JP2005185045A - Digital control power supply device and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To supply a stable output to a load from a power supply device of a digital control system even under the restriction of a control interval. <P>SOLUTION: An output Vmon(D) of a voltage monitor value Vmon from an A/D converter 111 is fetched, and stored in a memory 112. These outputs are sequentially taken in prescribed times in a sampling time 1, and stored in the memory 112. The average of the output Vmon(D) stored in the memory 112 is calculated by a CPU 109, and a calculated result Vmon(AVE) is stored in a memory of the CPU 109. An on-duty ratio of a PWM signal is determined according to control algorithm decided, in advance, by comparing a target monitor value and the Vmon(AVE) by the CPU 109. The PWM signal PWM in accordance with the decided on-duty ratio is generated by a pulse oscillator 110. As a result, a switching element 106 is repeatedly turned on/off in accordance with the duty of the PWM signal, and an output voltage accompanying the turning-on/off is generated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a power supply apparatus using a digital control system and a method for controlling the power supply apparatus, which is optimal for use in an image forming apparatus such as an electrophotographic printer or a copying machine.

[Analog control high voltage power supply]
First, a conventional analog control type high voltage power supply device will be described. Here, a high voltage power supply device used as a high voltage source or a high voltage current source in an image forming apparatus such as an electrophotographic printer or copier will be described. However, the present invention is also applied to a power supply device that is not "high voltage". Of course it is possible.
A so-called analog control type high-voltage power supply apparatus is configured as shown in FIG. In FIG. 1, the high-voltage power supply device includes a D / A converter 11, an ON / OFF determination circuit 12, a control circuit 13, a switching circuit 14, a step-up transformer 15, a rectifier circuit 16, a detection circuit 17, and the like. . Vin is an input voltage, and a PWM signal is a duty corresponding to a target voltage of a controller (not shown). The output from the rectifier circuit 16 is supplied to the output load 18.

This high-voltage power supply device controls the output as follows.
(1) In the case of voltage control, the output voltage is converted to a voltage value that can be input to the regulator IC or error amplifier in the control circuit 13 by the detection circuit 17 (high voltage is converted to low voltage, and if -output is converted to + output) Conversion) and input to the control circuit 13. In the case of current control, the output current is converted into a voltage value that can be input to the regulator IC or error amplifier in the control circuit 13 by the detection circuit 17 (the current amount is converted to + voltage) and input to the control circuit 13. .
(2) A PWM signal is input from a controller (not shown) such as an external MCU, the ON / OFF determination circuit 12 determines ON / OFF from the duty of the PWM signal, and the determination result is input to the control circuit 13 Further, a target value (analog value) is generated from the duty of the PWM signal by the D / A converter 11 and input to a regulator IC or an error amplifier in the control circuit 13.
(3) The control circuit 13 performs control so that the target value obtained in (2) and the detection value obtained in (1) match, and outputs a PWM signal corresponding to the result.
(4) The switching circuit (switching element) 14 is turned ON / OFF by the PWM signal output in the above (3), and an output according to the ON / OFF duty is generated on the secondary side of the step-up transformer 15.
(6) The output generated in (5) is detected, and the process returns to (1).
The output is controlled by repeating the above (1) to (6) and controlling the increase / decrease of the duty so that the detected value matches the target value.

  The problem here is that the output monitor value output from the detection circuit 17 (voltage detection circuit or current detection circuit) is not stable. This is because, due to the configuration of the detection circuit 17, the monitor value also fluctuates when ripples occur or the output fluctuates due to instantaneous arcing or the like. However, in the case of an analog control system circuit, in the control circuit 13, the comparison operation between the output monitor value and the target value is performed in real time by an error amplifier, an analog IC, or the like. Therefore, real-time reaction is possible to ripples in the output monitor value, arcing that occurs for a moment, and the like.

[Digitally controlled high voltage power supply]
For example, as disclosed in Patent Document 1, the output monitor of the power supply circuit is fed back to the CPU, the duty of the PWM signal is controlled so that the value matches the target value, and the switching element is driven by the signal, so-called digital Control type power supply circuits are widely known. This method eliminates the need for an analog control circuit unit as compared with the conventional circuit method (FIG. 1), and performs control by software using a CPU. According to this method, cost reduction can be realized.

  FIG. 2 shows an example of such a digital control type high-voltage power supply device. In FIG. 2, the parts corresponding to those in FIG. In FIG. 2, the high-voltage power source main body is provided with a switching circuit 14, a transformer 15, a rectifier circuit 16, a detection circuit 17, and the like. The control system includes a CPU 19, a pulse oscillator 20, and an A / D converter 21.

The digital control type high-voltage power supply device controls the output as follows.
(1) In the case of voltage control, the output voltage is converted into a voltage that can be input to the A / D converter 21 by the detection circuit 17 (high voltage is converted to low voltage, and if it is -output, it is converted to + output). / D converter 21 to input. In the case of current control, the output current is converted into a voltage that can be input to the A / D converter 21 by the detection circuit 17 (the amount of current is converted to + voltage) and input to the A / D converter 21.
(2) The value of the above (1) is converted into a digital value of the required number of bits by the A / D converter 21 and input to the CPU 19.
(3) The CPU 19 compares and calculates the preset target value and the monitor value obtained in the above (2) using a predetermined calculation formula, and sets a value for setting the duty value of the PWM signal. calculate.
(4) The pulse generator 20 generates a PWM signal having a duty value according to the set value obtained in (3) above.
(5) The switching circuit 14 (switching element) is turned ON / OFF by the PWM signal generated in the above (4), and an output according to the ON / OFF duty is generated on the secondary side of the step-up transformer 15.
(6) The output generated in (5) is detected, and the process returns to (1).
The output is controlled by repeating the above (1) to (6) and controlling the increase / decrease of the duty so that the monitor value coincides with the target value.

  By the way, this digital control system has the following problems.

(Control time constraint)
In the case of digital control, the CPU 19 performs a comparison operation between the output monitor value and the target value for controlling the output value, and is performed with a predetermined sampling time. This sampling time varies depending on the capability of the CPU 19, the number of media to be controlled, the control algorithm, and the like, but real-time control such as analog control cannot be realized. For this reason, it is impossible to react in real time to ripples in the output monitor value, arcing that occurs for a moment, and the following problems occur.

Problem (1): The ripple determined by the circuit interferes with the ripple generated by digital control, and the ripple voltage increases.

That is, the waveform of the output monitor value is as shown in FIG. The cause of this ripple is
-The ripple by charging / discharging in the rectification smoothing circuit (rectification circuit 16) which the output itself has is reflected.
It is generated when the wiring of the detection circuit 17 is routed or noise from other circuits is injected.

  The problem here is the sampling time for reading the output monitor value. If the timing of reading overlaps with the maximum and minimum values of ripple, the output will be suppressed or increased more than necessary, and the output ripple will increase. End up. In particular, the current monitor at the time of constant current control has a very small output current (several μA to several tens of μA) at the output of the high voltage power source, and the impedance of the current detection circuit is large, so that the detection value is small for some current fluctuations. Swings greatly. It is also susceptible to external noise. Therefore, the ripple of the current monitor tends to increase.

  In addition, there is a method of increasing the bypass capacitor constant of the detection circuit 17 to reduce the ripple. In this case, however, the rise time of the detection value is delayed, and the control cannot be performed because it is not in time for the digital control sampling time. is there.

  For this reason, the output voltage has ripples peculiar to digital control in addition to the ripples that have been used so far, and the ripples are larger than those of the analog control method. It will have an effect.

Problem (2): The output control value greatly exceeds the specified value due to output arcing or the like.

  That is, as a load to which the high-voltage power supply applies the voltage, there are a corotron, a BTR (transfer roller), and the like. When conductive dust or the like adheres to this load, arcing occurs, a large current flows at that time, and the conductive dust burns instantly and becomes non-conductive. Therefore, arcing that occurs for a moment occurs. In the case of constant voltage control, the waveform of the voltage monitor during arcing is as shown in FIG. As shown in the figure, since the output voltage droops during arcing, the voltage monitor gradually droops, and the output and voltage monitor are restored upon completion of arcing.

  The problem here is the sampling time for reading the output monitor value. If the reading timing coincides with the occurrence of an instantaneous occurrence of arcing, the monitor value at that time is judged as an output and an abnormal operation is performed. In the case of the constant voltage control, as shown in FIG. 6, the voltage monitor sampling at the time of arcing is very small with respect to the target value. Thereafter, since the voltage is large, control is performed so as to approach the target value according to a predetermined algorithm. When such output fluctuation occurs, the image quality may be affected or the photoconductor may be damaged.

  In addition, if the output becomes larger than necessary, the high-voltage power supply may be damaged.

  In the case of constant current control, the waveform of the current monitor during arcing is as shown in FIG. As shown in the figure, since the output current is discharged during arcing, the current monitor repeats potential fluctuations violently, and the output and current monitor are restored upon completion of arcing.

  The problem here is also the reading sampling time of the output monitor value. If an accidental occurrence of arcing coincides with the reading timing, the monitor value at that time is judged as an output and an abnormal operation is performed. In the case of constant current control, as shown in FIG. 8, when the current monitor sampling during arcing is very large with respect to the target value, the output will drastically become a very small value in the duty calculation of the next PWM signal. Thereafter, since the voltage is small, control is performed so as to approach the target value according to a predetermined algorithm.

When such output fluctuations occur, the image quality is affected. On the other hand, if the monitor is sampled when it is very small, the output will jump up greatly due to a very large value in the duty calculation of the next PWM signal. In this case, the image quality may be affected as described above, or the photoconductor may be damaged. In addition, if the output becomes larger than necessary, the high-voltage power supply may be damaged.
JP-A 62-279366

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a digital control type high-voltage power supply device capable of supplying a stable output to a load.

  According to the present invention, in order to achieve the above-mentioned object, the configuration as described in the claims is adopted.

  In the high voltage power supply device of the digital control system of the principle configuration example of the present invention, the output monitor value is compared with the target value by a predetermined control algorithm every predetermined sampling time, and the output value is changed to a constant voltage or a constant current. Control is performed as follows. An averaging means for averaging the detected output values is provided, and the switching means is controlled based on the averaging result.

  In this configuration example, it is possible to solve the problem that a ripple generated by switching interferes with a ripple generated by digital control to generate a large ripple. Also, the problem of abnormal detection values due to arcing or the like can be alleviated by averaging.

  In this case, the averaging means comprises storage means for storing the detected values and averaging means for calculating the average value of the stored detected values so that the average output value becomes a constant voltage or a constant current. It is preferable to perform control.

  Further, it is preferable that the averaging means perform averaging except for the maximum value and the minimum value of the detected values. In this case, an abnormality detection value such as arcing can be ignored.

  Further, in another configuration example of the present invention, a digital operation is performed in which an output monitor value and a target value are compared by a predetermined control algorithm at a predetermined sampling time, and the output value is controlled to be a constant voltage or a constant current. In the high voltage power supply apparatus of the control system, the control sampling frequency F is synchronized with the switching frequency f, and the switching frequency f is an integral multiple of the control sampling frequency F. In this case, it is possible to solve the problem that a ripple generated by switching and a ripple generated by digital control interfere to generate a large ripple.

  In still another configuration example of the present invention, digital control is performed so that the output monitor value is compared with the target value by a predetermined control algorithm every predetermined sampling time, and the output value is controlled to be a constant voltage or a constant current. In the high-voltage power supply apparatus of the system, when the read detection value has an abnormal value outside the predetermined range, the switching means is controlled with the previous duty without performing the next calculation. In this case, an abnormality detection value such as arcing can be ignored.

  In still another configuration example of the present invention, digital control is performed so that the output monitor value is compared with the target value by a predetermined control algorithm every predetermined sampling time, and the output value is controlled to be a constant voltage or a constant current. In the high-voltage power supply device of the system, when the read detection value has an abnormal value outside the predetermined range, the switching means is controlled at a predetermined duty without performing the next calculation. . In this case, an abnormality detection value such as arcing can be ignored.

  In still another configuration example of the present invention, digital control is performed so that the output monitor value is compared with the target value by a predetermined control algorithm every predetermined sampling time, and the output value is controlled to be a constant voltage or a constant current. In the high-voltage power supply device of the system, if the read detection value has an abnormal value outside the predetermined range, the switching means is switched at a duty obtained by multiplying the previous duty by a predetermined ratio without performing the next calculation. I try to control it. In this case, an abnormality detection value such as arcing can be ignored.

  Further, the present invention will be described.

  That is, according to one aspect of the present invention, in order to achieve the above-described object, a digital control type high-voltage power supply apparatus includes: a transformer; and a primary winding of the transformer according to a duty of an input pulse width modulation signal. Switch means for switching application of power to the power; detection means for detecting an output value for a load connected to the secondary winding side of the transformer; sampling means for sampling the output value detected by the detection means; Averaging means for averaging the sampled output values and outputting an average output value; and duty determining means for determining a duty corresponding to a target value based on the average output value output from the averaging means. I have to.

  In this configuration, since the ripple caused by sampling can be eliminated by averaging, there is no synergistic effect with the ripple caused by switching, and as a result, a large ripple can be eliminated.

  In this configuration, the averaging means can include storage means for storing the sampled output values and calculation means for calculating the average value of the stored output values.

  Further, at least one of the minimum value and the maximum value among the sampled output values may be excluded from the basis of the average value.

  The switching frequency of the switching means may be an integer multiple of the sampling frequency of the sampling means.

  The sampling means may perform sampling at a timing at which an output value applied to the load takes an average value due to charging / discharging by switching of the switching means.

  When the output value sampled by the sampling means includes an abnormal value outside the predetermined range, the switching means may be controlled with a predetermined duty determined before the previous time.

  In addition, when the output value sampled by the sampling unit includes an abnormal value outside a predetermined range, the switching unit may be controlled with a predetermined duty.

  In addition, when the output value sampled by the sampling means includes an abnormal value outside the predetermined range, the switching means is controlled with a duty obtained by multiplying the predetermined duty determined before the previous time by a predetermined ratio. It may be.

  The present invention is suitable for a power supply device that controls the output value by switching the primary side of the transformer and uses the pulse width as an operation amount, that is, by pulse width modulation. However, the output value is repeated in a predetermined control routine. Needless to say, the present invention can be widely applied to a digital control system power supply device for controlling the power.

  That is, according to another aspect of the present invention, to a digitally controlled power supply device that repeats a control routine that detects a value of an output supplied to a load and controls it to a target value: a value of an output supplied to the load Detecting means for detecting the output value; sampling means for sampling the output value detected by the detection means; and averaging means for averaging the sampled output values and outputting an average output value, and outputting from the averaging means The value of the output supplied to the load is controlled based on the average output value.

  Even in this configuration, since the ripple caused by sampling can be eliminated by averaging, there is no synergistic effect with the ripple caused by switching, and as a result, a large ripple can be eliminated.

  According to still another aspect of the present invention, the switching means switches the input power supply by the switching means to supply power to the load, and detects the value of the output supplied to the load so as to reach the target value. A digital control type power supply device that repeats a control routine for controlling the switching parameters of: a detection unit that detects a value of an output supplied to a load; a sampling unit that samples an output value detected by the detection unit; An averaging means for averaging the output values and outputting the average output value, and determining a switching parameter of the switching means based on the average output value output from the averaging means and supplying the output to the load The value of is controlled. The switching parameter is, for example, a frequency or a duty, but is not limited thereto.

  Even in this configuration, since the ripple caused by sampling can be eliminated by averaging, there is no synergistic effect with the ripple caused by switching, and as a result, a large ripple can be eliminated.

  The present invention can be realized not only as an apparatus or a system but also as a method. Of course, a part of the invention can be configured as software. Of course, a software product used to cause a computer to execute such software is also included in the technical scope of the present invention.

  The above and other aspects of the invention are set forth in the appended claims and are described in detail below using examples.

  ADVANTAGE OF THE INVENTION According to this invention, the digital control type high voltage power supply device which can supply a stable output to load is realizable.

  Examples of the present invention will be described below.

  FIG. 9 shows an outline of the first embodiment of the present invention. In this figure, the high-voltage power supply apparatus generates a high-voltage power supply unit 101 that generates high-voltage power to be supplied to the load 100, and generates a predetermined DC voltage. A DC power supply 102 and a main control unit 103 that controls the operation of the entire apparatus are provided.

  The high-voltage power supply unit 101 includes a step-up transformer 104, a rectifying / smoothing circuit 105, a switching element 106, a voltage detection circuit 107, a current detection circuit 108, and the like. The output terminal is connected, and the terminal of the secondary winding of the step-up transformer 104 is connected to the input terminal of the rectifying and smoothing circuit 105. Further, two of the three output terminals of the rectifying / smoothing circuit 105 are connected to the input terminals of the voltage detection circuit 107 and the current detection circuit 108, respectively. The other output terminal is connected to the load 100.

  The output terminal of the DC power supply 102 is connected to the other terminal of the primary winding of the step-up transformer 104, and the DC voltage Vin generated by the DC power supply 102 is applied to the other terminal of the primary winding of the step-up transformer 104. be able to.

  The main control unit 103 includes a CPU 109, a pulse oscillator 110, an A / D converter 111, a storage device 112, and the like, and the CPU 109 further includes an arithmetic unit.

  The output end of the CPU 109 is connected to the input end of the pulse oscillator 110, the input end of the CPU 109 is connected to the output end of the A / D converter 111, and the output end of the pulse oscillator 110 is connected to the input end of the switching element 106. Therefore, the PWM signal PWM generated by the pulse oscillator 110 can be input to the switching element 106.

  Further, the output terminals of the voltage detection circuit 107 and the current detection circuit 108 are connected to the two input terminals of the A / D converter 111, respectively. Therefore, the voltage monitor value Vmon indicated by the voltage monitor signal generated by the voltage detection circuit 107 and the current monitor value Imon indicated by the current monitor signal generated by the current detection circuit 108 can be input to the CPU 109 as digital values.

  Further, the input / output terminal of the storage device 112 is connected to the input / output terminal of the CPU 109. Therefore, the digitized voltage monitor value Vmon and current monitor value Imon can be stored in the storage device 112 in a timely manner.

  Hereinafter, constant voltage control will be described as an example, but the present invention can be similarly applied to constant current control. It is assumed that the high voltage power supply has a positive output.

FIG. 10 shows a configuration example of a main part related to the voltage control of FIG. 9. In FIG. 10, portions corresponding to FIG. The rectifying / smoothing circuit 105 includes a rectifying diode 105a and a smoothing capacitor 105b. The voltage detection circuit 107 includes voltage dividing resistors 107a and 107b, a buffer amplifier 107c, and resistors 107d and 107e. The switching element 106 includes a bipolar transistor 106a, resistors 106b and 106c, and the like.
Next, the operation will be described (operation related to the problem (1)).

[Rise operation]
First, the operation when starting up the power supply device will be described. In this example, a temporary target value is set separately from the target value, and the temporary target value is gradually set from the detected value to the final target value to avoid overshoot. Other control algorithms may be used. The rising operation is not shown in the figure.

[Step S1]: A target value of the output voltage is received from the MCU that controls the operation of the entire device on which the power supply device is mounted. (In this case, not the MCU but the operation from the display operation device may be used)
[Step S2]: A target monitor value corresponding to the received output target value is selected and set from a predetermined formula or table.
[Step S3]: The output Vmon (D) from the A / D converter 111 of the voltage monitor value Vmon is captured.
[Step S4]: The CPU 109 compares the target monitor value with the Vmon (D) and determines the ON duty ratio of the PWM signal according to a predetermined control algorithm (for example, the method disclosed in Japanese Patent Laid-Open No. 2000-134927). For example, when the final target monitor value is M _ok , the provisional target monitor value is R × M _ok . However, R is a constant smaller than 1. The ON duty ratio (D) is obtained by, for example, D = a × (R × M _ok ) −b. a and b are constants obtained by experiments.
[Step S5]: The ASIC (specific application IC; pulse oscillator 110) generates the PWM signal PWM according to the determined ON duty ratio.
[Step S6]: The switching element Q1 repeats ON / OFF according to the duty of the PWM signal, and the DC voltage applied to the primary winding of the step-up transformer 104 is switched accordingly, and the AC is boosted to the secondary winding side. A voltage is induced.
[Step S7]: The AC voltage is rectified and smoothed by the rectifying and smoothing circuit 105 and supplied to the load 100.
[Step S8]: A voltage monitor value Vmon obtained by stepping down the output voltage of the rectifying and smoothing circuit 105 to a low voltage that is proportional to the output voltage and suitable for the input conditions of the A / D converter 111 by the voltage detection circuit 107. Output.

  The operations in steps S1 to S8 are repeated at a predetermined sampling time, and the output voltage approaches the output target value. When the output voltage reaches ± 10% of the target value, the control proceeds from the rising control to the steady control.

[Steady operation] (Refer to the flowchart of FIG. 11)

  Next, the operation of steady control will be described. FIG. 11 is a flowchart for explaining this operation, and details thereof are as follows.

[Step S11]: A target value of the output voltage is received from the MCU that controls the operation of the entire device. (In this case, not the MCU but the operation from the display operation device may be used)
[Step S12]: A target monitor value corresponding to the received output target value is selected and set from a predetermined formula or table.
[Steps S13 to S17]: The output Vmon (D) of the voltage monitor value Vmon from the A / D converter 111 is fetched and stored in the storage device 112. This is sequentially fetched a predetermined number of times at a certain sampling time 1 and stored in the storage device 112. Although the number of times of sampling is 10 in FIG. 11, it is not limited to this. Typically, the number of times of sampling is fixed, but the number of times of sampling can be increased or decreased depending on the operation situation.
[Step S18]: The average value of Vmon (D) stored in the storage device 112 is calculated by the CPU 109, and the calculated Vmon (AVE) is stored in the storage unit (register or predetermined memory address, not shown) of the CPU 109. Store.
[Step S19]: The CPU 109 compares the target monitor value with the Vmon (AVE), and determines the ON duty ratio of the PWM signal according to a predetermined control algorithm (for example, the method disclosed in Japanese Patent Laid-Open No. 2000-134927). For example, assuming that the current duty ratio is Dn, the time duty ratio D is determined by D = Dn × (Vmok + (r−1) × Vmon (AVE)) / (r × Vmon (AVE)). However, r is a constant of 1 or more, and Vmok is a target monitor value.
[Step S20]: The ASIC (specific application IC; pulse oscillator 110) generates the PWM signal PWM according to the determined ON duty ratio. As a result, the switching element 106 repeats ON / OFF according to the duty of the PWM signal, and an output voltage is generated accordingly.
[Step S21]: It is confirmed whether or not the power is to be turned off. If it is turned off, the process is terminated. If not, the process returns to Step S11 to repeat the process.

  The voltage detection circuit 107 outputs the voltage monitor value Vmon that is stepped down to a low voltage that is proportional to the output voltage and suitable for the input conditions of the A / D converter 111. The control is repeated so that the output voltage approaches the output target value at the sampling time 2 that is much larger than the sampling time 1 (for example, 10 times).

  By performing the processing of steps S13 to S18, ripples peculiar to digital control other than the output ripple generated by the switching operation can be reduced, and more stable output can be supplied.

  Next, a second embodiment of the present invention will be described. The second embodiment deals with the above-described problem (2), that is, the problem of arcing. In this embodiment, the maximum and minimum voltage monitor values to be sampled and averaged are ignored. By doing so, it is possible to avoid malfunction due to the voltage monitor value at the time of abnormality such as arcing. Here, the high voltage power supply is a positive output, and the case where constant voltage control is performed will be described.

  The schematic configuration and the circuit configuration example are the same as those in the first embodiment, and refer to FIGS. 9 and 10.

[Rise operation]
The rising operation is the same as in the first embodiment.

[Steady operation] (Refer to the flowchart of FIG. 12)
The steady operation is as shown in FIG. 12, and the details are as follows.

[Step S31]: The target value of the output voltage is received from the MCU that controls the operation of the entire device. (In this case, not the MCU but the operation from the display operation device may be used)
[Step S32]: A target monitor value corresponding to the received output target value is selected and set from a predetermined formula or table.
[Steps S33 to S37]: The output Vmon (D) of the voltage monitor value Vmon from the A / D converter is fetched and stored in the storage device. This is sequentially fetched a predetermined number of times at a certain sampling time 1 and stored in the storage device 112.
[Steps S28 and S29]: The CPU deletes the maximum and minimum values of Vmon (D) stored in the storage device 112 and calculates the average value of the remaining DATA. The calculation result Vmon (AVE) is stored in a storage unit (register, etc., not shown) of the CPU 109.
[Step S30]: The CPU compares the target monitor value with the Vmon (AVE), and determines the ON duty ratio of the PWM signal according to a predetermined control algorithm (for example, the method disclosed in Japanese Patent Laid-Open No. 2000-134927).
[Step S31]: The ASIC (specific application IC; pulse oscillator 110) generates a PWM signal PWM according to the determined ON duty ratio. The switching element 106 repeats ON / OFF according to the duty of the PWM signal, and an output voltage is generated accordingly.
[Step S32]: It is confirmed whether or not the power is to be turned off. If it is turned off, the process is terminated. If not, the process returns to step S31 to repeat the process.

  The voltage detection circuit 107 outputs the voltage monitor value Vmon that is stepped down to a low voltage that is proportional to the output voltage and suitable for the input conditions of the A / D converter 111. The control is repeated so that the output voltage approaches the output target value at the sampling time 2 that is much larger than the sampling time 1 (for example, 10 times).

  The monitor value at that time can be deleted for an external abnormality such as arcing that occurs for a moment by the process of step S28. As a result, the output does not fluctuate greatly, and the process is performed by the processes of steps S23 to S27 and S29. As described in Example 1, a stable output can be supplied even when there is a ripple.

  Next, a third embodiment of the present invention will be described. The third embodiment solves the ripple problem as in the first embodiment.

  Here, the high voltage power supply is a positive output, and the case where constant voltage control is performed will be described.

  The outline and the circuit configuration example of the high-voltage power supply device of the example are the same as those of the example 1, and refer to FIG. 9 and FIG. FIG. 13 is a diagram showing the reading timing of the monitor.

  In this embodiment, the switching frequency f is set to a positive multiple of the control sampling frequency F to solve the above problem.

  That is, the output ripple is generated by the charge / discharge in the rectifying / smoothing circuit 105 on the circuit secondary side as described above, and the cycle (frequency) is determined by the switching frequency F. The switching frequency F is determined by a PWM signal sent from the MCU, and the frequency is determined by the CPU 109 to a predetermined value. On the other hand, the control sampling period (frequency f) is also set to a predetermined value by the CPU 109. Therefore, since the switching frequency f and the control sampling frequency F can be determined in advance by the CPU 109, the relationship is set so that the switching frequency f is an integral multiple of the control sampling frequency F. By doing so, the relationship between the output ripple and the sampling for reading the monitor is an integral multiple, and the ripple voltage value when reading the monitor is read as a value that substantially matches the charge / discharge as shown in FIG. As a result, ripples peculiar to digital control that are generated by reading values that vary from sampling to sampling do not occur.

  If the reading is synchronized at the timing when the average value of charge and discharge is reached, the output accuracy can be improved.

  Next, a fourth embodiment of the present invention will be described. The fourth embodiment solves the above-described problem of detected values such as arcing.

  The outline and circuit configuration example of the high-voltage power supply device are the same as those in the first embodiment, and refer to FIGS. 9 and 10.

  Here, the high voltage power supply is a positive output, and the case where constant voltage control is performed will be described.

[Rise operation]
The same as in the first embodiment.

[Steady operation] (Refer to the flowchart of FIG. 14)
Next, control of steady operation will be described. The details are as shown in FIG.

[Step S51]: The target value of the output voltage is received from the MCU that controls the operation of the entire device. (In this case, not the MCU but the operation from the display operation device may be used)
[Step S52]: The target monitor value Vmg corresponding to the received output target value is selected and set from a predetermined formula or table.
[Step S53]: The output Vmon (D) of the voltage monitor value Vmon from the A / D converter 111 is captured.
[Step S54]: It is determined whether Vmon (D) is in the normal range. Here, for example, within ± 20% of the target monitor value Vmg is regarded as normal, and when exceeding the range, it is determined as abnormal. If it is determined to be normal, the process proceeds to a calculation process in the normal state (step S55). If it is determined that there is an abnormality, the process proceeds to the process in the abnormal load state (step S57).
[Step S55]: When it is determined to be normal in Step S54, the CPU 109 compares the target monitor value with the Vmon (D) according to a predetermined control algorithm (for example, the method disclosed in Japanese Patent Laid-Open No. 2000-134927). The ON duty ratio of the PWM signal is determined.
[Step S56]: If it is determined in step S54 that there is an abnormality, the calculation processing in step S55 is not performed, and the ON duty ratio of the PWM signal is made the same as the previous time.
[Step S57]: The ASIC (specific application IC, pulse oscillator 110) generates a PWM signal PWM in accordance with the determined ON duty ratio. The switching element 106 repeats ON / OFF according to the duty of the PWM signal, and accordingly, the DC voltage applied to the primary winding of the step-up transformer 104 is switched, and the boosted AC voltage is induced on the secondary winding side. .
[Step S57]: It is confirmed whether or not the power is to be turned off. If it is turned off, the process ends. If not, the process returns to Step S51 to repeat the process.

  The AC voltage is rectified and smoothed by the rectifying and smoothing circuit 105 and supplied to the load 100. The voltage detection circuit 107 outputs the voltage monitor value Vmon that is stepped down to a low voltage that is proportional to the output voltage and suitable for the input conditions of the A / D converter 111. The above operation is repeated so that the output voltage approaches the output target value at a predetermined sampling time.

  After step S56, if the next Vmon value is within the normal range, it can be determined that the previous abnormal load state occurred for a moment, and the normal control operation is started. As a result, problems such as image abnormalities can be avoided.

  If the abnormal load state continues even after the process of step S56 is executed, when the predetermined number of cycles is reached, it is determined that the load is intermittently abnormal, and abnormality avoiding means (such as output stop) is performed.

  In step S56, the previous ON duty ratio is used. Alternatively, the ON duty ratio of the PWM signal may be set to a predetermined value (for example, 30%). Also, the target value Vmg to be compared in step S54 is set to a value corresponding to the ON duty ratio of the PWM signal having a predetermined value. If the next Vmon value is within the normal range, it can be determined that the previous abnormal load state occurred momentarily and the normal control operation is resumed. As a result, problems such as image abnormalities can be avoided. If the abnormal load state continues thereafter, when the predetermined number of cycles is reached, it is determined that the load is intermittently abnormal, and abnormality avoiding means (such as output stop) is performed.

  In this modification, the predetermined value is less affected by the power drop on the image, and even when the load is intermittently abnormal, the power of the high-voltage power supply is suppressed, so that the photoreceptor is damaged, the high-voltage power supply The value is such that no damage will occur.

  In step S56, the ON duty ratio of the PWM signal may be a value obtained by multiplying the previous duty by a predetermined ratio (for example, 2/3). The target value Vmg to be compared at this time is also set to a value corresponding to the ON duty ratio of the PWM signal multiplied by a predetermined ratio. If the next Vmon value is within the normal range, it can be determined that the previous abnormal load state occurred momentarily and the normal control operation is resumed. As a result, problems such as image abnormalities can be avoided. If the abnormal load state continues after that, when the predetermined number of cycles is reached, it is determined that the load is intermittently abnormal, and abnormality avoiding means (such as output stop) is performed.

  In this modification, the value obtained by multiplying the predetermined ratio has less influence on the image due to power reduction, and even when the load is intermittently abnormal, the power of the high-voltage power supply is suppressed, thereby causing damage to the photoreceptor. Use a value that does not cause damage to the high-voltage power supply.

  In addition, this invention is not limited to the above-mentioned Example, A various change is possible in the range which does not deviate from the meaning. For example, at least one of the configurations of the third and fourth embodiments may be adopted as the configuration of the first and second embodiments. That is, the power supply apparatus according to the first embodiment or the second embodiment may synchronize switching well-known and sampling well-known, or may use a duty determined by a special reference such as a fixed duty when an abnormality is detected.

It is a block diagram of a conventional analog control type high voltage power supply device. It is a block diagram of the conventional high voltage power supply device of a digital control system. It is a figure explaining the problem of the ripple increase of the conventional high voltage power supply device of a digital control system. It is a figure explaining the problem of the ripple increase of the conventional high voltage power supply device of a digital control system. It is a figure explaining the problem of the abnormality detection value by the arcing etc. of the conventional digital control system. It is a figure explaining the problem of the abnormality detection value by the arcing etc. of the conventional digital control system. It is a figure explaining the problem of the abnormality detection value by the arcing etc. of the conventional digital control system. It is a figure explaining the problem of the abnormality detection value by the arcing etc. of the conventional digital control system. It is a block diagram explaining the schematic structure of Example 1 of this invention. FIG. 3 is a circuit diagram illustrating a partial circuit configuration example of the first embodiment. It is a flowchart explaining the steady control operation | movement of the said Example 1. FIG. It is a flowchart explaining the steady control operation | movement of Example 2 of this invention. It is a figure explaining the principle of Example 3 of this invention. It is a flowchart explaining the steady control operation | movement of Example 4 of this invention.

Explanation of symbols

11 D / A converter 12 ON / OFF determination circuit 13 Control circuit 14 Switching circuit 15 Step-up transformer 16 Rectifier circuit 17 Detection circuit 18 Output load 19 CPU
20 Pulse Oscillator 21 A / D Converter 100 Load 101 High Voltage Power Supply Unit 102 DC Power Supply 103 Main Control Unit 104 Step-up Transformer 105 Rectifier Smoothing Circuit 106 Switching Element 107 Voltage Detection Circuit 108 Current Detection Circuit 109 CPU
110 Pulse Oscillator 111 A / D Converter 112 Storage Device

Claims (14)

With a transformer,
Switch means for switching the application of power to the primary winding of the transformer according to the duty of the input pulse width modulation signal;
Detecting means for detecting an output value for a load connected to the secondary winding side of the transformer;
Sampling means for sampling the output value detected by the detection means;
Averaging means for averaging the sampled output values and outputting an average output value;
A digital control type power supply apparatus comprising: a duty determining unit that determines a duty corresponding to a target value based on the average output value output from the averaging unit.   2. The digital control type power supply apparatus according to claim 1, wherein the averaging means includes storage means for storing the sampled output values and calculation means for calculating an average value of the stored output values.   3. The digital control system power supply device according to claim 1, wherein at least one of the minimum value and the maximum value among the sampled output values is excluded from the basis of the average value.   The switching unit according to any one of claims 1 to 3, wherein when the output value sampled by the sampling unit includes an abnormal value outside a predetermined range, the switching unit is controlled at a predetermined duty determined before the previous time. Digital control power supply.   4. The digital signal according to claim 1, wherein when the output value sampled by the sampling means includes an abnormal value outside a predetermined range, the switching means is controlled at a predetermined duty. Control system power supply.   2. The switching means is controlled with a duty obtained by multiplying a predetermined ratio determined before the previous time by a duty when an output value sampled by the sampling means is out of a predetermined range. The digital control system power supply device according to any one of? With a transformer,
Switch means for switching the application of power to the primary winding of the transformer according to the duty of the input pulse width modulation signal;
Detecting means for detecting an output value for a load connected to the secondary winding side of the transformer;
Sampling means for sampling the output value detected by the detection means;
Means for determining a duty corresponding to the target value based on the sampled output value;
A digital control type power supply apparatus characterized in that the switching frequency of the switching means is an integral multiple of the sampling frequency of the sampling means.   8. The digital control type power supply apparatus according to claim 7, wherein the sampling means performs sampling at a timing at which an output value applied to the load takes an average value due to charging / discharging by switching of the switching means. With a transformer,
Switch means for switching the application of power to the primary winding of the transformer according to the duty of the input pulse width modulation signal;
Detecting means for detecting an output value for a load connected to the secondary winding side of the transformer;
Sampling means for sampling the output value detected by the detection means;
Means for determining a duty corresponding to the target value based on the sampled output value;
A digital control type power supply apparatus that controls the switching means at a predetermined duty determined before the previous time when an output value sampled by the sampling means is out of a predetermined range. With a transformer,
Switch means for switching the application of power to the primary winding of the transformer according to the duty of the input pulse width modulation signal;
Detecting means for detecting an output value for a load connected to the secondary winding side of the transformer;
Sampling means for sampling the output value detected by the detection means;
Means for determining a duty corresponding to the target value based on the sampled output value;
A digital control type power supply apparatus that controls the switching means at a predetermined duty determined in advance when an output value sampled by the sampling means includes an abnormal value outside a predetermined range. With a transformer,
Switch means for switching the application of power to the primary winding of the transformer according to the duty of the input pulse width modulation signal;
Detecting means for detecting an output value for a load connected to the secondary winding side of the transformer;
Sampling means for sampling the output value detected by the detection means;
Means for determining a duty corresponding to a target value based on the sampled output value,
A digital control method for controlling the switching means with a duty obtained by multiplying a predetermined ratio determined before last time by a predetermined ratio when the output value sampled by the sampling means is out of a predetermined range. Power supply. A transformer, switch means for switching application of power to the primary winding of the transformer in accordance with the duty of the input pulse width modulation signal, and an output value for a load connected to the secondary winding side of the transformer In a high-voltage power supply control method for controlling a digital control power supply device comprising a detecting means for detecting
A sampling means for sampling an output value detected by the detection means;
An averaging means that averages the sampled output values and outputs an average output value;
And a step of determining duty corresponding to the target value based on the average output value output from the averaging means. In a digital control type power supply device that repeats a control routine that detects and controls a value of an output supplied to a load to a target value,
Detecting means for detecting a value of an output supplied to the load;
Sampling means for sampling the output value detected by the detection means;
Averaging means for averaging the sampled output values and outputting an average output value;
A digital control type power supply apparatus for controlling a value of an output supplied to the load based on an average output value output from the averaging means. A digital control system for switching an input power supply by a switching means to supply power to a load, detecting a value of an output supplied to the load, and repeating a control routine for controlling a switching parameter of the switching means so as to become a target value In power supply,
Detecting means for detecting a value of an output supplied to the load;
Sampling means for sampling the output value detected by the detection means;
Averaging means for averaging the sampled output values and outputting an average output value;
A digital control type power supply apparatus for controlling a value of an output supplied to the load by determining a switching parameter of the switching means based on an average output value outputted from the averaging means.

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