JP2792664B2 - Drive control device for light emitting element - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to devices such as an LED printer, an EL printer, and a facsimile in which light emitting elements are arranged in an array and printing is performed by an electrophotographic process. The present invention relates to a drive control device for a light emitting element that controls the driving of the light emitting device.

[Conventional technology]

As a device in which light emitting elements are arranged in an array inside, for example, an LED printer in which an LED (light emitting diode) light emitting element is disposed is known. Such a printer device is a device that selectively emits light from light-emitting elements provided in a row based on print data, performs optical writing on a photoconductor for each line, and creates an image on paper by an electrophotographic process.

However, since a large number of light emitting elements are used in the above-described device, and these light emitting elements require a large current for driving (for example, 10 to 15 mA per light emitting element),
The light emitting elements are driven by time division.

FIG. 10 is a diagram showing a drive circuit diagram of such a light emitting element. Each of the light emitting element arrays 1-1 to 1-n is formed of 2k light emitting elements, and each of the 2k light emitting elements in each of the light emitting element arrays 1-1 to 1-n has one end corresponding to a terminal L ₁ to L _{1. 2k} , and the other end is connected to one of the common electrodes COM1 to COMn. The light emitting element is driven by the common electrode COM1.
~ COMn are sequentially supplied to each of the light emitting element arrays 1-
While one of 1 to 1-n is selected, the print data D is input to the cascade-connected segment drivers 2 and 3 in synchronization with the rise of the clock signal CK as shown in FIG. Thereafter, from the outputs ₁ to _k of the segment drivers 2 and 3 synchronized with the latch signal LA, the light emitting element array 1-
1 to 1-n. Output of segment driver 2
₁ to _k are terminals L ₁ to L ₁ of each light emitting element array 1-1 to ₁ -n.
L _k and outputs ₁ to _{k of the} segment driver 3
Are connected to terminals L _{k + 1 to} L _2k of each of the LED arrays 1-1 to 1-n. Therefore, the outputs of segment drivers 2 and 3
_The video data D output from ₁ to _k is output to _{one of} the light emitting element arrays 1-1 to 1-n selected by the selection signal, and the lighting of each light emitting element is controlled according to the video data D. This processing is performed for common electrodes COM1 to COMn.
By repeating according to the selection signal sequentially output to the above, optical writing of one line is performed by time division.

FIG. 12 shows another conventional light emitting element drive control circuit. In the case of this conventional example, similarly to the conventional example of FIG. 10, each of the light emitting element arrays 1-1 to 1-n has common electrodes COM1 to COMn.
Each light-emitting element selected by the selection signal input from the lighting control in accordance with the video data to be input to the terminal L ₁ ~L _2k. However, in the case of the conventional example shown in FIG. 12, in order to lengthen the cycle of the clock signal input to the segment drivers 4 and 5, the segment drivers 4 and 5 are made independent without cascade connection, and are separated as shown in FIG. Clock signal
Video data D is input to segment drivers 4 and 5 using CK ₁ and CK ₂ . However, since the video data D is output serially from a control circuit (not shown), in this case, the output order of the video data D has been previously changed. That is, as shown in FIG. 13, “first data” → “k + 1th data” → “second data” →
"K + 2 th data" → video data D from the control circuit in the order of ... is outputted, "first data" in this video data D, "second data" a ... clock signal CK ₁ Driver 4 in synchronization with the rising edge of
Enter to, have entered "(k + 1) th data", the "k + 2 th data" ... in synchronization with the rising edge of the clock signal CK ₂ to zero segment driver 5. In this way,
The input state of the video data D after being input to each of the segment drivers 4 and 5 is the same as in FIG. 10, and the video data D is output to the light emitting element arrays 1-1 to 1-n selected in the same manner as described above. By doing so, the lighting of each light emitting element is controlled.

[Problems of the prior art]

The following problems occur in the above-described conventional drive control device for the light emitting element.

(A) First, in the drive control device shown in FIG. 10, the frequency of the clock signal for writing the video data D to the cascaded segment drivers 2 and 3 becomes extremely high. For example, when using A3 size paper (paper width of 297 mm) with a resolution of 400 dpi and a printing speed of 20 PPM, about 10 MH
Requires a very high frequency clock signal of z. Therefore, since a clock signal of such an extremely high frequency is transferred, noise due to high frequency is generated. As the distance between the control circuit and the light-emitting element increases, the amount of high-frequency noise increases because the signal line becomes longer.

(B) Further, the drive control device shown in FIG. 12 requires a process of rearranging the order of the video data D supplied to the segment drivers 4 and 5 in advance. In addition, the rearrangement of the video data D requires at least k pieces of video data D to be written into a buffer or the like in the control circuit, and then the rearrangement work must be performed. Is required.

[Object of the invention]

The present invention has been made in view of the above-mentioned conventional drawbacks, and by reducing the frequency of a clock signal for data transfer, it has become possible to drive a light emitting element in a short time without generating noise and without requiring an additional circuit. It is an object of the present invention to provide a drive control device for a light emitting element.

[Gist of the invention]

According to the present invention, there are provided a plurality of light dot generating chips in which m · k light emitting elements are arranged in an array, a plurality of light emitting element driving means having k-bit output and driving the light emitting elements. A data input terminal provided on the light emitting element driving means for inputting serial print data sent from an external device; and a clock input provided on the first light emitting element driving means for inputting a first clock signal having a different phase. A terminal, a clock input terminal provided in the second light emitting element driving means, for inputting a second clock signal having a different phase from the first clock signal, and a first of the plurality of light emitting element driving means. One of the driving signals output from the light emitting element driving means is connected to the first light emitting element of each of the optical dot generating chips, and one of the driving signals output from the second light emitting element driving means is connected to each of the respective light dot generating chips. It is achieved by providing a driving control apparatus of a light-emitting element, characterized in that connected to the second light-emitting element of the dot generation chip.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 is an overall configuration diagram of an LED printer to which an LED drive control device is applied. In the figure, the LED printer P is
A photoreceptor drum 6, a charger 7, an LED head 8, a developing device 9, and a transfer device 1, which are sequentially arranged near the peripheral surface of the photoreceptor drum 6.
0, a cleaner 11, and a slip roll 14 for transporting the paper T carried out by the paper feed roller 13 from the paper feed cassette 12,
Resist plate 15, fixing roll 16, discharge roll 17, guide plate
It is composed of a paper transport mechanism such as 18a to 18c. Also LE
An interface controller board 1 provided with an interface controller circuit below the D printer P
9 and a printer controller board 20 provided with a printer controller circuit. The interface controller circuit is a circuit that receives print data output from a host device (not shown) and converts the print data into video data.The printer controller circuit controls each unit including an LED element in the LED head 8 according to the video data.
A circuit for controlling the application of a high voltage to the charger 7, the transfer unit 10, and the like, and controlling other parts of the electrophotographic process.

The charging device 7 is a device that applies an initial charging voltage to the photosensitive surface of the photosensitive drum 6 that rotates in the direction of arrow A. The LED head 8 is a device that performs exposure based on the video data to the photosensitive surface. Is a device for converting the electrostatic latent image formed on the photosensitive surface by the above-described exposure into a toner image, and the transfer device 10 is a device for transferring this toner image to the paper T. The cleaner 11 is a device that removes toner remaining on the photosensitive surface, and the fixing roll 16 is a device that conveys the sheet on which the toner image has been transferred and thermally fixes the toner image on the sheet.

FIG. 1 is a diagram showing a detailed configuration of the LED head 8, and the LED head 8 is composed of segment drivers 22, 23 and LED arrays 24-1 to 24-n. Exposure to the photosensitive surface is performed by light emission of each LED element in the LED arrays 24-1 to 24-n. The LED head 8 and the aforementioned printer controller board 20 are connected by a signal line (not shown). LE
The clock signal CK ₁ , CK ₂ video data D and the latch signal LA are supplied to the D head 8 from the printer controller board 20, and a selection signal for selecting any one of the LED arrays 24-1 to 24-n is supplied. Is done.

FIG. 3 is a specific circuit diagram of the segment drivers 22 and 23. As shown in FIG. 3, the segment drivers 22 and 23 are both edge-triggered shift registers (hereinafter simply referred to as shift registers) 25, latch circuits 26, and constant circuits. Current buffer
It consists of 27. To the terminal I ₂ of the shift register 25 inputs the video data D, the clock signal CK ₁ or CK ₂ sequentially shift register 25 in synchronism with the input from terminal I ₁
Shift in. At the timing when the video data D is input all the shift register 25, a latch signal LA is input to the terminal I _3, video data D in the shift register 25 is outputted to the latch circuit 26. The video data D latched by the latch circuit 26 is output from the corresponding outputs ₁ to _k of the segment drivers 22 and 23 to the LED arrays 24-1 to 24-n via the constant current buffer 27.

The LED arrays 24-1 to 24-n each have 2k Ls shown in FIG.
It is formed of EDL ₁ ′ to L _2k ′. LEDL ₁ ′ ~
One end L _{1 to} L _2k of L _2k ′ is connected to the segment drivers 22 and 23 described above.
Connected to the output ₁ ~ _k of the other end thereof is connected to a common selection electrode (COM).

A common driver 28 having a circuit configuration shown in FIG. 5 is connected between each of the selection electrodes COM1 to COMn and the above-described printer controller board 20. When a selection signal output from the printer controller 20 is a high signal, an inverter is provided. The transistor 28b is turned on via 28a to supply a selection signal (voltage + Vcc) to one of the desired selection electrodes COM1 to COMn.

Connection of the output terminals ₁ ~ _k of the LED array 24-1 to 24-n of the terminal L ₁ ~L _2k and the segment driver 22 and 23 is as follows. That is, the output ₁ of the segment driver 22 as shown in FIG. 1 is connected to the terminal L ₁ of the LED array 24-1 to 24-n, the output Y ₂ is LED array 24-1 to 24-n
Is connected to the terminal L _3, output ₃ LED array 24-1 to 24
It is connected to the terminal L ₅ of -n, below the output _k in the same manner as the LE
It is connected to the D array 24-1 to 24-n terminal L _2k-1 of.
On the other hand, the output _{1 of the} segment driver 23 is the LED array 24
-1~24-n is connected to a terminal L _2, the output ₂ is connected to the terminal L ₄ of the LED array 24-1 to 24-n, the output ₃ LED
It is connected to the terminal L ₆ of the array 24-1～24N, outputs _k in the same manner is connected to the terminal L _2k of the LED array 24-1～24N. Therefore, the output of segment driver 22
₁ to the odd-numbered terminal L ₁ of each LED array 24-1 to 24-n from _k, L _3, and supplies the video data D into ..., from the output ₁ to _k of the segment driver 23 each LED array Two
In this configuration, video data D is supplied to even-numbered terminals L ₂ , L ₄ ,.

The drive control of the LEDs L ₁ ′ to L _{2 k} ′ arranged in the LED arrays 24-1 to 24-n in the LED printer P having the above-described configuration will be described with reference to the time charts of FIGS. It will be described using FIG.

Sequential video data D as described above in synchronization to the shift register 25 with the clock signal CK ₁ or CK ₂ output from the printer controller board 20 of the segment driver 22 and 23 are serially input. As described above, the video data D input to the shift register 25 is obtained by converting print data from a host device (not shown) into video data by an interface controller and supplying the video data to the printer controller board 20. First, first the 2k video data D inputted to the shift register 25 in synchronism with each k-number of the clock signal CK ₁ and CK ₂ outputted during a period V ₁ shown in Figure 6. At this time, the video data D input to the shift register 25 is synchronized with the rising edges of the clock signals CK ₁ and CK ₂ as shown in FIG. That is, the shift register 25 in the segment driver 22 in synchronization with the rise of the clock signal CK ₁ as shown in FIG. "1 th print data",
"3rd print data", "5th print data"
- is sequentially input, the shift register 25 in the segment driver 23 in synchronization with the rise of the clock signal CK ₂ "second print data", "4 th print data", "6 th print data",・ Enter sequentially. Thereafter, the latch signal LA ₁ of the input to each segment driver 22 and 23, first the latch circuit 26 in the segment driver 22, third, · · · 2k-1-th print data is latched, the segment driver The second, fourth,..., 2k-th print data is latched in the latch circuit 26 in the block 23.

Then, LED array 24-1 selection signal through a common driver 28 from the printer controller board 20 in synchronization with the falling edge of the latch signal LA ₁ is outputted to the selected electrode COM1 is selected. Therefore, the video data D latched by the latch circuit 26 as described above is output from the constant current buffer 27 to the corresponding output.
It is output to terminal L ₁ ~L _2k of LED array 24-1 via the ₁ ~ _k. At this time, segment drivers 22, 23 and LED array
Since 24-1 is connected as described above, LED array 24-
LEDL ₁ in 1 ', L _3', ··· lighting or non-lighting in accordance with video data D supplied from the output ₁ ~ _n of the segment driver 22 (driving) is _{controlled, LEDL 2 ', L 4'} , ·
Are driven and controlled according to the video data D supplied from the outputs ₁ to _n of the segment driver 23.

On the other hand, as described above, LEDL ₁ ′
When L _k ′ is controlled, the next 2k video data D are input to the shift register 25 in synchronization with the clock signals CK ₁ and CK ₂ during the period V ₂ . And the next latch signal
The output of LA ₂ latches the next 2k video data D input into the shift register 25 to the latch circuit 26. Then, the next selection signal is sent to the printer controller board.
When the video data D is output from 20 to the selection electrode 24-2 of the LED array 24-2, the video data D latched by the latch circuit 26 is output from the output ₁ to _k of the segment drivers 22 and 23 to the LED array 2
4-2 is the supply to the terminal L ₁ ~L _2k, L in the LED array 24-2
EDL ₁ ′ to L _k ′ are turned on / off (drive).

Hereinafter, similarly to LED array 24-3~24-n are sequentially selected in accordance with selection signals sequentially input to the selective electrode COM1~COMn by, LEDL ₁ in each LED array 24-3~24-n '~L _2k'
Drive control. And the LEDs in the last LED array 24-n
L ₁ ′ to L _2k ′ are driven and controlled, and all the LED arrays 24-1 to 24-
When the driving of n is completed, the optical writing of one line on the photosensitive surface is completed. Thereafter, by repeating the drive control processing of the LED in the same manner, optical writing according to the video data D can be performed on the photosensitive surface line by line.

As described above, in this embodiment, the segment drivers 22 and 23
Change the connection configuration between LED arrays 24-1 to 24-n
The video data is output to the segment drivers 22 and 23 by the two clock signals CK ₁ and CK _{2 having} a low frequency without generating noise at the time of clock transfer, and the LED arrays 24-1 to 24 are output.
24-n.

Next, another embodiment of the present invention will be described. This embodiment uses an LED as a light emitting element as in the above embodiment.
And is applied to the LED printer P. FIG. 8 shows the L of the LED printer P.
FIG. 3 is a diagram illustrating a circuit configuration in an ED head. In the case of the present embodiment, it is composed of six segment drivers 31 to 36 and n LED arrays 30-1 to 30-n. And one LE
D arrays 30-1, 30-2, ... have 3k (for example, 192)
An LED is formed and the adjacent LED arrays 30-1 and 30-2, 30-
Are connected to one of the selection electrodes COM1 to COMn / 2. Therefore, two adjacent LED arrays 30-
In this configuration, 1 and 30-2 are selected at the same time. The clock signal CK to six segment drivers 31 to 36, the video data D, but the latch signal LA is supplied, the video data D is selected alternately in the printer controller 20 inside the video data D ₁ and D ₂ And the clock signal CK is also 3
Is supplied is divided into the clock signal CK ₁ ~CK ₃ strains. The clock signal CK ₁ is output to the segment driver 31 and 32, enter the video data D ₁ to the segment driver 31 in synchronism with the rising edge, and inputs the video data D ₂ to the segment driver 32. The clock signal CK ₂ is output to the segment driver 33 and 34, enter the video data D ₁ to the segment driver 33 in synchronism with the rising edge, and inputs the video data D ₂ to the segment driver 34. Further, the clock signal CK ₃ is output to the segment driver 35 and 36, the segment driver 35 in synchronism with the rising
Enter the video data D ₁ to be inputted video data D ₂ to the segment driver 36.

The video data D ₁ and D ₂ are divided into 6k (for example, 384) video data D alternately by a printer controller, the odd-numbered video data is D ₁ , and the even-numbered video data is D ₁ and D _2.
It is an D _2. Then, the clock signals CK ₁ -C
Video data to each segment driver 31 to 36 by K ₃
Input timing of D ₁ and D ₂ is carried out as shown in Figure 9. In other words, "the first video data" in synchronism with the rising edge of the clock signal CK _1, "7 th video data"
.. Are sequentially input to the segment driver 31, and “second video data”, “eighth video data” are sequentially input to the segment driver 32. Further, in synchronization with "third video data" to the rising edge of the clock signal CK _2, "9 th video data" ... are sequentially input to the segment driver 33, "4 th video data",
"10th video data" are sequentially input to the segment driver. Further in synchronization with the rising of the clock signal CK ₃ "5 th video data", "11 th video data" ... are sequentially input to the segment driver 35,
"6th video data", "12th video data"
.. Are sequentially input to the segment driver 36.

Therefore, the "first video data", "seventh video data",... Are sequentially input to the shift register in the segment driver 31.
"2nd video data"
"Eighth video data" ... are sequentially input,
Hereinafter, video data according to the above input is also input to the shift registers in the segment drivers 33 to 36. Therefore, thereafter, for example, a selection signal is input to the selection electrode COM1,
When the LED arrays 30-1 and 30-2 are selected, 6k (384) input to the segment drivers 31 to 36 as described above
Is output to the LED arrays 30-1 and 30-2,
The LEDs in the LED arrays 30-1 and 30-2 are driven and controlled according to the video data.

Then, according to the time chart shown in FIG. 9, the next 6k video data are input to the segment drivers 31 to 36, and when the selection signal is input to the selection electrode COM2, the next LED array 30-
3,30-4 is selected and according to the video data D at this time
The driving of the LED arrays 30-3 and 30-4 is controlled. In the same manner, similarly, the LED arrays 30-5 to 30-n are sequentially driven and controlled according to the video data to write light on the photosensitive surface.

This embodiment as described above, the smaller the clock signal CK ₁ ~CK ₃ frequency capable of preventing further generation of noise from the clock signal CK _1, CK ₂ in the illustrated embodiment, the video data to the segment driver 31 to 36 In this case, the video data D is output simply by alternately dividing the data and outputting it as video data D ₁ and D _2. For example, k video data are buffered and then sequentially output as in the prior art. No such processing is required.

In this embodiment, the case where an LED is used as the light emitting element has been described. However, the present invention is not limited to the LED, and any other light emitting element such as an EL may be arranged in a row. Is not limited to LED printers,
It can be applied to a facsimile, an image reading device, and the like.

〔The invention's effect〕

As described above in detail, according to the present invention, since the frequency of the clock signal for transferring the video data is lower than in the related art, it is possible to prevent the generation of noise and the adverse effect on peripheral devices.

Further, a complicated control process for rearranging the video data in advance and an additional circuit are not required, so that the drive processing time of the light emitting element can be shortened and the cost of the device can be reduced.

[Brief description of the drawings]

FIG. 1 is a main part circuit diagram of a light emitting element drive control device of one embodiment, and FIG. 2 is an LED using the light emitting element drive control device of one embodiment.
FIG. 3 is a circuit diagram of a segment driver, FIG. 4 is a circuit diagram of an LED array, FIG. 5 is a circuit diagram of a common driver, FIG. 6 and FIG. 7 are light emitting elements of one embodiment. 8 is a time chart for explaining the operation of the drive control device, FIG. 8 is a main part circuit diagram of the light-emitting element drive control device of another embodiment, and FIG. FIGS. 10 and 12 are circuit diagrams of a conventional light-emitting element drive control device, and FIGS. 11 and 13 are time charts for explaining the operation of the conventional light-emitting element drive control device. 8 ... LED head, 20 ... Printer controller board, 22,23,31-36 ... Segment driver, 24-1-1-24-n, 30-1-30-n ... LED array, 25 ... Shift register , 26 …… Latch circuit, 27 …… Constant current buffer, L ₁ ′ ～ L _2k ′ …… LED.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B41J 2/45 B41J 2/455

Claims (1)

(57) [Claims] 1. A plurality of light dot generating chips in which m · k light emitting elements are arranged in an array, a plurality of light emitting element driving means having a k-bit output and driving the light emitting elements, and the light emitting elements A data input terminal provided in the driving means for inputting serial print data sent from an external device; a clock input terminal provided in the first light emitting element driving means for inputting a first clock signal having a different phase; A clock input terminal provided in the second light emitting element driving means for inputting a second clock signal having a different phase from the first clock signal; and a first light emitting element driving means among the plurality of light emitting element driving means. Is connected to the first light emitting element of each light dot generating chip, and one of the driving signals output from the second light emitting element driving means is connected to each light dot generating chip. Drive control device of a light emitting element, characterized in that connected to the second light emitting device flop.