KR950014200B1 - Electricity control l.e.d print head - Google Patents

Abstract

The printer head having a data shift register for shifting a serial printing data by a clock inputted to a clock terminal by having a printer enable signal terminal, a clock terminal, and a printer data input terminal, the data shift register being enabled by an input of the printer enable signal; a data latch for latching an output print data of the data shift register to a latch enable signal; and a gate array for gate-outputting the latching print data of the data latch through a strobe signal, comprises: a LED array having the LED turned on/off by an output of the gate array by the number of outputs of the gate array, and also having LED driver for controlling driving current of the LED by the number of LEDs; and a compensation data shift register for shifting compensation data corresponding to the number of print data to the data shift register, and providing LED driving current data of a predetermined bit to the LED driver of the LED array to input the gating data of 1 bit of the gate array, the compensation data shift register being operated by the data enable signal. Thereby, a LED output is compensated by controlling the driving current corresponding to the LED by the compensation data of a predetermined bit inputted to the LED driver of the LED array.

Description

Current Control LED Printhead

1 is a block diagram of the present invention.

2 is a detail of a portion of the FIG. 1 block diagram.

3 is an example of driving 3072 LEDs.

4 is an operation timing diagram of FIG.

* Explanation of symbols for main parts of the drawings

DSRB: Data Shift Register LATB: Latches

GAB: Gate Array LED AB: LED Array

CSRB: Correction data shift register LEDDR: LED driving circuit

The present invention relates to an LED printer head, and more particularly, to a current controlled LED printer head which executes high speed and high quality printing by minimizing light output variation according to LED characteristics by controlling driving current according to each LED characteristic.

In general, non-impact optical printers include lasers and LED printers. Laser printers such as electronics have a problem that the mechanical part is complicated and expensive, and the LED printer is light, small and simple, and the mechanical part is expected to be used in the future. The LED printer as described above is a typical example of manufacturing an optical printer using a high-density LED array. When manufactured using a high density LED array, the variation of the LED light output of the printhead has a great influence on the print quality. Therefore, in the LED printer using a high density LED array, the light output deviation of the LED array had to be corrected before printing. Conventional LED printheads for correcting light output deviations of LED arrays include a correction ROM that stores correction data for each LED, as described in patent application No. 88-7084, filed by the present applicant. ) And a light emitting time generating unit for generating various types of LED light emitting time. However, the method of adjusting the LED exposure time using the correction data and the method of reducing the LED light deviation using the LED light emitting time generator as described above have the following problems. There is a limitation of correction in reducing the LED exposure time by reducing the LED exposure time as external correction data, and there is a problem that the printing speed decreases as the number of bits of the correction data is combined because the correction data and the print data are combined.

Accordingly, an object of the present invention is to store correction data for LEDs having different light emission characteristics in an external correction memory, and to make constant the amount of light emission by varying the driving current for LEDs having different light output characteristics as the correction data accordingly. To provide an LED printer head.

Another object of the present invention is to set the drive current flowing through each LED by inputting correction data only during the initial initialization time, and to advance printing process only by printing data so that printing can be known at high speed. In providing a printhead.

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

1 is a block diagram of a high-density LED printer head according to the present invention. A data shift register (DSRB) for continuously shifting N pieces of print data, which is enabled by a predetermined pulse control and serially inputted, by a predetermined clock, and the data shift. A data latch LATB for latching the shift data under predetermined control upon completion of N print data shifts in the register DSRB, and a gate output of the print output data of the data latch LATB with a strobe signal. A gate array (GAB), a correction data shift register (CSRB) for shifting and storing 4 N bits of correction data for correcting N bits of printing data by a predetermined clock, and the gate array ( Input of N-bit printing data of GAB) and 4N-bit correction data to output N dots for printing N dots The flow is controlled and consists of an LED array (LEDAB). 1 of the N-bit printing data output from the gate array GAB in the LED array LEDAB of FIG. 1 and 4 of the 4N-bit correction data output from the correction data shift register CSRB. Each LED driver (LEDDR) for inputting data of bits consists of N bits. The LED driver LEDDR has a control circuit for controlling the driving current of the LED by one LED driven by the 1-bit printing data and the 4-bit correction data.

In this case, the 4N correction data is data for making the amount of light of each of the N LEDs printing N dots by N-bit print data constant, and is obtained in advance according to each LED light output characteristic. Now, when the LED of the LED array (LEDAB) and the LED of the LEDDR (LEDDR) to emit light to provide a pulsed data enable signal (ED: Data Enable) to execute the optical print, the correction data shift register (CSRB) is Is enabled.

At this time, if 4N serial correction data D are supplied by the clock DCLK, 4N bits of correction data are shifted and stored in the correction data shift register CSRB, which is N LED drivers in the LED array LEDAB. (LEDDR) 4 bits are supplied to each.

In the above state, after supplying and enabling a pulse-type print enable signal (EP :) to the data shift register (DSRB) and providing a clock (CLK), N-bit serial print data (SI) is generated. The output is shifted by the clock.

When N-bit print data provides a latch enable signal (LAE: Latch Enable) to the data latch (LATB) after shift completion, the N-bit shift print data output of the data shift register (DSRB) is driven by the data latch (LATB). It is latched and input to the gate array GAB.

Under the above conditions, when a strobe signal, which is a print on signal, is provided to the gate array GAB, the gate array GAB stores the input N bits of print data in the LED array LEDAB. Inputs are made to each of the two LED drivers (LEDDR).

Each of the LED drivers LEDDR in the LED array LEDAB allows one-bit printing data, that is, LED on and off control data, to be input.

In each of the LED drivers LEDDR, the current driving of the built-in LED is changed according to the 4-bit correction data for correcting the light quantity characteristic of the built-in LED among the 4N bits of correction data output from the correction data shift register CSRB. do.

Therefore, the LEDs of the plurality of LED drivers LEDDR in the LED array LEDAB are driven by print data of 1 bit, and the amount of light emitted by the drive is controlled to a certain amount of light according to the 4-bit correction data.

Therefore, the light quantity of the LED in the LED driver (LEDDR) is controlled according to the corresponding LED correction data, so it is easy to minimize the deviation from the light output of the neighboring LED.

FIG. 2 shows some specific circuit diagrams of the gate array GAB and the LED array LEDAB of FIG. 1, and the gate array GAB is composed of a plurality of end gates G. As shown in FIG. In addition, each of the LED drivers LEDDRs configured in the LED array LEDAB is connected between the LEDs and the cathodes of the LEDs and the ground, and a plurality of driving circuits are formed to drive a current loop of the LEDs under predetermined control. One common input of the output of the gate G in the gate array GAB, and one bit of the 4-bit correction data of the correction data register CSRB are input to the other terminal to control the plurality of driving circuits. And gate gates A1 to A4 provided as signals. In each of the plurality of driving circuits, the current limiting resistor R and the MOSFET Q are connected between the cathode of the LED and the ground, and the magnitudes of the current limiting resistors are different.

2 is for explaining the operation of the current control for one LED, and the data "D1-D2-D3-D4" input to each terminal of the AND gate (Al ... A4) is the light output amount of the "LED". It is assumed that the data is outputted from the correction data shift register (CSRB) as correction data for correcting the amount of light output with neighboring LEDs to be the same.

As described above in FIG. 1, when the print data SI is shifted to the data shift register DSRB and the latch enable signal LAE is supplied, data for printing one dot from the output terminal Q0. Is output.

If the output data is " 1 " at this time, it is gated by the strobe signal STB and input to the AND gates A1 ... A4, respectively.

Therefore, the LED is driven according to the input of the correction data D1, D2, D3, and D4.

In the above state, the current I0 flowing through the LED is represented by the sum of I0 = I1 + I2 + I3 + I4 by Kirchhoff'low (KCL) 's current law. Here, if the load resistances Rl, R2, R3, and R4 of the drains of the MOSFETs Ql, Q2, Q3, and Q4 are changed as described above, for example, 8R1 = 4R2 = 2R3 = R4, each current is equal to I1 =. 2 * I2 = 4 * I3 = 8 * I4.

Therefore, when the MOSFETs Ql, Q2, Q3 and Q4 are selected and driven by the correction data Dl, D2, D3 and D4, the driving current flowing through the LED can be changed accordingly. That is, adjustment of the quantity of light of LED can be made by current control.

가 된다.For example, setting the calibration data to D1 = 1, D2 = 0, D3 = 1, D4 = 0 so that only MOSFETs Ql and Q3 are "on" and MOSFETs Q2 and Q4 are off will cause the LED to turn on. Flowing current

Becomes

Therefore, it can be seen that the light quantity of the LED can be corrected by the 4-bit correction data to remove the light quantity deviation with the neighboring LED.

At this time, the operation state of each MOSFET by the 4-bit correction data and the LED current are shown in Table 1 below.

TABLE 1

As shown in (Table 1), the LED's luminous current (driving current) is compensated for the light output of each LED printing each dot by driving 16 steps including 0 (Zero) in the LED array (LEDAB). All LED light output characteristics can be detected and calibrated so that all LED light outputs are the same.

3 is a circuit diagram of an example in which the present invention is implemented in a B4 size 300DPI (Dot Per Inch) LED printer head (print head when driving 3072 LEDs).

In the figure, DSR0 ... DSR7 is a 384-bit output as a data shift register, and LAT0 ... LAT7 is a 384-bit latch output as a data latch. GA0 ... GA7 is a gate array each having 384 end gates, and CSR0... CSR7 is a correction data register with 1,536 bit output.

The LEDA0 LEDA7 are LED arrays, each containing 384 LEDDRs (LEDDRs) as shown in FIG.

4 is an operation timing diagram of FIG.

Hereinafter, the operation of the third embodiment will be described with reference to FIGS. 1, 2, 3, and 4 described above.

If the data enable signal ED and clock DCLK of 4MHZ are input to the correction data shift register CSR0 of FIG. 3 as shown in FIG. 4, the correction data of the number of LEDs of the B4 size LED printer is 3,072. (4x3,071 = 12,288 bits) is divided into eight blocks CD0 ... CD7 and shift-stored in each correction data shift register (CSR0, CSR1 ... CSR7).

The reason for dividing the correction data (12,288 bits) for 3,072 LEDs into 8 blocks in 1,536 bit units is to reduce the initialization time (shifting 4N bits of correction data. When shifting into blocks, only 4N / n bits of data need to be shifted for each block.)

In the case of a commonly used memory (ROM), the output is made in 8-bit units. When the 12,288 bits of correction data for the 3072 LEDs are divided and shifted into 8 blocks, the initialization time is greatly reduced by 12,288 / 8 = 1,536 bits per block. Can be.

As described above, when 12,288 bits of correction data for 3072 LEDs are divided and shifted into eight correction data shift registers CSR0 to CSR7, each of the correction data shift registers CSR0-CSR7 is shown in FIG. Shift data is stored in 1536 bits of data capable of correcting the light output of 384 LEDs.

When 1536 bits of correction data are shifted to each of the correction data shift registers CSR0-CSR7, each of the l536 bit outputs is configured as shown in FIG. 2 in each LED array (LEDA0 to LEDA7) in units of 4 bits. Each LEDDR is provided as an LED drive current control signal. At this time, if the data enable signal ED is one cycle of the clock DCLK, the data is 250ns, and the data stored in the correction data shift register CSR0 ... CSR7 is 1536, which is 1536 x 250ns = 384 µs.

The print data shift registers DSR0 to DSR7 are generated by the print enable signal EP of FIG. 4 after the shift storing time 384 μs of the data enable signal ED period 250 nsec + correction data 1536 bits has passed (Initialzation Time over) as described above. Is enabled.

As described above, when the number of print data bits 3,072 bits is also divided and shifted from the total N bits to n blocks, the data stored in each print data shift register (DSR0 ... DSR7) is stored by N / n bits.

Therefore, when 3,072 bits are divided into eight data shift registers (DSR0 ... DSR7) and shifted, the serial print data (SI0 ... SI7) inputted by 384 bits are stored in the data shift registers DSR0 ... DSR7. Is shown in FIG. As described above, the eight data shift registers DSR0-DSR7 divide and input 3072 print data by 384 pieces each, so that one-line print data (3,072 bits) is shifted when the time is 384 bits x 250 µnS = 96 µS.

At this time, if a latch enable signal LAE of l00 ns as shown in FIG. 4 is provided to the data latches LAT0 to LAT7, data shift registers DSR0 to DSR7, each of which contains print data at 384 bits, are latched and gated. They are input to the arrays GA0 to GA7, respectively.

In the above state, when the Storobe STB, which is the print "on" signal, is input "high" for 80 s as shown in Fig. 4, 3,072 bits of print data output 384 bits from each data latch (LAT0 ... LAT7) It is input to each of 3072 LED drivers (LEDDRs) in the LED arrays (LEDA0… LEDA7) to drive the corresponding LEDs.

At this time, the LED driving MOSFETs in each LED driver are determined by the correction data shifted and stored in the correction data registers CSR0 to CSR7 during the initialization period. The light output is corrected according to characteristics to emit light.

On the other hand, as shown in FIG. 4, when the print data is driven from the data latch LAT0 ... LAT7 to the latch enable signal LAE by the strobe signal STB, the LEDs of the LED arrays LEDA0 to LEDA7 are driven by the data shift register. In the DSR0 ... DSR7, the 3072 bit print data of the next line is shifted by the clock CLK as described above.

Therefore, when calculating the print speed when the B4 size LED printer head is manufactured as in the present invention, the initialization time is 250ns + 384μs and the 1-line print time is 96μs + 100ns, so it takes time to print one B4 size of 4320 lines. Is as follows.

250ns + 384μs + 250ns + 4320 × (96μs + 100ns) + 80μs = 0.416 seconds

Where 80μs is the last strobe (STB) time. Therefore, high speed printing of 60 seconds / 0.416 seconds = 144 sheets / minute can be achieved.

As described above, the present invention can make the light output of each LED in the high-density LED array constant by controlling the current flowing through each LED with 4 bits of correction data, and input the correction data only once at the initialization time. It is possible to have a high printing speed. In addition, in order to be compatible with a commercially available memory (ROM), the initialization time can be reduced by configuring the correction data shift register part with the number of blocks as many as the number of memory output terminals.

Claims (2)

Serial printing data having a print enable signal (EP) terminal, a clock terminal (CLK), and a printer data input terminal (SI), which are enabled by input of the printer enable signal (EP) and are input to the terminal (SI). Latches and outputs the data shift register (DSRB) and the output print data of the data shift register (DSRB) in parallel with the clock inputted to the terminal (CLK) in a latch enable signal (LAE). A print head having a data latch (LATB) and a gate array (GAB) for gating output of latching print data of the data latch (LATB) by a strobe signal (STB) for a predetermined period, the gate array (GAB). LEDs that are turned on and off by the output of the gate array and have the number of outputs of the gate array (GAB), and control the driving current of each of the LEDs according to the light amount correction data of a predetermined bit. LED array (LEDAB) having as many LEDs as the driver (LEDDR), data enable terminal (ED), clock input terminal (DCLK) and correction data input terminal (D) is operated by the data enable input and the Shift-stored correction data input corresponding to a predetermined number of bits of the print data inputted to the data shift register DSRB by the clock inputted to the clock terminal DCLK to store one bit of gating data of the gate array GAB. Comprising a correction data shift register (CDRB) for providing a predetermined bit of LED drive current data to each of the LED driver (LEDDR) in the input LED array (LEDAB) is output from the correction data shift register (CSRB) and the LED array ( LEDAB) specially corrects LED emission output by controlling the driving current of the corresponding LED differently according to the correction data of a predetermined bit inputted to each LED driver (LEDDR). Current control LED printhead. The method of claim 1, wherein the LED driver (LEDDR) in the LED array (LEDAB) is connected to the load resistor and switching transistor in series between the cathode of the LED and the predetermined second power supply of the plurality of LEDs to the first power supply to the anode A plurality of configured driving circuits are connected, and a plurality of inputs for outputting one bit of the gate array GAB in common and inputting correction data of a predetermined bit output from the correction data shift register CSRB are input to each other input. And an output of the AND gate of which is connected to a control terminal of the plurality of switching transistors, and operates in the driving circuit in accordance with the outputs of the plurality of AND gates to differently control the driving current of the LED.

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