JPS62200775A - Led array driving device - Google Patents

Abstract

PURPOSE:To obtain a low-costing LED driving device which can independently control an amount of light emitted by each light-emitting element of an LED array, by providing an applying means for applying significance data of one or more bits to printing data and a light amount controlling means for independently controlling the potential of a power supply supplying to each LED element based on the significance data. CONSTITUTION:An LED array driving device driving an LED array 9 based on printing data PD inputted to a shift register 1 is provided with means 7 for applying significance data of one or more bits to the printing data PD and with light amount controlling means 10 for independently controlling a potential of a power supply supplying to each LED element in the LED array 9 based on the significance data MD of 1 or more bits applied by the applying means 7. For example, the applying means 7 is provided by an AND gate 7 which obtains an AND of the mask data MD supplied from a latch 6 and an output (a) from a latch 2. A programmable power supply 10 as the light amount controlling means changes a potential of the power supply supplying to the LED array 9 based on an output of a counter 11 so as to independently control the amount of light emitted by each of the LED elements constituting the LED array.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an LED array driving device that controls the amount of light emitted from a lamp unit constituted by an LED array.

[Conventional technology]

In recent years, with the advancement of semiconductor manufacturing technology, a large number of fine L
LED arrays in which EDs are arranged in rows at high density have been commercialized and are attracting attention as write heads for electrophotographic printers.

[Problem that the invention seeks to solve]

However, when used for such purposes, individual L
Since there is variation in the amount of light emitted by the ED, this appears as a difference in shading on the printing paper surface, resulting in a problem in that the printing quality is significantly degraded.

These problems can be resolved by improving the quality of the LED array itself, such as improving the manufacturing process or selecting LEDs, or by averaging the amount of light emitted from the LED elements using an external circuit using a laser trimming resistor, etc. However, the former requires a quality control process, and the latter requires a complicated circuit configuration, both of which significantly impede commercialization and increase product costs. is the current situation.

Furthermore, there are many requests for gradation expression of images by varying the light intensity of the LED array, and there is a strong demand for the development of a device that satisfies these demands.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to provide an inexpensive LED driving device that can independently control the amount of light from each light emitting element of an LED array.

[Failure to solve the problem]

The LED array driving device according to the present invention includes an adding means for adding weight data of at least 1 bit or more to print data, and each LED element of the LED array based on the weight data of more than 1 bit added by the adding means. and a light emission amount control means for independently controlling the power supply potential supplied to the light source.

[Operation] In this invention, the adding means adds weight data of at least 1 bit or more to input print data,
Based on the weight data of at least one bit or more, the light emission amount control means independently controls the power supply potential supplied to each LED element of the LED array.

〔Example〕

FIG. 1 is a block diagram showing the configuration of an LED array driving device according to an embodiment of the present invention, and 1 is a shift register that converts input print data PD from serial to parallel in synchronization with a clock signal qB. , l block data is completed, it is transferred to latch 2. 3 is an address counter that specifies the address of the mask data storage R○M4 in which data for correcting the amount of light emission is stored. Mask data storage R
OM4 stores mask data (weight data).

Reference numeral 5 denotes a shift register for masking, which performs serial-to-parallel conversion of 3-bit mask data MD, which will be described later, from the mask data storage ROM 4 in synchronization with the clock A, and transfers it to the latch 6 when one block of mask data MD is complete.

Reference numeral 7 denotes an AND gate serving as addition means of the present invention, which performs an AND operation between the latch output 6a (mask data MD) sent out from the latch 6 in synchronization with the clock signal C and the output 2a of the latch 2. 8 is an LED driver that drives the LED array 9. Reference numeral 10 denotes a programmable power supply constituting the light emission amount control means of the present invention, and the potential 10a (second
each LED constituting the LED array 9.
Controls the amount of light emitted from each element independently. The counter 11 counts the clock signal C, for example from "0" to "3",
The count value 22 (described later) is
Output to i10.

Next, the light amount correction operation according to the present invention will be explained with reference to FIG.

FIG. 2 is a timing chart for explaining the light amount correction operation according to the present invention, and the same parts as in FIG. 1 are given the same reference numerals. Note that the figure shows the case of one LED array 9.

The print data PD is serial-parallel converted by the shift register 1, and transferred to the latch 2 in synchronization with the clock signal B when one block of data is complete.

On the other hand, when correcting the amount of light emitted, address counter 3
outputs predetermined address information to the mask data storage ROM 4, the selected mask data MD is shifted into the shift register 5 in synchronization with the clock signal A, and when the mask data of l block is complete, it is transferred to the latch 6. . Here, in synchronization with the input clock signal C, the mask data latched in the latch 6 is transferred to the AND gate 7.
Output to. AND gate 7 outputs print data PD latched by latch 2 (latch output 2a shown in FIG. 2).
) and the mask data MD (
AND with the latch output 6a) shown in FIG.
Outputs 0N10FF information to the D driver 8. that time,
The LED driver 8 has programmable power supplies 1o to 2nd.
Since the potential 10a that changes as shown in the figure is supplied, the amount of light emitted from the LED array 9 can be controlled in eight stages, for example, as shown in FIG.

FIG. 3 is a diagram explaining the light emission amount correction data according to the present invention, where 21 indicates the relative light amount value (%), and the relative light amount value 2
1 is 20~15.15~10°..., -15~-20
The light intensity can be adjusted in 8 steps in 5% increments. 22 indicates the count value of the counter 11, and the count value is "0".
” to “3” and the latch output 6a of the latch 6 is rlJ, the potential 10a shown in FIG. 2 is supplied from the programmable power supply 10. Note that the counter 11 always changes the input clock signal C from "0" to "
3" are counted cyclically.

As can be seen from this figure, for example, if you want to minimize the relative light amount value 21 for one LED, mask data MD(r
llllJ) is input to AND gate 7, so
The potential 10a shown in FIG. 2 from the programmable power supply 10
is supplied to the LED driver 8, so the amount of light emission is gradually limited. By performing this operation for each LED element that constitutes the LED array 9, the LED array 9
The light emission can be corrected programmably.

In the above embodiment, the case where the amount of light emitted from each LED element in the LED array 9 is averaged is explained. However, if the LED array has negligible variations in the amount of light emitted, the above-mentioned address counter 3 and Mask data storage RO
By removing M4 and inputting gradation information to the shift register 5, it can also be used as ε for multi-value printing. Further, in this case, if the amount of light emission is controlled by weighting the gradation information as in the above embodiment, the temporal overshoot associated with the gradation expression can be minimized and the device configuration can be simplified.

Furthermore, by configuring the programmable power supply 1o with a pulse width modulation device, each LED can be driven in PWM at a constant voltage.

〔Effect of the invention〕

As explained above, the present invention includes an adding means for adding weight data of at least 1 bit or more to print data, and supplying the weight data to each LED element of the LED array based on the weight data of 1 bit or more added by the adding means. Since a light emitting amount control means for independently controlling the power supply potential is provided,
Since the amount of light emitted by each LED element constituting the LED array can be corrected independently, the amount of light emitted from the entire LED array can be averaged, and an optimal image without density unevenness can be obtained. Furthermore, since gradation information can be added to the print data, it has excellent advantages such as being able to give gradation expression to the output image.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a lamp driving device showing an embodiment of the present invention, FIG. 2 is a timing chart for explaining the light amount correction operation according to the present invention, and FIG. 3 is a light emission amount correction according to the present invention. It is a figure explaining data. In the figure, 1 and 5 are shift registers, 2 and 6 are latches, 3 is an address counter, 4 is a mask data storage ROM, 7 is an AND gate, 8 is an LED driver, 9 is an LED array, ] 0 is a programmable power supply, 11 is a counter.

Claims (2)

[Claims] (1) In an LED array driving device that drives an LED array based on print data input to a shift register, an addition means for adding weight data of at least 1 bit or more to the print data, and a The LE based on weight data of bits or more
1. An LED array driving device comprising: a light emission amount control means for independently controlling a power supply potential supplied to each LED element of a D array. (2) The LED array driving device according to claim (1), wherein the weight data is gradation information.