KR20210125762A - Alternating current voltage selection for organic photo conductor charger based on direct current saturation thereof - Google Patents

Abstract

An image forming device is disclosed. The image forming device includes: a print engine including a charging member for charging a photosensitive member; a power device including a DC power circuit for generating DC power, an AC power circuit for generating AC power, superimposing DC power on the generated AC power, and providing the superimposed power to the charging member, and a sensing circuit for detecting an output value of a comparator of the DC power circuit; and a processor controlling the AC power circuit to vary the size of the AC power, and searching for a current saturation point of the charging member based on an output value detected by the sensing circuit while the size of the AC power is varied.

Description

AC voltage selection using saturated DC current flowing through the photoreceptor charger

An image forming apparatus is an apparatus for generating, printing, receiving, and transmitting image data, and representative examples include a printer, a scanner, a copier, a fax machine, and a multifunction device that integrates these functions.

1 is a block diagram illustrating a simplified configuration of an image forming apparatus according to an embodiment of the present disclosure;
2 is a block diagram illustrating a detailed configuration of an image forming apparatus according to an embodiment of the present disclosure;
3 is a view showing an embodiment of a specific configuration of the print engine of FIG. 1;
4 is a view showing an embodiment of a specific configuration of the power supply device of FIG. 1;
5 is a circuit diagram of a power supply device having a sensing circuit according to the first embodiment;
6 is a circuit diagram of a sensing circuit according to a second embodiment;
7 is a view showing the relationship between the charging current and the sensing current;
8 is a view for explaining a charge control method according to an embodiment of the present disclosure.

Hereinafter, various embodiments will be described in detail with reference to the drawings. The embodiments described below may be modified and implemented in various other forms. In order to more clearly describe the features of the embodiments, detailed descriptions of matters widely known to those of ordinary skill in the art to which the following embodiments belong will be omitted.

On the other hand, in the present specification, when a component is "connected" with another component, it includes not only a case of 'directly connected', but also a case of 'connected with another component interposed therebetween'. In addition, when a component "includes" another component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

As used herein, the term “image forming job” may mean various jobs (eg print, scan, or fax) related to an image, such as forming an image or creating/storing/transmitting an image file, and “job ( job)” not only means an image forming job, but may also include all a series of processes necessary for performing the image forming job.

In addition, the term "image forming apparatus" refers to a device that prints print data generated by a terminal device such as a computer on a recording paper. Examples of such an image forming apparatus include a copier, a printer, a facsimile, or a multi-function printer (MFP) that complexly implements these functions through one device.

The image forming apparatus performs a charging operation of charging the photosensitive member to a predetermined potential. If the charging voltage is higher than the reference value, the life of the photosensitive member is shortened. If the charging voltage is lower than the reference value, the print quality deteriorates. Therefore, an appropriate charging voltage should be used. .

In order to supply an appropriate charging voltage to the photosensitive member, a method capable of measuring the current saturation point of the charging member is required. Hereinafter, an image forming apparatus capable of measuring a current saturation point without using a bulky and expensive current sensor will be described.

1 is a block diagram illustrating a simplified configuration of an image forming apparatus according to an exemplary embodiment of the present disclosure.

Referring to FIG. 1 , the image forming apparatus 100 may include a power supply 110 , a print engine 120 , and a processor 130 .

The power supply 110 may supply power to each component in the image forming apparatus 100 . For example, the power supply 110 may receive commercial AC power from the outside and convert the input commercial AC power into DC power.

The power supply 110 may generate charging power and provide the generated charging power to the charging member 121 . Here, the charging power may be a power in which a DC power of a preset magnitude and an AC voltage of a peak voltage of a preset magnitude are superimposed.

For this operation, the power supply 110 may include an AC power circuit 200 and a DC power circuit 300 . Here, the DC power circuit 300 may generate DC power of a preset size, and the AC power circuit 200 generates AC power having a preset peak voltage, and overlaps the generated AC power and DC power to output can do. A detailed configuration and operation of the AC power circuit 200 and the DC power circuit 300 will be described later with reference to FIG. 5 .

The power supply 110 may include a sensing circuit 400 for detecting saturation of the charging current. Here, the sensing circuit 400 may sense an output value of the comparator of the DC power circuit 300 . A detailed configuration and operation of the sensing circuit 400 will be described later with reference to FIGS. 5 and 6 .

The print engine 120 forms an image. For example, the print engine 120 may form an image using an electrophotographic method, and may include a charging member 121 .

The charging member 121 may charge the photosensitive member to a predetermined potential. For example, the charging member 121 may charge the photosensitive member using charging power provided from the power supply 110 . A detailed operation of the charging member 121 will be described later with reference to FIG. 3 .

The processor 130 controls each component in the image forming apparatus 100 . The processor 130 may be configured as a single device such as a CPU, or may be configured as a plurality of devices such as a clock generation circuit, a CPU, and a graphic processor.

The processor 130 may determine whether it is necessary to determine the charging voltage. For example, the processor 130 may determine that the image forming apparatus 100 is initially installed, consumables (eg, photoconductors, toner, etc.) in the image forming apparatus 100 are changed, or the image forming apparatus 100 is installed. When more than a preset number of printing is performed, it may be determined that the determination of the charging voltage is necessary.

If it is necessary to determine the charging voltage, the processor 130 may control the power supply 110 to supply the superimposed power of the DC power of the preset size and the AC power of the preset peak voltage to the charging member 121 . have.

In addition, the processor 130 may sense the output value of the comparator of the DC power circuit 300 using the sensing circuit 400 . The reason for using the output value of the comparator will be described later with reference to FIG. 5 .

When the output value of the comparator in the state in which the initial AC power is supplied is sensed, the processor 130 may control the power supply 110 to vary the peak voltage of the AC power. For example, the processor 130 may control the power supply 110 to gradually increase the peak voltage of the AC power. For example, if the initial AC power supply is 300 Vpp, it is increased stepwise by + 100 Vpp, that is, 300 Vpp, 400 Vpp, 500 Vpp, ... . It is possible to gradually increase the peak voltage of AC power as shown in

In this case, the processor 130 may maintain the DC power at a preset value and continuously sense the output value of the comparator of the DC power circuit 300 using the sensing circuit 400 .

In addition, the processor 130 may determine whether the current of the charging member is saturated by checking whether the change in the output value of the comparator is less than a preset value according to the change in the peak voltage of the AC power.

If it is determined that the charging member is saturated, the processor 130 may stop the operation of searching for the current saturation point of the charging member and set the peak value of the AC voltage at the saturation point as the AC voltage value at the time of charging.

Accordingly, after the charging voltage is determined, the processor 130 controls the power supply device 110 to provide charging power in which the preset DC voltage and the previously determined AC voltage are superimposed to the charging member 121 when a print command is input. can do.

Meanwhile, although only a simple configuration of the image forming apparatus has been illustrated and described above, various configurations may be additionally provided in implementation. This will be described below with reference to FIG. 2 .

2 is a block diagram illustrating a detailed configuration of an image forming apparatus according to an exemplary embodiment of the present disclosure.

Referring to FIG. 2 , the image forming apparatus 100 includes a power supply 110 , a print engine 120 , a processor 130 , a communication device 140 , a memory 150 , a display 160 , and a manipulation input device ( 170) may be included.

Since the power supply 110 , the print engine 120 , and the processor 130 have been described with reference to FIG. 1 , a redundant description will be omitted.

The communication device 140 is formed to connect the image forming apparatus 100 to an external device, and is connected through a local area network (LAN) and the Internet network, as well as a USB (Universal Serial Bus) port and A form connected through a wireless module is also possible. Here, the wireless module may be WiFi, WiFi Direct, Near Field Communication (NFC), Bluetooth, or the like.

In addition, the communication device 140 may receive print data from an external device. Here, the print data means data converted into a printable format by the image forming apparatus, and may be, for example, data in a printer language such as Postscript (PS) or Printer Control Language (PCL).

The memory 150 may store print data. The memory 150 may be implemented not only as a storage medium in the image forming apparatus 100 , but also as an external storage medium, a removable disk including a USB memory, or a web server through a network.

In addition, the memory 150 may store setting information for each printing environment. Here, the setting information is various setting values related to the printing operation operation, such as the setting temperature for each environment such as the type of printing paper or temperature/humidity, and the charging voltage, and information about the peak voltage of the AC power corresponding to the current saturation point can be stored.

The display 160 displays various types of information provided by the image forming apparatus 100 . For example, the display 160 may display a user interface window for selecting various functions provided by the image forming apparatus 100 . The display 160 may be a monitor such as a liquid crystal display (LCD), a cathode ray tube (CRT), or organic light emitting diodes (OLED).

The manipulation input device 170 may receive a function selection and a control command for the corresponding function from the user. Here, the function may include a print function, a copy function, a scan function, a fax transmission function, and the like. Such a function control command may be input through a control menu displayed on the display 160 .

The manipulation input device 170 may be implemented as a plurality of buttons, a keyboard, a mouse, and the like, or may be implemented as a touch screen capable of simultaneously performing the functions of the above-described display 160 .

As described above, the image forming apparatus 100 according to the present exemplary embodiment can effectively check the current saturation point without using a separate current sensor for measuring the photoreceptor surface current. In addition, the image forming apparatus 100 can provide the photoconductor with charging power corresponding to the current saturation point detected at the time of printing, that is, the charging operation can be performed using minimal AC power, and thus image quality is deteriorated. It is possible to secure a long lifespan of the photoreceptor while preventing

1 and 2 , the sensing circuit 400 is illustrated and described as being a component in the power supply device 110 , but in implementation, the sensing circuit 400 may be a component in the print engine 120 . Also, the AC power circuit and DC power circuit in the power supply device 110 may also be configured in the print engine 120 .

FIG. 3 is a diagram illustrating an embodiment of a detailed configuration of the print engine of FIG. 1 .

Referring to FIG. 3 , the print engine 120 operates in a tandem manner. Here, the tandem method is a color printing method in which photoreceptors for each color individually form images for high-speed output. Hereinafter, it will be described that the print engine includes a plurality of photoconductors and a plurality of charging members on the assumption that color printing is possible.

An electrostatic latent image may be formed on the photoconductors 123-1, 123-2, 123-3, and 123-4. The photosensitive members 123-1, 123-2, 123-3, and 123-4 may be referred to as OPCs, photosensitive drums, photosensitive belts, or the like, depending on their shape. Here, the first photosensitive member 123-1 is a yellow photosensitive member that forms yellow, the second photosensitive member 123-2 is a purple photosensitive member that forms purple, and the third photosensitive member 123-3 is a blue photosensitive member that forms blue. It is a photoreceptor, and the fourth photoreceptor 123 - 4 may be a black photoreceptor that forms a black color.

The charging members 121-1, 121-2, 121-3, and 121-4 use the charging power provided from the power supply 110 to form the photosensitive members 123-1, 123-2, 123-3, and 123-4. ) each surface can be charged with a uniform potential. The charging members 121-1, 121-2, 121-3, and 121-4 may be implemented in various configurations such as a corona charging member, a charging roller, and a charging brush.

An exposure machine (not shown) changes the surface potential of the photosensitive members 123-1, 123-2, 123-3, and 123-4 according to image information to be printed, thereby changing the photosensitive members 123-1, 123-2, 123-3, 123-4) can form an electrostatic latent image on the surface. A developing device (not shown) accommodates a developer therein, and supplies the developer to the electrostatic latent image to develop the electrostatic latent image into a visible image.

The visible images formed on the photoconductors 123-1, 123-2, 123-3, and 123-4 may be primarily transferred to the intermediate transfer belt IBT. And the image transferred to the intermediate transfer belt (IBT) may be transferred to the printing paper by the transfer machine.

And the image may be fixed on the printing paper by a fixing device (not shown). The print job is completed by such a series of processes.

The power supply 110 may individually supply charging power in which DC power and AC power are superimposed to each of the charging members 121-1, 121-2, 121-3, and 121-4 during the charging operation described above. A detailed configuration and operation of the power supply device 110 for supplying a plurality of charging power will be described below with reference to FIG. 4 .

4 is a diagram illustrating an embodiment of a specific configuration of the power supply device of FIG. 1 .

Referring to FIG. 4 , the power supply 110 includes a plurality of AC power circuits 200-1, 200-2, 200-3, and 200-4, and a plurality of DC power circuits 300-1, 300-2, and 300- 3 and 300-4), a plurality of sensing circuits 400-1, 400-2, 400-3, and 400-4, and a MUX 115 may be included.

Each of the plurality of DC power circuits 300-1, 300-2, 300-3, and 300-4 may generate DC power. For example, the DC power circuit 300 may receive a control signal from the processor 130 and generate DC power having a size corresponding to the input control signal. Here, the input control signal may be a pulse width modulation (PWM) signal. A detailed configuration and operation of the DC power circuit 300 will be described later with reference to FIG. 5 .

Each of the plurality of AC power circuits 200 - 1 , 200 - 2 , 200 - 3 and 200 - 4 may generate AC power. For example, the AC power circuit 200 may receive a control signal from the processor 130 and generate AC power having a magnitude corresponding to the input control signal. In addition, the AC power circuit 200 may overlap the generated AC power and the DC power generated by the DC power circuit 300 to output to the charging member 121 . A specific configuration and operation of the AC power circuit 200 will be described later with reference to FIG. 5 .

The plurality of sensing circuits 400-1, 400-2, 400-3, and 400-4 measure the output voltage value of each of the comparators of the DC power circuits 300-1, 300-2, 300-3, and 300-4. can sense The reason for finding the saturation point of the charging current using the voltage value of the output node of the comparator among various nodes in the power supply device 110 will be described later with reference to FIG. 7 .

The MUX 115 may selectively output the output values of the plurality of sensing circuits 400-1, 400-2, 400-3, and 400-4 to the processor 130 (or MCU). For example, the MUX 115 may be individually connected to output values of the plurality of sensing circuits 400-1, 400-2, 400-3, and 400-4, and according to a control signal, the plurality of sensing circuits 400 -1, 400-2, 400-3, 400-4) may be output to an analog-digital converter (ADC) port of the processor 130 .

On the other hand, when the processor 130 has a sufficient number of ADC ports, the output voltage value of each of the plurality of sensing circuits 400-1, 400-2, 400-3, and 400-4 may be directly connected to the processor 130. have. However, if the ADC port of the processor 130 is not sufficient, as shown, a plurality of sensing circuits 400-1, 400-2, 400-3, 400-4 using only one ADC port using the MUX 115. ) can be input.

In the case of searching for saturation points for a plurality of charging voltages as described above, the processor 130 may sequentially sense the output voltage values of each of the four channels while simultaneously controlling the four channels.

In addition, when the processor 130 finds the saturation point for any one channel during the above-described process, the processor 130 terminates the control of the channel for which the saturation point is found, and continuously searches for the saturation point only for the remaining channels. can be done In addition, the processor 130 may end the operation of determining the charging voltage when the saturation points for all channels are found.

In addition, the processor 130 may control the power supply 110 to supply charging power corresponding to the corresponding channel for each channel during the printing process.

5 is a circuit diagram of a power supply device having a sensing circuit according to the first embodiment.

Referring to FIG. 5 , the power supply 110 may include an AC power circuit 200 , a DC power circuit 300 , and a sensing circuit 400 .

The AC power circuit 200 may include an AC frequency circuit 210 , a low pass filter 220 , an amplifier 230 , an AC switching circuit 240 , a transformer 250 , and an AC feedback circuit 260 .

The frequency switching circuit 210 may perform a switching operation at a preset frequency. For example, the frequency switching circuit 210 may receive a PWM control signal and perform a switching operation with a frequency corresponding to the received control signal. Here, the frequency may be 3 kHz to 5 kHz. In addition, the control signal may serve to adjust the frequency of the AC power generated by the AC power circuit 200 .

The low-pass filter 220 may receive a signal corresponding to the target AC voltage and output a voltage value corresponding to the target AC voltage. For example, the low-pass filter 220 may include two resistors connected in series with respect to a predetermined voltage and an RC circuit for charging an electric charge according to an input signal. Here, the target AC voltage is a PWM signal having a PWM duty, and may serve to adjust the peak-to-peak of the AC power according to the PWM duty.

The amplifier 230 may compare and amplify the feedback value of the AC power circuit 200 with the output value of the low-pass filter 220 . For example, the amplifier 230 may be implemented as an OP-AMP, and a negative terminal of the OP-AMP may be commonly connected to an output terminal of the AC feedback circuit 260, a parallel-connected capacitor, and a resistor, respectively, and a positive terminal The terminal may be connected to the output terminal of the low pass filter 220 through a resistor.

The AC switching circuit 240 may selectively provide power to the primary coil of the transformer 250 according to the output of the amplifier 230 and the output of the AC frequency circuit 210 . For example, the AC switching circuit 240 may switch the DC value output from the amplifier 230 to a level of 3 kHz to 5 kHz.

The transformer 250 includes a primary coil and a secondary coil, and may amplify and output the voltage on the primary coil side to the secondary side according to the turns ratio of the two coils. For example, one end of the primary coil of the transformer 250 is connected to the AC switching circuit 240 and the other end is grounded, and the secondary coil has one end connected to the output terminal of the power circuit, and the other end is It can be connected to the output terminal of a DC power circuit.

The AC feedback circuit 260 may provide information on the magnitude of the output value of the secondary coil of the transformer 250 to the amplifier 230 . For example, in order to provide only AC magnitude information, the AC feedback circuit 260 may extract only AC magnitude information using circuit elements such as capacitors and diodes and provide it to the amplifier 230 . By feeding back the AC magnitude information in this way, it is possible to maintain a constant Vpp even when the output load varies.

The DC power circuit 300 may generate and output DC power having a preset size. For example, the DC power circuit 300 may include a low pass filter 310 , a comparator 320 , a DC switching circuit 330 , a transformer 340 , a rectifier circuit 350 , and a DC feedback circuit 360 . can

The low-pass filter 310 may receive a signal corresponding to the target DC voltage and output a voltage value corresponding to the target DC voltage. For example, the low-pass filter 310 may include two resistors connected in series with respect to a preset voltage and an RC circuit for charging an electric charge according to an input signal. Here, the target DC voltage may be a PWM signal having a PWM duty.

The comparator 320 may compare the feedback value of the DC power circuit with the output value of the low-pass filter. For example, the comparator 320 may be implemented as an OP-AMP, a negative terminal of the OP-AMP may be connected to an intermediate node of two series-connected resistors of the low-pass filter 310, and a positive terminal may be a low The capacitor node of the pass filter 310 may be commonly connected to the output node of the DC feedback circuit 360 .

The DC switching circuit 330 may selectively provide power to the primary coil of the transformer according to the output of the comparator 320 . For example, the DC switching circuit 330 may include a switching element for selectively turning on/off the middle of the primary coil of the transformer 340 and an RC circuit connected to one end of the primary coil.

The transformer 340 may include a primary coil and a secondary coil, and may amplify and output the primary coil side voltage to the secondary side according to the turns ratio of the two coils. For example, one end of the primary coil may be connected to a preset power source, the other end may be connected to the RC circuit of the DC switching circuit 330 , and both ends of the secondary coil may be connected to the rectifier circuit 350 . .

The rectifier circuit 350 may rectify and output the output voltage of the secondary coil. For example, the rectifier circuit 350 may include two capacitors and two diodes, and may be a back voltage amplification circuit that simultaneously amplifies and rectifies a voltage.

The DC feedback circuit 360 may provide the voltage value of the output terminal of the rectifier circuit 350 to the comparator 320 . For example, the DC feedback circuit 360 may be configured as a resistor. As such, since the amount of change in the DC current of the output terminal is fed back to the comparator 320 , the DC power circuit 300 may maintain a constant voltage even if the output load is changed.

The sensing circuit 400 may sense an output value of the comparator 320 . The sensing circuit 400 may include a resistor 410 , a rectifier circuit 420 , and a voltage divider circuit 430 .

One end of the resistor 410 may be connected to an output terminal of the comparator 320 of the DC power circuit 300 , and the other end may be connected to one end of the rectifying circuit 420 .

The rectifier circuit 420 may rectify the output voltage of the comparator 320 . For example, the rectifier circuit 420 may include two diodes and a capacitor.

The voltage divider circuit 430 may divide the output value of the rectifier circuit 420 by voltage. For example, the voltage divider circuit 430 includes two resistors, and an intermediate node of the two resistors may be connected to the ADC port of the processor 130 .

6 is a circuit diagram of a sensing circuit according to the second embodiment. Specifically, the second embodiment is an embodiment in which the output value of the comparator is amplified and used in order to improve misrecognition when the output value of the comparator is low.

Referring to FIG. 6 , the sensing circuit 500 may sense an output value of the comparator. For example, the sensing circuit 500 may be positioned to replace the sensing circuit 400 of FIG. 5 . The sensing circuit 500 may include a resistor 510 , an amplifier circuit 520 , and a voltage divider circuit 530 .

The resistor unit 510 may include a fifth resistor R5 . One end of the fifth resistor R5 may be connected to the output terminal of the comparator of the DC power circuit, and the other end may be connected to one end of the amplification circuit 520 .

The amplifying circuit 520 may amplify and output the output voltage of the comparator. For example, the amplification circuit 520 may include an OP-AMP, a first capacitor C1 , a second capacitor C2 , a first resistor R1 , and a second resistor R2 .

In the OP-AMP, a positive terminal is commonly connected to one end of the fifth resistor R5 and one end of the first capacitor C1, and a negative terminal is one of the first resistor R1 and the second capacitor C2. However, it is commonly connected to one end of the second resistor R2, and the output terminal is common to the other end of the second capacitor C2, the other end of the second resistor R2, and one end of the third resistor R3. can be connected

One end of the first capacitor C1 may be commonly connected to the positive terminal of the OP-AMP and one end of the fifth resistor R5, and the other end may be grounded.

The second capacitor C2 may have one end commonly connected to a negative terminal of the OP-AMP, one end of the first resistor R1, and one end of the second resistor R2, and the other end of the OP-AMP may be connected in common. The output terminal may be commonly connected to the other end of the second resistor R2 and one end of the third resistor R3.

One end of the first resistor R1 may be commonly connected to a negative terminal of the OP-AMP, one end of the second capacitor C2, and one end of the second resistor R2, and the other end may be grounded. .

One end of the second resistor R2 may be commonly connected to the negative terminal of the OP-AMP, one end of the second capacitor C2, and one end of the first resistor R1, and the other end of the OP-AMP The output terminal may be commonly connected to the other end of the second capacitor C2 and one end of the third resistor R3.

Through this configuration, when the voltage Vin is input, the amplifying circuit 520 may output the amplified voltage as (1+R2/R1)*Vin. Through this amplification operation, the resolution of the ADC port of the processor can be improved.

The voltage divider circuit 530 may divide the output value of the amplification circuit 520 by voltage. For example, the voltage divider circuit 530 may include a third resistor and a fourth resistor.

One end of the third resistor R3 may be connected to the output terminal of the amplifying circuit 520 , and the other end may be connected to the ADC port of the processor 130 and one end of the fourth resistor R4 .

One end of the fourth resistor R4 may be connected to the ADC port of the processor 130 and the other end of the third resistor R3, and the other end may be grounded.

Through this configuration, the voltage divider circuit 530 may divide the output voltage of the amplification circuit 520 by a voltage ratio of R3/R4 and output it.

7 is a diagram illustrating a relationship between a charging current and a sensing current.

The surface potential of the photosensitive member may be determined by the amount of DC current flowing between the photosensitive member and the charging member. Accordingly, it is possible to sense the surface potential of the photosensitive member by measuring the amount of DC current flowing between the photosensitive member and the charging member even if the surface potential of the photosensitive member is not measured.

For example, if a surface potential of 500 V is to be formed on the photosensitive member, even if the surface potential of the photosensitive member is not measured, if a current of 36 μA flows between the photosensitive member and the charging member, the surface potential of the photosensitive member can be 500 V have.

On the other hand, when the photosensitive member is charged using only the DC power source, uniform charging is not performed according to the lifetime of the photosensitive member, which may adversely affect image quality. Conversely, if only AC voltage is applied, the surface potential of the photoreceptor can be made uniform, but the lifespan of the photoreceptor is shortened.

Therefore, in order to prevent deterioration of image quality while maintaining the life of the photoconductor, it is necessary to use both DC power and AC power, but use the minimum AC power. Accordingly, in the present disclosure, in a state in which DC power of a preset size is applied, charging power in which the minimum AC power is superimposed is used.

Here, the minimum AC power is a point in time when the amount of DC current flowing between the photosensitive member and the charging member is saturated, and the present disclosure uses a fixed DC power source and a gradually increasing AC power source to find this point.

As shown in FIG. 7 , as the peak voltage of the AC power increases, the amount of DC current provided to the photoconductor also increases, and the output value measured by the sensing circuit increases in proportion to this.

And when the AC peak voltage exceeds a certain level (eg, 500 Vpp), the charging DC current is saturated, and it can be confirmed that the actual charging current (dashed line in FIG. 5 ) maintains a constant value. In addition, it can be confirmed that the output value sensed by the sensing circuit 400 also maintains a substantially constant value when the charging DC current is saturated.

Even when the AC peak voltage is increased as described above, the point at which the change in the magnitude of the DC current is very small or the point at which the DC current starts to be maintained at a constant value is the point at which the amount of the DC current is saturated. Therefore, the saturation point of the charged DC current can be confirmed by using the change in the voltage value of the output terminal of the comparator.

On the other hand, when the voltage of another node (eg, an output node, etc.) in the DC power circuit is sensed, there is a problem that the value of the corresponding node also increases due to AC noise generated by the connected AC power even if there is no change in the amount of DC current. However, since the influence of AC noise is small on the output terminal of the comparator in the DC power circuit, the present disclosure uses the voltage of the output terminal of the comparator of the DC power circuit to find the saturation point.

As such, when the voltage of the AC peak is above a certain level, that is, when the charging DC current is saturated, the sensed output value no longer increases, the processor 130 increases the peak voltage of the AC power step by step, and When the change becomes less than or equal to a certain value, the AC power can be used as the charged AC power size.

For example, if the AC peak voltage is increased in the order of 300 Vpp, 400 Vpp, 500 Vpp, 600 Vpp, 700 Vpp, the difference between the previous output value and the current output value is 0.1 (300 Vpp vs 400 Vpp), 0.06 (400 Vpp). vs 500 Vpp), 0.01 (500 Vpp vs 600 Vpp), or 0 (600 Vpp vs 700 Vpp). In this case, the immediately preceding peak voltage (500 Vpp) when the difference value becomes 0.01 may be set as the AC charging voltage during the charging operation.

On the other hand, in implementation, the current peak voltage (600 Vpp) can be set as the AC charging voltage during the charging operation, and the AC voltage can be obtained by using an intermediate value between the two values (eg, 550 Vpp) or by using a specific equation. may decide

8 is a view for explaining a charge control method according to an embodiment of the present disclosure.

Referring to FIG. 8 , charging power obtained by superimposing DC power on AC power may be supplied to the charging member ( S810 ). For example, the minimum AC power may be superimposed on the DC power of a preset size. For example, the DC power supply may be -300 V, and the minimum AC power supply may be 300 Vpp. These figures are merely examples and may be changed according to the performance of the image forming apparatus and the surrounding environment when implemented.

In addition, it is possible to sense an output value of the comparator whose value is changed in response to the magnitude of the current flowing through the charging member (S820). For example, an output value of the sensing circuit may be checked, and the checked output value may be stored.

Then, the peak voltage of the AC power may be varied, and a current saturation point of the charging member may be searched based on the sensed output value during the variation of the peak voltage ( S830 ). For example, the peak voltage of the AC power may be gradually increased, and an output value of the sensing voltage at the increased time may be detected. In addition, it may be determined whether the charging current is saturated by whether a difference between the sensed output value and the output value sensed immediately before is less than or equal to a predetermined value.

Then, the AC voltage and the DC voltage at the current saturation point may be determined as the charging voltage (S840). For example, if the difference between the sensed output value and the output value detected immediately before is equal to or less than a predetermined value, the AC power value and the DC voltage value constituting the charging power at the corresponding time point may be set as the charging voltage value.

Accordingly, in the charging control method according to the present exemplary embodiment, it is possible to effectively check the current saturation point without using a separate current sensor for measuring the photoreceptor surface current. In addition, the present charging control method can provide charging power to the photoconductor using the determined current saturation point, thereby preventing image quality deterioration and ensuring a long lifespan of the photoconductor.

In addition, the game control method as described above may be implemented as at least one execution program for executing the driving control method as described above, and the execution program may be stored in a non-transitory computer-readable recording medium.

Here, the non-transitory computer-readable recording medium may be a compact disc (CD), a digital video disc (DVD), an HDD, a solid state drive (SSD) Blu-ray disc, a USB, a memory card, or a read-only memory (ROM).

In the above, preferred embodiments of the present disclosure have been shown and described, but the present disclosure is not limited to the specific embodiments described above, and without departing from the gist of the present disclosure as claimed in the claims, in the technical field to which the disclosure pertains. Any person skilled in the art can make various modifications, of course, and such modifications are within the scope of the claims.

100: image forming apparatus 110: power supply
120: print engine 130: processor
140: communication device 150: memory
160: display 170: operation input device
200: AC power circuit 300: DC power circuit
400: sensing circuit

Claims (15)

In the image forming apparatus,
a print engine including a charging member for charging the photosensitive member;
A DC power circuit for generating DC power, an AC power circuit for generating AC power and superimposing the DC power on the generated AC power to provide the charging member to the charging member, and a sensing circuit for sensing an output value of a comparator of the DC power circuit a power supply comprising; and
A processor that controls the AC power circuit to vary the size of the AC power, and searches for a current saturation point of the charging member based on an output value sensed by the sensing circuit while the size of the AC power is varied. forming device. According to claim 1,
The processor is
An image forming apparatus for controlling the power supply to vary a peak voltage of the AC power in a state in which DC power having a predetermined size is output. According to claim 1,
The processor is
An image forming apparatus for controlling the power supply to increase the peak voltage of the AC power in steps of a predetermined size. 4. The method of claim 3,
The processor is
The image forming apparatus determines that the current of the charging member is saturated when the change in the output value according to the change in the peak voltage of the AC power is less than a preset value. According to claim 1,
The processor is
An image forming apparatus for controlling the print engine to perform a printing job, and controlling the power supply device to supply AC power and DC power corresponding to the current saturation point to the charging member during the printing job. According to claim 1,
The DC power circuit is
a low-pass filter receiving a signal corresponding to a target DC voltage and outputting a voltage value corresponding to the target DC voltage;
a comparator comparing a feedback value of the DC power circuit with an output value of the low-pass filter;
a transformer including a primary coil and a secondary coil;
a DC switching circuit selectively providing power to the primary coil of the transformer according to an output of the comparator; and
and a rectifier circuit for rectifying and outputting the output voltage of the secondary coil. 7. The method of claim 6,
The sensing circuit is
a rectifying circuit for rectifying the output voltage of the comparator; and
and a voltage divider circuit for voltage dividing the output value of the rectifier circuit. 7. The method of claim 6,
The sensing circuit is
an amplifying circuit for amplifying the output voltage of the comparator; and
and a voltage divider circuit for voltage dividing the output value of the amplification circuit. 7. The method of claim 6,
The rectifier circuit is
and a back pressure amplifier circuit for rectifying and back pressure amplifying the output voltage of the secondary coil. According to claim 1,
The AC power circuit comprises:
a low-pass filter receiving a signal corresponding to a target AC voltage and outputting a voltage value corresponding to the target AC voltage;
an amplifier comparing and amplifying a feedback value of the AC power circuit with an output value of the low-pass filter;
a transformer including a primary coil and a secondary coil;
AC frequency circuit for switching operation at a preset frequency; and
An AC switching circuit selectively providing power to the primary coil of the transformer according to the output of the amplifier and the output of the AC frequency circuit;
The secondary coil of the transformer,
An image forming apparatus having one end connected to the output terminal of the DC power circuit and the other end connected to the charging member. 11. The method of claim 10,
The signal is a signal having a PWM duty corresponding to the target AC voltage,
The processor is
An image forming apparatus for transmitting a signal whose PWM duty is varied in stages to the low-pass filter. According to claim 1,
The print engine is
comprising a plurality of charging members;
The power supply is
a plurality of DC power circuits corresponding to the plurality of charging members, a plurality of AC power circuits, and a plurality of sensing circuits,
The power supply is
and a MUX selectively providing output values of the plurality of sensing circuits to the processor. According to claim 1,
The AC power circuit comprises:
An image forming apparatus for generating a sinusoidal wave AC having a frequency within 3 kHz to 5 kHz. A method for controlling charging of an image forming apparatus, the method comprising:
supplying charging power by superimposing DC power on AC power to a charging member;
detecting an output value of a comparator in a DC power circuit whose value is changed in response to the amount of current flowing through the charging member;
varying the peak voltage of the AC power and searching for a current saturation point of the charging member based on the sensed output value during the variation of the peak voltage; and
and determining an AC voltage and a DC voltage at the current saturation point as a charging voltage. 15. The method of claim 14,
The searching step is
In a state in which DC power of a predetermined size is output, the peak voltage of the AC power is increased by a unit of a predetermined size, and when the change in the output value according to the change in the peak voltage of the AC power is less than the predetermined value, the charging member is A charging control method for determining that the current is saturated.

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