JPH0811345A - Led printing head - Google Patents

Abstract

PURPOSE:To provide an inexpensive LED printing head of a dynamic drive type enabled in gradation printing, relatively simple in constitution and easy to produce. CONSTITUTION:In a dynamic drive type LED printing head, a plurality of LED arrays B1-B40 are driven at every LED array in a time sharing manner by time sharing drive transistors T1-T40. A plurality of LED driving drivers D1, D2, D3 having different output current drive capacities are provided. The number of outputs of the respective drivers D1-D3 corresponds to the number of the LEDs constituting the LED arrays B1-B40. The respective corresponding outputs between a plurality of the LED driving drivers D1, D2, D3 are parallelly connected to be connected to the respective LEDs corresponding to a plurality of the LED arrays B1-B40 in common. The LED arrays B1-B40 are subjected to gradation control by the ON/OFF combination of the LED driving drivers D1, D2, D3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic drive type LED print head capable of gradation printing by changing light output for each LED.

[0002]

2. Description of the Related Art Generally, an LED print head has a static drive system shown in FIG. 6 and a dynamic drive system shown in FIG.

The static drive system shown in FIG.
The same number of D driving driver ICs 61 and the same number of LED arrays 62 are required, and each driver output of the driver IC 61 and each LED of the LED array 62 have to be in a one-to-one correspondence. Need.

In particular, in the case of this method, in order to perform density gradation printing by changing the light output for each LED, a plurality of driver transistors 80 are required for each driver output as shown in FIG. To do. The output current is controlled by selectively determining the combination of ON and OFF of these driver transistors 80 by the logic circuit 85.
For example, two driver transistors 81 and 82 are turned on to pass a double output current, and others are turned off, and all driver transistors 81 to 8 are passed to pass a four times output current.
Turn 4 on. As a result, the light emission output of the LED is 1 to
It is possible to perform density gradation printing by changing four gradations. However, for that purpose, the driver IC 61 requires a complicated circuit configuration having a large number of driver transistors and logic circuits at each output.

On the other hand, the dynamic drive system L shown in FIG.
The ED printer head drives each LED array 72 in time division by time division by one or two LED driving driver ICs 71. Conventionally, in the case of this method, there is no one capable of density gradation printing.

[0006]

As described above, the conventional LED print head for gradation printing is of the static drive type and has a drawback that the structure is complicated, the manufacture is difficult, and the cost is high.

It is an object of the present invention to solve the above-mentioned drawbacks of the prior art by enabling dynamic driving type gradation printing, and having a relatively simple construction, easy manufacture, and low cost. The present invention is to provide an LED print head.

[0008]

SUMMARY OF THE INVENTION The present invention provides a plurality of LEDs.
In a dynamic drive type LED printer head for time-divisionally driving an array for each LED array, there are a plurality of drivers each having a different output current driving capability, and the number of outputs of each driver and L constituting each LED array.
An LED driving driver corresponding to the number of EDs is provided, each corresponding output between the plurality of LED driving drivers is connected in parallel, and each output connected in parallel is corresponding to each LED of the plurality of LED arrays. Is connected in common, and the gradation control is performed on each of the LEDs by a combination of ON / OFF of the plurality of LED driving drivers.

[0009]

A plurality of LEs having different output current driving capabilities
Depending on the combination of ON and OFF of the D drive driver, the sum current according to the combination flows through each LED. As a result, the light emission output of the LED changes, and density gradation printing becomes possible.

Since corresponding outputs of a plurality of LED driving drivers are respectively connected in parallel and a sum current for flowing to each LED is supplied between the drivers, the sum current is supplied in the drivers. In comparison, the number of transistors required for each output of the driver is small.

Further, since the outputs of the drivers connected in parallel are commonly connected to the corresponding LEDs of the plurality of LED arrays, a dynamic drive type can be realized.

[0012]

Embodiments of the present invention will be described below. FIG. 1 shows an LED printer head for explaining this embodiment.
This LED printer head has a plurality of LED arrays B
It is a dynamic drive type in which (B1 to B40) are time-divisionally driven for each LED array.

LED driving driver ICs (D1 to D3)
Are provided, and these have different output current driving capabilities. In the illustrated example, three driver ICs (D) are shown. Each driver IC (D1), (D
2) Output current from each output port of (D3) is IC
The ratio is set to 1: 2: 4. As a result, the drive current required for the LED can be classified into 8 levels from 0 to 7.

One LED array B is composed of 64 individual LEDs # 1, # 2, ..., # 64.
Forty linear D arrays B are arranged in a row to form a linear LED array.

The number of output ports of the LED driving driver IC (D) is 64 according to the number of individual LEDs of the LED array B, and these are connected in parallel between the driver ICs. Then, each driver IC for driving
The outputs of the 1st to 64th ports of (D) are commonly connected to the anodes of the 1st to 64th LEDs constituting the corresponding LED arrays B, respectively. Therefore, LED1
This means that the three ports of the driver ICs (D1 to D3) are connected in parallel.

The common electrodes of the 40 LED arrays B1 to B40 are electrically independent and connected to time-division drive transistors T1, T2, ..., T40, respectively, according to the LED array selection signals BS1, BS2 ,. LED
The dynamic display is driven for each array.

FIG. 3 shows an example of a block diagram of the contents of the LED driver IC (D) of FIG. 1, and FIG. 4 shows a simplified representation thereof. Here, STB is an output enable terminal of a 64-bit driver, SI is a serial data input terminal, CLK is a clock input terminal of a 64-bit shift register, LATCH is a strobe input terminal of a 64-bit data latch, and Q1 to Q64 are output ports. . Here, SI (SI0, S
I1, SI2) are independently input for each IC driver as shown in FIG.

The print data input from the serial data input terminal SI to the 64-bit shift register 31 is latched by the 64-bit latch 32. After that, logic unit 4
When 2 and the driver unit 41 are operated, 64-bit print data in the latch 32 is swept out, and the LED emits light correspondingly. Each driver unit 4 of the driver ICD
As shown in FIG. 5, each 1 is composed of one transistor, and the corresponding logic unit 42 has a simple structure accordingly. The 64-bit latch 32 and the 64-bit shift register 31 shown in FIG. 3 form the common logic unit 43 shown in FIG.

Now, the operation of the LED printer head described above will be described with reference to FIG.

With respect to the print data for the first LED array B1, each LED # 1, # 2, ... # 64 has its density rank set to “3, 5, 0, 2, 6, ... 7”. As print data signals to the serial data terminals SI0 to SI2 of the driver ICs (D1 to D3), "(" 1 "," 1 "," 0 "), (" 1 "," 0 ",
Input "1", ... ("1", "1", "1") ". These signals are sent to the 64-bit shift registers 31 of the driver ICs (D1) to (D3), and the second LED
It is latched by the 64-bit latch circuit 32 in the array data transmission section. This latch output is the enable signal STB
Output Q of each driver IC (D1) to (D3)
, Q2, ..., Q64. In FIG. 2, serial data SI0 to SI2 and parallel data Q1 to Q64
In order to clarify the relationship with, ○, □, Δ is "1",
The "0" signal is enclosed.

Therefore, in the data transmission section for the second LED array, Q1 of the driver IC (D1) and driver I
For LED # 1 of the LED array B1 to which Q1 of C (D2) and Q1 of the driver IC (D3) are commonly connected, the sum of the driver ICs (D1) and (D2) that are turned on (concentration rank 3) Current flows. Q of driver IC (D1)
2, Q2 of driver IC (D2), driver IC (D
A current of the sum of the driver ICs (D1) and (D3) that are turned on (concentration rank 5) flows through the LED # 2 to which Q2 of 3) is commonly connected. The driver IC (D1) Q64, the driver IC (D2) Q64, and the driver IC
LED # 64 to which Q64 of (D3) is commonly connected,
Driver ICs (D1), (D2) and (D
An electric current of the sum (3) (concentration rank 7) flows.

The print data for the second LED array B2, the print data for the third LED array B3, ...
Similarly, a current corresponding to the concentration rank flows through each LED.

In this way, each driver IC (D1 to D
3) Each print data signal S independently input to
Depending on the combination of I0 to SI2, the driver IC (D1) to
The output port for turning on (D3) is controlled according to the density ranks 0 to 7, and each LE has a brightness according to those ranks.
D emits light. This makes it possible to print in 8 gradations.

According to the present embodiment, the driver unit for driving one LED is composed of a plurality of driver transistors, and the gradation of the LED is not controlled by the combination of ON and OFF of these, but the driver unit is controlled. Instead of being composed of one driver transistor, a plurality of LED driving driver ICs having different output current driving capacities are provided.
Since the gradation of the LED is controlled by the combination of N and OFF, the number of driver transistors can be reduced, and the corresponding logic unit can also have a simple structure.

[0025]

According to the present invention, the LED driving currents having different output current driving capacities are combined to control the output current of the LED by gradation, so that the transistor constituting the output of the LED driving driver can be controlled. The number is small, the structure of the LED driver is simple, the manufacturing is easy, the cost can be reduced, and the reliability and the size can be reduced. Further, since the gradation printing control is realized by the dynamic driving method, the power consumption can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit block diagram for explaining an embodiment of an LED print head of the present invention.

FIG. 2 is a timing chart for explaining the operation of FIG.

3 is a circuit configuration diagram showing an internal configuration of the LED driving driver IC of FIG. 1. FIG.

FIG. 4 is a block diagram showing a simplified circuit configuration of FIG.

FIG. 5 is a circuit configuration diagram showing the inside of the driver unit shown in FIGS. 3 to 4;

FIG. 6 is a circuit block diagram showing a configuration of a conventional static drive type LED print head.

FIG. 7 is a circuit block diagram showing a configuration of a conventional dynamic drive type LED print head.

FIG. 8 is a circuit configuration diagram showing the inside of a driver unit for controlling gradation printing in a conventional example.

[Explanation of symbols]

 D1, D2, D3 LED driving driver IC B1 to B40 LED array T1 to T40 time division driving transistor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H04N 1/036 A

Claims (1)

[Claims] 1. A dynamic drive type LED printer head for time-divisionally driving a plurality of LED arrays, the plurality of drivers each having a different output current driving capability, the number of outputs of each driver and each driver. L
An LED driving driver corresponding to the number of LEDs forming the ED array is provided, each corresponding output between the plurality of LED driving drivers is connected in parallel, and each output connected in parallel is plural LED array. Each corresponding LE of
Commonly connected to D, and O of the plurality of LED driving drivers
An LED print head characterized in that gradation control is performed for each of the LEDs by a combination of N / OFF.