected to the other end of coil 131, and a
`
`15
`
`cathode connected to output wiring 130C of power factor corrector 130. First thyristor 135A
`
`includes a gate connected to controller 150.
`
`[0078]
`
`Second thyristor 135B includes an anode connected to ground wiring 130D of power
`
`factor corrector 130, and a cathode connected to the other end of coil 131.
`
`Second thyristor
`
`135B includes a gate connected to controller 150.
`
`20
`
`[0079] First switching device 135C includes a source connected to a negative electrode of
`
`external AC power supply 10, and a drain connected to output wiring 130C of power factor
`
`corrector 130. First switching device 135C includes a gate connected to controller 150.
`
`[0080]
`
`Second switching device 135D includes a source connected to ground wiring 130D of
`
`powerfactor corrector 130, and a drain connectedto the negative electrode of external AC power
`
`16
`
`

`

`supply 10.
`
`Second switching device 135D includes a gate connected to controller 150.
`
`[0081] Controller 150 controls first thyristor 135A, second thyristor 135B, first switching
`
`device 135C, and second switching device 135D,respectively, depending on whethera voltage
`
`value of AC poweris positive or negative. Thus, power factor corrector 130 corrects, while
`
`converting the AC power into DC power, the powerfactor of the DC power.
`
`[0082]
`
`Further, even with such a configuration, it is possible to prevent erroneousfiring of a
`
`thyristor by controlling thyristor firing when capacitor 134 is precharged as in the embodiment
`
`described above.
`
`[0083]
`
`Further,
`
`in the embodiment described above,
`
`in a case where the AC power has
`
`10
`
`fluctuated from the predetermined frequency,it is controlled such that the firing of the thyristor
`
`is not performed during the predetermined period from the zero-cross point, but the present
`
`disclosure is not limited thereto.
`
`Since a time when the voltage value becomes a voltage value
`
`at which the firing is to be started deviates when the AC power has fluctuated from the
`
`predetermined frequency, it may also be configured, for example, such that a start time of the
`
`15
`
`firing in accordance with a frequency after the fluctuation is estimated and the firing of the
`
`thyristor is then performedat the estimatedstart time, forexample.
`
`In this way, in a case where
`
`the AC powerhasfluctuated from the predetermined frequency, the firing of the thyristor is not
`
`performed after the predetermined time that has been set when the AC poweris at the zero-cross
`
`point, but is performed at the estimated start time.
`
`Thus,it is possible to eliminate a term when
`
`20
`
`operation of power conversion apparatus 100 stops, and to improve efficiency of operation.
`
`[0084]
`
`Further, in the embodimentdescribed above,it is controlled such that the firing of the
`
`thyristor is not performed with deviation of a voltage value of the AC power from a voltage
`
`range at a timing corresponding to the voltage value, but the present disclosure is not limited
`
`thereto. For example, it may also be controlled such that the firing of the thyristor is not
`
`17
`
`

`

`performed with o