JP3058726B2 - Print head and driving method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print head in which a plurality of light emitting element arrays are arranged in a row and a method of driving the same, and more particularly, to a dynamic driving method in which a plurality of light emitting elements are driven in a time-division manner by driving elements. The present invention relates to a print head and a driving method thereof.

[0002]

2. Description of the Related Art Generally, a large number of light emitting devices, for example, LEDs
2. Description of the Related Art An LED printer is known as a device for recording an image by an electrophotographic method or the like using a light emitting element array in which (light emitting diodes) are arranged at high density.

[0003] Such a printer device selectively emits light from light-emitting elements provided in a row on the basis of print data.
This is a device that performs optical writing on a photoconductor for each line and forms an image on paper by an electrophotographic process.

However, there are a large number of light-emitting elements used in the above-described apparatus, and these light-emitting elements require a relatively large current for driving (for example, 5 to 15 per light-emitting element).
mA), one line is usually divided into a plurality of blocks and sequentially driven, or a single driving element drives a plurality of light-emitting elements in a time-division manner.

FIG. 7 is a functional block diagram of a conventional print head.

As shown in FIG. 1, a print head 1 includes a self-focusing rod lens array 2 and a driving unit D for driving a light emitting element array of a light emitting body 3 having a plurality of light emitting element arrays arranged in rows. Consists of

The drive section D includes a drive circuit 5, a gate circuit 6, a latch circuit 7, and a shift register 8.
It comprises one or a plurality of drive elements (driver ICs) 10.

FIG. 8 shows an example of a basic circuit configuration of the driving element 10. As shown in FIG.

As shown, the constant current limiting circuit 5 comprises a current mirror circuit and a current determining circuit (not shown).
Equalize and stabilize the current of each bit. The drive circuit 4 includes source output type transistors Tr1 to Tr64.
Consists of The gate circuit 6 includes a latch circuit 7
Is composed of 64 AND circuits for switching the output of the circuit by the STROBE signal. The latch circuit 7 and the shift register 8 have a 64-bit configuration.

FIG. 9 is a circuit diagram of an A4 size, 300 dots per inch (dpi) printhead using the driving element 10 shown in FIG.

The luminous body 3 is composed of a total of 2560 luminous elements L1 to L2560 using 40 luminous element arrays LA1 to LA40 each composed of a 64-bit luminous element array chip. The driving section D uses one 64-bit driving element 10 shown in FIG.
Each output of 0 _O 1 _{~ O 64} respectively the light emitting element array LA
The light emitting element arrays LA1 to LA40 are connected one by one in a time-division manner.

A method of driving each of the light emitting element arrays LA1 to LA40 in the conventional printhead having the above-described configuration in a time-division manner will be described below.

FIG. 10 shows a drive timing in one line printing of the conventional print head. First, print data corresponding to the light emitting elements L1 to L64 in the light emitting element array LA1 is transmitted from the DATA IN terminal to the CLOCK.
The data is sent to the shift register 8 in synchronization with the signal, and then the print data is latched on the latch circuit 7 by the LATCH signal. Subsequently, the output transistor Tr1 is turned on by the common control circuit 11 of the external common select circuit 9.
Then, the light emitting element array LA1 is set in a state capable of emitting light.

Here, when the STROBE signal is turned on, the light emitting element L corresponding to the printing in the light emitting element array LA1.
1 to L64 emit light. At the same time when the STROBE signal is turned on, print data corresponding to printing in the next light emitting element array LA2 is input to the shift register 8 in synchronization with the CLOCK signal, and the latch circuit 7 is latched by the LATCH signal. After the light emitting elements L 65 to L 128 emit light for the time t necessary for printing, the STROBE signal is turned off to stop the light emitting elements from emitting light.

Subsequently, print data corresponding to the light emitting element array LA3 is input and latched in the same manner as described above.
At the same time, the output transistor Tr 3 of the common select circuit 9
The ON, and the light emitting element L 129 corresponding to the print data in the light-emitting element array LA 3 by turning ON the STROBE signal
ＬL 192 is emitted.

As described above, the light emitting element array LA1
To LA 40 to sequentially emit light to perform printing.

[0017]

However, in a print head using a conventional dynamic drive system as shown in FIG. 9, a common control circuit 11 uses a multi-bit general-purpose shift register and a plurality of transistor arrays. The circuit board including this shift register has become larger. This is disadvantageous for reducing the size and cost of the print head.

The present invention has been made in view of the above problems, and has as its object to provide an inexpensive and compact print head and a driving method thereof by simplifying the circuit configuration of the print head.

[0019]

The object of the present invention is to provide a light emitting element array LA1 comprising a plurality of light emitting elements L1 to L64,..., L2560 corresponding to print dots, as shown in FIGS. A plurality of LA40s are arranged in a row, and the cathode side of each of the light emitting element arrays LA1 to LA40 is commonly connected to form common electrodes C1 to C20. Each of the light emitting elements L1 to L2560 of the plurality of light emitting element arrays LA1 to LA40 Is divided into two groups G1 and G2 in a print head provided with a drive section D for driving the light-emitting element arrays LA1 to LA40 in a time-division manner. The light emitting element array LA includes two driving elements 10a and 10b for independently driving the groups G1 and G2.
The common electrode C1~C20 of 1~LA40 is a light-emitting element array LA1~LA40 of both groups G1, G2 that
These are connected one by one and connected in common.

[0020] The means for solving the problem according to claim 2 of the present invention comprises:
Of the N light emitting element arrays LA1 to LA40, 1 to N
The second light emitting element arrays LA1 to LA20 and (N + 1) to
2N-th light emitting element array LA2 1 ~LA40 and a separate drive element 10a, and driven at 10b, m-th (m = 1
To N) of the light emitting element arrays LA1 to LA20 and the (m + N) th light emitting element arrays LA21 to LA21.
LA40 of a common electrode C1~C20 respectively common, the 1~N th light emitting element array LA1~LA20 driven in time division while successively switching the common electrode C1~C20 at hand of the drive element 10a, the other Drive element 10b
At (N + 1) to 2N-th light emitting element arrays LA21 to LA21
The LA 40 is time-divisionally driven by switching its common electrodes C1 to C20.

The problem solving means according to the third aspect of the present invention is, as shown in FIGS. 3 to 6, the driving elements 10a and 10b according to the first aspect.
Is a shift register 8 to which a clock signal from the outside and print data synchronized therewith are inputted, a latch circuit 7 for latching the print data inputted to the shift register 8, and a switch of the output of the latch circuit 7. And a drive control circuit X1 for automatically generating a latch signal to the latch circuit 7 and a strobe signal to the gate circuit 6 from a clock signal to the shift register 8. is there.

According to a fourth aspect of the present invention, there is provided a driving control circuit X1 according to the third aspect, wherein a light emitting element array LA is provided.
1 to LA20, LA21 to LA40 common electrode C1 to
A common select circuit 9 for sequentially switching and driving C20 is provided.

[0023]

The common electrodes C1 to C20 of the light emitting element arrays LA1 to LA20 and LA21 to LA40 divided into two groups G1 and G2 are separated from the groups G1 and G2. By connecting the light emitting element arrays LA1 to LA20 and LA21 to LA40 of each group G1 and G2 in a time-division manner with the separate driving elements 10a and 10b, a common connection is achieved as compared with the related art. The number of the electrodes C1 to C20 is halved, and the control circuit connected thereto is simplified.

According to the third aspect of the present invention, a clock signal to be transmitted to the shift register 8 is also input to the drive control circuit X1, and based on the clock signal,
A latch signal is generated and output to the latch circuit 7, and a strobe signal is generated and output to the gate circuit 6. Thus, a latch terminal and a strobe terminal as external connection terminals are omitted.

According to the fourth aspect of the present invention, the common select circuit 9 in the drive control circuit X1 sequentially drives the common electrodes C1 to C20 of the light emitting element arrays LA1 to LA20 and LA21 to LA40. Thus, a common select terminal as an external connection terminal is omitted.

[0026]

【Example】

(First Embodiment) FIG. 1 is a circuit wiring diagram of an A4 size, 300 dpi printhead showing a first embodiment of the present invention, and FIG. 2 is a drive timing diagram thereof. The same reference numerals are given to the same functional components as those of the related art shown in FIGS.

As shown, the print head of the present invention comprises:
A plurality of light emitting element arrays (LED arrays) LA1 to LA4
A driving unit D that drives each of the light-emitting elements (LEDs) L1 to L2560 in a time-division manner, that is, performs dynamic driving.

As shown in FIG. 1, the driving section D includes two driving elements 10a and 10b (driver ICs), and the driving outputs O _{1 to} O ₆₄ of one of the first driving elements 10a generate light emitting element arrays LA1 to LA64. Light-emitting elements L1 to L64 and L6 of LA20
, L1217 to L1280 are driven in a time-division manner, and the other second driving element 10b is a light emitting element array L
A1 to LA40 light emitting elements L1281 to L1344
, L2497 to L2560 are driven in a time-division manner.

Each of the driving elements 10a and 10b has the same basic configuration as that of the conventional example shown in FIG. The DATA IN terminal, LATCH terminal, and CLOCK terminal of the driving elements 10a, 10b are common to both driving elements 10a, 10b. On the other hand, the terminals for inputting the strobe signal have the STROBE1 terminal and the STROBE2 terminal respectively for the driving elements 10a and 10b. The cathode-side common electrodes C1 to C20 of the light emitting element arrays LA1 to LA20 and LA21 to LA40 are connected to the light emitting element array LA1.
, LA21, LA2 and LA22, ..., LA20 and LA4
0 common electrodes are shared, and C1, C2,.
C20. The common electrodes C1 to C20 are output transistors Tr1 and Tr of the common select circuit 9.
2,..., Tr20.

In FIG. 1, reference numeral 11 denotes each of the common electrodes C1 to C1.
This is a common control circuit that controls the drive current to C20.

In the above configuration, as shown in FIG.
From the ATA IN terminal, 64-bit serial print data corresponding to the light emitting element array LA1 is transmitted to the clock (CL).
OCK) signal while driving elements 10a, 10b
To the 64-bit shift register 8. Subsequently, a latch (LATCH) signal is transmitted to the drive elements 10a and 10b.
When the print data is input to the 4-bit latch circuit 7, the print data is latched by both drive elements 10a and 10b.

Next, when the output transistor Tr1 in the common select circuit 9 is turned on, both groups G1, G
The two light emitting element arrays LA1 and LA21 enter a state capable of emitting light. Here, ON Then by the time t required for printing the STROBE1 is a strobe signal of the first drive element 10a corresponding to the group G1, the output _O 1 _{~ O 64} of the drive element 10a corresponding to the light emitting element array LA1 printing The data is output, and the light emitting element array LA1 emits light for the time t.

Subsequently, the 64-bit serial print data corresponding to the light emitting element array LA2 is clocked (CL).
OCK) signal while driving elements 10a, 10b
And sends a latch signal to the latch circuit 7 to latch the print data. Next, when the output transistor Tr2 is turned on and the STROBE1 is turned on again, the light emitting element array LA2 emits light corresponding to the print data. Hereinafter, driven sequentially to the light emitting element array LA20 similarly using drive elements 10a, after being latched by feeding print data corresponding to the light emitting element array LA21, output transistor Tr1 again
Turn ON.

Here, when the strobe signal STROBE2 of the driving element 10b corresponding to the group G2 is turned on, the light emitting element array LA21 of the group G2 emits light in accordance with the print data. Hereinafter, similarly, drive to LA 40 is performed using drive element 10b.

As described above, the light emitting element arrays LA1 to LA20 and LA21 divided into two groups G1 and G2.
To LA40, the common electrodes C1 to C20 of both groups G
1 and G2, one by one and connected in common, and the light emitting element arrays LA1 to LA20, L of the respective groups G1 and G2.
By driving A21 to LA40 in a time-division manner by the separate driving elements 10a and 10b, it is possible to drive even if the number of common electrodes C1 to C20 is reduced by half as compared with the related art. Therefore, the size of the connector connected to the common electrodes C1 to C20 can be reduced, and the control circuit can be simplified.

(Second Embodiment) FIG. 3 is a circuit diagram of a print head showing a second embodiment of the present invention, FIG. 4 is a circuit block diagram showing the inside of the drive control circuit, and FIG. FIG. 6 is a block diagram showing the basic functions of the same.

As shown in FIG. 3, the print head of this embodiment has light emitting element arrays LA1 to LA20 and LA21 to LA40 of two groups G1 and G2, as in the first embodiment.
Are driven independently by a pair of drive elements 10a and 10b, respectively. Each drive element 10a and 10b has a shift register 8 for inputting print data and an input to the shift register 8 as shown in FIG. A latch circuit for latching print data; and a gate circuit for switching data of the latch circuit. Based on a clock signal input from the outside, a latch signal for the latch circuit and a strobe signal for the gate circuit are provided. Are respectively provided, and the common electrodes C1 to C20 of the light emitting element arrays LA1 to LA20, LA21 to LA40 are respectively connected to the light emitting element arrays LA1 to LA20, LA21 to LA40 of the groups G1 and G2. Of the common electrodes C1 to C20 are connected one by one and connected in common. b was divided into two groups G1, G2 of the plurality of light emitting element arrays LA1～LA20,
The group of LA21 to LA40 is independently driven in a time division manner.

As shown in FIG. 4, the drive control circuit X1 applies a clock signal to each of the light emitting element arrays LA1 to LA40.
, A first counter Ct1 for counting the number of light emitting elements (hexadecimal), an internal gate circuit Ga1 for outputting a latch signal and a strobe signal based on a carryout signal generated by the first counter Ct1, and a synchronization with the carryout signal. And the light emitting element arrays LA1 to LA20,
And a common select circuit 9 for sequentially switching the common electrodes C1 to C20 of LA21 to LA40.

The common select circuit 9 counts the carry-out signal generated by the first counter Ct1 by a number (decimal or 20 + 1) corresponding to the number of the light emitting element arrays LA1 to LA20 or LA21 to LA40. Ct2 and each of the light emitting element arrays LA1
To the common electrode C1 of LA20 or LA21 to LA40
To output transistor Tr for sequentially switching from C20 to C20
And 1～Tr20, and a decoder Dc for sequentially ON the output transistor Tr1～Tr 20 decodes the output of the second counter Ct2. Other configurations are the same as in the first embodiment.

Next, the printing operation for one line in the print head of this embodiment will be described with reference to FIG.

First, 64-bit serial print data corresponding to the first light emitting element array LA1 is sent from the DATA IN terminal to the 64-bit shift register 8 of the driving elements 10a and 10b while synchronizing with the clock signal (CLOCK). The clock signal is sent to the first 64-bit counter Ct1 of the drive control circuit X1. The first counter Ct1 sends a carry-out signal to the internal gate circuit Ga1, and the internal gate circuit Ga1 outputs a latch signal to the latch circuit 7 in synchronization with the carry-out signal. Through the above process, the 64-bit print data is latched by the 64-bit latch circuit 7 of the driving elements 10a and 10b.

On the other hand, the second counter Ct2 receiving the carry-out signal from the first counter Ct1 counts up by one. Then, when this counter output is output to the decoder Dc, the decoder Dc first turns on the first transistor Tr1, and the light emitting element arrays LA1 and LA21 corresponding to this turn on.
Here, ON only the internal gate circuit Ga1 time t required for printing the STROBE1 a strobe signal to the first drive element 10a Then, the output _O 1 _{~ O 64} of the first drive element 10a light-emitting element array The print data corresponding to LA1 is output, and the light emitting element array LA1 emits light for the time t. Here, the strobe pulse width t is determined by counting a clock signal by a strobe counter (not shown).

Subsequently, the second light emitting element array L
A 64-bit print data corresponding to A2 is clocked (C
LOCK) signal while driving elements 10a, 10a
b, a latch signal is generated in the same manner as in the above operation.
The 64-bit print data is latched in the latch circuits 7a and 10b. Further, since the line Nau second counter Ct2 yet another count up-decoder D
c turns on the output transistor Tr2, and when the internal gate circuit Ga1 turns on STROBE1 again, the light emitting element array LA2 emits light in accordance with the print data. Hereinafter, similarly, the light-emitting element array LA is sequentially driven by the first driving element 10a.
20 and the print data corresponding to the light emitting element array LA21 is sent, the driving elements 10a, 10a,
The print data is latched by the latch circuit 7 of 10b.
On the other hand, since the second counter Ct2 operates as a 20-digit counter, the output transistor Tr1 is turned on again.
At this time, the second counter Ct2 is set to the internal gate circuit Ga1.
, A strobe switching signal is output to the second drive element 10b.
2 is turned on, and the light emitting element array LA21 emits light in accordance with the print data. Hereinafter, similarly it second Yotsute the driving element 10b emitting element array LA 22 ~LA40 is the print data connexion emission, and terminates the printing operation for one line.

In FIG. 5, after inputting the print data corresponding to the last light emitting element array LA40, another 64 clocks are input because of the light emitting element array LA4.
This is for determining the pulse width of the strobe signal with respect to 0 and the ON time of the transistor Tr40. Therefore, the second counter Ct2 operates as a 21-ary counter at this time.

As described above, in the dynamic drive type print head in which the number of common electrodes of the light emitting element array is half that of the conventional light emitting element array, the print data latch can be obtained simply by inputting the print data and the clock signal. Then, the light emission of the light emitting element array by the strobe signal and the switching of the common electrode of the light emitting element array can be automatically performed.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that many modifications and changes can be made to the above-described embodiment within the scope of the present invention.

For example, in the above embodiment, the light emitting elements in each light emitting element array were divided into two groups.
It may be divided into more than two groups.

In the above embodiment, A4 size,
Although a 300 dpi printhead has been described, the invention is not so limited.

[0049]

As is clear from the description above, according to the present invention, according to the present invention according to claim 1, divides the light-emitting element array into two groups, common to the one at pair the common electrode from each group connect, by driving the light emitting element array of each group in separate driving device, so that the common electrode wirings number be half of the conventional. Accordingly, the number of output transistors of the common select circuit is reduced to half, and a compact and inexpensive print head can be provided.

According to the third aspect of the present invention, only by inputting the print data and the clock signal, the print data latch and
The light emission of the light emitting element array by the strobe signal can be automatically performed, the latch terminal and the strobe terminal as external connection terminals can be omitted, and the size of the connector can be reduced and the external control circuit can be simplified.

According to the fourth aspect of the present invention, the common electrode of the light emitting element array can be automatically switched inside the print head, and the excellent effect can be obtained when the common select terminal as the external connection terminal can be omitted. There is.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a printhead showing a first embodiment of the present invention.

FIG. 2 is a drive timing chart of the same.

FIG. 3 is a circuit diagram of a printed head showing a second embodiment of the present invention.

FIG. 4 is a circuit block diagram showing the inside of the drive control circuit.

FIG. 5 is a drive timing chart of the same.

FIG. 6 is a basic function block diagram of the same.

FIG. 7 is a basic functional block diagram of a conventional print head.

FIG. 8 is an internal circuit wiring diagram of the driving element.

FIG. 9 is a circuit wiring diagram of the print head.

FIG. 10 is a drive timing chart in a conventional example.

[Explanation of symbols]

 L1 to L2560 Light emitting element LA1 to LA40 Light emitting element array C1 to C20 Common electrode D Drive unit X1 Drive control circuit 6 Gate circuit 7 Latch circuit 8 Shift register 9 Common select circuit 10a, 10b Drive element

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-235660 (JP, A) JP-A-51-84649 (JP, A) JP-A-61-234652 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B41J 2/335 B41J 2/44 B41J 2/45 B41J 2/455 G03G 15/04

Claims (4)

(57) [Claims] 1. A light emitting element array comprising a plurality of light emitting elements corresponding to printing dots is arranged in a plurality of rows, and the cathode side of each light emitting element array is connected in common to form a common electrode to form a plurality of light emitting elements. In a print head including a drive unit that drives each light emitting element of the element array in a time-division manner, the plurality of light emitting element arrays are divided into two groups, and the drive unit is configured to control each group of the light emitting element array. A print head comprising two driving elements which are independently driven, and wherein the common electrode of the light emitting element array is connected in common with each pair of the light emitting element arrays of both groups. Wherein among the 2N pieces of light emitting element array, 1 to N
Th light emitting element array and the (N + 1) and ~2N th light emitting element array and driven by separate drive elements, m-th (m =
A common electrode of the light-emitting element common electrode and the m + N-th light-emitting element array of an array of 1 to N) are replaced with a common, a 1 to N-th light-emitting element array in one <br/> side of the driving element, the common A method of driving a print head, comprising: driving electrodes in a time-division manner while sequentially switching the electrodes; and driving the (N + 1) -th to (2N) -th light-emitting element arrays by the other driving element in a time-division manner by switching their common electrodes. 3. A driving element according to claim 1, wherein a shift register to which a clock signal from the outside and print data synchronized with the clock signal are inputted; a latch circuit for latching the print data inputted to the shift register; and a gate circuit for switching-output of said latch circuit, wherein the clock signal to the shift register, automatically drive control circuit is provided for generating a latch signal for the latch circuit, and a strobe signal for said gate circuit Print head characterized by having been done. 4. A print head according to claim 3, further comprising a common select circuit for sequentially switching and driving the common electrodes of the light emitting element array.