JP6100128B2 - Output detection device, power supply device, and image forming apparatus - Google Patents

Description

  The present invention relates to an output detection device, a power supply device, and an image forming apparatus, and can be applied to, for example, an electrophotographic image forming apparatus.

  In a conventional high voltage power supply apparatus used as a bias power supply for a transfer roller or the like in an image forming apparatus, a bias is output using a transformer, and a result of detecting the output is fed back to drive control of the transformer.

  As a high-voltage power supply device using a conventional transformer, for example, there is one described in Patent Document 1. The high-voltage power supply device described in Patent Document 1 describes a configuration using an operational amplifier (op-amp) for output detection.

JP 2007-43804 A

  However, in the conventional high-voltage power supply device, the output of the transformer is usually detected by an operational amplifier connected to a single power supply. For example, a conventional high-voltage power supply device is configured to detect a negative bias output current using the non-inverting input terminal of the operational amplifier as a reference potential. However, when an operational amplifier in which a non-inverting input terminal is connected as a reference potential is used for detecting the output of the transformer as in a conventional high-voltage power supply device, the output sink current of the transformer does not flow when the operational amplifier output potential is low. . Therefore, in this case, in the operational amplifier, the operational amplifier output does not change in the range from the potential of the non-inverting input terminal to the ground potential, and when the current exceeds a certain amount, the potential of the inverting input terminal becomes higher than the potential of the non-inverting input terminal. There was a problem that.

  The conventional high-voltage power supply device has a double problem that the current detection value may not be detected correctly due to the problems described above, and the detection voltage value may also become incorrect due to a rise in the reference potential. It has occurred.

  Also, in an electrophotographic image forming apparatus, a positive polarity or negative polarity output, such as a photosensitive drum, a drum for charging the photosensitive drum, or a blade for removing developer adhering to each drum, is output in both polarities. Since there are components that require (bias), the output polarity may need to be changed depending on the components to be output and the output timing. In the conventional operational amplifier used for transformer output detection, when the output polarity of the transformer is changed, it is necessary to switch the input voltage to the non-inverting input terminal with the change of the output polarity.

  In view of the above-described problems, an output detection device, a power supply device, and an image forming apparatus that can detect the output of a power supply device that outputs both positive and negative biases with higher accuracy are desired. Yes.

The first aspect of the present invention includes a negative transformer for outputting a negative bias, a negative drive unit for driving the negative transformer, and a negative electrode for rectifying the output of the negative transformer and outputting the negative bias A negative polarity bias output unit having a positive rectification unit, a positive polarity transformer for outputting a positive polarity bias, a positive polarity drive unit for driving the positive polarity transformer, and a positive polarity by rectifying the output of the positive polarity transformer A positive polarity rectification unit having a positive rectification unit that outputs as a positive bias, and an output detection device that detects the output of the device itself, and is output by the negative polarity bias output unit or the positive polarity bias output unit. in the output detecting device constituting a power supply unit for outputting a bias for the output load comprising, (1) to the single supply side ground, contacting the non-inverting input terminal to ground And, through the detection element for the inverting input terminal and an output terminal to detect an output of the power supply, an operational amplifier connected to the output of the power supply device, with (2) the operational amplifier, An output detection circuit for detecting a positive / negative bipolar current by setting the voltage detection position to both the inverting input terminal of the operational amplifier and the output terminal of the operational amplifier ; and (3) the inverting input terminal of the operational amplifier is: (4) When a positive polarity bias is output from the power supply device, the reference ground potential of the output detection circuit is inverted by the operational amplifier when connected to each of the positive polarity rectification unit and the negative polarity rectification unit. an input terminal, when the negative bias is outputted from the power supply, the reference ground potential of the output detection circuit and an output terminal of said operational amplifier, (5) the output detection circuit, the cathode When a positive polarity bias is output from the bias output unit, the inverting input terminal of the operational amplifier is set to the ground potential, and when a negative polarity bias is output from the negative polarity bias output unit, the output terminal of the operational amplifier is set to the ground potential. In either case where a positive polarity bias is output from the positive polarity bias output unit or a negative polarity bias is output from the negative polarity bias output unit, the inverting input terminal of the operational amplifier or the A positive / negative bipolar current is detected from a potential difference with respect to the ground potential with reference to the potential of the output terminal of the operational amplifier as the ground potential .

According to a second aspect of the present invention, a negative transformer for outputting a negative bias, a negative driver for driving the negative transformer, and a negative that rectifies the output of the negative transformer and outputs it as a negative bias A negative polarity bias output unit having a positive rectification unit, a positive polarity transformer for outputting a positive polarity bias, a positive polarity drive unit for driving the positive polarity transformer, and a positive polarity by rectifying the output of the positive polarity transformer A positive polarity rectification unit having a positive rectification unit that outputs as a positive bias, and an output detection device that detects the output of the device itself, and is output by the negative polarity bias output unit or the positive polarity bias output unit. In the power supply device that outputs a bias to the output load, the output detection device of the first aspect of the present invention is used to detect the output of the power supply device, and based on the detection result , And controlling the negative driver and the positive drive unit.

  According to a third aspect of the present invention, in an image forming apparatus including a power supply device that outputs a bias to an output load, the power supply device according to the second aspect of the present invention is applied as the power supply device.

  According to the present invention, it is possible to accurately detect the output of a power supply device that outputs both positive and negative biases.

It is a block diagram which shows the functional structure of the high voltage power supply device which concerns on 1st Embodiment. 1 is a schematic sectional view of an image forming apparatus according to a first embodiment. FIG. 2 is a block diagram illustrating a configuration of a control system of the image forming apparatus according to the first embodiment. It is a circuit diagram shown about the example of a circuit structure of the high voltage power supply device concerning a 1st embodiment. It is a schematic sectional drawing of the image forming apparatus which concerns on 2nd Embodiment. FIG. 6 is a block diagram illustrating a configuration of a control system of an image forming apparatus according to a second embodiment. It is a block diagram which shows the functional structure of the high voltage power supply device which concerns on 2nd Embodiment. It is a circuit diagram shown about the circuit structural example of the high voltage power supply device which concerns on 2nd Embodiment. It is explanatory drawing shown about operation | movement of the high voltage | pressure control part (microcomputer) which concerns on 2nd Embodiment. It is a circuit diagram shown about the circuit structural example of the high voltage power supply apparatus which concerns on the modification of 2nd Embodiment.

(A) First Embodiment Hereinafter, a first embodiment of an output detection device, a power supply device, and an image forming apparatus according to the present invention will be described in detail with reference to the drawings. Note that the output detection device and the power supply device of this embodiment are an output detection unit and a high-voltage power supply device.

(A-1) Configuration of the First Embodiment First, the overall configuration of the image forming apparatus 101 of the first embodiment will be described.

  FIG. 2 is a schematic sectional view of the image forming apparatus 101 of this embodiment.

  The image forming apparatus 101 is an electrophotographic color image forming apparatus, and a multi-color developing device 102 (in FIG. 2, a black developing device 102K, a yellow developing device 102Y, a magenta developing device 102M, and a cyan developing device 102C). And a light emitting diode (hereinafter referred to as “LED”) head 103 (for example, a black LED head 103K, a yellow LED head 103Y, a magenta LED head 103M, and a cyan LED head 103C) as an exposure apparatus for each color. Within each color developing device 102 (102K, 102Y, 102M, 102C), each color toner cartridge 104 (104K, 104Y, 104M, 104C), each color charging roller 136 (136K, 136Y, 136M, 136C), each color Supply roller 133 (133K, 133Y, 133M, 133C), each color developing roller 134 (134K, 134Y, 134M, 134C), each color developing blade 135 (135K, 135Y, 135M, 135C), each color photosensitive drum 132 ( 132K, 132Y, 132M, 132C), and cleaning blades 137 (137K, 137Y, 137M, 137C) of the respective colors are provided.

  Each developing device 102 is uniformly charged by each charging roller 136 in contact with each internal photosensitive drum 132. An electrostatic latent image is formed on each charged photosensitive drum 132 by the light emission of each LED head 103. Each supply roller 133 supplies toner as a developer to each development roller 134. When each developing blade 135 uniformly forms a toner layer on the surface of each developing roller 134, a toner image is developed on each photosensitive drum 132. Each cleaning blade 137 cleans residual toner after transfer. Each toner cartridge 104 is detachably attached to each developing device 102, and is configured to supply the internal toner to each developing device 102.

  Below each developing device 102, a transfer roller 105 (105K, 105Y, 105M, 105C) for each color, an intermediate transfer belt stretching roller 106, and an intermediate transfer belt drive roller 107 are provided. Each transfer roller 105 is arranged so that a bias voltage (hereinafter also simply referred to as “bias”) can be applied from the back surface of the intermediate transfer belt 108 to the transfer position. The intermediate transfer belt stretching roller 106 and the intermediate transfer belt driving roller 107 stretch the intermediate transfer belt 108 and rotate the intermediate transfer belt 108 by driving the intermediate transfer belt stretching roller 106. Thus, the toner image by the image forming apparatus 101 of each color is transferred onto the outer peripheral surface of the intermediate transfer belt 108.

  The upper portion of the intermediate transfer belt 108 is sandwiched between the photosensitive drum 132 and the transfer roller 105 of each color image forming apparatus 101, and the lower portion of the intermediate transfer belt 108 is The secondary transfer backup roller 120 and the secondary transfer roller 130 are nipped. Then, at the nip portion (hereinafter also referred to as “secondary transfer nip”) formed between the secondary transfer backup roller 120 and the secondary transfer roller 130, the sheet 115 is sandwiched together with the intermediate transfer belt 108, and the intermediate transfer is performed. The toner image formed on the outer peripheral surface of the belt 108 is transferred to the paper 115. That is, when the paper 115 passes through the secondary transfer nip formed between the secondary transfer backup roller 120 and the secondary transfer roller 130, the toner image formed on the intermediate transfer belt 108 is transferred. The secondary transfer roller 130 is applied with a bias voltage that promotes the transfer of the toner image and the removal of the toner remaining after the transfer by the secondary transfer bias generator 150.

  An intermediate transfer belt cleaning blade 111, a waste toner container 112, and a paper detection sensor 140 are provided in the vicinity of the intermediate transfer belt 108, and a paper cassette 113 is detachably attached to the lower side of the intermediate transfer belt 108. It has been. The intermediate transfer belt cleaning blade 111 can scrape off the toner on the intermediate transfer belt 108, and the scraped toner is stored in a waste toner container 112. Sheets 115 are stacked in the sheet cassette 113.

  A hopping roller 114 and a pair of registration rollers 116 and 117 are disposed between the front end of the paper cassette 113 and the secondary transfer roller 130. The hopping roller 114 takes out the paper 115 from the paper cassette 113 and feeds (feeds) the paper 115 to the registration rollers 116 and 117. Then, the fed paper 115 abuts against the pair of registration rollers 116 and 117 in a stopped state and is subjected to skew correction (shift correction). The pair of registration rollers 116 and 117 are driven at a predetermined timing based on detection by the paper detection sensor 140 after skew correction of the paper 115, and the paper 115 is conveyed to the intermediate transfer belt 108 (secondary transfer nip). It has become.

  A fixing device 118 is disposed on the downstream side of the secondary transfer nip. The fixing device 118 has a pair of heat fixing rollers 118a and 118b, and fixes the toner image on the paper 115 by heat and pressure. In the fixing device 118, a fixing device heater 259 as a heat generating unit and a thermistor 265 as a heat detecting means (temperature measurement sensor) are provided.

  A pair of discharge rollers 119 a and 119 b, a paper guide 119, and a paper discharge tray 121 are provided on the downstream side of the fixing device 118. The paper 115 is transported along a paper guide 119 by a pair of discharge rollers 119a and 119b, and is discharged face down to the paper discharge tray 121.

  In addition, a paper detection sensor 140, a temperature / humidity sensor 290, a toner concentration sensor 291 and the like are disposed as various sensors in the housing of the image forming apparatus 101.

  The density sensor 291 is a sensor that detects the density of each region of a predetermined print density inspection pattern (details will be described later) formed on the intermediate transfer belt 108 by reflected light (reflection density). The temperature / humidity sensor 290 is a sensor for detecting the temperature inside the housing of the image forming apparatus 101. The paper detection sensor 140 is a sensor for detecting the timing at which the paper 115 enters the secondary transfer nip between the secondary transfer backup roller 120 and the secondary transfer roller 130.

  FIG. 3 is a block diagram illustrating a configuration of a control system in the image forming apparatus 101.

  The image forming apparatus 101 has a host interface unit 250 as a control system, and the host interface unit 250 controls the command / image processing unit 251. The command / image processing unit 251 outputs image data to the LED head interface unit 252. The LED head interface unit 252 is controlled by the printer engine control unit 253 with a head drive pulse or the like, and causes the LED heads 103K, 103Y, 103M, and 103C to emit light.

  The printer engine control unit 253 supplies control values such as a charging bias, a developing bias, and a transfer bias to the high voltage control unit 260. The high voltage controller 260 supplies a signal corresponding to the supplied control value to each of the charging bias generator 261, the development bias generator 262, the primary transfer bias generator 263, and the secondary transfer bias generator 150.

  The charging bias generator 261 outputs a bias to each of the charging rollers 136K, 136Y, 136M, and 136C based on a signal from the high voltage controller 260. The developing bias generator 262 outputs a bias to the developing rollers 134K, 134Y, 134M, and 134C based on a signal from the high voltage controller 260. Furthermore, the primary transfer bias generator 263 applies a bias to each of the transfer rollers 105K, 105Y, 105M, and 105C based on a signal from the high voltage controller 260. Further, the secondary transfer bias generator 150 applies a bias to the secondary transfer roller 130 based on a signal from the high voltage controller 260.

  In FIG. 3, the high-voltage power supply device 301 is configured to include a high-voltage control unit 260, a charging bias generation unit 261, a development bias generation unit 262, a primary transfer bias generation unit 263, and a secondary transfer bias generation unit 150. Show. Although details will be described later, in the high-voltage power supply device 301, the LED head 103 for each color, the developing device 102 for each color, the primary transfer roller 105 for each color, and the secondary transfer roller 130 serve as high voltage output loads.

  The printer engine control unit 253 drives the hopping motor 254, the registration motor 255, the belt motor 256, the fixing device heater motor 257, and the drum motors 258K, 258Y, 258M, and 258C for each color at a predetermined timing. The printer engine control unit 253 controls the temperature in the fixing device 118 by driving the fixing device heater 259 in accordance with the detection value of the thermistor 265.

  Further, the printer engine control unit 253 controls each component based on the detection contents of each sensor (paper detection sensor 140, temperature / humidity sensor 290, toner density sensor 291 and the like). The printer engine control unit 253 performs image formation for each color so as to form a toner image of the print density inspection pattern on the outer peripheral surface of the intermediate transfer belt 108 prior to the printing operation on the paper 115 of the image forming apparatus 101. The apparatus 101 and the intermediate transfer belt driving roller 107 are controlled. Then, the printer engine control unit 253 causes the toner density sensor 291 to detect the reflection density of the print density test pattern, and corrects the print density (for example, adjustment of the developing bias) by the image forming apparatus 101 of each color.

  Next, the configuration of the high-voltage power supply device 301 in the first embodiment will be described with reference to FIG.

  1, among the configurations of the high-voltage power supply device 301 shown in FIG. 3, the circuit configuration of the high-voltage controller 260 and the secondary transfer bias generator 150 (for one bias output target load (secondary transfer roller 130). Only the configuration for outputting the bias is illustrated. That is, in the high-voltage power supply device 301 of the first embodiment, it is assumed that the configuration shown in FIG. 1 is provided for each bias output target load (transfer roller 105 or secondary transfer roller 130). Note that the high-voltage power supply device of the first embodiment may be configured as an independent device only by the circuit configuration for one bias channel shown in FIG. 1, or may be configured for a plurality of channels as shown in FIG. It is good also as a structure accommodated in one apparatus.

  As shown in FIG. 1, the secondary transfer bias generator 150 includes a detection value comparison circuit 310, a transformer drive circuit 311, a transformer 312, a positive rectification circuit 313, a detection value comparison circuit 314, a transformer drive circuit 315, a transformer 316, It has a negative rectifier circuit 317, a resistor 318, a resistor 319, a resistor 320, a constant voltage element 321, a current-voltage conversion element 322 as a detection element, and an operational amplifier 323.

The secondary transfer bias generator 150 includes a first DAC output 330 and a second DAC output 331 which are DA output terminals (output terminals of a digital / analog converter) of the high voltage controller 260, and an AD input terminal (A analog / digital). A first ADC input 332 and a second ADC 333 which are converter input terminals) are connected. The high voltage controller 260 can be configured by a microcomputer having an AD input terminal and a DA output terminal. The high voltage controller 260 outputs a voltage corresponding to the indicated value of the bias output from the first DAC output 330 and the second DAC output 331 to the secondary transfer bias generator 150. The high voltage controller 260 receives the input from the secondary transfer bias generator 150 by the first ADC input 332 and the second ADC 333 and reads the output value of the bias. In this embodiment, the DAC output of the high voltage controller 260 is described as a voltage based on an 8-bit output set value (8-bit DAC). In addition, in the ADC input of the high voltage controller 260, the description will be made assuming that the input value is converted into 10-bit data (10-bit ADC).

  The secondary transfer bias generator 150 performs constant voltage control when the toner image is transferred to the paper 115 by the secondary transfer roller 130, and performs constant current control when a reverse polarity bias is applied. When there is no paper 115 in the secondary transfer nip and the toner of the secondary transfer roller 130 is transferred to the intermediate transfer belt 108 side, constant current control is optimal. However, when toner is transferred to the paper 115, the paper 115 is used. The constant voltage control is suitable because there are various sizes of. This is because the area where the intermediate transfer belt 108 and the secondary transfer roller 130 are in contact with each other differs depending on the width of the paper 115 and the transfer current value at the optimum transfer bias is different. However, since the resistance value of the member constituted by the secondary transfer roller 130, the intermediate transfer belt 108, and the secondary transfer backup roller 120 differs depending on the environmental temperature, the high voltage control unit 260 previously sets a constant voltage before transferring to the paper 115. It is desirable to detect the current value at the output and set the bias accordingly. In FIG. 1, the resistance value of the member constituted by the secondary transfer roller 130, the intermediate transfer belt 108, and the secondary transfer backup roller 120 is illustrated as the output load R <b> 1 of the secondary transfer bias generator 150. In the following, when the toner image is transferred (secondary transfer) to the paper 115 by the secondary transfer roller 130, the voltage output to the secondary transfer roller 130 (output load R1) is referred to as “secondary transfer”. Also referred to as “voltage”.

  In the secondary transfer bias generation unit 150, the detection value comparison circuit 310, the transformer drive circuit 311, the transformer 312, and the positive polarity rectification circuit 313 form a positive polarity bias output unit for outputting a positive polarity bias. . Further, in the positive polarity bias output unit, the transformer driving circuit 311 drives the transformer 312 for outputting the positive polarity bias. In the positive polarity bias output unit, the positive rectification circuit 313 rectifies the output from the transformer 312. Further, in the positive polarity bias output unit, the detection value comparison circuit 310 compares the output of the positive polarity rectifier circuit 313 detected through the output detection unit described later with the input of the first DAC output 330, and compares the comparison. Based on the result, the transformer 312 is driven.

  In the secondary transfer bias generator 150, the detection value comparison circuit 314, the transformer drive circuit 315, the transformer 316, and the negative rectifier circuit 317 form a negative bias output unit for outputting a negative bias. ing. In the negative bias output unit, the transformer driving circuit 315 drives a transformer 316 for outputting a negative bias. Further, in the negative polarity bias output unit, the negative polarity rectifier circuit 317 rectifies the output from the transformer 316. Furthermore, in the negative polarity bias output unit, the detection value comparison circuit 314 compares the output of the negative polarity rectifier circuit 317 detected through the output detection unit described later with the input of the second DAC output 331, and Based on the comparison result, the transformer 316 is driven.

  Further, in the secondary transfer bias generator 150, the output (that is, the positive rectifier circuit 313 or the negative electrode) is output by the resistor 319, the resistor 320, the current-voltage conversion element 322, the operational amplifier 323, and the high-voltage controller 260. Output detector (the output detector of this embodiment) is formed.

  FIG. 4 is an explanatory diagram showing an example of a specific circuit configuration inside the secondary transfer bias generator 150 shown in FIG.

  In the example of FIG. 4, the secondary transfer bias generator 150 is shown connected to the high voltage controller 260. In FIG. 4, it is assumed that the high voltage control unit 260 (arithmetic processing by a computing means such as a microcomputer) uses a 3.3V power source 400 as a driving power source.

  In the example of FIG. 4, a reference numeral 401 is attached to a 24V power supply applied to each part of the secondary transfer bias generation unit 150, and a reference numeral 402 is attached to the ground (ground) of the secondary transfer bias generation unit 150. . The specific operation of the circuit of the secondary transfer bias generator 150 shown in FIG. 4 will be described in detail in the operation description to be described later.

  As shown in FIG. 4, the secondary transfer bias generator 150 includes a resistor 410, a capacitor 411, a capacitor 412, a resistor 413, an operational amplifier 414 (differential amplifier), a resistor 415, a capacitor 416, a resistor 417, an NPN transistor 418, Mold transformer 419, resistor 430, capacitor 431, capacitor 432, resistor 433, operational amplifier 434, resistor 435, capacitor 436, resistor 437, NPN transistor 438, winding open transformer 440, high voltage diode 441, high voltage diode 442, high Withstand voltage capacitor 443, high withstand voltage capacitor 444, 47kΩ resistor 445, 10kΩ resistor 446, resistor 447, capacitor 448, 1000V varistor 449, capacitor 450, 15kΩ resistor 451, capacitor 452, Anti 453, capacitor 454, operational amplifier 456, resistor 457, capacitor 458, diode 459, resistor 460, capacitor 461, operational amplifier 462, resistor 463, and a capacitor 464, and diode 465. The mold transformer 419 includes a winding transformer 420, a high voltage diode 421, a high voltage diode 422, a high voltage capacitor 423, a high voltage capacitor 424, a 10MΩ high voltage resistor 425, and a 30MΩ high voltage resistor 426 as one component. It is configured (for example, insulated by sealing with epoxy or the like).

Next, the correspondence between each component shown in FIG. 4 and each component shown in FIG. 1 will be described. In the following description, among the components shown in FIG. 4, those that are not described as included in the components shown in FIG. 1 do not realize the functions of the components shown in FIG. 1 . not, but in realizing the function of each component shown in FIG. 1, is a component on the desired mounting placing.

In the example of the secondary transfer bias generator 150 shown in FIG. 4, the detection value shown in FIG. 1 is obtained by the resistor 410, the capacitor 411, the capacitor 412, the resistor 413, the operational amplifier 414 (driven by the 24V power supply 401), the resistor 415, and the capacitor 416. A comparison circuit 310 is configured. In the example of the secondary transfer bias generator 150 shown in FIG. 4, the resistor 417, the NPN transistor 418, and the 24 V power supply 401 constitute the transformer drive circuit 311 shown in FIG. 1 . Further, in the example of the secondary transfer bias generator 150 shown in FIG. 4, the winding transformer 420 of the mold transformer 419 corresponds to the transformer 312 illustrated in FIG. Furthermore, in the example of the secondary transfer bias generator 150 shown in FIG. 4, the high voltage diode 421, the high voltage diode 422, the high-voltage capacitor 423, the high-voltage capacitor 424, and the high-voltage resistor 425, a positive electrode shown in FIG. 1 The rectifying circuit 313 is configured.

In the example of the secondary transfer bias generator 150 shown in FIG. 4, resistor 430, capacitor 431, capacitor 432, resistor 433, operational amplifier 434 (driven by the 24V power supply 401), the resistor 435, and capacitor 436, in FIG. 1 A detected value comparison circuit 314 shown in FIG. Further, in the example of the secondary transfer bias generator 150 shown in FIG. 4, the resistor 437, the NPN transistor 438, and the 24 V power supply 401 constitute the transformer driving circuit 315 shown in FIG. 1 . Furthermore, in the example of the secondary transfer bias generator 150 shown in FIG. 4, the winding type open transformer 440 corresponds to the transformer 316 shown in FIG. 1 . In the example of the secondary transfer bias generator 150 shown in FIG. 4, the high voltage diode 441, the high voltage diode 442, the high-voltage capacitor 443, and the high-voltage capacitor 444, constituting the negative polarity rectifier circuit 317 shown in FIG. 1 Has been.

Further, in the example of the secondary transfer bias generation unit 150 illustrated in FIG. 4, the high voltage resistance 426, the resistance 445, and the resistance 446 correspond to the resistance 318, the resistance 319, and the resistance 320, respectively. Further, in the example of the secondary transfer bias generator 150 shown in FIG. 4, the operational amplifier 462 (driven by the 24V power supply 401) corresponds to the operational amplifier 323 shown in FIG. Furthermore, in the example of the secondary transfer bias generator 150 shown in FIG. 4, the resistor 451 corresponds to the current-voltage converting element 322 shown in FIG.

(A-2) Operation of the First Embodiment Next, the operation of the image forming apparatus 101 of the first embodiment having the above configuration will be described.

[Overall Operation of Image Forming Apparatus]
First, an overall operation of the image forming apparatus 101 according to the first embodiment will be described with reference to FIGS.

  First, in the image forming apparatus 101, it is assumed that print data described in PDL (Page Description Language) or the like is supplied from an external device (not illustrated) to the host interface unit 250 illustrated in FIG. The host interface unit 250 converts the supplied print data into bitmap data by the command / image processing unit 251 and outputs the bitmap data to the LED head interface unit 252 and the printer engine control unit 253. The printer engine controller 253 controls the heat fixing roller of the fixing device 118 to a predetermined temperature by controlling the fixing device heater 259 according to the detection value of the thermistor 265, and then starts the printing operation.

  The printer engine control unit 253 feeds the paper 115 set in the paper feed cassette 113 by the hopping roller 114. The printer engine control unit 253 uses the registration roller pair 116 and 117 to transfer the paper 115 by the secondary transfer roller 130 and the secondary transfer backup roller 120 on the intermediate transfer belt 108 at a timing synchronized with an image forming operation described later. It is conveyed to the secondary transfer nip to be formed. In addition, the printer engine control unit 253 controls the developing devices 102 of the respective colors and forms a toner image on the photosensitive drum 132 in the developing device 102 by an electrophotographic process. At this time, the printer engine control unit 253 performs control so that the LED heads 103 of the respective colors are turned on according to the bitmap data. The printer engine control unit 253 transfers the toner image developed by the developing device 102 of each color onto the intermediate transfer belt 108 by a bias applied to the transfer roller 105 of each color. After the four color toner images are transferred to the intermediate transfer belt, the printer engine control unit 253 transfers the paper 115 to the secondary transfer formed by the secondary transfer roller 130 and the secondary transfer backup roller 120 at a predetermined timing. The toner image is conveyed to the nip, and the four color toner images are collectively transferred. Further, the printer engine control unit 253 causes the fixing device 118 to fix the paper 115 on which the toner image is transferred, and discharges the paper. Prior to the printing operation, the printer engine control unit 253 forms toner images of four colors on the intermediate transfer belt 108, detects the reflection density thereof, detects the toner density, and adjusts the developing bias.

  Each color toner cartridge container 104 is detachably attachable to each color developing device 102 and has a structure capable of supplying the internal toner to the developing device 102 of the supply destination. Then, the printer engine control unit 253 sets a high-voltage output voltage according to a predetermined table value, and a charging bias generation unit 261, a development bias generation unit 262, a primary transfer bias generation unit 263, and a secondary transfer bias generation unit 150. A predetermined signal is output. The charging bias generator 261 and the developing bias generator 262 supply the charging bias and the developing bias to the developing device 102 for each color. The primary transfer bias generator 263 supplies a primary transfer bias to the primary transfer roller 105 of each color. The secondary transfer bias generator 150 applies a positive bias while the secondary transfer roller 130 performs secondary transfer onto the paper 115 (while the paper 115 passes through the secondary transfer nip). Otherwise, a negative polarity bias is applied. As a result, the image forming apparatus 101 prevents contamination due to residual toner on the surface of the secondary transfer roller 130 during non-printing (when not during secondary transfer).

[Overview of high-voltage power supply operation]
Next, an outline of operations of the high voltage controller 260 and the secondary transfer bias generator 150 in the high voltage power supply apparatus will be described with reference to FIG.

The high-voltage control unit 260 is configured by a microcomputer, of which the first DAC output 330 and the second DAC output 331 are used as output instruction values for the secondary transfer bias generation unit 150, and the first ADC input 332 The second ADC 333 functions as a part of the output detection unit.
As for the secondary transfer bias, constant voltage control is performed when the paper 115 is applied to the paper, and constant current control is performed when a reverse polarity bias is applied. When transferring (removing) the toner on the secondary transfer roller 130, constant current control is optimal. However, when transferring a toner image onto the paper 115, there are various sizes of the paper 115, so that the constant voltage is controlled. Control shall be performed. This is because the area where the intermediate transfer belt 108 and the secondary transfer roller 130 are in direct contact with each other in the region outside the range of the sheet 115 varies depending on the width of the sheet 115, and the transfer current value at the time of the optimal transfer bias varies. However, since the resistance value (output load R1) of the member constituted by the secondary transfer roller 130, the intermediate transfer belt 108, and the secondary transfer backup roller 120 is different depending on the environmental temperature, the printer engine control unit 253 applies to the paper 115. Before the toner image is transferred, the printer engine control unit 253 is controlled so that a current value at a constant voltage output is detected in advance and a bias is set accordingly. The printer engine control unit 253 determines the output load R1 based on the detection result described above, and controls the high-voltage control unit 260 so as to perform bias setting according to the calculated output load R1.

  Next, details of the operation in which the high-pressure control unit 260 operates based on the control of the printer engine control unit 253 to obtain the output load R1 will be described.

  First, the high voltage control unit 260 performs current detection for obtaining the output load R1 (resistance value of the secondary transfer load). The high voltage controller 260 sets and outputs a predetermined voltage from the first DAC output 330 to the detection value comparison circuit 310 in order to apply a predetermined voltage to the output load R1 (set and output to output a positive polarity bias). . It is assumed that the output voltage from the high voltage control unit 260 to the detection value comparison circuits 310 and 314 is in the range of 0 to 3.3 V (within the drive voltage range of the high voltage control unit 260).

  The detection value comparison circuit 310 compares the voltage obtained by dividing the output of the positive rectification circuit 313 by the resistors 318, 319 and 320 with the output value of the first DAC output 330. A negative rectifier circuit 317 between the resistor 318 and the resistor 319 bypasses the positive output by a diode when not operating. A constant voltage element 321 is connected to one side of the positive rectifier circuit 313, and the same current as the output current of the positive rectifier circuit 313 flows to the constant voltage element 321. The output current of the positive rectifier circuit 313 is the sum of the current flowing through the output load R1 and the current flowing through the resistor 318. The current flowing through the constant voltage element 321 is also equal to this, but the current-voltage conversion element 322 has an output load R1. A current equal to the current flowing through the

  The output of the positive rectifier circuit 313 is controlled by driving the transformer driving circuit 311 by the detection value comparison circuit 310 so that the divided voltage is equal to the voltage of the first DAC output 330. The high voltage controller 260 detects the output voltage of the operational amplifier 323 by converting the input voltage of the first ADC input 332 port from analog to digital after allowing for a predetermined rise time after setting the output. The high voltage controller 260 calculates the resistance value of the output load R1 from the detected voltage value by calculation or the like. Then, the high voltage controller 260 determines a secondary transfer voltage set as a table value in advance based on the calculated resistance value and the detected value of the temperature / humidity sensor 290 according to the type of the paper 115, the width of the paper 115, and the like. Note that the arithmetic processing necessary for determining the secondary transfer voltage may be performed by either the high voltage control unit 260 or the printer engine control unit 253, or another component (for example, a dedicated IC for the arithmetic processing). Etc.) may be used.

  As described above, after obtaining the resistance value of the output load R1 (after detecting the current when the positive bias is applied), the high voltage controller 260 sets the output of the first DAC output 330 to 0 V and turns off the positive bias. At the same time, the second DAC output 331 is set to a predetermined voltage, and a negative bias is output.

  Regarding the negative polarity bias control of the secondary transfer bias generation unit 150, the detection value comparison circuit 314 converts the current value flowing through the resistor 322, the resistor 320, and the resistor 319, which are current-voltage conversion elements, from current to voltage, and This is performed by controlling the transformer driving circuit 315 so that the output of the second DAC output 331 becomes equal.

  The output of the transformer 316 is converted to a negative bias (negative DC bias) by a negative rectifier circuit 317. The output current of the negative rectifier circuit 317 becomes the output (sink current) of the operational amplifier 323 via the resistor 319, the resistor 320, and the current-voltage conversion element 322. At this time, the input potential of the operational amplifier 323 increases by the amount of current flowing through the current-voltage conversion element 322. This is because the output of the operational amplifier 323 does not become negative below the power supply voltage. The output voltage of the negative rectifier circuit 317 is applied to the output load R1 via the resistor 318. When the output voltage obtained by subtracting the voltage drop due to the resistor 318 from the voltage applied to the resistor 318 from the negative rectifier circuit 317 is higher than the threshold voltage of the constant voltage element 321, a current flows through the constant voltage element 321. To -1000V. As a result, the secondary transfer bias generator 150 has a configuration in which the output of the transformer 316 does not endlessly increase due to the constant current control even when the resistance value of the output load R1 is high. The current flowing through the output load R1 is input not only to the operational amplifier 323 but also to the second ADC 333 of the high voltage controller 260. In the high voltage control unit 260, the potential of the current is detected by analog-digital conversion.

  As described above, the negative polarity bias from the secondary transfer bias generator 150 to the output load R1 is always applied when the intermediate transfer belt 108 is driven and the sheet 115 is not in the secondary transfer nip. On the surface of the intermediate transfer belt 108, a toner image for detecting toner density (toner density detection patch) and the like are also formed. However, these toner images are not transferred to the paper 115. If the toner image adheres to the secondary transfer roller 130, the back side of the paper 115 during printing is generated. In order to prevent this, the image forming apparatus 101 applies a negative bias from the secondary transfer bias generator 150 to the secondary transfer roller 130. Further, in the image forming apparatus 101, before printing (before secondary transfer), a positive polarity bias and a negative polarity bias are alternately applied for each rotation of the roller (hereinafter, the operation of alternately applying the “cleaning sequence”). (Referred to also as “removing the toner on the secondary transfer roller 130”). Thus, the secondary transfer roller 130 can remove the reversely charged toner such as so-called “fogging toner”. At this time, the high voltage controller 260 reads the current value at the time of applying the negative bias with the second ADC 333, becomes a bias exceeding the threshold voltage of the constant voltage element 321, and the current flowing through the output load R1 is lower than the instruction value. In this case, the number of alternating bias application in the cleaning sequence may be increased.

  With the above operation, in the secondary transfer bias generator 150, the output terminal and the non-inverting input terminal of the operational amplifier 323 generate a predetermined offset voltage when no current flows through the current-voltage conversion element 322. When a sink current flows from the non-inverting input terminal to the output terminal, the output terminal is at the ground level. On the other hand, when a source current flows from the output terminal of the operational amplifier 323 to the non-inverting input terminal, the non-inverting input terminal is at the ground level. With this characteristic, the high voltage controller 260 can detect the current flowing through the output load R1 with high accuracy by detecting the potential of the non-inverting input terminal and the potential of the output terminal according to the direction of each current.

[Details of operation of high-voltage power supply]
Next, the detailed operation of the high-voltage power supply device will be described in more detail with reference to FIG.

  The image forming apparatus 101 detects an output load R1 that is a resistance value of a system constituted by the secondary transfer roller 130, the intermediate transfer belt 108, and the secondary transfer backup roller 120. In the initialization operation), a positive polarity bias is applied to the output load R1. This output load R1 is usually about 10 to 100 MΩ, and a voltage for detection, for example, a positive polarity of 2000 V is applied. For the second DAC output 331, the high voltage controller 260 sets an output set value (for example, an output having 00h (hexadecimal, 8 bits) as an output setting) at which the output of the negative polarity bias is turned off. For the DAC output 330, an output set value corresponding to 2000V is assumed. Calculation of the set values of the first DAC output 330 and the second DAC output 331 may use the following equation (1). In the equation (1), VF is a forward voltage of the diodes 441 and 442.

255 × {(2000−VF × 2) × 10 × 10 ^ 3
/(30×10^6+47×10^3+10×10^3)}/3.3 (1)
The integrating circuit composed of the operational amplifier 414 includes a voltage obtained by dividing the output of the positive rectifier circuit 313 into 10/30047 by a 30 MΩ resistor 426, a 47 kΩ resistor 445, and a 10 kΩ resistor 446, and the first DAC. The output of the operational amplifier 414 is temporarily increased by a predetermined time constant (time constant determined by the resistor 413 and the capacitor 412) so that the output of the output 330 becomes equal. As a result, the current flowing through the base of the NPN transistor 418 increases and the exciting current of the transformer 420 increases.

  The switching of the NPN transistor 418 is self-excited oscillation due to resonance with the transformer winding, and the control circuit (transformer drive circuit 315) controls only the base current. The reference potential at the time of voltage division is 0 V because the non-inverting input terminal of the operational amplifier 456 is at the ground level. After setting the first DAC output 330, the high voltage control unit 260 converts the input from the first ADC input 332 after a predetermined time (for example, after 20 to 30 msec) when the voltage rises. The AD conversion by the high-voltage control unit 260 may use an average value of a plurality of times. The current flowing through the transformer 420 is an AC current, but the AC component is removed by the capacitors 452, 450, and 458, and the smoothed DC signal is input to the first ADC input 332. Since the resistance 451 is 15 kΩ, the detection range is 0 to 220 μA with respect to the ADC input 0 to 3.3 V. For example, if the number of AD conversion bits by the high voltage controller 260 is 10 bits (10 Bit ADC), the output load R1 can be calculated by the following equation (2). Since the resistance 425 is 10 MΩ, the resistance value corresponding to the resistance 425 is subtracted in the equation (2).

Resistance value of output load R1 =
{2000 / (ADC detection value × 220 × 10 ^ −6 / 1023)}
−10 × 10 ^ 6 (Ω) (2)
In the high voltage control unit 260, the resistance value of the output load R1 obtained as described above is used to determine the secondary transfer bias by referring to a table value obtained in advance through experiments or the like.

  When the current detection by the positive bias output is completed, the high voltage control unit 260 sets the output setting of the first DAC output 330 to “00he” (hexadecimal number, 8-bit DAC) corresponding to 0 V, and turns off the positive bias. Subsequently, the high voltage controller 260 turns on the negative polarity bias. As described above, in the secondary transfer bias generator 150, the negative bias is constant current control, and for example, −20 μA is applied. In this case, in the secondary transfer bias generator 150, the current based on the negative polarity bias flows through the resistors 445, 446 and 451, and the output of the operational amplifier 456 is at the ground level at this time. Therefore, the high voltage control unit 260 sets “6Fh” obtained by converting the value 111 (decimal number) obtained by the following expression (3) into a hexadecimal number as the second DAC output 331.

255 × {20 × 10 ^
−6 × (47 × 10 ^ 3 + 10 × 10 ^ 3 + 15 × 10 ^ 3)} / 3.3 (3)
Then, the base current of the NPN transistor 438 is controlled by the integrating circuit configured by the operational amplifier 434, and the transformer 440 is driven. The output of the negative rectifier circuit 317 composed of the diodes 441 and 442 and the capacitors 443 and 444 is applied to the output load R1 via the resistors 426 and 425.

  At this time, when the potential at the connection point between the resistor 426 and the resistor 425 exceeds “− (1000 + VF × 2)”, a current flows through the varistor 449 and the output voltage is clamped. If the forward voltage of the diodes 421 and 422 is neglected and assumed to be −1000 V, the resistor 425 is 10 MΩ, so that it is clamped when the output load R1 exceeds 40 MΩ. For example, this may be the case when no current flows through the output load R1, or when the contacts are disconnected due to device failure or assembly failure.

  Since no current flows through the resistor 451, the input of the operational amplifier 456 is almost 0V. The second DAC output 331 indicated value corresponds to a resistance value of 47 k + 10 k + 15 k = 72 kΩ, but since no current flows through the 15 kΩ resistor, the current flowing for the 20 μA indicated value is 2 μA × 72 k / (47 k + 10 k) = 25.3 μA. This current value is equivalent to the current flowing through the varistor 449. Further, since this current is output through 30 MΩ of the resistor 426, the voltage drop (25.3 × 10 ^ −6 × 30 × 10 ^ 6 = 759V) and the varistor voltage 1000V are added. At no load, it is clamped at about 1759V.

  When the second DAC output 331 is the maximum value (FFh (hexadecimal number), equivalent to 3.3V), the current value is 3.3 / (57 × 10 ^ 3) = 57.9 μA, and the voltage Even if the drop 57.9 × 10 ^ −6 × 30 × 10 ^ 6 = 1737V and the varistor voltage 1000V are added, it is clamped at about −2737V when there is no load. In the positive / negative high voltage power supply used in the electrophotographic image forming apparatus, the transformer of the positive / negative bipolar output circuit is shared with the unipolar one so as to reduce the cost. One of them is an open type like a transformer 440 having a negative polarity output. When the transformer is placed open on a paper phenol substrate, the risk of creeping discharge increases when the output voltage exceeds 3 kV. Therefore, the circuit as described above is used in the first embodiment.

  The high voltage control unit 260 obtains a voltage value at which the positive polarity bias is 40 μA immediately before performing the secondary transfer operation by the following equation (4). Further, the high voltage control unit 260 calculates the set value by the following equation (5) similarly to the above, and sets the negative polarity bias to −20 μA. Then, the high-pressure control unit 260 performs cleaning of the toner attached on the secondary transfer roller 130 by alternately applying both polarities to the secondary transfer roller 130 every round.

β (V) = {α (MQ) +10 (MΩ)} × 40 (μA) (4)
255 × {(β (V) −VF × 2) × 10 × 10 ^ 3
/(30×10^6+47×10^3+10×10^3)}/3.3 (5)
At this time, the high voltage controller 260 detects the current value when the negative polarity bias is applied by the second ADC 333. And the high voltage | pressure control part 260 converts this detection value into an electric current value, and also calculates N of the following (6) formulas. The high-pressure control unit 260 multiplies the cleaning time by N when N is 1 or more. Thus, even when the resistance value of the output load R1 is high and the bias current is insufficient, sufficient cleaning can be performed by increasing the number of polarity changes.

  Further, when the current detection value at the time of bias application at each of the first ADC input 332 and the second ADC 333 is 0 (00h (hexadecimal number)), the high voltage control unit 260 is disconnected. Alternatively, it may be determined that a failure has occurred, the operation of the image forming apparatus 101 is stopped, and an error display or the like may be performed.

(A-3) Effects of First Embodiment According to the first embodiment, the following effects can be achieved.

  In the secondary transfer bias generator 150, the non-inverting input terminal of the operational amplifier 323 (the operational amplifier 456) is connected to the ground (ground potential), and the load current (positive rectifier circuit 313 or negative rectifier circuit 317) of the positive / negative bipolar circuit is connected. Current equal to the output current from the non-inverting input terminal to the output terminal. In other words, in the secondary transfer bias generation unit 150, the voltage detection position for current detection is set to the operational amplifier 323 (the operational amplifier 323 (operational amplifier 456) while the potential of the non-inverting input terminal is fixed to the ground (ground potential). By using both the inverting input terminal and the output terminal of the operational amplifier 456), positive and negative bipolar currents can be detected. Further, in the case of voltage detection, the secondary transfer bias generation unit 150 utilizes the fact that the inverting input terminal potential of the operational amplifier 323 (the operational amplifier 456) becomes the ground potential at the time of positive polarity bias output, and at the time of negative polarity bias output. The output terminal of the operational amplifier 323 (the operational amplifier 456) is used for detecting a negative bias voltage by utilizing the ground potential. As a result, the operational amplifier 323 (the operational amplifier 456) is configured to detect the current from the potential difference relative to the ground, with the ground serving as the reference potential at any polarity output. Therefore, the high voltage control unit 260 can detect current with high accuracy regardless of the power supply voltage and the power supply accuracy. In the image forming apparatus 101 to which such a secondary transfer bias generation unit 150 is applied, it is possible to detect transfer current with high accuracy (detection of a bias value for a transfer roller such as the secondary transfer roller 130).

  Although the operational amplifier has an offset in the input and output, in the secondary transfer bias generation unit 150 of the first embodiment, when a current flows between the inverting input terminal and the output terminal of the operational amplifier 323 (the operational amplifier 456), the potential is reduced. The lower side is always at ground potential. This is because each terminal of the operational amplifier does not have a potential lower than that of the negative power supply terminal. Therefore, by using the secondary transfer bias generator 150, the high voltage controller 260 can accurately detect the current value in the microampere order used for each bias.

(B) Second Embodiment Hereinafter, a second embodiment of an output detection device, a power supply device, and an image forming apparatus according to the present invention will be described in detail with reference to the drawings. Note that the output detection device and the power supply device of this embodiment are an output detection unit and a high-voltage power supply device.

(B-1) Configuration of Second Embodiment First, the overall configuration of the image forming apparatus 1101 of the second embodiment will be described.

  FIG. 5 is a schematic sectional side view of the image forming apparatus 1101 according to the second embodiment. FIG. 6 is a block diagram illustrating a configuration of a control system in the image forming apparatus 1101. 5 and 6, the same or corresponding reference numerals are given to the same or corresponding parts as those in the drawings of the first embodiment (the above-described FIGS. 2 and 3).

  The image forming apparatus 1101 according to the second embodiment is different from the first embodiment in that a pair of bending rollers 1100 and 1110 are disposed. A pair of bending rollers 1100, 1110 sandwich the intermediate transfer belt 108 between the secondary transfer roller 130 and the intermediate transfer belt stretching roller 106 (between the secondary transfer nip and the cleaning blade 111), and further intermediate transfer It is disposed at a position where the belt 108 is bent inward. The bending roller 1110 is disposed outside the intermediate transfer belt 108 and is in a state where the intermediate transfer belt 108 is stretched in the inner direction. In the second embodiment, by a pair of bending rollers 1100 and 1110, the distance between the secondary transfer nip formed between the secondary transfer roller 130 and the secondary transfer backup roller 120 and the fixing device (paper transport direction). ) Is shortened, and it is possible to print a shorter sheet in the sheet conveyance direction.

  The bending roller 1100 is connected to a bending roller bias generator 1150 for applying a bias voltage, and the bending roller 1110 is grounded.

  Further, the second embodiment differs from the first embodiment in that the high-voltage power supply device 301 is replaced with a high-voltage power supply device 1301 including a bending roller bias generator 1150. Furthermore, the high voltage power supply apparatus 1301 is different from the first embodiment in that the high voltage control unit 260 is replaced with a high voltage control unit 1260 that can be controlled (supply of control signals, etc.) including the bending roller bias generation unit 1150. Is different.

  Since the bending roller 1100 is disposed between the secondary transfer nip and the cleaning blade 111, it does not touch the toner image (toner image to be transferred to the paper 115) formed on the surface of the intermediate transfer belt 108. In some cases, the secondary transfer residual toner, a toner image for detecting the toner density (density detection patch), or the like may be touched. For this reason, in the image forming apparatus 1101, the bending roller bias generator 1150 is connected to the bending roller 1100, and positive and negative polarity biases are applied to prevent toner adhesion (toner cleaning). The bending roller bias generator 1150 applies a negative polarity bias to the bending roller 1100 when a toner image (toner density detection patch) for toner density detection passes or when the toner image is not transferred due to a jam. At other times, the positive polarity bias and the negative polarity bias are alternately applied every rotation of the roller, and a cleaning sequence operation for returning the adhering toner onto the intermediate transfer belt 108 is performed. When a negative bias is applied to the bending roller 1100, the toner on the roller is negatively charged (negatively charged) by the negative bias, and when a positive bias is applied to the bending roller 1100, the toner is negative by the positive bias. The charged toner moves onto the intermediate transfer belt 108. When a negative polarity bias is applied to the bending roller 1100, the bending roller bias generator 1150 applies a bias necessary for charging the adhered toner or the like to a negative polarity. In the second embodiment, the bending roller bias generator 1150 performs constant current control of −40 μA when a negative bias is applied. The bending roller bias generator 1150 is not charged with a bias necessary for transferring toner so as not to hinder the transfer of the toner image from the intermediate transfer belt 108 to the paper 115 when a positive bias is applied. A constant 20 μA constant current control is performed. Similarly, the bending roller bias generator 1150 performs constant current control of 20 μA even when a positive bias is applied in the cleaning sequence.

FIG. 7 is a block diagram showing only components related to the bending roller bias generator 1150 extracted from the high-voltage power supply device 1301 of the second embodiment.

  7, among the configurations of the high-voltage power supply device 1301 illustrated in FIG. 6, the circuit configuration of the high-voltage control unit 1260 and the bending roller bias generation unit 1150 (one bias application target load (each transfer roller 105 or bending roller 1110). Only a configuration for applying a bias to () is illustrated. That is, in the high-voltage power supply device 1301 of the second embodiment, a circuit shown in FIG. 7 is provided for each load (transfer roller 105, secondary transfer roller 130, or bending roller 1110) to which a bias is applied. . Note that the high-voltage power supply device of the second embodiment may be configured as an independent device only by the circuit configuration for one bias channel shown in FIG. 7, or a plurality of channels as shown in FIG. It is good also as a structure accommodated in one apparatus. In FIG. 7, an output load (an output load of the bending roller bias generation unit 1150) having a configuration including the bending roller 1100, the bending roller 1110, and the intermediate transfer belt 108 is illustrated as an output load R2.

  As shown in FIG. 7, the bending roller bias generator 1150 functionally includes a detection value comparison circuit 1310, a transformer drive circuit 1311, a piezoelectric transformer 1312, a negative rectifier circuit 1313, a detection value comparison circuit 1314, and a transformer drive circuit. 1315, a piezoelectric transformer 1316, a positive polarity rectifier circuit 1317, a resistor 1318, a resistor 1319, a resistor 1320, a current bypass circuit 1321, a current-voltage conversion element 1322, and an operational amplifier 1323. Further, the bending roller bias generation unit 1150 is connected to the first port output 1350, the second port output 1351, the first DAC output 1330, the second DAC output 1331, and the ADC input 1332 of the high voltage control unit 1260. Has been.

  As shown in FIG. 7, the high-voltage power supply device 1301 of the second embodiment differs from that of the first embodiment in that the transformer used for bias output is replaced from a winding type to a piezoelectric type (piezoelectric transformers 1312 and 1316). ing. The second embodiment is different from the first embodiment in that the position of the positive polarity bias output unit and the position of the negative polarity bias output unit are interchanged. The position of the sexual bias output unit is not limited. Further, the high-voltage power supply device 1301 of the second embodiment differs from the first embodiment in that the constant voltage element 321 is replaced with a current bypass circuit 1321. As described above, in the high voltage power supply device (power supply device) of the present invention, even if the arrangement of the circuit and the configuration of the transformer to be configured are changed according to the content of the bias required for the output load, the first implementation is performed. As in the case of the embodiment, it is possible to detect the bias output.

In bending roller bias generator 1150, the detection value comparator circuit 1310, transformer drive circuit 1311, by the piezoelectric transformer 1312, and the positive polarity rectifier circuit 131 7, positive bias output unit for outputting a positive bias is formed Yes. In the positive polarity bias output unit, the transformer driving circuit 1311 drives the piezoelectric transformer 1312 for outputting the positive polarity bias. Further, the positive bias output unit, the positive rectifier circuit 131 7 rectifies the output from the piezoelectric transformer 1312. Furthermore, the positive bias output unit, the detection value comparator circuit 1310, the output of the positive polarity rectifier circuit 131 7 detected through the output detector, which will be described later, the input of the first DAC output 1330 are compared, the The piezoelectric transformer 1312 is driven based on the comparison result.

Further, the bending roller bias generator 1150, the detection value comparator circuit 1314, transformer drive circuit 1315, by the piezoelectric transformer 1316, and negative rectifier circuit 131 3, the negative bias output unit for outputting a negative bias formed Has been. In the negative bias output unit, the transformer driving circuit 1315 drives a piezoelectric transformer 1316 for outputting a negative bias. Also, the negative bias output unit, by the negative polarity rectifier circuit 131 3 rectifies the output from the piezoelectric transformer 1316. Furthermore, the negative bias output unit, the detection value comparator circuit 1314, the output of the negative polarity rectifier circuit 131 3 detected through the output detector, which will be described later, the input of the second DAC output 331 is compared, the Based on the comparison result, the piezoelectric transformer 1316 is driven.

Further, in the bending roller bias generating unit 1150, a positive rectifier circuit 131 7 (positive bias output unit) is formed by a resistor 1319, a resistor 1320, a current-voltage conversion element 1322 as a detection element, an operational amplifier 1323, and a high voltage control unit 1260. And an output detection unit (output detection unit of this embodiment) that detects and feeds back the output of the negative rectifier circuit 131 3 (negative bias output unit).

FIG. 8 is an explanatory diagram showing an example of a specific circuit configuration inside the bending roller bias generator 1150 shown in FIG.

  8 shows a state in which the bending roller bias generation unit 1150 is connected to the high voltage control unit 1260. In FIG. 8, the high voltage control unit 1260 (calculation processing by a microcomputer) is a 3.3V power supply 400. Is a driving power source.

  Further, in the example of FIG. 8, a reference numeral 401 is attached to the 24V power source applied to the bending roller bias generator 1150, and 402 is attached to the ground of the secondary transfer bias generator 150. Note that the specific operation of the circuit of the bending roller bias generator 1150 shown in FIG. 8 will be described in detail in the operation description to be described later.

  8, the bending roller bias generator 1150 includes a resistor 1400, a capacitor 1401, a capacitor 1402, a resistor 1403, an operational amplifier 1404, a voltage controlled oscillator (VCO) 1405, an inductor 1406, an N-channel power MOSFET 1407, a capacitor 1408, Resistor 1420, capacitor 1421, capacitor 1422, resistor 1423, operational amplifier 1424, VCO 1425 (voltage controlled oscillator), inductor 1426, N-channel power MOSFET 1427, capacitor 1428, piezoelectric transformer 1430, high voltage diode 1431, high voltage diode 1432, high voltage capacitor 1433, 10 MΩ high withstand voltage resistor 1434, 10 kΩ resistor 1435, diode 1440, capacitor 1441, resistor 144 2, capacitor 1443, resistor 1444, capacitor 1445, resistor 1446, capacitor 1447, resistor 1448, capacitor 1449, resistor 1450, capacitor 1451, operational amplifier 1452, resistor 1453, capacitor 1454, P-channel FET 1470, resistor 1471, NPN transistor 1472, resistor 1473, a P-channel FET 1480, a resistor 1481, an NPN transistor 1482, and a resistor 1483. The molded piezoelectric transformer 1409 includes a piezoelectric transformer 1410, a high voltage diode 1411, a high voltage diode 1412, a high voltage capacitor 1413, a 50 MΩ high voltage resistor 1414, a high voltage diode 1415, and a 200 MΩ high voltage resistor 1416 made of resin or the like. Insulated and sealed.

  Next, the correspondence between each component shown in FIG. 8 and each component shown in FIG. 7 will be described. In the following description, among the components shown in FIG. 8, those that are not included in the components shown in FIG. 7 are not intended to realize the functions of the components shown in FIG. However, in order to realize the function of each component shown in FIG.

  In the example of the bending roller bias generation unit 1150 shown in FIG. 8, the detection value comparison circuit 1310 shown in FIG. 7 is configured by the resistor 1400, the capacitor 1401, the capacitor 1402, the resistor 1403, and the operational amplifier 1404 (driven by the 24V power supply 401). ing.

  In the example of the bending roller bias generator 1150 shown in FIG. 8, the VCO 1405, the inductor 1406, the N-channel power MOSFET 1407, the capacitor 1408, the P-channel FET 1470, the resistor 1471, the NPN transistor 1472, the resistor 1473, and the 24V power supply 401 are used. 7 is configured. Further, in the example of the bending roller bias generator 1150 shown in FIG. 8, a piezoelectric transformer 1410 1409 of the molded piezoelectric transformer corresponds to the piezoelectric transformer 1312 shown in FIG. Furthermore, in the example of the bending roller bias generator 1150 shown in FIG. 8, the high voltage diode 1411, the high voltage diode 1412, and the high voltage capacitor 1413 constitute the negative rectifier circuit 1313 shown in FIG.

  In the example of the bending roller bias generation unit 1150 shown in FIG. 8, the detection value comparison circuit 1314 shown in FIG. 7 is configured by the resistor 1420, the capacitor 1421, the capacitor 1422, the resistor 1423, and the operational amplifier 1424. Further, in the example of the bending roller bias generator 1150 shown in FIG. 8, the inductor 1426, the N-channel power MOSFET 1427, the capacitor 1428, the P-channel FET 1480, the resistor 1481, the NPN transistor 1482, the resistor 1483, and the 24V power supply 401 are shown in FIG. A transformer driving circuit 1315 shown in FIG. Furthermore, in the example of the bending roller bias generator 1150 shown in FIG. 8, the piezoelectric transformer 1430 corresponds to the piezoelectric transformer 1316 shown in FIG. In the example of the bending roller bias generator 1150 shown in FIG. 8, the high voltage diode 1431, the high voltage diode 1432, and the high voltage capacitor 1433 constitute the positive rectifier circuit 1317 shown in FIG.

  Further, in the example of the bending roller bias generation unit 1150 shown in FIG. 8, the high withstand voltage resistor 1414, the high withstand voltage resistor 1434, and the resistor 1435 correspond to the resistor 1318, the resistor 1319, and the resistor 1320 shown in FIG. Furthermore, in the example of the bending roller bias generator 1150 shown in FIG. 8, the high voltage diode 1415 and the high voltage resistor 1416 constitute the current bypass circuit 1321 shown in FIG. Further, in the example of the bending roller bias generator 1150 shown in FIG. 8, the resistor 1448 corresponds to the current-voltage conversion element 1322 shown in FIG. Furthermore, in the example of the bending roller bias generator 1150 shown in FIG. 8, the operational amplifier 1452 driven by the 24V power supply 401 corresponds to the operational amplifier 1323 shown in FIG.

(B-2) Operation of Second Embodiment Next, the operation of the image forming apparatus 1101 of the second embodiment having the above configuration will be described.

  The overall operation of the image forming apparatus 1101 is the same as that of the first embodiment except that an operation related to the bending roller bias generator 1150 is added. Therefore, in the following, the operation of the image forming apparatus 1101 of the second embodiment will be described focusing on the operation relating to the bending roller bias generating unit 1150 that is a difference from the first embodiment.

  First, an outline of the operation of the bending roller bias generator 1150 will be described with reference to FIG.

The output of the operational amplifier 1 323 is input to the detection value comparison circuit 1314 on the piezoelectric transformer 1316 side to which the positive rectifier circuit 1317 is connected, and the inverting input terminal of the operational amplifier 1 323 is a piezoelectric to which the negative rectifier circuit 1313 is connected. is input to the detection value comparator circuit 1310 of the transformer 131 6 side. The detection value comparison circuits 1310 and 1314 receive a DAC signal (a signal from the first DAC output 1 330 or the second DAC output 1 331) from the high voltage controller 1260 and receive a signal input from the operational amplifier 1 323. In comparison, the signals to the transformer drive circuits 1311 and 1315 are increased or decreased. The transformer drive circuits 1311 and 1315 convert the input signal into a frequency signal, and apply a voltage to the primary side of the piezoelectric transformers 1312 and 1316 based on the frequency signal. The piezoelectric transformers 1312 and 1316 output a high voltage to the secondary side at a boost ratio corresponding to the frequency of the input voltage signal. The high voltages output from the piezoelectric transformers 1312 and 1316 are rectified by the negative rectifier circuit 1313 and the positive rectifier circuit 1317, respectively, and applied to the output load R2.

  The first port output 1350 and the second port output 1351 are signals for driving the negative piezoelectric transformer 1312 (transformer driving circuit 1311) and the positive piezoelectric transformer 1316 (transformer driving circuit 1315), respectively. H level or L level signal). The high voltage control unit 1260 outputs the H level (circuit for driving the piezoelectric transformer) only to either the first port output 1350 or the second port output 1351, and the other port to the L level. (A signal for stopping the driving of the piezoelectric transformer) is output. As a result, the bending roller bias generator 1150 can apply a positive or negative bias to the output load R2 under the control of the high voltage controller 1260.

  In the high voltage control unit 1260, the output voltage value of the positive rectifier circuit 1317 divided by the resistors 1319 and 1320 is input to the ADC input 1332 and can be detected. The output of the positive rectifier circuit 1317 is applied to the output load R2 via the resistor 1318.

A current bypass circuit 1321 is connected to the output of the negative rectifier circuit 1313 as a load separately from the output load R2. In the high voltage controller 1260, the ADC input 1332 can detect the value of the current flowing through the resistor 1320 when a negative bias is output. Specifically, the high-pressure control unit 1260, from the inverting input terminal voltage of the first output command voltage and the operational amplifier 1 323 of the DAC output 1330 is equal, the first DAC output from the detected voltage of the ADC input 1332 The value of the current flowing through the resistor 1320 can be calculated by subtracting the output voltage value 1330.

  Since the difference between the current flowing through the current-voltage conversion element 1322 and the current flowing through the resistor 1320 is equal to the current flowing through the current bypass circuit 1321, the high-voltage controller 1260 can detect the output voltage of the negative rectifier circuit 1313. . The ADC input 1332 can detect the output voltage of the rectifier circuit (bias voltage by the negative rectifier circuit 1313 or the positive rectifier circuit 1317) at the time of both positive and negative outputs by the internal program of the high voltage controller 1260. As a result, the bending roller bias generator 1150 can detect an overvoltage and stop the output even when there is an abnormality such as no load (abnormal). In the high voltage control unit 1260, the first port output 1350 and the second port output 1351 are respectively input to the drive circuit (piezoelectric transformer 1312 or transformer drive circuit 1315), and supply power to the drive circuit when the H level is input. It is like that. In the high voltage control unit 1260, when the DAC output (the first DAC output 1330 or the second DAC output 1331) is 0 V, the output level of the first port output 1350 or the second port output 1351 is set to the L level ( The power supply to the drive circuit is cut off as an output stop instruction signal).

  Next, the details of the operations of the high-pressure controller 1260 and the bending roller bias generator 1150 will be described with reference to FIG.

  The high-voltage control unit 1260 can be obtained using the following equation (6) when -40 μA is output as the negative polarity bias from the bending roller bias generation unit 1150. In addition, the following formula (6) is a content in which the resistance 1448 is 30 kΩ.

255 × (30 × 10 ^ 3) × (40 × 10 ^ 6) /3.3≈93 (6)
Then, when “93” obtained by the above equation (6) is hexadecimal-converted, “5Dh” is obtained. Therefore, in this case, the high voltage control unit 1260 sets “5Dh” (hexadecimal number) to the output of the first DAC output 1330. At this time, the high voltage controller 1260 outputs 0 V (output corresponding to 00h (hexadecimal number)) from the second DAC output 1331. At this time, the high voltage controller 1260 outputs an H level from the first port output 1350 and outputs an L level from the second port output 1351. As a result, in the bending roller bias generator 1150, the collector potential of the NPN transistor 1472 is lowered, and the P-channel FET 1470 is turned on. As a result, the input voltage from the 24V power supply 401 is applied to the drain of the N-channel power MOSFET 1407 via the inductor 1406. Further, the integrating circuit constituted by the operational amplifier 1404 outputs VOH in the initial state, and the VCO 1405 drives the N-channel power MOSFET 1407 with a pulse having an upper limit frequency in the output frequency range. The integration circuit configured by the operational amplifier 1404 reduces the voltage input to the VCO 1405 until the set target current becomes −40 μA. When the input voltage decreases, the VCO 1405 decreases the output frequency. As a result, the step-up ratio of the piezoelectric transformer increases, and the absolute value of the negative rectifier circuit 1313 output increases. A member having a resistance value (resistance value of the output load R2) of the system by the pair of bending rollers 1100, 1110 and the intermediate transfer belt 108 is selected in the range of about 10M to 100MΩ, and is negative by constant current control of −40 μA. The output voltage of the rectifier circuit is about −400 to −4000V. When the inverting input terminal of the operational amplifier 1452 reaches the target current value of −40 μA, the potential becomes 1.2V. At this time, the high voltage controller 1260 detects the input voltage of the ADC input 1332. The current flowing through the resistor 1435 is added to the current flowing through the resistor 1416 in addition to the 40 μA. For example, assume that the detection voltage of the ADC input 1332 is 1.8V. The difference between the detection voltage (1.8 V) of the ADC input 1332 and the set voltage 1.2 V of the first DAC output 1330 is 0.6 V, and the resistance 1435 is 10 kΩ. It is calculated that a current of −60 μA flows. In this case, the difference from the command current (the command current value “−40 μA” output from the first DAC output 1330) is 20 μA, and this difference flows through the resistor 1416 of 200 MΩ. The output voltage is −4000 V (except for the diode VF (the forward voltage of the diodes 1411 and 1412)). The high voltage controller 1260 sets the output of the first DAC output 1330 to 0 V when the contact with the output load R2 is disconnected or the calculated voltage value (negative rectifier circuit 1313 output voltage) exceeds the threshold value due to a failure. And error display. The threshold is determined in consideration of the withstand voltage of the molded piezoelectric transformer 1409, the upper limit voltage depending on the load fluctuation range, and the like, but may be a value of 7 kV or more, for example.

  When the high voltage controller 1260 switches the bending roller bias generator 1150 to the negative bias output and then switches to the positive bias output, first the first DAC output 1330 instruction output is set to 0 V (hexadecimal 00h). And the output of the first port output 1350 is L. Subsequently, the high voltage controller 1260 sets the output of the second DAC output 1331 to 20 μA. Specifically, the high voltage controller 1260 controls the output of the second DAC output 1331 to 20 μA based on the value (46 (decimal number)) obtained by the following (7).

255 × (30 × 10 ^ 3) × (20 × 10 ^ −6) /3.3≈46 (7)
The high voltage control unit 1260 sets “2Eh” (hexadecimal number) obtained by performing hexadecimal conversion of “46” (decimal number) obtained by the above expression (7) as an output of the second DAC output 1331. Subsequently, the high voltage control unit 1260 sets the output of the second port output 1351 to the H level. As a result, in the bending roller bias generator 1150, the piezoelectric transformer 1430 is driven this time as described above, and the output of the positive rectifier circuit 1317 increases. As a result, in the high voltage controller 1260, the detected value of the ADC input 1332 becomes a voltage divided by the 10 MΩ resistor 1434 and the 10 kΩ resistor 1435, and therefore, from the voltage (hereinafter referred to as “ADC detected value”), The output voltage of the positive rectifier circuit 1317 can be obtained by the following equation (8).

(10 × 10 ^ 6 + 10 × 10 ^ 3) × (3.3 × ADC detection value / 1023)
/ (10 × 10 ^ 3) (8)
The high voltage controller 1260 then decreases the set value of the second DAC output 1331 by 1 when the voltage obtained by the above equation (8) exceeds 3000V.

  Next, an operation in which the high voltage control unit 1260 sets the set value of the second DAC output 1331 based on the output voltage of the positive rectifier circuit 1317 will be described with reference to FIG.

  First, the high voltage controller 1260 obtains the output voltage of the positive rectifier circuit 1317 by calculation similar to the above-described equation (8) (S1001).

  Next, the high voltage control unit 1260 determines whether or not the output voltage of the positive rectifier circuit 1317 exceeds a threshold value (in this case, 3000 V) (S1002). The output set value of the DAC output 1331 is reduced (decremented) by 01h (hexadecimal number) (S1003).

  Then, the high voltage controller 1260 determines whether or not the output setting value of the second DAC output 1331 is 00h (hexadecimal number) (S1004). If it is 00h, the process is terminated. Otherwise, the operation returns to step S1001 described above.

  The high voltage controller 1260 adjusts the current value output from the positive rectifier circuit 1317 to the target, for example, according to the operation of the above-described flowchart. Note that when the output voltage of the positive polarity rectifier circuit 1317 does not exceed the upper limit of 3000 V, the high voltage control unit 1260 may not change the output set value of the second DAC output 1331. In particular, when the positive rectifier circuit 1317 of the piezoelectric transformer 1430 is mounted without being molded on the substrate, control is performed so that the output of the positive rectifier circuit 1317 does not exceed the upper limit voltage (the above-described 3000 V). It is desirable to do.

(B-3) Effects of Second Embodiment According to the second embodiment, the following effects can be achieved.

  In the image forming apparatus 1101 constituting the image forming apparatus 1101 of the second embodiment, not only a winding type transformer but also a piezoelectric type transformer can detect a current with high accuracy by using a reference potential as a ground, and can accurately determine the current. Current control is possible.

(C) Other Embodiments The present invention is not limited to the above-described embodiments, and may include modified embodiments as exemplified below.

(C-1) In the first embodiment, the case where the power supply apparatus to which the output detection apparatus of the present invention is applied is applied to the secondary transfer bias of the intermediate transfer system has been described. In the second embodiment, the case where the power supply device to which the output detection device of the present invention is applied is applied to a bending roller has been described. However, the power supply apparatus of the present invention is an electrophotographic image forming apparatus to which the output detection apparatus is applied and applies a positive / negative bipolar bias to other bias sources such as a transfer roller bias of a monochrome image forming apparatus. Is also applicable.

(C-2) FIG. 10 is a diagram illustrating a circuit configuration of the bending roller bias generator 1150 according to a modification of the second embodiment. In the modification of FIG. 10, a diode 2400, a Zener diode 2401, and a resistor 2402 are added to the configuration of the second embodiment (the configuration of FIG. 8 described above), and the wiring is changed. In the modification of FIG. 10, the second DAC output 1331 corresponding to the current flowing through the resistor 1448 is set from the voltage obtained by subtracting the forward voltage of the diode 2400 from the operational amplifier output voltage when positive current is detected. Thus, the positive polarity bias is controlled at a constant current. In the modification of FIG. 10, the negative bias sets a voltage corresponding to a voltage obtained by dividing the Zener voltage of the Zener diode 2401 and the negative rectifier circuit output by the resistor 1416 and the resistor 2402 to the first DAC output 1330. Thus, constant voltage control is performed. Furthermore, in the modification of FIG. 10, the negative bias current can be calculated from the detected voltage of the ADC input 1332.

DESCRIPTION OF SYMBOLS 101 ... Image forming apparatus, 102 ... Developing device, 103 ... LED head, 104 ... Toner cartridge, 105 ... Transfer roller, 106 ... Intermediate transfer belt stretching roller, 107 ... Intermediate transfer belt drive roller, 108 ... Intermediate transfer belt, 111 ... intermediate transfer belt cleaning blade, 115 ... paper, 150 ... secondary transfer bias generator, 120 ... secondary transfer backup roller, 130 ... secondary transfer roller, 150 ... secondary transfer bias generator, 290 ... temperature / humidity sensor, DESCRIPTION OF SYMBOLS 132 ... Photosensitive drum, 133 ... Supply roller, 134 ... Developing roller 136 ... Charging roller, 137 ... Cleaning blade, 250 ... Host interface part, 251 ... Command / image processing part, 252 ... LED head interface part, 253 ... Printer engine Control unit, 260... High pressure control unit, DESCRIPTION OF SYMBOLS 61 ... Charging bias generation part, 262 ... Development bias generation part, 263 ... Transfer bias generation part, 254 ... Hopping motor, 301 ... High voltage power supply device, 310 ... Detection value comparison circuit, 311 ... Transformer drive circuit, 312 ... Transformer, 313 ... Positive rectifier circuit, 314 ... Detection value comparison circuit, 315 ... Transformer drive circuit, 316 ... Transformer, 317 ... Negative rectifier circuit, 318 ... Resistor, 319 ... Resistor, 320 ... Resistor, 321 ... Constant voltage element, 322 ... Current-voltage conversion element, 323, operational amplifier, 330, first DAC output, 331, second DAC output, 332, first ADC input, 333, second ADC input, R1, output load, 401, 24V Power source, 402: Ground (ground).

Claims (10)

Negative electrode having negative polarity transformer for outputting negative polarity bias, negative polarity drive unit for driving negative polarity transformer, and negative polarity rectification unit for rectifying output of negative polarity transformer and outputting as negative polarity bias A positive-polarity bias output unit, a positive-polarity transformer for outputting a positive-polarity bias, a positive-polarity drive unit that drives the positive-polarity transformer, and a positive-polarity that rectifies the output of the positive-polarity transformer and outputs it as a positive-polarity bias A positive-polarity bias output unit having a rectification unit and an output detection device that detects the output of the device itself, and the negative-polarity bias output unit or the positive-polarity bias output unit biases the output load to be output In the output detection device constituting the power supply device that outputs
Connect to a single power supply with one side ground, connect the non-inverting input terminal to the ground, and connect the inverting input terminal and the output terminal to the output of the power supply device via a detection element for detecting the output of the power supply device Operational amplifier,
Using the operational amplifier, an output detection circuit that detects a positive / negative bipolar current by making the voltage detection position both an inverting input terminal of the operational amplifier and an output terminal of the operational amplifier , and
The inverting input terminal of the operational amplifier is connected to each of the positive rectification unit and the negative rectification unit,
When a positive polarity bias is output from the power supply device, a reference ground potential of the output detection circuit is used as an inverting input terminal of the operational amplifier, and when a negative polarity bias is output from the power supply device, the output the reference ground potential of the detection circuit to an output terminal of said operational amplifier,
The output detection circuit, when a positive bias is output from the positive bias output unit, the inverting input terminal of the operational amplifier is a ground potential, and when a negative bias is output from the negative bias output unit, When the output terminal of the operational amplifier is set to the ground potential and the positive bias is output from the positive bias output unit, or the negative bias is output from the negative bias output unit, An output detection apparatus, wherein positive and negative bipolar currents are detected from a potential difference with respect to a ground potential with reference to a potential that is a ground potential of an inverting input terminal of the operational amplifier or an output terminal of the operational amplifier . The output current equal to the output current to the load, the output detecting device according to claim 1, characterized in that flow in both directions through a detection device which is the connection between the inverting input terminal and the output terminal of the operational amplifier. The detection element constituting the output detection circuit is a resistor,
In the output detection circuit ,
Increases with current potential of the inverting input terminal of the pre-Symbol operational amplifier flows through the output load, according to claim 1 or 2, characterized in that the detecting means is provided for detecting the increased potential Output detection device. The output detection circuit divides the voltage between the output of the positive polarity bias output unit and the inverting input terminal of the operational amplifier using a plurality of voltage dividing resistors, and detects the potential of the divided voltage. The output detection device according to claim 3 , wherein an output voltage when a positive bias is output from the power supply device is detected. The output detection circuit detects an output voltage when a positive polarity bias is output from the power supply device based on a difference between a current flowing through the detection element and a current flowing through the voltage dividing resistor. The output detection apparatus according to claim 4 . The detection element constituting the output detection circuit is a resistor,
The output detection circuit calculates an output voltage when a positive polarity bias is output from the power supply device based on a difference between a current flowing through a resistor as the detection element and a current flowing through the voltage dividing resistor. 6. The output detection apparatus according to claim 5 , further comprising means. In the output detection circuit, from the difference between the current flowing through the constant voltage element serving as the detection element and the current flowing through the voltage dividing resistor, the negative bias voltage output from the power supply device serves as the detection element. The output detection device according to claim 4 , wherein it is detected whether or not the threshold voltage is higher than or equal to a constant voltage element. 6. The output detection device according to claim 5 , wherein in the output detection circuit, the terminals of the detection elements are connected via a diode. Negative electrode having negative polarity transformer for outputting negative polarity bias, negative polarity drive unit for driving negative polarity transformer, and negative polarity rectification unit for rectifying output of negative polarity transformer and outputting as negative polarity bias A positive-polarity bias output unit, a positive-polarity transformer for outputting a positive-polarity bias, a positive-polarity drive unit that drives the positive-polarity transformer, and a positive-polarity that rectifies the output of the positive-polarity transformer and outputs it as a positive-polarity bias A positive-polarity bias output unit having a rectification unit and an output detection device that detects the output of the device itself, and the negative-polarity bias output unit or the positive-polarity bias output unit biases the output load to be output In the power supply device that outputs the output, the output detection device according to any one of claims 1 to 8 is used to detect the output of the power supply device, and based on the detection result And controlling the negative drive unit and the positive drive unit. An image forming apparatus comprising a power supply device that outputs a bias to an output load, wherein the power supply device according to claim 9 is applied as the power supply device.

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