JP2010148216A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To drive an AD-driven heater for both 100 V and 200 V by a proper electric power regardless of the magnitude of the voltage of a commercial power supply, without providing an exclusive circuit for the detection of AC input voltage. <P>SOLUTION: A control unit 90 detects a PFC drive current Ipfc using a structure used originally in the PFC circuit 20 of the power supply. The control unit decides whether the AC input voltage is 100 V or 200 V based on the detected current value, and controls the drive of a triac 63 based on the decided AC input voltage, optimizing the power supplied to a ceramic heater 62. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus provided with a PFC power supply device.

  For electric loads of image forming apparatuses such as copying machines and printers, the rated power based on the voltage value of the power supply is determined. In the model for Japan, products and loads are based on an AC voltage of 100V. Has been designed. However, in most overseas models, the AC voltage is not 100V. For example, if an AC voltage of 200 V is input in a waveform pattern as it is to an AC load of a product designed with an AC voltage of 100 V as a reference, twice the voltage is supplied to the AC load. In this case, since the power consumption of the AC load is proportional to the square of the AC input voltage, the power consumption is four times that in the case of 100 V input, and equipment failure or malfunction may occur.

Here, a ceramic heater for keeping the recording paper accommodated in the image forming apparatus in a dry state is considered as an example of an AC load. For example, when power is supplied to a ceramic heater having a rated power of 200 W with respect to a voltage of AC voltage of 100 V under the same condition as 100 V at a voltage of 200 V, the power consumption of the ceramic heater is 800 W, and the failure or performance of the ceramic heater It causes deterioration. Therefore, in Patent Document 1, when the magnitude of the input voltage is determined and the input voltage is larger than the rated voltage, the power supplied to the load is kept constant by switching the power supply state and the non-power supply state with respect to the load. We are taking measures such as
JP 2007-110839 A

  However, in the above method, a dedicated voltage detection circuit for determining the input voltage is required, so that it is necessary to secure a space for that purpose, and this also increases the cost of the apparatus.

  In order to solve the above-described problem, an image forming apparatus according to claim 1 is an image forming apparatus having an AC load to which an AC voltage from a commercial power supply is supplied. A power supply circuit that outputs a voltage; a current detection circuit that detects a current flowing through a switching element of the power supply circuit; and a power supply control circuit that controls the output of the power supply circuit based on the detected current; and the AC load A power control element that controls the power to be supplied; and a control unit that controls the power control element. The control unit inputs an output of the current detection circuit and outputs an output of the current detection circuit. The voltage of the commercial power supply is determined based on the magnitude, and the drive of the power control element is controlled based on the determined voltage.

  According to a second aspect of the present invention, there is provided an image forming apparatus having an AC load to which an AC voltage from a commercial power supply is supplied, and a power supply circuit that inputs the AC voltage from the commercial power supply and outputs a predetermined DC voltage. A power control circuit that has a voltage detection circuit that detects the output voltage of the power supply circuit, controls the output of the power supply circuit based on the detected voltage, and a power control element that controls the power supplied to the AC load And a control unit that controls the power control element, wherein the control unit inputs an output of the voltage detection circuit and determines a voltage of the commercial power source based on a magnitude of the output of the voltage detection circuit The driving of the power control element is controlled based on the determined voltage.

  According to the present invention, it is possible to determine the input voltage of the commercial power supply with an inexpensive configuration without providing a dedicated voltage detection circuit.

  Hereinafter, an image forming apparatus according to the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic cross-sectional view of the image forming apparatus according to the first embodiment of the present invention. The image forming apparatus according to the present embodiment is not manufactured for each region where the voltage of the commercial power supply is different. For example, the image forming device can be used with the same configuration in both the 100V region and the 200V region. Therefore, the power supply to the AC load to which the commercial power supply is directly supplied is varied according to the input voltage of the commercial power supply.

  The image forming apparatus shown in the figure includes four image forming units (image forming stations) in the image forming apparatus main body M, that is, a first image forming unit PA, a second image forming unit PB, and a third image forming unit. The part PC and the fourth image forming part PD are arranged in parallel. In each of the image forming portions PA to PD, for example, toner images of colors of yellow, magenta, cyan, and black are formed through charging, exposure, development, and transfer processes.

  Each of the image forming sections PA to PD has a dedicated photosensitive drum 1A, 1B, 1C, 1D. These photosensitive drums 1A, 1B, 1C, and 1D are charged by the charging rollers 2A, 2B, 2C, and 2D, and electrostatic latent images are formed by the laser beam scanners 3A, 3B, 3C, and 3D. Each electrostatic latent image is attached with toner by the developing devices 4A, 4B, 4C, and 4D to form a toner image of each color.

  An intermediate transfer belt (intermediate transfer member) 23 is disposed adjacent to the photosensitive drums 1A to 1D. Here, in the present embodiment, the intermediate transfer belt 23 corresponds to a transfer target. Further, as the intermediate transfer member, an intermediate transfer drum can be used instead of the intermediate transfer belt. The intermediate transfer belt 23 is stretched around a driving roller 24, a driven roller 25, and a secondary transfer counter roller 26. Inside the transfer belt 23, primary transfer rollers (transfer members) 9A, 9B, 9C, 9D are arranged. The intermediate transfer belt 23 is pressed against the photosensitive drums 1A to 1D by the primary transfer rollers 9A to 9D. Thus, a primary transfer nip portion (transfer portion) T1 is formed between the intermediate transfer belt 23 and the photosensitive drums 1A to 1D. The yellow (first color) toner image formed on the photosensitive drum 1A is primary-transferred onto the intermediate transfer belt 23 by applying a primary transfer bias to the primary transfer roller 9A by a transfer bias application power source (not shown). Is done. Similarly, magenta (second color), cyan (third color), and black (fourth color) toner images are sequentially primary-transferred and superimposed on the intermediate transfer belt 23 in the same manner.

  The four color toner images formed on the intermediate transfer belt 23 are transferred to the recording material P supplied from the paper feed cassette 5. The recording material P stored in the paper feed cassette 5 is fed by the feed roller 6 and is timed by the registration roller 7 between the intermediate transfer belt 23 and the secondary transfer roller (transfer member) 27. The toner is supplied to a secondary transfer nip portion (transfer portion) T2 as a transfer portion. The recording material P in the paper feeding cassette 5 is designed to remove moisture absorbed by a cassette heater, that is, a ceramic heater 62 serving as an AC load. A secondary transfer bias is applied to the secondary transfer roller 27 by a transfer bias application power source (not shown). As a result, the four color toner images on the intermediate transfer belt 23 are secondarily transferred onto the recording material P all at once. At this time, the transfer voltage applied to the secondary transfer roller 27 is also determined in the same manner as the primary transfer bias described above.

  During the secondary transfer, toner (transfer residual toner) that is not transferred onto the recording material P and remains on the intermediate transfer belt 23 is removed by a belt cleaning device 28 that is an intermediate transfer member cleaning unit.

  The toner image transferred to the recording material P is fixed by the fixing device 11 at the time of recording P and is discharged outside the apparatus.

  FIG. 2 shows a configuration diagram of the power supply circuit in the first embodiment. The AC voltage from the commercial AC power supply is full-wave rectified by the rectifier circuit 10 and its output is pulsated through a small-capacitance capacitor C1 for absorbing high-frequency ripples. Is converted into a stable DC output. This DC output is supplied to the first load 50. The first load 50 will be described later.

  The PFC circuit 20 includes a switching element Q1, an inductor L1 connected in series between the output of the rectifier circuit 10 together with the switching element Q1, a diode D1, and a capacitor C2. The diode D1 is connected so that a current flows through the inductor L1 when the switching element Q1 is non-conductive. The switching element Q1 drives the converted DC voltage at a frequency sufficiently higher than the frequency of the AC power supply (ON) / non-conduction (OFF). As a result, a smoothed and voltage stabilized DC output is taken out from both ends of the capacitor C2. The output of the PFC circuit 20 is controlled by a PFC control circuit 70 as a power supply control circuit. The control unit 90 controls power supply to the ceramic heater 62 that is an AC load by controlling driving of the triac 63 as a power control element.

  Although not shown, a power source for operating the control unit 90 is separately provided.

  FIG. 3 is a circuit diagram showing details of the PFC control circuit 70 shown in FIG. A voltage V3 obtained by dividing the output voltage V2 of the PFC circuit 20 by the resistors R2 and R3 is one input of the multiplier MUL40 (terminal B of the multiplier MUL40). Further, the input voltage V1 (AC input full-wave rectified waveform) of the PFC circuit 20 is input to the multiplier MUL40 (terminal A of the multiplier MUL40). A multiplier MUL outputs a threshold signal having a full-wave rectified waveform in phase with the input voltage V1 of the PFC circuit 20 and an amplitude corresponding to the voltage V3 obtained by dividing the output voltage V2 of the PFC circuit 20.

  The current Ipfc flowing through the switching element Q1 is converted into a voltage by the resistor R1, and the signal is input from the terminal C of the PFC control circuit 70 and detected by the drive current detection circuit 30. The current detection signal and the threshold signal from the multiplier MUL are compared by the comparator CO. If the current detection signal is smaller than the threshold signal, the drive pulse generation circuit 60 receives a signal from the comparator CO and outputs a drive pulse for operating the switching element Q1 from the terminal D. When the switching element Q1 becomes conductive, the current Ipfc flowing through the switching element Q1 through the inductor L1 gradually increases, but when the current detection signal reaches the threshold signal level, the output of the comparator CO outputs a predetermined signal. Note that the signal detected by the drive current detection circuit 30 is also output to the control unit 90.

  When the current detection signal becomes larger than the threshold signal, drive pulse generation circuit 60 stops outputting the drive pulse, and switching element Q1 becomes non-conductive. When the switching element Q1 becomes non-conductive, the current flowing from the inductor L1 through the diode D1 to the output side gradually decreases.

  When a predetermined time elapses after the switching element Q1 is turned off, the switching element Q1 is turned on again, and the current Ipfc gradually increases. When the current Ipfc reaches the level of the threshold signal, switching element Q1 becomes nonconductive, and the current flowing through inductor L1 gradually decreases. By repeating the above operation, the switching element Q1 is driven to be conductive / non-conductive at a frequency sufficiently higher than that of the AC power supply, and control is performed so that the current Ipfc matches the threshold signal. The ratio between conduction and non-conduction is called duty, and its value is determined by the input voltage of the commercial power supply.

  The drive pulse generation circuit 60 receives a remote signal from the control unit 90. When the remote signal is off, the drive pulse output is stopped regardless of the output from the comparator CO. . That is, the PFC circuit 20 operates only after the remote signal is turned on.

  By the control as described above, the envelope of the current I of the pulsating input becomes a sine wave, and the power factor is improved by suppressing the harmonic component.

  Next, a method for controlling the ceramic heater 62 that is an AC load will be described. As described above, the ceramic heater 62 is used as the cassette heater in FIG.

  In FIG. 2, the zero cross signal detection circuit 80 outputs a zero cross signal when the value of the alternating current from the commercial alternating current power supply becomes zero. In the PFC circuit 20, the drive current (PFC drive current Ipfc) of the switching element Q1 increases in inverse proportion to the decrease in input voltage. In order to keep the output voltage constant, it is necessary to decrease the PFC drive current Ipfc as the input voltage increases. Therefore, as shown in FIG. 5, the relationship between the input voltage and the PFC drive current Ipfc differs in the PFC drive current value Ipfc depending on the input voltage.

  FIG. 6 is a diagram showing an input voltage waveform and a PFC switching current waveform when the input voltage is 100V and 200V. In FIG. 6, a broken line indicates a case where the input voltage is 100V, and a solid line indicates a case where the input voltage is 200V. The PFC drive current is smaller when the input voltage is 200V than when the input voltage is 100V.

  The control unit 90 controls the entire image forming apparatus and also controls the power supplied to the ceramic heater 62. The current detection signal detected by the drive current detection circuit 30 is also input to the control unit 90. As shown in FIG. 5, the control unit 90 serves as an input voltage determination unit that determines the input voltage based on the drive current value of the PFC circuit from the relational expression: Vin = α × Ipfc + Vo between the PFC drive current value and the AC input voltage. Function. The PFC drive current is detected immediately after the image forming apparatus is turned on. In this way, even if a dedicated voltage detection circuit for determining the AC input voltage is not separately provided, the AC input is performed using the PFC control circuit 70 (drive current detection circuit 30) and the circuit originally provided as the resistor R1. The voltage can be determined.

  FIG. 4 is a configuration diagram showing details of the first load 50. The first load 50 includes a switching power source 501, motors 502 and 503, a high voltage power source 504, and the like. The switching power supply 501 is a motor for feeding and discharging the recording material P, and the feed / discharge motor 502 that converts the output voltage V2 of the PFC circuit 20 to DC24V. The photosensitive drum motor 503 includes a plurality of motors that rotate the photosensitive drums 1A to 1D, respectively. A high voltage power source 504 supplies high voltage to the chargers 2 </ b> A to 2 </ b> D, the developing devices 4 </ b> A to 4 </ b> D, the primary transfer rollers 9 </ b> A to 9 </ b> D, and the secondary transfer roller 27. Immediately after the image forming apparatus is turned on, these loads are in a predetermined state.

  The control unit 90 receives a PFC drive current value (current detection signal) and obtains an AC input voltage from a relational expression between a PFC drive current value and an AC input voltage prepared in advance. With respect to the detection of the PFC drive current Ipfc, a signal is input from the circuit originally provided for controlling the PFC circuit 20 to the control unit 90, so that it is not necessary to provide a new current detection circuit. Then, the control unit 90 controls the power supplied to the ceramic heater 62 based on the obtained AC input voltage.

The control unit 90 has a function of controlling the triac 63 as a power control element so that constant power is supplied regardless of the magnitude of the input voltage supplied to the ceramic heater 62 in each cycle of the AC waveform. Yes. That is, the control unit 90 functions as a heater control unit. As described above, when a 200V AC power supply is put under the same condition as 100V with respect to a ceramic heater having a rated power of 100V, the power to the ceramic heater is quadrupled. Therefore, the number of half-waves of the AC voltage supplied to the ceramic heater 62 is adjusted so that the power when the input voltage is 200 V is the same as the power when the input voltage is 100 V.
When the input voltage is 100 V, the controller 90 supplies all the half waves of the sine wave of the AC input voltage to the ceramic heater 62.

  On the other hand, when the input voltage is 200V, the power supplied to the ceramic heater 62 is the same as that when the input voltage is 100V. AC voltage is supplied at a rate. The controller 90 controls the triac 63 to be energized and supplies power to the ceramic heater until the first predetermined number of zero cross signals are output from the zero cross signal detection circuit 80 for the first time when AC is input. When the zero-cross signal is output for the first predetermined number of times, the control unit 90 controls the triac 63 to be in a non-energized state and stops power supply. Then, when the zero cross signal is output for the second predetermined number of times, the power supply to the ceramic heater is resumed. As described above, the control unit 90 controls the power supplied to the ceramic heater 62 in units of half waves of the AC voltage.

  FIG. 7 shows a flowchart of power control by the control unit 90 based on the above example.

  When the image forming apparatus is first turned on, the control unit 90 detects the PFC drive current Ipfc (S101), determines the AC input voltage from the relationship shown in FIG. 5, and turns on the remote signal after the determination (S102). ). The controller 90 determines whether or not the determined AC input voltage is a 100V system (S103), and if it is a 100V system, outputs a signal to turn on the triac 63 (S104). In the case of the 100 V system, the triac 63 is driven so that all the half waves of the sine wave of the AC input voltage are shared with the ceramic heater 62. On the other hand, when the AC input voltage is not a 100V system, that is, a 200V system, the control unit 90 determines whether a zero cross signal is input from the zero cross signal detection circuit 80 (S105). When the zero cross signal is input, the control unit 90 outputs a signal for turning on the triac 63 (S106). Next, the value of the counter Z that counts the zero cross signal is set to 0 (S107), and it waits for the zero cross signal to be input again (S108). When the zero cross signal is input, the control unit 90 increments the counter Z by one (S108), and determines whether the value of the counter Z is 1 (S110). If Z = 1, the control unit 90 outputs a signal for turning off the triac 63 (turns off the drive signal) (S111). If not Z = 1, the control unit 90 determines whether or not the value of the counter Z is 4 (S112). If not Z = 4, the control unit 90 again waits for the input of the zero cross signal in step S108. If Z = 4, the control unit outputs a signal for turning on the triac 63 (S113), returns to step S107, and initializes the counter Z to zero. The control of this flowchart is continued until the power of the image forming apparatus is turned off.

  In this way, power is supplied to the ceramic heater until the zero cross signal is output and the first (first predetermined number of times) zero cross signal is output, and the power supply is stopped in synchronization with the first zero cross signal. To do. Then, the power supply to the ceramic heater 62 is resumed in synchronization with the third (second predetermined number) zero-cross signal after the power supply is stopped, and the power supply is stopped again with the next zero-cross signal. By repeating this, even when the input voltage is 200V, the number of half waves in the sine wave of the AC input voltage is adjusted, and the power supplied to the ceramic heater 62 is made equal to 100V. .

  This is shown in FIGS. FIG. 8 shows the situation when the input voltage is 100V, and FIG. 9 shows the situation when the input voltage is 200V. When the input voltage is 100 V, the ceramic heater 62 is turned on during all half-wave periods of the AC voltage waveform. However, when the input voltage is 200 V, only one out of every four half-waves. The ceramic heater 62 is turned on. The number of zero-cross signals during power supply and the number of zero-cross signals during power supply stop are stored in advance in an SRAM or the like in the control unit 90.

  As described above, according to the first embodiment, the commercial power supply is controlled by the PFC drive current value controlled by the PFC control circuit 70 already provided for power supply control without using a dedicated voltage detection circuit. Therefore, it is possible to suppress an increase in the cost of the apparatus.

(Second Embodiment)
The image forming apparatus according to the second embodiment has the same configuration for image formation as that shown in FIG.

  FIG. 10 is a circuit diagram showing a configuration of a power supply circuit used in the second embodiment. A difference from the circuit of FIG. 2 is that a signal input from the PFC circuit 20 to the control unit 90 is different. In the circuit of FIG. 2, the PFC drive current Ipfc is input to the control unit 90, but in the circuit of FIG. 10, a voltage V <b> 3 obtained by dividing the PFC output voltage V <b> 2 is input to the control unit 90. Since the other parts are common and the operation of the PFC circuit 20 is the same as that of the first embodiment, the description thereof is omitted.

  Also, regarding the AC input voltage determination method, the input voltage is determined from the PFC drive current value in the first embodiment, whereas the PFC output voltage generated by the difference in the AC input voltage value in the second embodiment. The difference is that the AC input voltage is determined from the difference in voltage before the rise.

  The rise of the PFC output voltage will be described. In the PFC circuit 20, the rise time of the PFC output voltage increases in half proportion to the decrease in input voltage. When the AC input voltage is input to the PFC control circuit 70 and the switching element Q1 is OFF, the PFC output voltage value is the peak voltage value of the AC input voltage waveform (strictly speaking, from this value the order of the rectifier circuit 10 and the diode D1). The value obtained by subtracting the directional voltage drop). In this state, when the control unit 90 outputs a remote signal to the PFC control circuit 70 to operate the PFC circuit 20, the output V2 of the PFC circuit 20 rises. Since the rising slope hardly changes at 100V or 200V, the higher the original AC input voltage value, the shorter the rising time.

  Therefore, as shown in FIG. 11, the rise time of the PFC output voltage varies depending on the input voltage. In FIG. 11, the broken line indicates the PFC output rising waveform when the input voltage is 100V, and the solid line indicates the PFC output rising waveform when the input voltage is 200V. The rise time T1 when the AC input voltage is 200V is shorter than the rise time T2 when the input voltage is 100V.

  Until the remote signal is input to the PFC control circuit, the voltage is divided by resistors R2 and R3 corresponding to the magnitude of the AC input voltage and input to the PFC control circuit 70. By inputting the divided voltage to the control unit 90, the control unit 90 detects the voltage before the remote signal is turned on. The controller 90 can determine whether the AC input voltage is 100V or 200V based on the detected voltage.

  For example, if the detected voltage before turning on the remote signal is smaller than a value corresponding to 150V, it is determined that the AC input voltage is a 100V system, and if it is larger than a value corresponding to 150V, it is determined to be a 200V system.

  FIG. 12 is a flowchart showing processing of the control unit in the second embodiment.

  When the image forming apparatus is turned on, the control unit 90 detects the magnitude of the voltage V3 obtained by dividing the PFC output voltage V2 before the remote signal is turned on (S201). Then, the control unit 90 determines whether the AC input voltage is a 100V system or a 200V system based on the detected voltage, and turns on the remote signal after the determination (S202). Thereafter, the control unit 90 controls the power supply to the ceramic heater 62 according to the determined AC input voltage, and the power supply control method is the same as that after step S103 in FIG. 7 in the first embodiment.

  According to the second embodiment, an inexpensive configuration can be obtained by detecting the PFC output voltage detected by the PFC control circuit 70 already provided for power supply control without using a dedicated voltage detection circuit. Can determine the AC input voltage.

  In the first and second embodiments, the ceramic heater 62 is energized while the power of the image forming apparatus is turned on. However, the power of the image forming apparatus is turned off. You may comprise so that electricity supply to a ceramic heater may be performed. In this case, when the power of the image forming apparatus is turned on, the AC input voltage is determined, and after the power of the image forming apparatus is turned off based on the determined AC input voltage, the control unit 90 performs the processing after step S103. And the drive of the triac 63 is controlled. The power source of the control unit 90 is configured to operate even when the power source of the image forming apparatus is turned off.

  In addition to controlling the power supply to the ceramic heater 62, if the heater of the fixing device, which is an AC load, is common between the 100V system and the 200V system, the power supply is controlled according to the AC input voltage. May be.

  In the first and second embodiments, the 100V system and 200V system AC input voltages are determined. However, any first voltage or second voltage may be determined as the AC input voltage.

1 is a schematic sectional view of an image forming apparatus. The figure which shows the power supply circuit in 1st Embodiment. The figure which shows the detail of a PFC control circuit. The block diagram of the 1st load. The figure which shows the relationship between an input voltage and PFC drive current. The figure which shows an input voltage waveform and a PFC drive current waveform. The flowchart of the control part in 1st Embodiment. The figure which shows the state of the electric power supply at the time of 100V input. The figure which shows the state of the electric power supply at the time of 200V input. The figure which shows the power supply circuit in 2nd Embodiment. The figure which shows the rising waveform of the PFC output voltage in the case of input 100V and 200V. The flowchart of the control part in 2nd Embodiment.

Explanation of symbols

20 PFC circuit 30 Current detection circuit 62 Ceramic heater 63 Triac 70 PFC control circuit 80 Zero-cross signal detection circuit 90 Control unit

Claims (6)

In an image forming apparatus having an AC load to which an AC voltage from a commercial power supply is supplied,
A power supply circuit that inputs an AC voltage from the commercial power supply and outputs a predetermined DC voltage;
A power detection circuit that detects a current flowing through the switching element of the power supply circuit, and controls an output of the power supply circuit based on the detected current;
A power control element for controlling the power supplied to the AC load;
A control unit for controlling the power control element;
And the control unit inputs an output of the current detection circuit, determines a voltage of the commercial power source based on a magnitude of the output of the current detection circuit, and controls the power control based on the determined voltage. An image forming apparatus that controls driving of an element. In an image forming apparatus having an AC load to which an AC voltage from a commercial power supply is supplied,
A power supply circuit that inputs an AC voltage from the commercial power supply and outputs a predetermined DC voltage;
A power detection circuit having a voltage detection circuit for detecting an output voltage of the power supply circuit, and controlling an output of the power supply circuit based on the detected voltage;
A power control element for controlling the power supplied to the AC load;
A control unit for controlling the power control element;
And the control unit receives an output of the voltage detection circuit, determines a voltage of the commercial power source based on a magnitude of the output of the voltage detection circuit, and determines the power control element based on the determined voltage. An image forming apparatus that controls driving of the image forming apparatus.   The controller controls the AC voltage supplied to the AC load when the determined voltage is the first voltage, and supplies the AC load when the determined voltage is the second voltage lower than the first voltage. The image forming apparatus according to claim 1, wherein the power control element is controlled so as to reduce power supplied.   The image forming apparatus according to claim 1, wherein the control unit controls electric power supplied to the AC load in units of a half wave of an AC voltage of the commercial power source.   The image forming apparatus according to claim 1, wherein the AC load is a heater driven by an AC voltage.   The image forming apparatus according to claim 2, wherein the control unit determines an input voltage of the commercial power supply based on an output of the voltage detection circuit before the power supply circuit operates.

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