JP4655671B2 - Power supply - Google Patents

Description

  The present invention relates to a power supply device, and more particularly to a power supply device that is provided in an electrophotographic image forming apparatus or the like and that selectively outputs the outputs of two power supply circuits.

  An image forming apparatus that forms an image by an electrophotographic method such as a printer or a copying machine forms an electrostatic latent image on a photosensitive drum, develops it with toner, forms a toner image, and a contact transfer device (hereinafter referred to as a transfer device). The toner image is transferred to an intermediate transfer member and transferred to a sheet. In the transfer device, the intermediate transfer member is charged to minus (−), for example, opposite to the toner charged to plus (+). That is, the transfer device supplies a minus high voltage output to a contact roll for supplying electric charges to the intermediate transfer member. In this case, there is a case where unnecessary toner charged positively adheres to the intermediate transfer member by the contact roll supplied with the minus high voltage output. If unnecessary toner adheres to the intermediate transfer member, the toner may adhere to the paper and stain the paper. Therefore, it is necessary to clean unnecessary toner adhering to the intermediate transfer member. Therefore, during non-transfer, the transfer device applies reverse polarity (plus high voltage output) to the contact roll.

  Such power supply systems that apply voltages of different polarities include a circuit system in which positive and negative converters are connected in series and a circuit system in which positive and negative converters are connected in parallel via a switch.

  The circuit system in which the positive and negative converters are connected in series is an effective technique for reducing the size of the power supply device and reducing noise during switching between positive and negative, while the output current and voltage on the secondary side can reduce the bypass resistance. Since the power loss increases with the square of the current value and the voltage value, the range of use of the circuit has been limited.

In order to reduce the power loss of this bypass resistor, for example, in the technique described in Patent Document 1, a first power supply circuit that generates a negative output and a second power supply that generates an output having a polarity opposite to that of the first power supply output In a power supply device in which the output side of the circuit is connected in series with a bypass resistor and selectively output from the first power supply circuit and the second power supply circuit, when the output of the second power supply circuit is off, the second power supply Bypass means for bypassing the bypass resistor connected in parallel to the circuit with a resistance value lower than the bypass resistor is provided on the output side of the second power supply circuit.
JP 2000-232729 A

  However, for example, when the transfer method is changed, a positive output is generated in the first power supply circuit, and an output having a polarity opposite to that of the first power supply output is generated in the second power supply circuit. Cannot be used.

  As the bypass means, a mechanical switch element, for example, a high voltage relay may be used. However, noise or the like is generated at the time of switching, and countermeasures for the device and peripheral devices are required, and the circuit becomes complicated.

  There is also a method in which the bypass resistor is not bypassed. In this case, when the output of the first power supply circuit is on, current flowing through the bypass resistor connected in parallel to the second power supply circuit is connected to both ends of the bypass resistor. Voltage is generated. For this reason, the output voltage to the load is a difference voltage between the output voltage of the first power supply circuit and the voltage generated in the bypass resistor connected in parallel to the second power supply circuit, so as to achieve a desired output voltage. In this case, the set voltage of the first power supply circuit must be increased, which deteriorates the power supply efficiency and the stability of the power supply output.

  In addition, the circuit system in which the positive and negative converters are connected in parallel via a switch is an effective technology for increasing the efficiency of the power supply, increasing the output voltage, and increasing the power, but it generates noise when switching the output. Therefore, it is necessary to take measures for the device and the peripheral device, which is costly. Further, the size of the switching device and the device for noise suppression are increased, and the switching speed is limited, so that the use is limited.

  The present invention has been made in view of the above facts, and includes a first power supply circuit that generates a positive output voltage and a second power supply circuit that generates an output voltage having a polarity opposite to the output voltage of the first power supply circuit. It is an object of the present invention to provide a power supply device that can achieve low noise and high efficiency in a power supply device that selects and outputs any of the above.

In order to achieve the above object, the invention according to claim 1 includes a first power supply circuit that outputs a positive voltage to the load side, and a second power supply circuit that outputs a negative voltage to the load side, In the power supply device that selectively outputs the voltage output from the first power supply circuit and the second power supply circuit to the load side, the plus side of the first power supply circuit and the minus side of the second power supply circuit are connected. The first power supply circuit is connected via a switch means that is turned on when the output of the first power supply circuit is on and a first resistor, and the negative side of the first power supply circuit and the positive side of the second power supply circuit are connected to each other. The second power supply circuit is connected via a second resistor, and the negative side of the first power supply circuit and the negative side of the second power supply circuit are connected via a third resistor.

According to the present invention, when the first power supply circuit is turned on, the switch means is turned on, so that energy is supplied to the load side only through the third resistor, and when the second power supply circuit is turned on, Since the switch means is turned off, energy is supplied to the load side via the first resistor. Therefore, low noise and high efficiency can be achieved.

The invention according to claim 2 includes a first power supply circuit that outputs a positive voltage to the load side, and a second power supply circuit that outputs a negative voltage to the load side, the first power supply circuit, In the power supply apparatus that selectively outputs the voltage output from the second power supply circuit to the load side, the positive side of the first power supply circuit and the negative side of the second power supply circuit are connected to the first resistor and the second power supply circuit. Through a switch means for turning on the negative side of the first power supply circuit and the positive side of the second power supply circuit when the output of the first power supply circuit is on. The negative side of the first power supply circuit and the negative side of the second power supply circuit are connected via a third resistor.

According to the present invention, similarly to the first aspect of the present invention, when the first power supply circuit is turned on, the switch means is turned on, energy is supplied to the load side via only the third resistor, the When the power supply circuit 2 is turned on, the switch means is turned off, so that energy is supplied to the load side via the first resistor. Therefore, similarly to the first aspect of the invention, it is possible to achieve low noise and high efficiency.

  As described above, according to the present invention, there is an effect that low noise and high efficiency can be achieved.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In the present embodiment, as an example, a case where the present invention is applied to a transfer device in an image forming apparatus that forms an image by an electrophotographic method such as a printer or a copying machine will be described.

  As shown in FIG. 1, the power supply device 10 boosts the primary side input to generate a positive output, and the first transformer 50 and the half-wave rectifier circuit (diode) 51 boosts the primary side input to be negative. A second transformer 60 and a half-wave rectifier circuit (diode) 61 for generating an output are provided.

  The primary side of the first transformer 50 has a constant voltage control on the primary side input and a transfer voltage control unit 14 for controlling the secondary side output to a predetermined voltage, and a constant current control on the primary side input. A transfer current control unit 16 that controls the secondary output to a predetermined voltage is connected.

  The transfer voltage control unit 14 and the transfer current control unit 16 are connected to a switching circuit 12 that switches them. The switching circuit 12 receives a constant voltage / constant current select signal that drives (enables) either the transfer voltage control unit 14 or the transfer current control unit 16.

  On the primary side of the second transformer 60, a reverse bias voltage control unit 26 that controls the primary side input and controls the secondary side output to a constant voltage (a voltage that can be cleaned) and reverse bias output voltage detection. The unit 28 is connected.

  The switching circuit 12 and the reverse bias voltage controller 26 are connected to a signal determination circuit 30 for inputting a transfer signal for transfer and a cleaning signal for cleaning. The signal determination circuit 30 receives a transfer / cleaning select signal.

  The anode of the half-wave rectifier circuit 51 is connected to the secondary side of the first transformer 50. A smoothing capacitor 13 is connected to the cathode of the half-wave rectifier circuit 51, and a reverse bias current bypass resistor 18 (hereinafter, resistor 18) is connected in parallel with the smoothing capacitor 13.

  The cathode of the half-wave rectifier circuit 61 is connected to the secondary side of the second transformer 60. A smoothing capacitor 15 is connected to the anode of the half-wave rectifier circuit 61, and a transfer current bypass rush current suppression resistor 19 (hereinafter referred to as a resistor 19) and a reverse bias discharge resistor 20 connected in series with the smoothing capacitor 15 in parallel. (Hereinafter, resistor 20) is connected. In the present embodiment, as an example, the resistance values of the resistors 18 and 20 are 10 MΩ, and the resistance value of the resistor 19 is 100 kΩ.

A transfer current bypass switch 25 (hereinafter referred to as a switch 25) is connected to the resistor 20 in parallel. The resistors 18, 19, and 20 are connected in series. A transfer output voltage detector 22 is connected to the output side (V _OUT ) of the first transformer 50 and the second transformer 60.

  Further, a transfer output current detector 24 is connected in series to the resistors 18, 19, and 20. The transfer output current detection unit 24 is connected to the switch 25 and the transfer current control unit 16, and the transfer output voltage detection unit 22 is connected to the transfer voltage control unit 14 and the monitor voltage correction circuit 32.

  The switch 25 is turned on / off in accordance with, for example, a transfer signal and a cleaning signal output from the signal determination circuit 30, and is turned on when the signal determination circuit 30 outputs a transfer signal, and is turned off when a cleaning signal is output.

  The output voltage Vout output from the power supply apparatus 10 having such a configuration is supplied to the transfer roll 40 of the transfer apparatus 38 as shown in FIG. A backup roll 42 is provided opposite to the transfer roll 40. The backup roll 42 is brought into contact with the grounded contact roll 44, and negative charges are supplied from the contact roll 44. The sheet P is nipped and conveyed by the transfer roll 40 and the backup roll 42 in a state where the transfer voltage is output from the power supply device 10. As a result, the positively charged toner image formed on the intermediate transfer belt 46 is transferred onto the paper P.

  Next, the operation of this embodiment will be described.

  First, the transfer will be described. At the time of transfer, a transfer / cleaning select signal is input to the signal determination circuit 30 so as to output a transfer signal. The transfer signal is input to the switching circuit 12. The switching circuit 12 to which the transfer signal is input inputs a drive signal to the transfer voltage control unit 14 or the transfer current control unit 16 based on the constant voltage / constant current select signal, and the transfer voltage control unit 14 and the transfer current control. Either one of the parts 16 is driven. When the primary side input is controlled at a constant voltage, the transfer voltage control unit 14 is driven. As a result, the primary side input is controlled at a constant voltage, and a positive output is generated on the secondary side via the first transformer 50 and the half-wave rectifier circuit 51. Although the reverse bias voltage control unit 26 is driven but the switch 25 is on, the reverse bias voltage control unit 26 is in a short-circuit state, and an output is generated on the secondary side of the second transformer 60. It is not supplied to the load side.

  At the time of transfer, a positive output is generated on the secondary side of the first transformer 50, the switch 25 is turned on, and the resistor 20 is short-circuited. Therefore, no current flows through the resistor 20 during transfer. When a positive output is generated on the secondary side of the first transformer 50, the voltage on the secondary side is detected by the transfer output voltage detection unit 22, and a detection signal is input to the transfer voltage control unit 14 and also a positive output. Is detected by the transfer output current detection unit 24, and this detection signal is input to the transfer current control unit 16, and any one of the transfer voltage control unit 14 and the transfer current control unit 16 determined by the constant voltage / constant current select signal is detected. The switching control of the first transformer 50 is performed in comparison with the respective reference values.

  Next, the non-transfer time (cleaning time) will be described. At the time of non-transfer, a transfer / cleaning select signal is input to the signal determination circuit 30 so that a cleaning signal is output. The cleaning signal is input to the reverse bias voltage control unit 26. In this case, the switching circuit 12 does not output a drive signal to the transfer voltage control unit 14 and the transfer current control unit 16. Therefore, they are not driven. On the other hand, the reverse bias voltage control unit 26 to which the cleaning signal is input performs constant voltage control on the primary side input. As a result, the second transformer 60 and the half-wave rectifier circuit 61 generate a negative output on the secondary side. At this time, the reverse bias output voltage detection unit 28 detects the magnitude of the secondary side voltage, and based on the detected value, the reverse bias voltage control unit 26 determines that the secondary output is a predetermined voltage (a voltage that can be cleaned). The primary side input is controlled so that Further, at the time of non-transfer, the switch 25 is turned off.

  Here, the secondary side of the first transformer 50 and the second transformer 60 will be described in detail with reference to FIG. As shown in FIG. 3A, the secondary sides of the first transformer 50 and the second transformer 60 are the first power supply circuit 50A, the second transformer 60, and the like configured by the first transformer 50 and the like. It can be considered that the second power supply circuit 60A configured by the above is connected in series, and the resistors 18, 19, and 20 connected in series are connected thereto. As described above, the switch 25 is connected to the resistor 20 in parallel. A load (transfer device) 38 is connected to the resistors 18, 19, and 20 in parallel.

  During transfer, that is, when the first power supply circuit 50A is turned on and the second power supply circuit 60A is turned off, the switch 25 is turned on. For this reason, as shown in FIG. 3B, the second power supply circuit 60A acts as a diode, and the route of the output current from the first power supply circuit 50A is the route through the resistor 18, the load 38, and the switch. 25, a route through the resistor 19 is formed.

  Further, at the time of non-transfer, that is, when the first power supply circuit 50A is turned off and the second power supply circuit 60A is turned on, the switch 25 is turned off. For this reason, as shown in FIG. 3C, the first power supply circuit 50A functions as a diode, and the route of the output current from the second power supply circuit 60A is the route through the resistor 20 and the resistor 19, and the load 38, a route through the resistor 18 is formed.

  As described above, the switch 25 is turned on at the time of transfer, the resistor 20 (10 MΩ) is short-circuited, and the internal loss generated in the resistor 20 can be avoided, and the loss in the resistors 18 and 19 can be suppressed.

  Next, a specific example of the switch 25 will be described.

  FIG. 4 shows a configuration using a P-channel type FET 25 </ b> A as the switch 25. In the figure, the resistors 19 and 20 are collectively referred to as a resistor 21 for simplification.

  Thus, when the FET 25A is used as the switch 25, the gate of the FET 25A is connected to the negative output constant voltage power source 72 via the resistors 70 and 71 and grounded via the resistor 73. Further, the collector of a pnp transistor 74 is connected to one end of the resistor 70, and the emitter of the transistor 74 is grounded. Thereby, the first power supply circuit 50A is turned on by the transfer signal, the transistor 74 is turned on, and the FET 25A is turned on. When the second power supply circuit 60A is turned on by the cleaning signal, the transistor 74 is turned off and the FET 25A is also turned off.

  Further, as shown in FIG. 5, a semiconductor relay 25 </ b> B may be used as the switch 25. In this case, the constant voltage power supply 77 is connected to the anode of the photodiode 75 constituting the semiconductor relay 25B via the resistor 76, the cathode of the photodiode 75 is connected to the collector of the npn transistor 78, and the emitter is grounded. . As a result, the first power supply circuit 50A is turned on by the transfer signal, the transistor 78 is turned on, a current flows through the photodiode 75, and the MOS-FET 79 is turned on. That is, the semiconductor relay 25B is turned on. When the second power supply circuit 60A is turned on by the cleaning signal, the transistor 78 is turned off and the semiconductor relay 25B is also turned off.

  The constant voltage power supply 77 uses the input voltage (24V) to the power supply device 10, and does not require a separate power supply.

  Further, as shown in FIG. 6, not only the semiconductor relay 25B that bypasses the output current of the first power supply circuit 50A but also a semiconductor relay 25C that bypasses the output current of the second power supply circuit 60A may be provided. Good. Thereby, the second power supply circuit 60A is turned on by the cleaning signal, the transistor 80 is turned on, and the semiconductor relay 25C is turned on. When the first power supply circuit 50A is turned on by the transfer signal, the transistor 80 is turned off and the semiconductor relay 25C is also turned off. Thus, by providing the bypass means in each of the first power supply circuit 50A and the second power supply circuit 60A, the loss can be further suppressed.

  FIG. 7 shows a result of comparison of basic electrical performance, input power, noise, common circuit configuration, and cost for each of the above-described configurations. In the table, configuration 1 is the configuration shown in FIG. 4, configuration 2 is the configuration shown in FIG. 5, and configuration 3 is the configuration shown in FIG. Further, as the configuration 4, the configuration using the high-voltage relay 25D as the switch 25 as in the conventional example shown in FIG. 8, and the configuration without the switch 25 as the configuration 5 as in the conventional example shown in FIG. Indicated. Note that circuit sharing is performed when the output of the first power supply circuit 50A is negative and the output of the second power supply circuit 60A is positive, as in the power supply device described in Patent Document 1 as shown in FIG. This shows how easy it is to share the circuit configuration. In the configuration shown in FIG. 10, an N-channel type FET 25E is used as the switch 25, and the gate of the FET 25E is connected to the positive output constant voltage power supply 86 through the resistors 82 and 84 and grounded through the resistor 88. Yes. The collector of the npn transistor 90 is connected to one end of the resistor 82, and the emitter of the transistor 90 is grounded. Further, the transfer roll 40 is grounded, and the output voltage Vout of the power supply device is supplied to the contact roll 44.

  As shown in FIG. 7, it can be seen that the configuration according to the present embodiment is generally excellent compared to the conventional example, and particularly, the configuration 2 is excellent.

  As described above, in the present embodiment, the switch 25 is turned on and bypassed with a resistance value lower than the bypass resistance, so that the internal loss can be reduced and the occurrence of noise during switching is prevented. Can do. That is, the following various effects can be obtained.

  That is, since no noise is generated when switching between the minus output and the plus output, no cost is required for measures for the device and peripheral devices. Even if an increase in the bypass resistance value switching device is anticipated, the cost of the entire device can be extremely reduced. The shape of the additional device of the bypass resistance variable device is smaller than the shape of the power supply device corresponding to the power up because the power loss of the bypass resistor increases with the square of the current value and the voltage value depending on the output current and voltage. is there. The switching speed at the time of the above switching can be extremely high. In addition, there are very few restrictions on the increase in output voltage and current value (high power can be supported). In addition, since the increase in the voltage of each (positive and negative) power supply device is extremely small, processing such as withstand voltage is not required, and cost and size can be reduced.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.

  In the first embodiment, the configuration in which the switch 25 that bypasses the resistor 20 is provided has been described. In the present embodiment, a configuration in which the switch 25 is provided in the power supply line will be described. In addition, the same code | symbol is attached | subjected to the same part as 1st Embodiment, and detailed description is abbreviate | omitted.

  FIGS. 11A and 11B show circuit configurations on the secondary side of the first transformer 50 and the second transformer 60 of the power supply device according to the present embodiment.

  As shown in FIGS. 11A and 11B, the switch 25 is provided between the cathode of the half-wave rectifier circuit 51 and the load 38. One end of the resistor 18 (10 MΩ) is connected between the switch 25 and the load 38, and the other end is connected to one end of the resistor 20 (10 MΩ) and the anode of the half-wave rectifier circuit 61. The other end of the resistor 20 is connected to the other end of the first transformer 50 and one end of the resistor 19 (100 kΩ), and the other end of the resistor 19 is connected to the other end of the second transformer 60.

  11A shows a state in which the first transformer 50 is on and the second transformer 60 is off, and FIG. 11B shows a state in which the first transformer 50 is off and the second transformer 60 is on. It shows about the state. The dotted line in the figure indicates the route through which current flows.

  12A and 12B show simplified circuits equivalent to the circuits shown in FIGS. 11A and 11B, respectively.

  As shown in FIG. 12A, at the time of transfer, that is, when the first power supply circuit 50A is turned on and the second power supply circuit 60A is turned off, the switch 25 is turned on. For this reason, as shown in FIG. 6A, the second power supply circuit 60A functions as a diode. Then, as the route of the output current from the first power supply circuit 50A, the load 38, the route through the resistor 19, the switch 25, the route through the resistors 18 and 20, the resistor 18, the second power supply circuit 60A (diode), the resistor A route through 19 is formed. In this case, the same effect as the circuit configuration of FIG.

  Note that the voltage Vz across the load 38 is expressed by the following equation, where the impedance of the load 38 is Z, the resistance value of the resistor 19 is R19, and the output voltage of the first power supply circuit 50A is V1.

Vz = {Z / (R19 + Z)} × V1 (1)
On the other hand, as shown in FIG. 12B, at the time of non-transfer, that is, when the first power supply circuit 50A is turned off and the second power supply circuit 60A is turned on, the switch 25 is turned off. For this reason, as shown in FIG. 3B, the first power supply circuit 50A functions as a diode. Then, the route of the output current from the second power supply circuit 60A is the load 38, the route through the resistor 18, the route through the resistors 19 and 20, the resistor 18, the second power supply circuit 60A (diode), and the resistor 19. A route is formed. In this case, the same effects as the circuit configuration of FIG.

  Note that the voltage Vz across the load 38 is expressed by the following equation, where the resistance value of the resistor 18 is R18 and the output voltage of the second power supply circuit 60A is V2.

Vz = {Z / (R18 + Z)} × V2 (2)
As described above, when the first power supply circuit 50A is turned on, energy is supplied to the load 38 only through the resistor 19, and when the second power supply circuit 60A is turned on, only the resistor 18 is supplied. Energy is supplied to the load 38. Thereby, low noise and high efficiency can be achieved.

  As shown in FIGS. 13A and 13B, the switch 25 may be connected between the other end of the first transformer 50 and the other end of the second transformer 60. In this case, the resistor 19 is connected between the half-wave rectifier circuit 51 and the load 38. That is, the circuits shown in FIGS. 12A and 12B have a configuration in which the switch 25 and the resistor 19 are replaced in the circuits shown in FIGS.

  FIGS. 14A and 14B show simplified circuits equivalent to the circuits shown in FIGS. 13A and 13B, respectively.

  As shown in FIG. 14A, at the time of transfer, that is, when the first power supply circuit 50A is turned on and the second power supply circuit 60A is turned off, the switch 25 is turned on. For this reason, as shown in FIG. 6A, the second power supply circuit 60A functions as a diode. Then, as the route of the output current from the first power supply circuit 50A, the route through the resistor 19, the load 38, the switch 25, the route through the resistor 19, the resistor 18, the resistor 20, the resistor 19, the resistor 18, and the second power source A route is formed through circuit 60A (diode). In this case, the same effect as the circuit configuration of FIG. The voltage Vz across the load 38 is expressed by the above equation (1).

  On the other hand, as shown in FIG. 14B, at the time of non-transfer, that is, when the first power supply circuit 50A is turned off and the second power supply circuit 60A is turned on, the switch 25 is turned off. For this reason, as shown in FIG. 3B, the first power supply circuit 50A functions as a diode. The route of the output current from the second power supply circuit 60A is only the route through the load 38 and the resistor 18. In this case, the same effects as the circuit configuration of FIG. The voltage Vz across the load 38 is expressed by the above equation (2).

  As described above, when the first power supply circuit 50A is turned on, energy is supplied to the load 38 only through the resistor 19, and when the second power supply circuit 60A is turned on, only the resistor 18 is supplied. Energy is supplied to the load 38. Thereby, low noise and high efficiency can be achieved.

  As a specific example of the switch 25 in the configuration of FIGS. 11 and 13, a semiconductor element (such as an FET), a semiconductor relay, a high-voltage relay, or the like can be used as in the circuit described in the first embodiment.

It is a block diagram of a power supply device. It is a schematic block diagram of a transfer apparatus. (A) is an equivalent circuit diagram of the power supply device, (B) is an equivalent circuit diagram when the first power supply circuit is turned on, and (C) is an equivalent circuit diagram when the second power supply circuit is turned on. It is the equivalent circuit schematic which concerns on the specific example of the switch of a power supply device. It is an equivalent circuit diagram which shows the modification of the switch of a power supply device. It is an equivalent circuit diagram which shows the modification of the switch of a power supply device. It is a table | surface which compares the performance of each structure. It is the equivalent circuit schematic of the power supply device which concerns on a prior art example. It is the equivalent circuit schematic of the power supply device which concerns on a prior art example. It is the equivalent circuit schematic of the power supply device which concerns on a prior art example. (A) is a circuit diagram of the secondary side when the first transformer is turned on, and (B) is a circuit diagram of the secondary side when the second transformer is turned on. 11A is an equivalent circuit diagram of FIG. 11A, and FIG. 11B is an equivalent circuit diagram of FIG. (A) is a circuit diagram of the secondary side when the first transformer is turned on, and (B) is a circuit diagram of the secondary side when the second transformer is turned on. FIG. 14A is an equivalent circuit diagram of FIG. 13A, and FIG. 13B is an equivalent circuit diagram of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 50 1st transformer 50A 1st power supply circuit 51 Half wave rectifier circuit 60 2nd transformer 60A 2nd power supply circuit 61 Half wave rectifier circuit 18 Resistance (1st resistance)
19 Resistance (third resistance)
20 resistance (second resistance)
21 Resistance (second resistance)
25 switches (second resistance bypass means, switch means)

Claims (2)

A first power supply circuit that outputs a positive voltage to the load side; and a second power supply circuit that outputs a negative voltage to the load side, and is output from the first power supply circuit and the second power supply circuit. In the power supply device that selectively outputs the voltage to the load side,
The positive side of the first power supply circuit and the negative side of the second power supply circuit are connected via switch means and a first resistor that are turned on when the output of the first power supply circuit is on, and The minus side of the first power circuit and the plus side of the second power circuit are connected via a second resistor, and the minus side of the first power circuit and the minus side of the second power circuit Is connected via a third resistor. A first power supply circuit that outputs a positive voltage to the load side; and a second power supply circuit that outputs a negative voltage to the load side, and is output from the first power supply circuit and the second power supply circuit. In the power supply device that selectively outputs the voltage to the load side,
The positive side of the first power supply circuit and the negative side of the second power supply circuit are connected via a first resistor and a second resistor, and the negative side of the first power supply circuit and the second side are connected. And the negative side of the second power supply circuit and the negative side of the second power supply circuit, and the positive side of the first power supply circuit is connected via a switching means that is turned on when the output of the first power supply circuit is on. Is connected via a third resistor.

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