JPH0527855A - High voltage power controller - Google Patents

Abstract

PURPOSE:To suppress the increase of the transcription current and to prevent the occurrence of the defective transcription by switching the high voltage output received from a high voltage transformer for transcription to a lower level in response to the increase of altitude of a working site. CONSTITUTION:When an altitude is designated by a keyboard 29, a microprocessor 27 reduces the reference level of transcription set at a PWM control path 24 for transcription. Thus the constant voltage control is attained in a state where the high voltage output produced from a high voltage transformer 22 is reduced by the switching operation of a switching transistor 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-voltage power supply controller used in an electrophotographic mechanism section having a photoconductor in, for example, a copying machine or a laser printer.

[0002]

2. Description of the Related Art An electrophotographic mechanism unit used in a copying machine, a laser printer or the like is provided with, for example, a photoconductor drum, and the photoconductor of the photoconductor drum is charged by a charging unit and then exposed by an exposure unit. A latent electrostatic image is formed on the body, toner is attached to the latent electrostatic image in the developing section, and the toner image is transferred to the transfer sheet in the transfer section.

In such an electrophotographic mechanism section, a high-voltage power supply controller is provided to apply a high voltage to the charging charger in the charging section, the developing sleeve in the developing section and the transfer charger in the transfer section.

Conventionally, as such a high voltage power supply control device, the one shown in FIG. 7 has been known. This is because a high voltage is generated in the charging high voltage transformer 2 by the switching operation of the switching transistor 1 and the high voltage is applied to the charging charger 3, and the switching transistor 4
Of the high voltage transformer 5 for transfer and applies the high voltage to the transfer charger 6, and the high voltage transformer 8 for bias generates a high voltage by the switching operation of the switching transistor 7 to develop the high voltage. The voltage is applied to the sleeve 9.

Each of the switching transistors 1, 4,
7 is a charging PWM (pulse width modulation) controller 1
The switching control is performed by pulse signals from 0, the transfer PWM control unit 11, and the bias PWM control unit 12.

The high voltage changes generated in the high voltage transformers 2, 5 and 8 are monitored by the monitor voltage detecting circuits 13 and 1, respectively.
4 and 15 monitor, and the monitor outputs are charged A / D (analog / digital) converter 16 and transfer A / D, respectively.
After the A / D conversion is performed by the D converter 17 and the bias A / D converter 18, the charges are supplied to the charging PWM control unit 10, the transfer PWM control unit 11, and the bias PWM control unit 12.

The charging PWM control unit 10 and the transfer PW
The M control unit 11 and the bias PWM control unit 12 also receive a charging ON signal and a charging reference value from the microprocessor 19.
A transfer ON signal and a transfer reference value, and a bias ON signal and a bias reference value are input respectively.

Therefore, the charging PWM control unit 10,
Transfer PWM control unit 11, bias PWM control unit 12
Are the digital values of the monitor voltage input from the A / D converters 16 to 18, and the monitor voltage reference value (charging reference value, which is set by the microprocessor 19).
Transfer reference value, bias reference value) is compared and calculated, and each switching transistor 1, 4, based on the calculated output.
By controlling the duty ratio for switching 7
The high voltage output from each of the high voltage transformers 2, 5 and 8 is controlled to a constant voltage.

In such a high-voltage power supply controller, when a positive constant voltage control is performed with the specific circuit of the high voltage output system for the transfer charger 6 shown in FIG. There is a relationship shown in FIG. 1, and there is a relationship shown in FIG. 2 between the altitude and the transfer resistance. Here, FIG.
2 and FIG. 2, the characteristics indicated by the two-dot chain line A are the case where the high voltage output is controlled to a constant voltage of 5.2 kV, the characteristics indicated by the one-dot chain line B are the case where the constant voltage is controlled to 4.9 kV, and the solid line B The characteristics indicated by are when the constant voltage is controlled to 4.6 kV.

As is apparent from FIGS. 1 and 2, when constant voltage control of high voltage output is performed, the transfer current increases as the altitude increases, and conversely the transfer resistance decreases. This is because the atmospheric pressure decreases as the altitude increases, and the corona discharge inception voltage decreases.

Therefore, when the electrophotographic apparatus using the above-mentioned high-voltage power supply control device is used at high altitude, the current flowing to the transfer charger increases and the current flowing to the transfer paper also increases as compared with the case of using it on the flat ground. As a result, the amount of current flowing into the photoconductor drum via the transfer paper increases, the toner on the photoconductor drum is positively charged, and the transfer efficiency decreases, which is a high voltage determined by the monitor voltage reference value fixed in advance. Depending on the constant voltage control value of the voltage output, transfer defects such as print blurring may occur. This transfer failure was particularly remarkable in the black solid portion and the gray scale portion of the image.

[0012]

As described above, in the conventional high voltage power supply control device of this type, the high voltage applied to the load generated by the high voltage transformer with the monitor voltage reference value fixed in advance is subjected to constant voltage control. For this reason, when used at high altitude, the transfer current greatly increases, resulting in defective transfer, which may cause deterioration in quality such as print blur.

Therefore, according to the present invention, the high voltage output from the high-voltage transformer can be controlled at a constant voltage in a state where the high voltage output is lowered as the altitude of the place of use rises, and it is possible to suppress the increase of the transfer current due to the rise of the altitude. An object of the present invention is to provide a high-voltage power supply control device capable of ensuring good print quality regardless of altitude.

[0014]

According to the present invention, a high voltage transformer is provided, a high voltage is generated in a high voltage transformer by a switching operation of a switching means and applied to a load, and a high voltage generated in the high voltage transformer is monitored. In a high-voltage power supply control device that compares a monitor voltage with a reference value and controls the switching operation of the switching means based on the calculated output to control the high-voltage output from the high-voltage transformer at a constant voltage, a means for designating altitude or altitude And a reference value switching means for switching the reference value of the monitor voltage in the direction of decreasing the reference value as the designated altitude or the detected altitude increases.

[0015]

According to the present invention having such a structure, when the altitude designated by the altitude designating means or the altitude detected by the altitude detecting means rises, the reference value switching means lowers the reference value of the monitor voltage, thereby increasing the high voltage. Constant voltage control is performed with the high voltage output from the transformer being lowered. As a result, it is possible to prevent the transfer current from increasing and prevent the transfer failure from occurring.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to high voltage generation control for a transfer charger of an electrophotographic mechanism will be described with reference to the drawings.

As shown in FIG. 3, a high voltage is generated in the transfer high-voltage transformer 22 by the switching operation of the switching transistor 21, and the high voltage is applied to the transfer charger 23. The switching transistor 21 includes a PWM (pulse width modulation) controller 24.
Switching control is performed by a pulse signal from.

Further, a high voltage change generated in the high voltage transformer 22 is monitored by a monitor voltage detection circuit 25, and the monitor output is A / D converted by a transfer A / D (analog / digital) converter 26. The digital value is supplied to the transfer PWM control unit 24.

A transfer ON signal is input from the microprocessor 27 to the PWM control section 24, and a transfer reference value is input as write data.

A keyboard 29 is connected to the microprocessor 27 via a keyboard controller 28. The keyboard 29 is provided with keys and the like for inputting and designating the altitude of the land where the electrophotographic mechanism section is used. (Altitude designation means)

Then, the microprocessor 27 is
As the altitude designated by the keyboard 29 rises, the transfer reference value for the PWM control unit 24 is switched to a lower direction. (Reference value switching means)

As shown in FIG. 4, the PWM control unit 24 includes a calculation unit 31, a monitor voltage reference value setting unit 32, a frequency reference value setting unit 33, a reference clock generator 34, and a reference clock generator 34. Reference counter 35 for counting reference clock, latch circuit 36, first and second comparators 37, 38, flip-flop (F / F) 39
Further, a timing controller 40 is provided, and the digital value of the monitor voltage from the A / D converter 26 is input to the arithmetic unit 31 and the monitor voltage reference value of the monitor voltage reference value setting unit 32 is input. The monitor voltage reference value (transfer reference value) is set in the monitor voltage reference value setting section 32 by the microprocessor 27.

The arithmetic unit 31 compares the input digital value with the monitor voltage reference value and supplies the arithmetic output value obtained by adding and subtracting the difference to the latch circuit 36. The latch circuit 37 supplies the latched calculation output value to the second comparator 38 and also supplies it to the calculation unit 31 as a feedback value.

The first comparator 37 compares the frequency reference value from the frequency reference value setting section 33 with the count value of the reference counter 35, and when the count value matches the frequency reference value, activates its output. The comparator 37
The output of is supplied to the ON terminal of the flip-flop 39 and the CL terminal of the reference counter 35.

The second comparator 38 is a latch circuit 36.
The arithmetic output value from the arithmetic unit 31 which is latched in is compared with the count value of the reference counter 35, and when the count value matches the arithmetic output value, the output is activated.
The output of the comparator 38 is supplied to the OFF terminal of the flip-flop 39.

The flip-flop 39 is cleared by the ON signal from the microprocessor 39, and thereafter, when the ON terminal is activated by the output of the first comparator 37, it outputs a high level signal and the output of the second comparator 38. When the OFF terminal is activated, the signal is switched to a low level signal.

The timing controller 40 receives the ON signal from the microprocessor 27 and determines the operation timing of the A / D converter 26 and the operation timing of the arithmetic unit 31.

As shown in FIG. 5, the arithmetic unit 31 includes an inverting circuit 41, first and second adders 42 and 43, and "01".
It is composed of a “H” and “FEH” data generation circuit 44, a comparator 45 and a selector 46, and supplies the digital value from the A / D converter 26 to the first adder 42 via the inverting circuit 41. ing. The first adder 4
The reference value from the monitor voltage reference value setting unit 32 is also input to 2.

8-bit data is output from the first adder 42, and 7-bit data of the 8-bit data is output to the AND gate 47.
And the remaining 1 bit is supplied to the OR gate 48.

The "01H" and "FEH" data generating circuit 44 is controlled by the timing controller 40, and the digital value from the A / D converter 26 becomes the reference value from the monitor voltage reference value setting section 32. "01H" data is output until the coincidence, and "FEH" data is output when the digital value exceeds the reference value, and the data is supplied to the AND gate 47 and the OR gate 48.

The outputs of the AND gate 47 and the OR gate 48 are supplied to the second adder 43. The second adder 43 also includes the latch circuit 36.
The feedback value from is input.

The second adder 43 adds the feedback value and the data from the AND gate 47 and the OR gate 48 and supplies the added value to the selector 46 and the comparator 45.

The frequency reference value from the frequency reference value setting section 33 is also input to the selector 46 and the comparator 45. The comparator 45 compares the added value with the frequency reference value, outputs a signal for selecting the added value to the selector 46 until the added value reaches the frequency reference value, and when the added value becomes equal to or higher than the frequency reference value. A signal for selecting the frequency reference value is output to the selector 46.

Each of the adders 42 and 43 sets the signal from the carry terminal CA to the low level when the addition result becomes negative,
The enable state of the selector 46 is released. As a result, the selector 46 makes the calculated output value zero.

Next, the operation of this embodiment constructed as described above will be described. When the power is turned on, the microprocessor 27 first sets the transfer reference value in the monitor voltage reference value setting unit 32 of the PWM control unit 24.

In this state, when a transfer ON signal is input from the microprocessor 27 to the timing controller 40, the timing controller 40 starts its operation, and A / A
A conversion request is issued to the D converter 26.

The digital value from the A / D converter 26 is supplied to the arithmetic unit 31. Since the output of the monitor voltage is zero after the output is turned on, the A / D converted digital value is also zero.
Therefore, immediately after the output is turned on, "01H" data is output from the "01H" and "FEH" data generation circuits 44 and supplied to the second adder 43. Since the feedback value input to the second adder 43 is also initially zero, the adder output is "01H".

Since this data value "01H" is smaller than the frequency reference value, the selector 46 selects the adder output.
In this way, the output of the adder is selected by the selector 46 as the output of the arithmetic unit and supplied to the latch circuit 36.

On the other hand, the first comparator 37 compares the frequency reference value from the frequency reference value setting section 33 with the count value of the reference counter 35, and if they match, the output of the comparator 37 becomes active and the flip-flop 39 is activated.
Is turned on and the reference counter 35 is cleared.
As a result, the output of the flip-flop 39, that is, P
The output of the WM control unit 24 becomes high level.

The output value of the arithmetic unit 31 latched by the latch circuit 36 by the second comparator 38 is compared with the count value of the reference counter 35. If they match, the output of the comparator 38 becomes active and the flip-flop 39 is activated. Turns off. As a result, the output of the flip-flop 39, that is, the output of the PWM control unit 24 becomes low level.

The switching transistor 21 has the above P
When the output of the WM control unit 24 is at a high level, it turns on,
When it is low level, it turns off. That is, the duty ratio of the switching transistor 21 is controlled at the timing when the output of the PWM control unit 24 becomes low level.

Then, this switching transistor 2
A high voltage is generated from the high voltage transformer 22 for transfer by the switching operation 1 and is applied to the transfer charger 23. The high voltage generated in the high-voltage transformer 22 is monitored by the monitor voltage detection circuit 25, and the monitor output is digitally converted by the transfer A / D converter 26.
It is supplied to the calculation unit 31 of the PWM control unit 24. And
After being inverted by the inversion circuit 41, it is added to the reference value of the reference value setting unit 32 by the first adder 42. That is, the difference between the reference value and the monitor voltage is calculated by the first adder 42.

Since the latched value is zero at the beginning of output, the duty ratio is one clock of the reference clock from the reference clock generator 34. Then, after that, the duty ratio is gradually increased by one clock of the reference clock, and when the A / D-converted digital value becomes equal to or larger than the reference value from the reference value setting unit 32, the output from the data generation circuit 44 is " FEH ”data.

As a result, the output from the first adder 42 is input to the second adder 43. That is, the difference between the reference value and the monitor voltage is input to the second adder 43 and added to the feedback value.

When the reference value is larger than the monitor voltage, the value obtained by increasing the difference feedback value becomes a new duty ratio to increase the output, and when the reference value is smaller than the monitor voltage. The value obtained by decreasing the difference feedback value becomes a new duty ratio, and the output decreases. Further, when the output value of the second adder 43 in the comparator 45 becomes equal to or higher than the frequency reference value, the selector 46 operates to select the frequency reference value.

Thus, according to the output of the arithmetic unit 31, the PWM
The ON / OFF of the control unit 24 is controlled, the switching operation of the switching transistor 21 is controlled by the output of the PWM control unit 24, and the high voltage generated from the high voltage transformer 22 is set in the reference value setting unit 32. The constant voltage is controlled so that it becomes equal to the reference value.

In this embodiment, when the altitude of the place of use is designated by the keyboard 29, the transfer reference value corresponding to the altitude is selected by the microprocessor 27 and written in the reference value setting section 32. ing.

Therefore, for example, as shown in FIGS. 1 and 2, a transfer reference value of 5.2 kV (characteristic curve A) is selected up to an altitude of 1000 m designated by the keyboard 29 and 10
A transfer reference value of 4.9 kV (characteristic curve B) is selected from 00 m to 2000 m, and a transfer reference value of 4.
The microprocessor 27 is configured to select 6 kV (characteristic curve C).

By doing this, altitudes from 0 m to 300
When used within the range of 0m, the transfer current is about 180μ.
It varies within the range of A to 340 μA. Therefore, even when a laser printer or the like equipped with an electrophotographic mechanism using the high-voltage power supply control device of this embodiment is used at a high altitude of 3000n, the transfer current can be obtained by simply inputting the current altitude from the keyboard 29. Can be suppressed as low as about 340 μA. As a result, good print quality can be secured without causing print blurring due to transfer failure. Further, since the transfer current can be suppressed low, a small capacity transformer can be used as the high voltage transformer 22, and the cost can be reduced.

In the above embodiment, the altitude is manually designated by the keyboard 29, and the reference value is switched according to the designated altitude. For example, a commercially available altimeter is used. The transfer reference value may be switched and set according to the altitude automatically detected by the altimeter.

Further, since the duty ratio of the signal for switching the switching transistor 21 increases as the transfer current increases as the altitude increases, the altitude is automatically detected using this and the altitude is automatically detected. It is also possible to switch the reference value.

That is, as shown in FIG. 6, the output of the comparator 45 in the arithmetic unit 31 is supplied to the microprocessor 27 via the timing controller 40. In the comparator 45, the switching transistor 2
When the duty ratio of the signal for switching 1 is increased, the output value of the second adder 43 eventually becomes equal to or higher than the frequency reference value (for example, the duty ratio is 50%), and the output signal of the comparator 45 changes. Therefore, the microprocessor 27 detects the change in the output signal and switches the transfer reference value to a lower value. In this case, it is necessary to set the transfer reference value to the maximum value immediately after the power is turned on. Of course, various modifications can be made without departing from the scope of the present invention.

[0053]

As described above in detail, according to the present invention, the high voltage output from the high-voltage transformer can be controlled at a constant voltage in a lowered state as the altitude of the place of use rises, and the transfer current of the altitude increases. It is possible to provide a high-voltage power supply control device capable of suppressing an increase and ensuring good print quality regardless of the altitude of the place of use.

[Brief description of drawings]

FIG. 1 is a diagram showing a change characteristic of a transfer current with respect to an altitude when a transfer voltage is controlled to a constant voltage by a conventional high voltage power supply control device.

FIG. 2 is a diagram showing a change characteristic of a transfer resistance with respect to an altitude when a transfer voltage is controlled to a constant voltage by a conventional high voltage power supply control device.

FIG. 3 is an overall block diagram according to an embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a PWM control unit in FIG.

5 is a block diagram showing a configuration of a calculation unit in FIG.

FIG. 6 is a block diagram showing the configuration of an arithmetic unit according to another embodiment of the present invention.

FIG. 7 is an overall block diagram of a conventional example.

FIG. 8 is a specific circuit diagram of a conventional example.

[Explanation of symbols]

21 ... Switching transistor, 22 ... Transfer high voltage transformer, 23 ... Transfer charger, 24 ... Transfer PWM control unit, 25 ... Monitor voltage detection circuit, 26 ... Transfer A / D
Converter, 27 ... Microprocessor, 28 ... Keyboard controller, 29 ... Keyboard.

Claims (1)

Claim: What is claimed is: 1. A high voltage transformer is provided, and a high voltage is generated in the high voltage transformer by a switching operation of a switching means and applied to a load, and a high voltage generated in the high voltage transformer is monitored. A means for designating an altitude in a high-voltage power supply control device for comparing and calculating a monitor voltage and a reference value and controlling the switching operation of the switching means based on the calculated output to control the high-voltage output from the high-voltage transformer at a constant voltage. Alternatively, it comprises a means for detecting the altitude, and a reference value switching means for switching the reference value of the monitor voltage in the direction of decreasing with the increase of the altitude designated by the designating means or the altitude detected by the detecting means. Characteristic high voltage power supply control device.