JPS5818296Y2 - Luminance control circuit for light emitting elements - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brightness control circuit for a light emitting element that automatically changes the brightness of a display device, illuminator, etc. using a light emitting body according to the brightness of its surroundings.

Conventionally, when the ambient brightness changes in light-emitting display panels and illuminators in cockpits of navigational vehicles such as ships, aircraft, and automobiles, variable resistors and voltage regulators are manually changed each time the illuminators and light-emitting devices are adjusted. Brightness was adjusted by changing the voltage applied to the display.

At twilight, the brightness changed from moment to moment, so it was necessary to make adjustments each time.

In addition, especially at night, if the adjustment is insufficient, you may be dazzled by looking directly at the illumination device or light emitting indicator, or the light from the illuminant may reflect on crows in the cockpit, and may even be emitted from the opposing craft. There was a risk that it might be mistaken for light.

Therefore, the present invention was developed to solve the above-mentioned problems, and the relative ratio of the time corresponding to the on-time and the time corresponding to the off-time of the oscillation output signal of the astable multi-by-break is calculated based on the surrounding brightness. An object of the present invention is to provide a circuit that controls the brightness of a light emitting body by changing it accordingly.

Next, the present invention will be described with reference to an illustrated embodiment.

In FIG. 1, the anode of the supplied DC power supply 1 is connected to the terminal 2a of the astable multi-by-break 2 and the terminal 2b via the current limiting resistor 3 and a light emitting element 4, such as a light emitting diode.
Furthermore, the cathode of the supply DC power source 1 is connected to the terminal 2c,
The base of the transistor 5 is connected to the terminal 2a via the coupling resistor 7.
In addition, the base is connected to the terminal 2a through the coupling capacitor 8 and the resistor 9, and the coupling capacitor 8 and the resistor 9 are connected to the terminal 2a.
The connection point with the transistor 6 is the terminal 2b, and the terminal 2b is the transistor 6.
The collector of the transistor 5 is connected to the terminal 2a through a coupling capacitor 10 and the light receiving element 11, and the collector is connected to the terminal 2a through a resistor 12. The connection point between the coupling capacitor 10 and the light receiving element 11 is connected to the transistor The emitters of transistors 5 and 6 are connected to terminal 2c.

FIG. 2 shows the characteristics of the resistance value B of the light receiving element 11, which is made of a photoconductor element, for example, with respect to the amount of light received, A. For example, when the amount of received light is small, such as A1, the resistance value of the light receiving element 11 is large, such as B1. When the amount of light received is large as shown in A2, the resistance value of the light receiving element 11 becomes small as shown in B2.

FIG. 3 shows an output signal due to a change in the amount of light A received by the light receiving element 11 as a coupling resistance of the astable multi-vib break 2.

In the circuit configured as shown in FIG.
oscillates by repeating on and off states, and its period T is T=T1+T2(1), where T1-0.7 BoCl(2) T2O,7R2C2(3).

The amount of light received by the light receiving element 11 is now A.

In this case, the resistance value is B.

If the respective resistance values and capacitances of the coupling resistors and coupling capacitors of the astable multivibrator 2 are Bo-R2, C and C2, then from equation (2) and (3), T becomes T2 and the astable multivibrator 2 The oscillation output from the output terminal 2b becomes an output signal whose on time (T2) and off time (T1) are equal as shown in FIG. 4 is supplied as a predetermined IF by the current limiting resistor 3.

Next, when the brightness of the wheelhouse changes and it becomes dark, for example at night, the light receiving element 11 receives a small amount of light A as A1, so the resistance value B1 becomes B as shown in FIG.

Since it becomes larger, T1>T2, and the output of the astable multi-by-break 2 is such that the off time T1 is longer than the on time T2 as shown in Figure 3C, reducing the percentage of time the light emitting element 4 is emitting light. This means that the brightness has been reduced.

On the other hand, the amount of light received is A.

When the resistance value B2 of the light receiving element 11 increases further to A2, the resistance value B2 of the light receiving element 11 becomes B.

As a result, T1<T2, and the output of the astable multi-by-break 2 as shown in FIG. 3 is obtained.

Therefore, the brightness of the light emitting element can be increased.

In this way, by automatically controlling the brightness of the light-emitting element according to the brightness of the wheelhouse, the brightness of the light-emitting indicator and illuminator can always be kept in the optimal state. Can be done.

Therefore, according to the present invention, by adjusting the brightness of light-emitting indicators and illuminators in the cockpit of navigational objects such as ships, aircraft, and automobiles to the optimum brightness, the brightness can be adjusted from moment to moment not only during the day and night but also at twilight. It also prevents dazzling caused by looking directly at displays, etc., especially during long periods of time at night.
In addition, it is possible to prevent the situation in which the light from the light emitting body is often mistaken for the light emitted by an opposing navigation vehicle due to reflection by the glass in the cockpit.

[Brief explanation of drawings]

Figure 1 is a brightness control circuit diagram of a light emitting element according to the present invention, Figure 2
The figure shows the resistance percentage of a light-receiving element made of a photoconductive element with respect to the amount of light received, and FIG. 3 shows the output signal of the astable multivib break according to the present invention due to changes in the amount of light received by the light-receiving element. 2... Astable multi-bye break, 3...
...Current limiting resistor, 4...Light emitting element, 5,6.
...Transistor, 7...Coupling resistance, 8
, 10... Coupling capacitor, 11...
Light receiving element.

Claims (1)

[Scope of utility model registration request] In a device that drives a light emitting element by the oscillation output of an astable multi-by-break, by using a light receiving element whose resistance value changes depending on the amount of light received as one of the coupling resistors, the oscillation period of the one coupling circuit can be changed depending on the amount of light received. A brightness control circuit for a light emitting element, characterized in that the brightness of the light emitting element is controlled by the oscillation output of a variable astable multi-by-break.