JPH103199A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of obtaining an excellent image forming condition, without affecting high-voltage output value. SOLUTION: When a photoreceptor 1 is subjected to a corona discharge from a corona discharger 2, an output current is obtained from the surface of the photoreceptor 1. This output current is detected by current detection resistance R, a voltage obtained as the product of the resistance of the detection resistance R and a current I is fed back to the ADC 22 of a control part 21 and a PWM signal is transmitted to a switching element Q from a CNT 23, and the primary side of a transformer T is excited so as to always make the output current equal to a target value. At this time, the upper limit value of the duty of the PWM signal is corrected according to a value detected by the resistance R.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer, and more particularly to a switching PWM signal which is supplied to a high voltage generating section comprising a flyback transformer, and a feedback voltage value from the high voltage generating section. The present invention relates to an image forming apparatus including a high-voltage generating circuit that updates a duty of a PWM signal based on a difference between the PWM signal and a predetermined reference value and generates a predetermined high-voltage output.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, a charger, an exposure optical system (optical writing system), a developing device, a transfer device (transfer belt), a separator, a cleaning device are arranged around a photosensitive member in the order of an electrophotographic process. Unit and an electrophotographic process unit such as a static eliminator (static elimination lamp). In some cases, a pre-transfer static eliminator is provided on the upstream side of the transfer unit (upstream in the rotation direction of the photoconductor).

Incidentally, a high voltage from a high voltage generating circuit is applied to these electrophotographic process units. For example, the charger generates corona discharge when a high voltage is applied, and uniformly charges the surface of the photoconductor. When a high voltage is applied to the transfer unit, the transfer unit attracts the toner charged to one polarity via the sheet and transfers the toner onto the sheet.
In addition, the separator and the static eliminator have a function of making the surface of the photoreceptor uniform by discharging a high AC voltage. Also in the developing device, a developing bias is applied to the developing roller from the high voltage generating circuit.

As described above, the electrophotographic image forming apparatus is provided with a high voltage generating circuit for supplying a high voltage to each electrophotographic process unit. In general, the high voltage generating circuit outputs a switching PWM signal to a high voltage generating section. Supply to
A type that generates a predetermined high-voltage output by updating the duty of the PWM signal based on the difference between the feedback voltage value from the high-voltage generation unit and a predetermined reference value is employed.

[0005]

Here, the high-voltage output of the high-voltage generating circuit cannot be obtained with high accuracy unless the PWM output value is changed or updated due to a high-voltage-side load fluctuation. Voltage) also has a significant effect on high voltage output. In addition, the high-voltage output greatly affects the high-voltage output characteristics due to the change or update amount of the PWM output value and the operation amount. In recent years, a self-diagnosis function of an image forming apparatus has been general. However, in the case of an abnormality of a high-voltage output, it is often difficult to clearly distinguish between an abnormality on a low-voltage side and an abnormality on a high-voltage side.

SUMMARY OF THE INVENTION The present invention has been made in view of such a background, and reduces output variations due to fluctuations on the low voltage side, malfunctions of the abnormality detection circuit, and improves image forming conditions without affecting high voltage output values. It is an object of the present invention to provide an image forming apparatus capable of obtaining the following.

[0007]

According to a first aspect of the present invention, a PWM signal for switching is supplied to a high voltage generator, and a feedback voltage value from the high voltage generator and a predetermined reference value are provided. In the image forming apparatus provided with a high voltage generating circuit for generating a predetermined high voltage output by updating the duty of the PWM signal based on the difference between the power supply voltage and the high voltage generation voltage of the feedback voltage detecting unit detecting the feedback voltage from the high voltage generating unit. And a detection circuit for detecting a change in at least one power supply voltage value of a power supply voltage supplied to the unit and correcting an upper limit value of a PWM signal duty in accordance with the output value.

A second invention is a switching PWM.
A high voltage generating circuit for supplying a signal to the high voltage generating unit, updating the duty of the PWM signal by a difference between a feedback voltage value from the high voltage generating unit and a predetermined reference value, and generating a predetermined high voltage output. In the image forming apparatus, the operation amount of the PWM duty is corrected based on a difference between a power supply voltage of a feedback voltage detection unit that detects a feedback voltage from the high voltage generation unit and a reference value.

A third invention is a switching PWM.
An image including a high-voltage generating circuit that supplies a signal to a high-voltage generating unit, updates a duty of a PWM signal based on a difference between a feedback voltage value from the high-voltage generating unit and a predetermined reference value, and generates a predetermined high-voltage output. In the forming apparatus, a change in at least one power supply voltage value of a power supply voltage of a feedback voltage detection unit that detects a feedback voltage from the high voltage generation unit and a power supply voltage supplied to the high voltage generation unit is detected, and the output value is equal to or more than a predetermined value. In the case of
A detection circuit for stopping the M signal is provided.

A fourth invention is a switching PWM.
An image including a high-voltage generating circuit that supplies a signal to a high-voltage generating unit, updates a duty of a PWM signal based on a difference between a feedback voltage value from the high-voltage generating unit and a predetermined reference value, and generates a predetermined high-voltage output. In the forming apparatus, a change in at least one power supply voltage value of a power supply voltage of a feedback voltage detection unit for detecting a feedback voltage from the high voltage generation unit and a power supply voltage supplied to the high voltage generation unit is detected, and a reference value is corrected based on an output thereof. A detection circuit for performing the operation.

A fifth invention provides a switching PWM.
An image including a high-voltage generating circuit that supplies a signal to a high-voltage generating unit, updates a duty of a PWM signal based on a difference between a feedback voltage value from the high-voltage generating unit and a predetermined reference value, and generates a predetermined high-voltage output. In the forming apparatus, a change in at least one power supply voltage value of a power supply voltage of a feedback voltage detection unit that detects a feedback voltage from the high voltage generation unit and a power supply voltage supplied to the high voltage generation unit is detected, and a feedback voltage is determined by a combination of the outputs. A detection circuit for correcting the value is provided.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a configuration diagram of an image forming unit of the image forming apparatus. A drum-shaped photoreceptor 1 is composed of a charging corona discharger 2, an exposure optical system (optical writing system) 3, a developing unit 4, a transfer belt 5, a fur brush 7, and a cleaning blade 8 in the order of the electrophotographic process. A cleaning device 6 and a static eliminator (quenching lamp) 9 are arranged.

The transfer belt 5 is stretched between a first roller 11 and a second roller 12.
A third roller 13 for applying a transfer bias is provided between the rollers 12. The transfer bias power supply 14 is connected to the first roller 11
And the third roller 13.

A fixing roller 16 is provided downstream of the transfer belt 5.
And a fixing device 15 including a pressure roller 17 for pressing the fixing roller 16. A high voltage is applied to the corona discharger 2, the developing device 4, and the transfer belt 5 from a high voltage generating circuit. In such a configuration, charging, exposure,
An image is formed on a sheet by an electrophotographic process of development, transfer and separation.

FIG. 2 is a control block diagram of the entire image forming apparatus. The control unit includes a CPU 21 for controlling the whole, a ROM 22 for storing a control program, a RAM 23 for storing various data, input gate arrays 24 and 26, a video gate array 25 for outputting to a laser diode, an output gate array 27, and the like. I have.

The first paper supply unit 28 and optional second and third paper supply units 29 and 30 are provided with serial parallel receivers, solenoids such as pickups and tray locks, various loads such as a paper supply clutch and a tray lifting motor. And various sensors such as a paper size, a paper end, a tray set, and the like, and are electrically connected to the CPU 21 directly or via the input gate array 24.

In addition, for sheet feeding and conveyance, for door open detection,
The input gate array 26 is connected to an input data source 31 including various other sensors and various data sources taken into the CPU 21 such as a feedback voltage of a high-voltage power supply described later. On the other hand, a load group 32 including various clutches, solenoids, motors, high-voltage power supplies, and the like is connected to the output gate array 27.

As the high voltage output, there are a constant current and a constant voltage output system. The only difference is whether the high voltage output current is constant or the high voltage output voltage is constant. Since the operation is substantially the same, the schematic configuration operation of the constant current circuit will be described below.

FIG. 3 is a configuration diagram of a high voltage generating circuit of a constant current system. This example shows a high voltage generating circuit of the corona discharger 2 for charging, and includes a control unit 21, a switching transistor Q, a step-up transformer T, and a voltage detection resistor R.
To control the output current Iout generated by the corona discharge from the corona discharger 2 to the photoreceptor 1 constant,
A current detection resistor R is provided in the current path of out. Assuming that the resistance value of the current detection resistor R is R, Iout ·
The feedback voltage value is determined by R.

This voltage value is fed back to an ADC (AD converter) 22 of the control unit 21, and the data converted into a digital value is input to a CNT (controller) 23. The controller 23 performs PWM control so that this digital value is always equal to the target value.

Specifically, when the AD conversion value is larger than the target value, the duty of the PWM signal is reduced. If it is smaller than the target value, the duty of the PWM signal is increased. Then, by the PWM signal, PG
By turning on / off the switching element Q via a (pulse generator) 24, the transformer T is driven to obtain an output.

However, depending on the output polarity of the high voltage power supply, A
The polarity may not match the polarity of the input voltage of the DC 22. Therefore, it is necessary to perform a polarity inversion process, a level shift process, and the like of the ADC feedback voltage.

FIG. 6 shows a change in the high voltage output due to a change in the control power supply voltage (also used for the polarity inversion processing of the feedback voltage for the ADC, the level shift processing, etc.). (1) shows the case where the control unit 21 and the 5V system of the high voltage power supply are different systems, and (2) shows the case where the 5V system is the same system. Update of PWM is an example.
New PWM value = Old PWM value + K (feedback voltage value−target value), where K is a fixed value, a value determined by digit alignment and rising, and the duty of the PWM signal does not cause magnetic saturation of transformer T Limited by level. In addition, when the output T is short-circuited during the constant voltage control or the output is released during the constant current control, the load is short-circuited when the predetermined upper limit PWM before the magnetic saturation is continued for a predetermined interval. Judge as open and stop output.

FIG. 4 is a block diagram showing a first example of the ADC shown in FIG. A feedback voltage from a high-voltage power supply (centered on a transformer T) is input to input terminals AN0 to AN5 of the ADC 22, and a constant voltage is input to the input terminal AN6 from a control power supply via a zener diode ZD.

FIG. 5 is a block diagram showing a second example of the ADC shown in FIG. In this example, the input terminal AN0 of the ADC 22
The high-voltage power supply feedback voltage is input to .about.AN5, and the constant voltage from the control power supply similar to the above is input to AN7. Further, the driving power supply (+24 V) is divided by a resistor into AN6, and AD6 is supplied.
A voltage that matches the C input voltage is input.

In the ADC 22 shown in FIGS. 4 and 5, when a voltage fluctuation occurs on the control side, the ADC reference voltage AVc
c, AGND fluctuates. That is, the A / D conversion value of the constant voltage is reduced by the Zener diode 20 or the like from the control power supply in the direction of increase in the fluctuation, and the A / D conversion value of the constant voltage is reduced in the direction of the fluctuation component. Becomes larger. Reference voltage 5V, 8-bit resolution, Zener diode ZD
Constant voltage: 3.0V AD conversion value 153 Voltage increase 5V → 5.1V Constant voltage: 3.0V AD conversion value 150 Voltage decrease 5V → 4.9V Constant voltage: 3.0V AD conversion value 156 Driving power supply (24V) The partial pressure (when divided at 5.6K, 1K) is 24V · 1K / (5.6K + 1K) and about 3.
Since the voltage is 6 V, which is a resistance partial voltage, it is possible to easily detect a driving power supply voltage value that fluctuates due to each load fluctuation of the image forming apparatus. Driving power supply voltage 24V Divided value 3.60V AD converted value 183 Driving power supply voltage 24V → 22V Divided value 3.30V AD converted value 168 Driving power supply voltage 24V → 25V Divided value 3.75V AD converted value 191

Further, the fluctuation of the driving power supply causes the fluctuation of the high-voltage output, and the relation is as shown in FIG. 24V system is 1.0
When V fluctuates, the high voltage output fluctuates by 100V. Low pressure side 2
When an abnormality occurs at 4V and the 24V power supply is cut off, the voltage value gradually decreases due to load capacity or the like.
Since the high-voltage output decreases, the PWM duty greatly increases. The update of the PWM is not caused by the correction of the high pressure load fluctuation, which is the original aim, but is caused by the fluctuation on the low pressure side. If this state continues, the upper limit PWM before the magnetic saturation is reached, and the "high-pressure load abnormality"
Will be. In order to prevent this, the drive power supply voltage 24V → 17V divided value 2.76V AD conversion value 140 The drive power supply voltage 24V → 28V divided value 4.20V AD conversion value 214 The value which is originally close to the AD conversion value 183 140 or less, 21
When the value is 4 or more, it is determined that the voltage is equal to or higher than the low-voltage side power supply, and the high-voltage output is stopped.

When the low voltage side 24V power supply fluctuates between 22 and 25V, the AD conversion value fluctuates between 168 and 191, and the high voltage output changes when the low voltage side 24V power supply fluctuates by 1V.
It changes by about 100V. In other words, when converted into an AD conversion value, the high-voltage output of 300 V fluctuates in 23 bits. Therefore, the accuracy can be improved by calculating and correcting the target value for the feedback voltage comparison. Example: High-voltage output 2000V Feedback voltage 4V High-voltage output 1000V If the condition of feedback voltage 2V is the target value 2000V (4V) output, drive power supply voltage 24V Target value AD conversion value 204 Target value AD conversion value remains 204 bits When the high-voltage output is controlled by using
(183-168) / 23 · 300 = 1804 V is output. In the case of a driving power supply voltage of 25 V, 2000- (1
83-191) / 23 · 300 = 2104V. Therefore, as a correction example, the target value is changed from a drive power supply voltage of 24 V to 22 V 204 · 183/168 = 222 bits (corresponding to a target value of 4.35 V). A drive power supply voltage of 24 V → 25 V 204 · 183/191 = 195 bits Target value (target value 3.82V equivalent)

Note that the value of 183 is an AD conversion value under a predetermined condition.
A value sampled by the DC 22 and stored in a nonvolatile RAM such as a control unit may be used. This is the same in the case of the control voltage. The calculation for the correction may be a method of multiplying a difference from the AD conversion value by a predetermined value, and then performing addition and subtraction.

Since the PWM is updated by the following equation: new PWM value = old PWM value + K (feedback voltage value−target value), the following is based on the feedback voltage value and target value after correcting the low-voltage side power supply voltage fluctuation. Configuration. Value: A Difference between target value and latest feedback voltage value Value: B Difference between latest feedback voltage value and previous feedback voltage Assuming that the relationship between high output value and feedback voltage is positive, K
When a large value is used, the rising characteristic of the high-voltage output is improved, but the amount of operation increases near the target value, and ripples are likely to occur due to the large amount of control operation.

When K is reduced, control ripple is not generated because the control operation amount is small, but the start-up characteristic is deteriorated. That is, it is desirable to appropriately change the value of K depending on the difference from the target value and the feedback voltage value at the time of rising, when the output is stable, and the like. Therefore, by obtaining a corresponding value from the data table as shown in FIG. 8 and updating K with the value, it is possible to prevent the output from overshooting immediately after the rising with the fast rising characteristic and to reduce the control ripple when the output is stabilized. Can be suppressed. The value obtained above is integrated with a constant K (K at the start can be large and K at the stable time can be small).

As described above, when the drive voltage fluctuates, the high-voltage output also fluctuates. Therefore, depending on the direction of the fluctuation, the high-voltage output is set for abnormality detection in the case of an output load short-circuit during constant voltage control or an output open during constant current control. The operating margin is reduced for the PWM that is used.

Therefore, as an example, in the case of the abnormality detection processing in which the feedback voltage is 2.0 V or less and the PWM duty is 60% and the state of 60% continues for 100 ms or more in a constant current configuration, the drive voltage and the like decrease. If a voltage fluctuation occurs in the direction in which the high-voltage output decreases, the threshold value of the feedback voltage is corrected in a gradual direction, and in the opposite case, the threshold value is corrected in a stricter direction. This correction may be performed in the same manner as the above-described calculation of calculating and correcting the target value, and either a predetermined value may be added or subtracted from the data table. As a result, it is possible to reduce the difference in the margin and sensitivity for the abnormality detection processing in the machine, and it is possible to reliably prevent the erroneous detection and the abnormality detection from slowing down.

According to the present embodiment, since the fluctuation of the power supply voltage on the low voltage side is detected by the detection circuit, the maximum PWM duty that can be operated can be updated based on the detected value. Even if the abnormal condition is such that high voltage output is not generated even though the voltage is high, the optimum PWM threshold value without taking into account the fluctuation of the low voltage power supply can be handled. Further, since the operable maximum PWM value is updated according to the fluctuation of the low-voltage side power supply voltage, erroneous detection of abnormality detection can be prevented.

In general, the following items are required in PWM control of a high-voltage power supply. (1) The PWM operation amount is increased to speed up the start-up characteristics. (2) No ripple output is generated due to excessive PWM correction. In other words, when starting the output, increase the PWM operation amount,
When the feedback voltage is near the reference value (target value), it is necessary to reduce the PWM operation amount. However, in the embodiment of the present invention, the lookup table is used to reduce the processing time for the control unit, and the operation amount is switched. Is also obtained from the change and the difference from the target value.

That is, since the optimum manipulated variable is always obtained in accordance with the change state and the difference of the feedback voltage, it is possible to improve the rising characteristic and to reduce the ripple output, and it is possible to reduce the ripple output depending on the image forming condition depending on the high voltage output. In the case where the output value is output, the output is stabilized by the same processing, so that the output value can be easily changed as compared with the method of switching the operation amount at a predetermined level.

Further, since the required processing time and calculation time are constant, there is no need to delay the sampling cycle of the high-voltage feedback voltage more than necessary, so that the high-voltage output processing can be performed stably and good image formation can be achieved. We can provide any requirements.

By the way, in the above-described correction calculation, if the accuracy is improved, the control power supply voltage and the drive power supply voltage are all related to the actual feedback voltage value and the target value. The processing time increases significantly. For this reason, it is also possible to divide the processing such as the variation of the control power supply voltage, the variation of the driving power supply voltage, the feedback voltage value and the target value, and correct each correction by the lookup table shown in FIG. .

By having the above table,
The variation of the control power supply voltage and the drive power supply voltage can be corrected without complicated calculations, and the value obtained in the above table is corrected by a predetermined constant and added to the feedback voltage value or target value. The configuration may be such that

According to the present embodiment, whether the leak is at the high voltage output section during the image forming operation, or is the voltage at the low voltage side due to an abnormality of the commercial power supply of the apparatus low voltage side or the apparatus, etc.
It can be easily determined from the high voltage feedback voltage and the output of the power supply voltage detection circuit. If only the feedback voltage fluctuates greatly, it is an abnormality on the high voltage side such as leakage.If both the high voltage feedback voltage value and the power supply voltage detection circuit become abnormal such as a voltage drop, it is not an abnormality of the high voltage section. The low voltage side and low voltage power supply side become abnormal. This makes it possible to determine in detail the high-voltage side or the low-voltage side even with a simple configuration, even with the conventional high-pressure section abnormality caused by the self-diagnosis function or the like, and to provide an accurate self-diagnosis function.

In many cases, the image forming apparatus has a plurality of high-voltage output sections and a plurality of high-voltage feedback voltage values.
Therefore, if there is an abnormality in the power supply section on the low voltage side, etc., the plurality of high voltage feedback voltages fluctuate at substantially the same timing. At this time, the same effect as described above can be obtained by monitoring the output of the power supply voltage detection circuit. Thus, the load of software processing for control can be reduced.

By the way, as a condition for stably controlling the high voltage output during the image forming operation, it is necessary to cope with a high voltage load fluctuation, a low voltage driving voltage fluctuation, and a low voltage control voltage fluctuation. The high voltage output voltage (current) fluctuates due to the high voltage load fluctuation, and the high voltage feedback voltage value also fluctuates. Generally, the main cause of the fluctuation of the feedback voltage is this case, which updates the PWM output.

However, when the feedback voltage fluctuates, the low-voltage driving voltage for generating a high voltage also fluctuates.
In general, the low-voltage drive power supply (24 V, 12 V) is common to the drive power supply for various loads in other image forming apparatuses.
It is affected by voltage fluctuations caused by turning on / off other loads. The same is true for the control voltage fluctuation.
Since it is used as the ADC reference voltage, even if the high-voltage output is constant, the ADC detects it as a different value due to the control voltage fluctuation.

In this embodiment, since the voltage fluctuation on the low voltage side is detected in advance, the fluctuation in the high voltage feedback voltage fluctuation is
The voltage fluctuation on the low voltage side can be corrected by the output value of the power supply voltage detection circuit, and unnecessary updating of the PWM output can be prevented. Thereby, high-voltage output processing can be performed stably, and favorable image forming conditions can be provided.

Further, in the prior art, if the calculation processing only for the high-voltage load fluctuation is performed by all the fluctuation factors, the amount of calculation becomes three times as large as that, and if the calculation time becomes longer, the sampling period of the high-voltage feedback voltage is delayed. However, in the present embodiment, for the voltage fluctuation on the low voltage side, the difference from the previous time, the latest sampling value, and the look-up table are configured to increase the processing time by the calculation, Eliminates the effects of loss of time and quantization errors.

That is, no matter what value is sampled, the processing time and the like required for correcting the voltage fluctuation on the low voltage side are the same. If the high voltage output is corrected based on the corrected feedback voltage value, the influence of the power supply voltage fluctuation on the low voltage side is reduced. Since the necessary processing time and calculation time are constant, it is not necessary to delay the sampling cycle of the high-voltage feedback voltage more than necessary, the high-voltage output processing can be performed stably, and good image forming conditions can be provided.

[0047]

According to the first aspect of the present invention, it is possible to reduce the output variation due to the fluctuation on the low voltage side and the malfunction of the abnormality detection circuit.

According to the second and fifth aspects of the present invention, even in each condition of the high voltage output (steady state, at the time of rising), the CP
It is possible to stabilize the high-voltage output without increasing the U load, and obtain favorable image forming conditions.

According to the third aspect of the present invention, it is possible to accurately grasp the location where the abnormality has occurred, and it is possible to reliably prevent the danger to the high-pressure section due to the abnormality on the low-pressure side.

According to the fourth aspect of the present invention, good image forming conditions can be obtained without affecting the high voltage output value even with the load fluctuation on the low voltage side.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an image forming unit of an image forming apparatus.

FIG. 2 is a control block diagram of the entire image forming apparatus.

FIG. 3 is a configuration diagram of a constant current type high voltage generation circuit.

FIG. 4 is a configuration diagram showing a first example of the ADC shown in FIG. 2;

FIG. 5 is a configuration diagram illustrating a second example of the ADC illustrated in FIG. 2;

FIG. 6 is a characteristic diagram illustrating a change in a high-voltage output due to a change in a control power supply voltage.

FIG. 7 is a characteristic diagram showing a relationship between a change in a driving power supply and a change in a high-voltage output.

FIG. 8 is a diagram showing a data table.

FIG. 9 is a diagram showing a data table.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor 2 corona discharger 3 exposure optical system (optical writing system) 4 developing device 5 transfer belt 6 cleaning device 7 fur brush 8 cleaning blade 9 static eliminator (quenching lamp) 11, 12, 13 roller 14 transfer bias power supply Reference Signs List 15 fixing device 16 fixing roller 17 pressure roller 21 control unit 22 ADC 23 CNT 24 PG Q switching transistor R current detection resistor

Claims (5)

[Claims] 1. A switching PWM signal is supplied to a high voltage generator, and the duty of the PWM signal is updated based on a difference between a feedback voltage value from the high voltage generator and a predetermined reference value to generate a predetermined high voltage output. An image forming apparatus provided with a high-voltage generating circuit, wherein at least one of a power supply voltage of a feedback voltage detecting unit for detecting a feedback voltage from the high-voltage generating unit and a power supply voltage supplied to the high-voltage generating unit is provided.
Of the two power supply voltage values, and according to the output value, P
An image forming apparatus comprising a detection circuit for correcting an upper limit value of a WM signal duty. 2. A switching PWM signal is supplied to a high voltage generator, and the duty of the PWM signal is updated based on a difference between a feedback voltage value from the high voltage generator and a predetermined reference value, and a predetermined high voltage output is output. An image forming apparatus having a high-voltage generating circuit that generates a PWM duty is corrected by a difference between a power supply voltage of a feedback voltage detecting unit that detects a feedback voltage from the high-voltage generating unit and a reference value. Image forming apparatus. 3. A PWM signal for switching is supplied to a high voltage generator, and a duty of the PWM signal is updated by a difference between a feedback voltage value from the high voltage generator and a predetermined reference value to generate a predetermined high voltage output. An image forming apparatus provided with a high-voltage generating circuit, wherein at least one of a power supply voltage of a feedback voltage detecting unit for detecting a feedback voltage from the high-voltage generating unit and a power supply voltage supplied to the high-voltage generating unit is provided.
An image forming apparatus comprising: a detection circuit for detecting fluctuations of two power supply voltage values and stopping a PWM signal when an output value of the power supply voltage value is equal to or more than a predetermined value. 4. A PWM signal for switching is supplied to a high voltage generator, and a duty of the PWM signal is updated based on a difference between a feedback voltage value from the high voltage generator and a predetermined reference value to generate a predetermined high voltage output. An image forming apparatus provided with a high-voltage generating circuit, wherein at least one of a power supply voltage of a feedback voltage detecting unit for detecting a feedback voltage from the high-voltage generating unit and a power supply voltage supplied to the high-voltage generating unit is provided.
An image forming apparatus comprising: a detection circuit for detecting a change in two power supply voltage values and correcting a reference value based on the output. 5. A switching PWM signal is supplied to a high voltage generator, and a duty of the PWM signal is updated by a difference between a feedback voltage value from the high voltage generator and a predetermined reference value to generate a predetermined high voltage output. An image forming apparatus provided with a high-voltage generating circuit, wherein at least one of a power supply voltage of a feedback voltage detecting unit for detecting a feedback voltage from the high-voltage generating unit and a power supply voltage supplied to the high-voltage generating unit is provided.
An image forming apparatus, comprising: a detection circuit for detecting a change in two power supply voltage values and correcting a feedback voltage value based on a combination of the outputs.