JP2009089360A - A / D conversion control device and image forming apparatus having the same - Google Patents

Abstract

An A / D conversion control apparatus and an image forming apparatus capable of further improving the calculation accuracy when calculating an analog input voltage from a digital value.
A reference voltage generation unit 408 generates a plurality of analog reference voltages, and an A / D conversion unit 405 converts the generated analog reference voltages and an analog input voltage input from an external device into a digital reference value. The CPU 402 converts the analog input voltage to be converted into a digital value between the plurality of digital reference values based on the plurality of analog reference voltages and the plurality of digital reference values obtained by converting the plurality of analog reference voltages. Is calculated, and an analog input voltage for the converted digital value is calculated using the generated arithmetic expression.
[Selection] Figure 4

Description

  The present invention relates to an A / D conversion control device that increases the calculation accuracy of an analog input voltage from a digital value, and in particular, to accurately perform control in an image forming apparatus that performs control to improve fixing performance in a fixing unit. The present invention relates to an image forming apparatus capable of

  A fixing roller used in an electrophotographic image forming apparatus is heated to a predetermined temperature by a fixing heater using a halogen heater that generates heat by electric power from an external power source (commercial power source or the like). In addition, when there is a margin in the power usage of the input power supply during standby, etc., the auxiliary power supply such as an electric double layer capacitor that can be charged is charged. Conventionally, a method of heating the fixing heater by the electric power stored in the power source and assisting the heating of the fixing roller has also been adopted.

  In recent years, from the viewpoint of energy saving, the operation of the fixing heater, which consumes a large amount of power during operation standby, is stopped, and at the time of recovery, the fixing heater is operated by the power from both the external power supply and the auxiliary power supply. A method of heating (warming up) has been developed. If the fixing roller is heated in a short time, the fixing roller ambient temperature and the pressure roller that presses the recording medium against the fixing roller are not sufficiently heated. The heat of the fixing roller is dissipated to the pressure roller, and the fixing roller temperature rapidly decreases. In particular, when left at a low ambient temperature for a long time, the temperature of the transfer paper and the pressure roller is also low, and thus a temperature drop is likely to occur. Even when the external power supply voltage is low, the supply voltage to the fixing heater is small, so the amount of heat generated by the heater is small, and the temperature of the fixing roller is likely to decrease.

  In order to improve the fixing roller temperature drop during image formation immediately after warming up from the standby state as described above, the fixing heater using the power supplied from the auxiliary power source is operated even when the fixing roller temperature drops. A method of assisting heating of the roller is also used. However, in order to assist warming up and lowering the fixing roller temperature under all conditions, it is necessary to increase the power supply capacity that can be supplied with auxiliary power. Problems such as restrictions on size arise.

  In addition, there is a limit to the capacity of the auxiliary power supply that can be installed. When the auxiliary power supply is used to heat the fixing roller during warm-up by controlling only the fixing roller temperature, the fixing roller warms up when the input power supply voltage drops or in a low-temperature environment. Since it takes a long time, the power consumption of the auxiliary power source also increases, and there may be a case where there is not enough power left to assist the temperature reduction of the fixing roller during image formation immediately after warm-up.

  To solve these problems, it detects external power supply voltage, auxiliary power supply voltage, ambient temperature, fixing / pressing roller temperature, etc., for warming up the fixing roller for a short time and assisting in lowering the fixing roller temperature during image formation. There has already been proposed a method of determining the optimal power distribution of the auxiliary power source used for the recovery and controlling the fixing heater (see the description of FIGS. 1 and 2 to be described later).

  Here, as a method of detecting analog signals such as external power supply voltage, auxiliary power supply voltage, ambient temperature, fixing / pressure roller temperature, etc., A (analog) / D (built-in or connected to the CPU for controlling the apparatus) A method using a (digital) converter is common, but in order to perform control accurately, it is necessary to detect an analog signal with high accuracy. In particular, in the detection of the input power supply voltage, it is necessary to detect with an accuracy of about ± 1V with respect to the input power supply voltage AC100V, and when using an A / D converter or the like built in the CPU with a relatively low accuracy, It is necessary to correct the conversion error that occurs during A / D conversion to be smaller.

  However, in a conventional image forming apparatus, analog signals such as an input power supply (commercial AC power supply) voltage, an auxiliary power supply voltage, an ambient environment temperature, and a fixing / pressure roller temperature are detected in a control CPU. Since the A / D converter connected to is used, it is necessary to correct the analog signal with high accuracy in order to perform the control accurately. In particular, in the detection of the input power supply voltage, it is necessary to be able to detect the input power supply voltage AC90 to 110V with high accuracy of about ± 1V, but the AC voltage is converted into a DC voltage that can be input to the A / D converter. Since the detection circuit also includes an error, a method for reducing the conversion error generated at the subsequent A / D conversion is required.

  Specifically, since the A / D converter has a conversion error (offset error, full-scale error, non-linearity error, etc.) that occurs at the time of conversion, the digital value includes the conversion error. Here, the offset error is an analog input voltage at which the digital value A / D converted by the A / D converter becomes a minimum value (for example, 0). The full scale error is an analog input voltage that becomes the maximum digital value (FS) that can be A / D converted by the A / D converter. The non-linearity error is an error caused by a non-linear change in the digital value with respect to the analog input voltage input to the A / D converter. For example, if a 10-bit A / D converter has a conversion error of 10 LSB, the conversion value of the input voltage as the detection result includes a conversion error of 10/1023 (about 1%). . Further, an error of the reference power source of the A / D converter is added to the converted value. As a method for detecting an analog signal with high accuracy, a method in which a high-performance A / D converter with a small conversion error and a high-accuracy reference power supply are combined is generally used. It is expensive compared with the method using the A / D converter.

  As described above, the method of using the A / D converter built in or connected to the control CPU of the image forming apparatus for detecting the analog signal has a problem that the conversion accuracy of the A / D converter is low.

  Therefore, as a conventional technique for reducing variation after A / D conversion, for example, Patent Document 1 discloses an A / D converter that performs A / D conversion by switching a plurality of input ports. A high-accuracy voltage whose voltage fluctuation is smaller than the reference voltage is generated, and the digital value obtained by A / D converting the high-accuracy voltage is corrected by the digital value obtained by A / D-converting the input voltage of the other input port. It is disclosed.

  Next, the background of the A / D conversion control device according to the present invention will be described in detail with reference to FIGS. 11 and 12. 11 and 12 are diagrams showing a configuration of a control unit in a conventional image forming apparatus. A configuration example (FIG. 11) of the control unit based on a general A / D converter usage mode and the above-mentioned patent document. FIG. 13 is a diagram illustrating a configuration example (FIG. 12) of a control unit based on a usage mode of the A / D converter disclosed in FIG.

  11, a control unit 1100 includes a CPU (Central Processing Unit) 1102, a ROM (Read Only Memory) 1103, a RAM (Random Access Memory) 1104, an A / D conversion unit 1105, an input switching unit 1106, A / D conversion control. A one-chip microcomputer 1101 having a unit 1107 and an I / O control unit 1109, and a reference voltage generation unit 1108 that generates a voltage. A ROM 1103 is a read-only storage device that stores a basic processing program of the control unit 1100, a control program of each unit included in a conventional image forming apparatus such as a fixing device and a scanner, and data necessary to execute these programs It is. The RAM 1104 is a storage device that can temporarily store data necessary for program execution.

  The power supply unit 1111 drives the one-chip microcomputer 1101 of the control unit 1100 and is also used as an input for the reference power supply of the reference voltage generation unit 1108. The voltage generated by the reference voltage generation unit 1108 is input to the A / D conversion unit 1105 and used as a reference voltage for A / D conversion.

  Further, the control unit 1100 is connected to a one-chip microcomputer 1101 via a sensor 1110 that generates an analog signal for performing temperature detection and voltage detection of each unit for fixing control, and an I / O control unit 1109, and the fixing roller A fixing heater driving circuit 1112 for turning on / off the heating fixing heater is connected.

  The A / D conversion unit 1105 can sequentially convert a plurality of analog signal inputs to digital data while switching them in a time division manner by an input switching unit 1106 configured by a semiconductor switch such as an analog switch. Input switching of the input switching unit 1106 is controlled by the A / D conversion control unit 1107 in accordance with the operation of the A / D conversion unit 1105.

  FIG. 12 shows a control unit of an image forming apparatus to which the conversion error correction method of the A / D converter disclosed in Patent Document 1 for correcting an A / D conversion error is applied to the control unit 1100 shown in FIG. It is a schematic block diagram which shows 1200. FIG. Note that the configuration of the control unit 1200 is substantially the same as that of the control unit 1100 shown in FIG. The power supply unit 1202 drives the one-chip microcomputer 1101 of the control unit 1200 and is used as an input to the reference voltage generation unit 1201. Further, the power supply unit 1202 is input to the A / D conversion unit 1105 and used as a reference voltage for A / D conversion. The voltage (reference power supply) generated by the reference voltage generation unit 1201 is input to the A / D conversion unit 1105 via the input switching unit 1106 and used for conversion error correction of the A / D conversion unit 1105.

  FIG. 13 is a conversion characteristic diagram showing conversion errors of a general A / D converter. As a general method for calculating the analog input voltage from the digital value converted by the A / D conversion unit 1105 shown in FIG. 11, the analog input voltage is converted from the digital value based on the ideal A / D conversion characteristic shown in FIG. There is a method to calculate. In this method, the analog input voltage when the digital value takes the minimum value (0) is 0 V, and the analog input voltage when the digital value takes the maximum value (FS) is the reference voltage of the A / D converter 1105. It is calculated as being equal to (Vref).

  Assuming that an analog input voltage to be A / D converted (input from a sensor 1110 such as a temperature sensor or a voltage sensor) is V and the digital value thereof is D, it is calculated from the digital value D by the ideal A / D conversion characteristic shown in FIG. In order to calculate the converted value V ′ of the analog input voltage V, the following arithmetic expression 1 is used.

V ′ = Vref / FS × D... Equation 1
However, as described above, an A / D converter that converts an analog input voltage into a digital value generally includes an offset error, a full-scale error, and a non-linearity error due to the circuit characteristics inside the A / D converter. Therefore, using the digital value (D) obtained by A / D converting the actual analog input voltage (V), a voltage (A) obtained by calculating the analog input voltage based on the ideal A / D conversion characteristics shown in FIG. V ′) and a voltage (V) obtained by calculating the analog input voltage based on the actual A / D conversion characteristics shown in FIG. 13 cause a conversion error as shown in FIG.

  Further, since the reference voltage (Vref) of the A / D converter is included in the arithmetic expression, Vref is also required to have high accuracy. Some high-accuracy A / D converters have a function of reducing the conversion error inside these converters or adjusting the conversion error, but they are generally expensive because the circuit becomes complicated. There are also problems such as complicated control.

  Therefore, as in the configuration of FIG. 12, a method of correcting a digital value corresponding to another analog input voltage is proposed with reference to a digital value obtained by A / D converting a known analog input voltage. According to the prior art disclosed in Patent Document 1, a certain A / D conversion is performed based on a digital value (D) obtained by A / D conversion of a known high-precision analog input voltage (V). The converted value (V1 ′) of the analog input voltage (V1) is calculated from the digital value (D1) of the unknown analog input voltage (V1).

  When this calculation method is expressed by an arithmetic expression, the following arithmetic expression 2 is obtained.

V1 ′ = V / D × D1 Equation 2
The A / D conversion characteristic by the arithmetic expression 2 is shown as “A / D conversion characteristic by the prior art” in FIG. According to this method, the converted value of the analog input voltage can be obtained without being affected by the fluctuation of Vref.

JP 2005-26830 A

  As described above, in the image forming apparatus, it varies depending on the environment of the connected external power source (decrease in input voltage due to use of a power source such as a private power generator or connection with the image forming apparatus and other devices via a foot-to-mouth connection). In order to perform the power control of the fixing heater suitable for the analog input voltage, it is necessary to calculate the analog input voltage with high accuracy as described above.

  In Patent Document 1 described above, in a general A / D converter, the digital value of the analog input voltage is corrected based on the digital value of the analog input voltage with higher accuracy than the reference voltage for A / D conversion. However, it is based on one highly accurate analog input voltage and its digital value, the generated arithmetic expression 2 is used to convert an analog input voltage having a wide range of voltage values into A / D. Variations occur in the converted values, causing problems in the accuracy of A / D conversion. Although details will be described later, no consideration is given to the non-linearity error of the A / D converter.

  Specifically, the A / D conversion characteristic (the A / D conversion characteristic according to the prior art shown in FIG. 13) according to Equation 2 takes into account the conversion error of the A / D converter, particularly the non-linearity error. Therefore, depending on the setting of the known analog input voltage (V), the conversion error increases as the unknown analog input voltage (V1) for A / D conversion approaches Vref, which may exceed the full-scale error. There is a problem.

  An object of the present invention is to provide an A / D conversion control device and an image forming apparatus that can improve the accuracy of calculating an analog input voltage from a digital value.

  In order to solve the above-mentioned problems and achieve the object, the invention according to claim 1 is a first generation means for generating a plurality of analog reference voltages, and the generated plurality of analog reference voltages are converted into a plurality of digital references. A / D conversion means for converting an analog input voltage that is converted into a value and input from an external device into a digital value, and the plurality of digital reference values based on the plurality of analog reference voltages and the plurality of digital reference values A second generation means for generating an arithmetic expression that complements the analog input voltage converted into a digital value between the first and second calculation means, and a calculation for calculating the analog input voltage for the converted digital value using the generated arithmetic expression Means.

  According to a second aspect of the present invention, in the first aspect of the invention, the second generation unit is configured to generate the digital reference value closest to the digital value for calculating the analog input voltage and less than or equal to the digital value and the digital value. The arithmetic expression is generated based on the analog reference voltage converted into a reference value, the digital reference value closest to the digital value and greater than or equal to the digital value, and the analog reference voltage converted into the digital reference value It is characterized by doing.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the first generation means includes the analog reference voltage that is the same as the analog input voltage, and voltage fluctuation is smaller than the analog input voltage. The plurality of analog reference voltages are generated.

  According to a fourth aspect of the present invention, in the first aspect of the invention according to any one of the first to third aspects, the first generating means is more than an upper limit value of the analog input voltage and a digital value is obtained by the A / D conversion means. The analog reference voltage smaller than the voltage converted into the maximum value is generated.

  Further, the invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the first generation means has a digital value greater than or equal to a lower limit value of the analog input voltage and by the A / D conversion means. Generating the analog input voltage greater than the voltage converted to a minimum value;

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the range of digital values that can be converted by the A / D conversion means is converted from the plurality of analog reference voltages. Dividing means for dividing into a plurality of sections according to a plurality of digital reference values, the second generating means, the plurality of analog reference voltages in the divided sections and the plurality of analog reference voltages converted from the plurality of analog reference voltages The arithmetic expression is generated for each section based on a digital reference value.

  According to a seventh aspect of the present invention, the analog input voltage calculated from the digital value indicating the state of each part of the image forming apparatus by the A / D conversion control device according to any one of the first to sixth aspects is used. Each part of the image forming apparatus is controlled.

  According to the present invention, based on a plurality of digital reference values obtained by A / D-converting a plurality of analog reference voltages and the plurality of analog reference voltages, an analog input voltage of a digital value between the plurality of digital reference values is complemented. Generated when the analog input voltage is converted into a digital value by the A / D conversion characteristic of the A / D converter by calculating the analog input voltage for the digital value using the generated arithmetic expression. Since the analog input voltage can be calculated from the digital value in consideration of the conversion error, particularly the non-linearity error, the calculation accuracy when calculating the analog input voltage from the digital value can be further improved. .

  The A / D conversion control apparatus according to the present embodiment will be described in detail below with reference to FIGS. First, an outline of a digital copying machine constituting an image forming apparatus using an A / D conversion control device according to the present embodiment will be described with reference to FIG.

  FIG. 1 is a diagram showing an outline of a digital copying machine constituting an image forming apparatus using an A / D conversion control apparatus according to this embodiment. 1 is a longitudinal sectional view of a digital copying machine 1, and this digital copying machine 1 embodies an image forming apparatus according to this embodiment, and is a so-called multifunction machine. The digital copying machine 1 has a copying function and other functions such as a printer function and a facsimile function, and the copying function, the printer function, and the facsimile function are sequentially performed by operating an application switching key of an operation unit (not shown). It is possible to switch to and select. Thus, the copy mode is selected when the copy function is selected, the print mode is selected when the printer function is selected, and the facsimile mode is selected when the facsimile mode is selected. In this embodiment, an example in which an A / D conversion control device is used in a digital copying machine will be described. However, an image using an analog input voltage calculated from a digital value A / D converted by an A / D converter is used. Any device that controls each part of the forming apparatus can be applied to an image forming apparatus such as a facsimile, a copier, or a printer.

  Next, the schematic configuration of the digital copying machine 1 and the operation in the copy mode will be described. In FIG. 1, in an automatic document feeder (hereinafter referred to as ADF) 101, a document placed on a document table 102 with the image surface facing upward is pressed when a start key on an operation unit (not shown) is pressed. 103, and is fed to a predetermined position on the contact glass 105 by the feeding belt 104. The ADF 101 has a count function that counts up the number of documents every time a document is fed. After the image information is read by the image reading device 106, the document on the contact glass 105 is discharged onto the paper discharge tray 108 by the feeding belt 104 and the discharge roller 107.

  When the document set detector 109 detects that the next document is present on the document table 102, the lowermost document on the document table 102 is similarly contacted by the feed roller 103 and the feed belt 104. It is fed to a predetermined position on the glass 105. After the image information is read by the image reading device 106, the original on the contact glass 105 is discharged onto the paper discharge tray 108 by the feeding belt 104 and the discharge roller 107. Here, the feeding roller 103, the feeding belt 104, and the discharging roller 107 are driven by a conveyance motor.

  When selected, the first paper feeding device 110, the second paper feeding device 111, and the third paper feeding device 112 feed the stacked transfer paper, and the transfer paper is photosensitized by the vertical conveyance unit 116. It is transported to a position where it contacts the body. For example, a photosensitive drum 117 is used as the photosensitive member, and is rotated by a main motor (not shown).

  Image data read from the document by the image reading device 106 is subjected to predetermined image processing by an image processing device (not shown) and then converted into optical information by a writing unit 118, and a charging device (not shown) is provided on the photosensitive drum 117. Are uniformly charged and then exposed to light information from the writing unit 118 to form an electrostatic latent image. The electrostatic latent image on the photosensitive drum 117 is developed by the developing device 119 to become a toner image. The printer engine is composed of the writing unit 118, the photosensitive drum 117, the developing device 119, and other well-known devices around the photosensitive drum 117 (not shown).

  The conveyance belt 120 serves as a sheet conveyance unit and a transfer unit, and a transfer bias is applied from the power source. The conveyance belt 120 is transferred onto the photosensitive drum 117 while conveying the transfer sheet from the vertical conveyance unit 116 at a constant speed with the photosensitive drum 117. The toner image is transferred onto the transfer paper. The transfer paper is fixed with a toner image by a fixing device 121 and is discharged to a paper discharge tray 123 by a paper discharge unit 122. The photosensitive drum 117 is cleaned of residual toner by a cleaning device (not shown) after the toner image is transferred.

  The above operation is an operation for copying an image on one side of a sheet in a normal mode. When an image is copied on both sides of a transfer sheet in a duplex mode, one of the paper feed trays 113 to 115 is copied. The transfer paper that is further fed and has an image formed on the surface as described above is switched by the paper discharge unit 122 to the double-sided paper feed path 124 side instead of the paper discharge tray 123 side, and is switched back by the reversing unit 125. Then, the front and back sides are reversed and conveyed to the duplex conveying unit 126.

  The transfer paper transported to the double-sided transport unit 126 is transported to the vertical transport unit 116 by the double-sided transport unit 126, transported to the position where it abuts on the photoconductive drum 117 by the vertical transport unit 116, and is transferred onto the photoconductive drum 117. The toner image formed in the same manner as above is transferred to the back surface, and the toner image is fixed by the fixing device 121, whereby double-sided copying is performed. This double-sided copy is discharged to the paper discharge tray 123 by the paper discharge unit 122.

  Further, when the transfer paper is reversed and discharged, the transfer paper that is switched back by the reversing unit 125 and turned upside down is not conveyed to the duplex conveying unit 126 but is discharged via the reverse discharge conveyance path 127. The paper is discharged to the paper discharge tray 123 by the unit 122.

  In the print mode, image data from the outside is input to the writing unit 118 instead of the image data from the above-described image processing apparatus, and an image is formed on the transfer paper as described above.

  Further, in the facsimile mode, the image data from the image reading device 106 is transmitted to the other party by a facsimile transmission / reception unit (not shown), and the image data from the other party is received by the facsimile transmission / reception unit. As a result, the image is formed on the transfer paper as described above.

  Further, the digital copying machine 1 includes a large-volume sheet supply device (hereinafter referred to as LCT), a finisher that performs sorting, punching, stapling, and the like, a mode for reading a document, setting of a copy magnification, and paper feeding And an operation unit for setting a stage, setting a post-processing by a finisher, displaying to an operator, and the like.

  Next, the configuration of the fixing device 121 in the image forming apparatus according to the present embodiment will be described with reference to FIG. FIG. 2 is a diagram illustrating a configuration of a fixing device in the digital copying machine according to the present embodiment. As shown in FIG. 2, the fixing device 121 has a configuration related to the A / D conversion control device according to the present embodiment and has a fixing function. A fixing roller 201 that is a heating member is provided with silicon rubber or the like. The pressure roller 202 made of the elastic member is pressed with a constant pressure by a pressure means (not shown). In many cases, the fixing member and the pressure member are generally in the form of a roller, but for example, one or both of them may be configured in an endless belt shape. In the fixing device 121, heaters HT1 and HT2 are provided at arbitrary positions. For example, the heaters HT1 and HT2 are disposed inside the fixing roller 201 and heat the fixing roller 201 from the inside.

  The fixing roller 201 and the pressure roller 202 are rotationally driven by a driving mechanism (not shown). The temperature sensor TH21 is in contact with the surface of the fixing roller 201 and detects the surface temperature (fixing temperature) of the fixing roller 201. The temperature sensor TH22 is in contact with the surface of the pressure roller 202 and detects the surface temperature of the pressure roller 202. The sheet 207, which is a medium such as transfer paper carrying the toner 206, is heated and pressed by the fixing roller 201 and the pressure roller 202 when passing through the nip portion between the fixing roller 201 and the pressure roller 202. Is established.

  The fixing heater HT2 that is the second heat generating member is a main heater that is turned on (ON) to heat the fixing roller 201 when the maximum temperature Tt that is the reference of the fixing roller 201 has not been reached. The fixing heater HT1, which is the first heat generating member, is likely to interrupt a predetermined temperature Tmin when the temperature of the fixing roller 201 is lower than the above-described maximum temperature Tt at the time of start-up from the off mode for energy saving until copying becomes possible. This is an auxiliary heater that is turned on at times to heat the fixing roller 201.

  Next, temperature control of the fixing device according to this embodiment will be described below with reference to FIG. FIG. 3 is a block diagram of a general-purpose fixing control unit used in the digital copying machine 1. The auxiliary power supply 301 is an auxiliary power supply using the electric double layer capacitor 302, and is used to charge the auxiliary power supply 301 from the normal AC power supply 303 and turn on the fixing heater HT1. Shortening or preventing temperature drop. This is because the rise time and the like are determined by the capacity of the heater, but the power that can be supplied from the AC power supply 303 is limited.

  The AC power supplied from the AC power supply 303 can be charged to the electric double layer capacitor 302 by the charger 307 by controlling the cutoff circuit 305 and the charge / discharge switching circuit 306 by the control unit 304. The power supply to the fixing heater HT1 can also be realized by controlling the charge / discharge switching circuit 306 by the control unit 304. Further, the AC power supplied from the AC power supply 303 is also supplied to the fixing heater HT <b> 2 of the fixing device 121 by the control unit 304 controlling the cutoff circuit 308.

  The control unit 304 includes a temperature sensor TH21 for the temperature of the fixing roller 201, a temperature sensor TH22 for the temperature of the pressure roller 202, a temperature sensor TH23 for the environmental temperature (room temperature or in-machine temperature) where the image forming apparatus is placed, The voltage sensor 309 detects the voltage of the AC power supply 303, and the voltage sensor 310 detects the voltage of the electric double layer capacitor 302. The ON / OFF control of the fixing heaters HT1 and HT2 is performed according to the situation, and the temperature of the fixing roller 201 is adjusted. Control to the optimum state.

  Next, an A / D conversion control apparatus according to the present embodiment and a digital copying machine including the same will be described with reference to FIGS. 4 and 5. FIG. FIG. 4 is a block diagram showing a control unit of a digital copying machine using the A / D conversion control apparatus according to this embodiment. FIG. 5 is a diagram showing a more detailed configuration of the A / D conversion control device in the control unit of the digital copying machine using the A / D conversion control device according to the present embodiment.

  In FIG. 4, a plurality of reference power sources 1 to n (analog reference voltages) of the reference voltage generation unit 408 are known voltages from a voltage supplied from the power supply unit 411 by a high-precision reference voltage generation circuit such as a shunt regulator. Generated as a source and input to the A / D conversion unit 405 via the input switching unit 406. In the present embodiment, the analog reference voltage is generated by a highly accurate reference voltage generation circuit, but the present invention is not limited to this. For example, the reference voltage generation unit 408 may generate a plurality of analog reference voltages without using a shunt regulator or the like. The power supply unit 411 drives the one-chip microcomputer 401 of the control unit 304 and is input to the A / D conversion unit 405 directly or through a noise removal filter or the like, and is used as a reference voltage for A / D conversion. Used as. The control unit 304 is connected to a one-chip microcomputer 401 via an I / O control unit 409, and a fixing heater driving circuit 412 for turning ON / OFF a fixing heater for heating the fixing roller is connected.

  In FIG. 5, the positive side (+) terminal of the power supply unit 411 is connected to the power supply input terminal VDD of the one-chip microcomputer 401, and the negative side of the power supply unit 411 is connected to the ground input terminal GND of the one-chip microcomputer 401. -) Terminal is connected. The one-chip microcomputer 401 is driven based on the power supply voltage supplied from the power supply unit 411.

  Further, the plus side terminal of the power supply unit 411 is connected to the analog circuit power supply input terminal AVDD and the A / D conversion reference power supply input terminal AREF of the A / D conversion unit 405, and the minus side terminal of the power supply unit 411 and A The analog ground input terminal AGND of the / D conversion unit 405 is connected. The A / D converter 405 of the one-chip microcomputer 401 converts the input voltage applied to the input terminal AIN of the A / D converter 405 into a digital value based on the reference voltage applied to the input terminal AREF.

  Here, the input voltage applied to the input terminal AIN of the A / D conversion unit 405 is output from a plurality of reference power sources 1 to n (higher accuracy than the reference voltage for A / D conversion from the power source unit 411). An analog reference voltage from a high-precision reference voltage generation circuit that supplies a voltage) and an output from a sensor 410 that outputs an analog input voltage such as a temperature of a fixing device or a voltage of an input power source are alternatively selected. It is a thing.

  The positive terminals of the plurality of reference power supplies 1 to n of the reference voltage generation unit 408 that generates a known analog reference voltage by a high-precision reference voltage generation circuit such as a shunt regulator from the voltage supplied from the power supply unit 411 are Are input to the channels AN1 to ANn of the input switching unit 406 of the one-chip microcomputer 401. Negative terminals of the plurality of reference power sources 1 to n of the reference voltage generation unit 408 are connected to the GND terminal of the one-chip microcomputer 401 and the AGND terminal of the A / D conversion unit 405.

  The positive terminal of the sensor 410 is input to the channel AN0 of the input switching unit 406 of the one-chip microcomputer 401. The negative terminal of the sensor 410 is connected to the GND terminal of the one-chip microcomputer 401 and the AGND terminal of the A / D conversion unit 405.

  The CPU 402 controls the input switching unit 406 and the A / D conversion unit 405 via the A / D conversion control unit 407 according to the program stored in the ROM 403.

  By selecting one of the inputs for A / D conversion from the channels AN0 to ANn by the input switching unit 406 (closing the switch), the voltage input to the selected input channel is input to the A / D conversion unit 405. Input to terminal AIN. The voltage input to the input terminal AIN of the A / D converter 405 is converted into a digital value based on the voltage of the input terminal AREF of the A / D converter 405 and the voltage of the input terminal AGND. The converted digital value is read from the A / D converter 405 by the CPU 402 and stored in the RAM 404. In this manner, by controlling the input switching unit 406, a single A / D conversion unit 405 is used to sequentially switch a plurality of inputs and perform A / D conversion.

  6 shows a voltage sensor 309 for detecting the output voltage of the AC power supply 303 (the sensor 410 shown in FIG. 4 represents a voltage sensor for detecting the voltage of the AC power supply in addition to the temperature sensor for detecting the temperature of the fixing device. ). That is, by inputting the AC power source 303 to the transformer 601 having a separately determined turn ratio, the voltage sensor 309 side and the AC power source 303 side are insulated, and convenient for use in the internal circuit of the voltage sensor 309. Step down to a good voltage level. Further, the output voltage on the secondary side of the transformer 601 is full-wave rectified by the diode bridge 602, and the voltage smoothed by the smoothing capacitor 605 is divided as it is or by the voltage dividing resistors 603 and 604, and then the impedance by the buffer 606 is obtained. The analog input voltage is input to the control unit 304 via a predetermined interface such as a conversion circuit.

  The voltage of the AC power supply 303 and the output voltage of the voltage sensor 309 are adjusted so as to have a certain proportional relationship or correlation. Thereby, the control unit 304 can determine the voltage of the AC power supply 303 from the output voltage of the voltage sensor 309.

  FIG. 7 is a diagram illustrating a circuit configuration of a reference voltage generation unit 408 that generates a plurality of analog reference voltages in the A / D conversion control device according to the present embodiment. In the reference voltage generation unit 408, the positive terminal of the power supply unit 411 and the cathode terminal (K) of the shunt regulator 701 are connected via a resistor 702, and the negative terminal of the power supply unit 411 and the anode terminal of the shunt regulator 701 are connected. (A) is connected. The reference terminal (Ref) of the shunt regulator 701 is connected to a voltage dividing point obtained by dividing the cathode terminal and the anode terminal of the shunt regulator 701 with resistors 703 and 704. An operation stabilizing capacitor 705 is connected between the cathode terminal and the anode terminal of the shunt regulator 701. Further, a voltage (analog reference voltage) applied to the cathode terminal of the shunt regulator 701 is input to the input terminal AN 2 of the one-chip microcomputer 401 in the control unit 304. A voltage (analog reference voltage) obtained by dividing the voltage applied to the cathode terminal of the shunt regulator 701 by the resistors 706 and 707 is input to the input terminal AN 1 of the one-chip microcomputer 401 in the control unit 304. Further, the anode terminal of the shunt regulator 701 and the analog ground input terminal AGND of the A / D conversion unit 405 in the one-chip microcomputer 401 are connected.

  The shunt regulator 701 adjusts the current flowing into the cathode terminal so that the voltage Vref of the reference terminal becomes 2.5V, for example. In the circuit shown in FIG. 7, the voltage divided by the resistors 703 and 704 connected between the cathode terminal and the anode terminal is controlled to be Vref, and the voltage at the cathode terminal is determined by the voltage dividing ratio of the resistors 703 and 704. It is determined. When the ratio between the resistors 703 and 704 is R: 1, the analog reference voltage V2 at the cathode terminal is V2 = Vref × (R + 1). Further, the analog reference voltage V2 at the cathode terminal is divided by the resistors 706 and 707 to generate the analog reference voltage V1. When the ratio of the resistors 706 and 707 is S: 1, the analog reference voltage V1 at the voltage dividing point is V1 = V2 / (S + 1).

  The analog reference voltage V2 at the cathode terminal of the shunt regulator 701 is connected to the input terminal AN2 of the one-chip microcomputer 401, and the analog reference voltage V2 is applied to the input terminal AN2. The input terminal AN1 of the one-chip microcomputer 401 is connected to the voltage dividing point obtained by dividing the analog reference voltage V2 at the cathode terminal of the shunt regulator 701 by the resistors 706 and 707, and the analog reference voltage V1 is connected to the input terminal AN1. Is applied. The resistor 702 is provided to consume the voltage difference between the voltage of the power supply unit 411 and the analog reference voltage V2 of the cathode terminal of the shunt regulator 701.

  Further, the shunt regulator 701 is used such that the voltage accuracy of the reference voltage Vref of the shunt regulator 701 is, for example, ± 0.5%, and the resistance accuracy of the voltage dividing resistors 703, 704 and the voltage dividing resistors 706, 707 is, for example, ± By using a highly accurate resistor of 0.1%, the reference voltage generation unit 408 can generate the analog reference voltage V1 and the analog reference voltage V2 with high accuracy.

  FIG. 7 shows an example in which two voltages of the analog reference voltages V1 and V2 are generated. However, by preparing a plurality of sets of resistors that divide the cathode voltage, an arbitrary analog reference voltage can be easily added with high accuracy. A plurality of circuits shown in FIG. 7 that can be generated and have different output voltage settings may be prepared. Further, instead of the shunt regulator 701, the output voltage generated by using a high-precision step-down regulator IC with an output voltage accuracy of ± 1%, for example, can be divided by resistors.

  FIG. 8 is a flowchart illustrating an A / D conversion operation and a control operation in the A / D conversion control device according to the present embodiment. First, in step S801, the A / D conversion unit 405 of the one-chip microcomputer 401 mounted on the control unit 304 uses a plurality of high-precision analog reference voltages V1 to Vn supplied from the reference voltage generation unit 408 as digital reference values. Convert to D1 to Dn. Then, the CPU 402 records the digital reference values D1 to Dn corresponding to the known analog reference voltages V1 to Vn in the RAM 404 of the one-chip microcomputer 401.

  In step S802, the A / D conversion unit 405 of the one-chip microcomputer 401 converts the actual analog input voltage VIN from the sensor 410 into a digital value. Then, the CPU 402 records the digital value DOUT in the RAM 404 of the one-chip microcomputer 401.

  Next, in step S803, the CPU 402 obtains a known value recorded in the RAM 404 in step S801 by using the smallest value that is the same as or closest to the digital value DOUT of the actual analog input voltage VIN from the sensor 410 obtained in step S802. The digital reference values D1 to Dn corresponding to the analog reference voltages V1 to Vn are searched, and the digital reference value DL and the known analog reference voltage VL corresponding thereto are recorded in the RAM 404 of the one-chip microcomputer 401. If not found, it is recorded as a digital reference value DL = 0 and a known analog reference voltage VL = 0V.

  Next, in step S804, the CPU 402 obtains a known value recorded in the RAM 404 in step S801 by using a value that is the same as or closest to the digital value DOUT of the actual analog input voltage VIN from the sensor 410 obtained in step S802. Search from the digital reference values D1 to Dn corresponding to the analog reference voltages V1 to Vn, and record the digital reference value DH and the known analog reference voltage VH corresponding thereto in the RAM 404 of the one-chip microcomputer 401. If not found, the CPU 402 causes the digital reference value DH = the maximum value (FS) of the digital reference value that can be converted by the A / D conversion unit 405, the known analog reference voltage VH = the reference voltage for A / D conversion (Vref). ) To record.

  Next, in step S805, the CPU 402 determines that the digital reference value DL closest to the digital value DOUT of the actual analog input voltage VIN from the sensor 410 obtained in steps S803 and S804 and its known analog reference voltage VL, Then, based on the digital reference value DH and the known analog reference voltage VH, an arithmetic expression 1 that complements the two points with a straight line is generated, and the actual analog input voltage VIN from the sensor 410 is generated by the generated arithmetic expression 1. An analog input voltage VIN ′ with respect to the digital value DOUT is calculated. In the present embodiment, the analog input voltage VIN ′ with respect to the digital value DOUT is calculated by an arithmetic expression that complements two points with a straight line. However, the present invention is not limited to this. For example, in steps S803 and S804, a digital reference value corresponding to three or more known analog reference voltages is searched, and three or more based on the three or more known analog reference voltages and corresponding digital reference values. The analog input voltage VIN ′ for the digital value DOUT may be calculated by an arithmetic expression that complements the points with straight lines or curves.

VIN '= VL + (VH-VL) / (DH-DL) x (DOUT-DL)
In step S806, the CPU 402 of the one-chip microcomputer 401 uses the analog input voltage VIN ′ obtained in step S805 as the analog input voltage VIN from the sensor 410, and performs predetermined control (for example, fixing heater control). Do.

  FIG. 9 is a diagram illustrating the A / D conversion characteristics of the A / D conversion unit according to the present embodiment. The high-precision analog reference voltage V1 and the analog reference voltage V2 are generated and generated by the reference voltage generation unit 408 in the control unit 304 of A / D conversion, which shows the features of the present embodiment shown in FIGS. Consider the case of high-precision A / D conversion using the analog reference voltage V1 and the analog reference voltage V2. At this time, the analog reference voltage V1, the analog reference voltage V2, and the A / D conversion reference voltage (Vref) have a relationship of Vref> V2> V1.

  For example, a digital reference value obtained by A / D converting the analog reference voltage V1 is D1, and a digital reference value obtained by A / D converting the analog reference voltage V2 is D2. The CPU 402 determines an A / D conversion characteristic interval (a range of digital values (0 to FS) that can be A / D converted by the A / D conversion unit 405) based on the obtained digital reference value D1 and digital reference value D2. Dividing into a plurality of sections, and generating an arithmetic expression for complementing the A / D conversion characteristics for each section based on a plurality of digital reference values in the divided sections and an analog reference voltage for the plurality of digital reference values. .

  Assuming that the output voltage of the sensor 410 in FIG. 5, that is, the analog input voltage for A / D conversion is VIN, and the digital value obtained by A / D conversion is DOUT, for each section divided by the digital reference value D1 and the digital reference value D2, An arithmetic expression that complements the A / D conversion characteristics of the section is obtained. An arithmetic expression for complementing the analog input voltage VIN ′ from the digital value DOUT is as follows.

When the digital value DOUT is less than or equal to the digital reference value D1 (section 1)
When the digital reference value takes the minimum value (0), the analog reference voltage is 0 V, and when the digital reference value takes D1, the analog reference voltage is V1, and the following arithmetic expression 3 is obtained.

VIN ′ = V1 / D1 × DOUT Equation 3
When the digital value DOUT is not less than the digital reference value D1 and not more than the digital reference value D2 (section 2)
When the digital reference value is D1, the analog reference voltage is V1, and when the digital reference value is D2, the analog reference voltage is V2.

VIN '= V1 + (V2-V1) / (D2-D1) × (DOUT-D1) ・ ・ ・ ・ ・ ・ Operation formula 4
When the digital value DOUT is greater than or equal to the digital reference value D2 (section 3)
When the digital reference value is D2, the analog reference voltage is V2, and when the digital reference value is the maximum value (FS), the analog reference voltage is A / D conversion reference voltage (Vref), and the following calculation formula 5 Get.

VIN '= V2 + (Vref-V2) / (FS-D2) × (DOUT-D2)
For example, in FIG. 9, it is assumed that a digital value D1 obtained by A / D conversion of the same analog input voltage V1 as a highly accurate analog reference voltage is obtained. In the method of calculating the analog input voltage with respect to the digital value D1 using the ideal A / D conversion characteristics shown in FIG. 9, the calculated analog input voltage becomes V1 ′ and a conversion error occurs. However, according to the method of calculating the analog input voltage using the A / D conversion characteristic indicated by the arithmetic expression 3 or the arithmetic expression 4 of the present embodiment, the analog input voltage with respect to the digital value D1 becomes V1, and no conversion error occurs.

  According to the method of calculating the analog input voltage VIN ′ from the A / D conversion characteristics in the present embodiment, the analog input voltage VIN to be A / D converted is the analog reference voltage V1 generated by the reference voltage generation unit 408 and the analog input voltage. As the reference voltage V2 is approached, the analog input voltage VIN ′ can be calculated with higher accuracy.

  In an image forming apparatus that performs control to bring the output voltage of the sensor 410 in FIG. 5 close to the target, or control to switch the operation when the output voltage of the sensor 410 is around the threshold, the target value or threshold voltage is used as the reference voltage. By generating in the generation unit 408, it is possible to perform control with high accuracy according to the accuracy of the output voltage of the reference voltage generation unit 408.

  As described above, in the A / D conversion characteristics (section 1 and section 2 shown in FIG. 9) in the present embodiment, the A / D conversion reference voltage (Vref) is not included in the arithmetic expression. It is possible to suppress the influence due to the fluctuation of the reference voltage for D conversion. In particular, the reference voltage generation unit 408 generates an analog reference voltage V2 that is equal to or higher than the upper limit voltage of the analog input voltage VIN to be A / D converted and is equal to or lower than the voltage obtained by subtracting the full scale error. The accuracy can be detected.

  In this case, it is not necessary to prepare a highly accurate power source for the reference power source Vref for the A / D converter. Further, since the offset error is included only in the section 1 shown in FIG. 9, the reference voltage generation unit 408 generates the analog reference voltage V1 that is equal to or lower than the use lower limit voltage of the analog input voltage VIN to be A / D converted and equal to or higher than the offset error. As a result, it is possible to perform highly accurate detection that does not include an offset error. Further, by adding an analog reference voltage generated by the reference voltage generation unit 408 and further subdividing the section 2, it is possible to easily increase the points that can be detected with high accuracy. In this case, the non-linearity error in the section 2 can be further reduced.

  As described above, the image forming apparatus according to the present embodiment includes the A / D conversion unit 405, the CPU 402, and the memories (ROM 403 and RAM 404) illustrated in FIG. It has an input switching unit 406 that selectively outputs each output voltage from the reference power supply and the output voltage from the sensor 410 and outputs the selected output voltage to the A / D conversion unit 405, and further includes an A / D conversion unit 405, a reference voltage A generation unit 408, a power supply unit 411 that supplies power to other circuits, and a sensor (temperature sensor, input power supply voltage sensor, etc.) 410 that outputs an analog input voltage for A / D conversion are further included. A plurality of high-accuracy analog reference voltages are input to the A / D converter 405 from a high-accuracy reference power supply, and each is A / D converted to obtain a digital reference value. Further, the output voltage (analog input voltage) of the sensor 410 is A / D converted, and using an arithmetic expression based on the plurality of digital reference values and the plurality of high-precision analog reference voltages supplied, The output voltage of the sensor 410 is calculated from a digital value obtained by A / D converting the output voltage of the sensor 410.

  As a result, the analog input voltage is converted from the digital value in consideration of the conversion error generated when the analog input voltage is converted into a digital value by the A / D conversion characteristic of the A / D converter, in particular, the nonlinearity error. Since it can be calculated, the calculation accuracy when calculating the analog input voltage from the digital value can be further increased. The range of the highest output voltage and the lowest output voltage among the plurality of analog reference voltages from the high-accuracy reference voltage supply unit 408 is set as an effective use voltage range for calculating the analog input voltage input from the sensor 410. This makes it possible to obtain a highly accurate output result of the sensor 410 that does not include the full-scale error or offset error of the A / D conversion unit 405, thus increasing the calculation accuracy when calculating the analog input voltage from the digital value. Furthermore, the influence of fluctuations in the power supply voltage applied to the A / D conversion unit 405 can be suppressed. In addition, at least one of the plurality of high-precision analog reference voltages from the high-precision reference voltage supply unit 408 is the same voltage as the analog input voltage that should be detected with the highest accuracy among the output voltages from the sensor 410. By doing so, it is possible to prevent the non-linearity error of the A / D conversion unit 405 from occurring, so that the calculation accuracy of the analog input voltage can be further increased.

(Modification)
In the above-described embodiment, the analog input voltage is calculated from the digital value obtained by A / D converting the analog input voltage from the temperature sensor that detects the temperature of the fixing roller or the voltage sensor that detects the voltage of the AC power supply, and the calculated analog Although the example of determining the power usage distribution of the auxiliary power source to the fixing device using the input voltage has been described, the present invention is not limited to this. For example, when the image reading apparatus included in the image forming apparatus is driven by receiving power supply from the auxiliary power supply, the A according to the present embodiment is also used when determining the power usage distribution from the auxiliary power supply to the image reading apparatus. The image reading apparatus can also be controlled using the analog input voltage calculated by the / D conversion control apparatus. Except for the configuration in which power is supplied from the auxiliary power source to the image reading apparatus, the configuration is substantially the same as that in the above-described embodiment, and therefore, only the processing different from that in the above-described embodiment will be described.

  Here, an outline of power supply processing to the image reading device 106, the fixing device 121, and other loads included in the digital copying machine 1 of this modification will be described with reference to FIGS. 10A and 10B. FIG. 10A is an explanatory diagram showing an example of power supply processing by the digital copying machine according to the present modification. FIG. 10B is an explanatory diagram illustrating an example of a power supply level from the AC power supply and the auxiliary power supply to the load.

  An AC power source 303 is a main power source that drives other loads such as the image reading device 106, the fixing device 121, a printer engine, and various motors. The auxiliary power supply 301 is a chargeable / dischargeable power storage unit that is charged by receiving power from the AC power supply 303 and drives a load with the charged power. In FIG. 10A, the auxiliary power supply 301 is a capacitor but may be a storage battery. Specific examples of the capacitor include an aluminum electrolytic capacitor and an electric double layer capacitor having a relatively large capacitance. The switch 1001 switches on / off charging from the AC power source 303 to the auxiliary power source 301 and on / off of power feeding from the auxiliary power source 301. The switch 1001 is a switch that connects, for example, a common contact on the auxiliary power supply 301 side, a contact on the AC power supply 303 side, a contact on the image reading apparatus 106 side, or a contact not connected to either. Further, the function of the switch 1001 may be realized by combining two or more relays and FETs. In the present embodiment, the power supply device turns off the switch 1001 during normal times such as startup, and supplies power from the AC power supply 303 to the system system including the image reading device 106, other loads, and the fixing device 121. Further, when there is a margin in the power supplied from the AC power supply 303, the auxiliary power supply 301 is charged by connecting the switch 1001 to the contact on the AC power supply 303 side. On the other hand, when the auxiliary power supply is used, such as when the image reading device 106 and the fixing device 121 are moved simultaneously, the power supply device connects the switch 1001 to the contact on the image reading device 106 side and supplies the image from the auxiliary power supply 301. The device 106 is driven to increase the amount of power supplied from the AC power supply 301 to the fixing device 121.

1 is a diagram showing an outline of a digital copying machine constituting an image forming apparatus using an A / D conversion control device according to the present embodiment. 1 is a diagram illustrating a configuration of a fixing device in a digital copying machine according to an exemplary embodiment. FIG. 2 is a block diagram illustrating a general-purpose fixing control unit used in a digital copying machine. 1 is a configuration diagram showing a control unit of a digital copying machine using an A / D conversion control device according to the present embodiment. FIG. 2 is a diagram illustrating a more detailed configuration of an A / D conversion control device in a control unit of a digital copying machine using an A / D conversion control device according to the present embodiment. FIG. 5 is a circuit diagram of a voltage sensor that detects an output voltage of an AC power supply (the sensor shown in FIG. 4 also represents a voltage sensor that detects the voltage of an AC power supply in addition to a temperature sensor that detects the temperature of the fixing device). It is a figure which shows the circuit structure of the reference voltage production | generation part which produces | generates the several analog reference voltage in the A / D conversion control apparatus which concerns on this embodiment. It is a flowchart explaining the A / D conversion operation | movement and control operation | movement in the A / D conversion control apparatus which concerns on this embodiment. It is a figure which shows the A / D conversion characteristic of the A / D conversion part regarding this embodiment. It is explanatory drawing which shows an example of the electric power supply process by the digital copying machine concerning this modification. It is explanatory drawing which shows an example of the electric power supply level to load from AC power supply and auxiliary power supply. It is a figure which shows the structure of the fixing control part in the conventional image forming apparatus, and is a figure which shows the structural example of the fixing control part based on the usage condition of a general A / D converter. It is a figure which shows the structural example of the control part based on the usage condition of the A / D converter disclosed by patent document 1. FIG. It is the conversion characteristic figure explaining the conversion error which a general A / D converter has.

Explanation of symbols

1 Digital copier 101 ADF
DESCRIPTION OF SYMBOLS 102 Document base 103 Paper feed roller 104 Feed belt 105 Contact glass 106 Image reading device 107 Discharge roller 108 Paper discharge stand 109 Document set detector 110 1st paper feed device 111 2nd paper feed device 112 3rd paper feed device 113 115 Paper feed tray 116 Vertical transport unit 117 Photosensitive drum 118 Writing unit 119 Developing device 120 Transport belt 121 Fixing device 122 Paper discharge unit 123 Paper discharge tray 124 Double-sided paper feed path 125 Reverse unit 126 Double-side transport unit 127 Reverse paper discharge Conveying path 201 Fixing roller 202 Pressure roller 206 Toner 207 Sheet HT1, HT2 Heater TH21, TH22, TH23 Temperature sensor 301 Auxiliary power supply 302 Electric double layer capacitor 303 AC power supply 304, 1100, 120 Controller 305 cutoff circuit 306 charging switching circuit 307 charger 308 interrupting circuit 309, 310 voltage sensor 401,1101 one-chip microcomputer 402,1102 CPU
403, 1103 ROM
404, 1104 RAM
405, 1105 A / D conversion unit 406, 1106 Input switching unit 407, 1107 A / D conversion control unit 408, 1108, 1201 Reference voltage generation unit 409, 1109 I / O control unit 410, 1110 Sensor 411, 1111, 1202 Power supply Unit 412, 1112 Fixing heater driving circuit 601 Transformer 602 Diode bridge 603, 604 Voltage dividing resistor 605 Smoothing capacitor 606 Buffer 701 Shunt regulator 702, 703, 704, 706, 707 Resistor 705 Capacitor 1001 SW

Claims (7)

First generating means for generating a plurality of analog reference voltages;
A / D conversion means for converting the generated plurality of analog reference voltages into a plurality of digital reference values and converting an analog input voltage input from an external device into a digital value;
Second generating means for generating an arithmetic expression that complements the analog input voltage converted into a digital value between the plurality of digital reference values based on the plurality of analog reference voltages and the plurality of digital reference values;
Using the generated arithmetic expression, calculation means for calculating the analog input voltage for the converted digital value;
An A / D conversion control device comprising:   The second generation means is closest to the digital value for calculating the analog input voltage and is equal to or less than the digital reference value equal to or less than the digital value, the analog reference voltage converted to the digital reference value, and the closest digital value. 2. The A / D conversion control device according to claim 1, wherein the arithmetic expression is generated based on the digital reference value greater than or equal to the digital value and the analog reference voltage converted to the digital reference value. .   The said 1st production | generation means contains the said analog reference voltage same as the said analog input voltage, and produces | generates these analog reference voltages whose voltage fluctuation is smaller than the said analog input voltage. The A / D conversion control device described.   2. The first generation means generates the analog reference voltage that is equal to or higher than an upper limit value of the analog input voltage and smaller than a voltage that is converted to a maximum digital value by the A / D conversion means. The A / D conversion control device according to any one of items 1 to 3.   2. The first generation means generates the analog input voltage that is greater than or equal to a lower limit value of the analog input voltage and greater than a voltage that is converted to a minimum digital value by the A / D conversion means. To A / D conversion control device according to any one of 4. A dividing unit that divides a range of digital values that can be converted by the A / D conversion unit into a plurality of sections by the plurality of digital reference values obtained by converting the plurality of analog reference voltages;
The second generation means generates the arithmetic expression for each section based on the plurality of analog reference voltages in the divided section and the plurality of digital reference values obtained by converting the plurality of analog reference voltages. The A / D conversion control device according to any one of claims 1 to 5, wherein   The A / D conversion control device according to claim 1 controls each part of the image forming apparatus using an analog input voltage calculated from a digital value indicating a state of each part of the image forming apparatus. An image forming apparatus.

Images