JPH0645654A - Light emitting device - Google Patents

Abstract

PURPOSE:To suppress the output fluctuation of a luminous body for stabilization by suppressing the temperature fluctuation accompanied by self heat build-up of the luminous body such as an LED and the drive circuit. CONSTITUTION:The temperature of an LED array 4 and that of an LED array drive circuit 5 are detected by a temperature sensor 9. A temperature control circuit 6 controls the calorifit value of an electrical heating element part 7 according to the control signal given to the electrical heating element part 7 to maintain the temperature of the LED array 4 to be at the set value based on a detection temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device, and more particularly to a light emitting device suitable for suppressing a fluctuation in light output of an LED array head applied to an electrophotographic optical printer.

[0002]

2. Description of the Related Art Conventionally, as an electrophotographic optical printer, one using a laser beam as a light source has been known, but in recent years, an optical printer using an LED array head as a light emitting source has been proposed. In such an optical printer, it is necessary to use a light emitting device for appropriately modulating the light emission of the LED array to form an image on the photoconductor.

FIG. 3 is a schematic configuration diagram of such a conventional light emitting device. In the figure, 1 is a mother board, 2 is a printed board on which the various circuits are mounted on the mother board 1, and 4 is an LED array in which a plurality of LEDs are arranged in rows on the mother board 1 and mounted. Reference numeral 3 is an LED array drive integrated circuit element for supplying a power supply and a drive signal to the LED array 4 based on an electric signal from a circuit on the printed board 2.

The operation of the above arrangement will be described below.

Power and drive signals externally applied to this device are supplied to the circuit on the printed board 2 on the mother board 1 and further to the LED array drive integrated circuit element 3.
Given to. As a result, each LED element of the LED array 4 is appropriately modulated and driven by the power supply and the drive signal from the LED array driving integrated circuit element 3.

[0006]

Since the conventional light emitting device is configured as described above, the LED array 4 and the LED
The array driving integrated circuit element 3 self-heats with the power consumption. This heat generation gradually increases immediately after the power is turned on until the thermal equilibrium state is reached. However, LED array 4
Since the output of the LED configuring the above changes with temperature, the output decreases as the temperature increases, as shown in the explanatory view of FIG. As described above, when the output of the LED array 4 fluctuates, the density of the print image output in an electrophotographic printer using this light emitting device fluctuates with the passage of time, and the quality of the output image deteriorates. There was a problem inviting me.

The present invention has been made in order to solve the above-mentioned problems of the prior art. By incorporating a heating element for applying heat to the LED array and a temperature control circuit for controlling the heating element, the LED is An object of the present invention is to obtain a light emitting device that suppresses output fluctuation of an LED array due to heat generation and temperature fluctuation of an array or an LED array driving integrated circuit element and is applied to an LED printer or the like to obtain a high quality output image To do.

[0008]

To achieve the above object, the present invention provides a light emitting means for emitting light, a temperature detecting means for detecting the temperature of the light emitting means, and a heat generating means for overheating the light emitting means. And a control means for controlling the heat generating means based on the output of the temperature detecting means to suppress temperature fluctuation of the light emitting means.

[0009]

As described above, in the light emitting device of the present invention, the temperature detecting means detects the temperature of the light emitting means, and the control means heats the light emitting means based on the output of the temperature detecting means. Is controlled to suppress the temperature fluctuation of the light emitting means with the passage of time.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a partial schematic configuration diagram of a light emitting device according to an embodiment of the present invention, and particularly relates to the configuration of an LED array driving integrated circuit element 3. In the figure, 5 is an LED array drive circuit which constitutes the LED array drive integrated circuit element 3 and drives the LED array 4, 7 is a heating element section having a function of generating heat by energization, and 6 is a heating element section 7
2 is a temperature control circuit for controlling the energizing current to control the heat generation temperature. In the temperature control circuit 6, 9 is a temperature sensor for detecting the temperature, 8 is a temperature sensor which compares the temperature detected by the temperature sensor 9 with a set temperature to generate an error signal, and the temperature control circuit 6 causes the heating element portion 7 to operate. It is a comparison circuit which is used as a control signal to be given to. By the way, the LED array drive circuit 5, the temperature control circuit 6, the heating element section 7, the comparison circuit 8 and the temperature sensor 9 are formed on the same chip.

The operation of the above arrangement will be described below.

When the light emitting device is turned on to start its operation, the LED array drive circuit 5 causes the LED array 4 to operate.
Is supplied with a power source and a drive signal appropriately modulated.
The LED array 4 and the LED array drive circuit 5 are normally at the same temperature as room temperature at the start of the operation, but as the operation continues, the temperature rises with the passage of time. On the other hand, the temperature sensor 9 constantly detects the temperatures of the LED array 4 and the LED array drive circuit 5, and the detected temperature does not reach the set value at the start of the operation. Therefore, the comparison circuit 8 generates an error signal. To do. As a result, a control signal is given from the temperature control circuit 6 to the heating element section 7 to raise the temperature, and the temperature of the LED array 4 is forcibly raised to the set value in the temperature control circuit 6. on the other hand,
As time passes, the LED array 4 and the LED array drive circuit 5 self-heat and try to raise the temperature. On the other hand, the temperature control circuit 6 keeps the temperature of the LED array 4 at the set value. The heat generation amount of the heating element portion 7 is reduced by the control signal given to the. As a result, temperature control is performed so that the sum of the heat generation amounts of the LED array 4 and the LED array drive circuit 5 and the heat generation amount of the heat generating element portion 7 becomes constant, and the LED array 4 is extremely short after the start of operation. The temperature reaches a steady temperature in time, and the temperature is maintained thereafter.

By performing the above operation, the temperature of the LED array 4 rises to the steady temperature immediately after the start of the operation and is maintained at the steady temperature as shown in the explanatory view of FIG. Since the light output of No. 4 also becomes a steady output within an extremely short time after the start of the operation, the fluctuation of the light output after the start of the operation is suppressed, and a stable output state can be maintained.

Therefore, in the optical printer using this light emitting device, the quality of the output image can be improved and a stable print output can be obtained.

In the above embodiment, the temperature control circuit 6 and the heat generating element portion 7 are incorporated in the chip of the LED array driving integrated circuit element 3, but this is the kind of temperature control. Compared to the case of combining a single component with, it has the feature that it can be downsized,
Further, since the heating element portion 7 and the LED array 4 can be brought close to each other, accurate temperature control can be performed. By the way, the temperature sensor 9 is incorporated in the LED array 4 instead of being incorporated in the LED array driving integrated circuit element 3,
The temperature of the element may be directly detected, and more accurate temperature control becomes possible.

[0017]

As described above, according to the present invention,
In order to suppress the temperature fluctuation due to self-heating of the light-emitting body such as the LED, the heating element is configured to overheat the LED to control the temperature so that the temperature of the LED from the start of operation becomes the steady temperature quickly. It is possible to quickly stabilize the output of the LED, and it is possible to prevent deterioration of the output image quality of an optical printer or the like using this light emitting device.

[Brief description of drawings]

FIG. 1 is a partial schematic configuration diagram of a light emitting device according to an embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of FIG.

FIG. 3 is a schematic configuration diagram of a conventional light emitting device.

FIG. 4 is an operation explanatory diagram of FIG. 2;

[Explanation of symbols]

 1 Motherboard 2 Printed board 3 LED array drive integrated circuit element 4 LED array 5 LED array drive circuit 6 Temperature control circuit 7 Heating element section 8 Comparison circuit 9 Temperature sensor

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[Procedure amendment]

[Submission date] December 25, 1991

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

[Correction content]

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

[0007] The present invention has been made to solve the prior art problems as described above, LED array driving integrated
By incorporating a heating element for applying heat to the circuit element and a temperature control circuit for controlling the heating element, the output fluctuation of the LED array due to the heat generation and temperature fluctuation of the LED array or the LED array driving integrated circuit element is suppressed, An object of the present invention is to obtain a light emitting device that can be applied to a printer or the like to obtain a high quality output image.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

[0008]

In order to achieve the above object, a light emitting device according to claim 1 is an LED array driving integrated device.
The circuit elements are the LED drive circuit, the temperature detection means, and the heating hand.
And the temperature detected by the temperature detecting means.
Control means for controlling the heating means to maintain a predetermined temperature;
And are formed on the same chip.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

[0009]

As described above, the light emitting device of the present invention includes the heating means and
The control means for controlling the heating means is the LED array drive assembly.
By incorporating the integrated circuit element into the chip, the temperature can be
It keeps a constant temperature regardless of the time and obtains high quality.
It ─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 9, 1992

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B41J 2/455 29/377

Claims (1)

[Claims] 1. A light emitting means for generating light, a temperature detecting means for detecting a temperature of the light emitting means, a heat generating means for heating the light emitting means, and the heat generating means controlled on the basis of an output of the temperature detecting means. Then, the light emitting device is provided with a control means for suppressing the temperature fluctuation of the light emitting means.