JPS6316975Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dimming circuit that adjusts the display brightness of, for example, a vehicle display.

Conventionally, light-emitting display devices using fluorescent display tubes, etc. in vehicles emit light during the day at the maximum brightness unique to the display, and at night, depending on the driver's preference, the light may be too bright or too dark, which may be harmful to the eyes. In order to avoid fatigue, the maximum brightness is set to, for example, half the maximum brightness inherent to the display, and the brightness is arbitrarily adjusted up to 0 to display light. However, such conventional devices have a configuration that does not allow daytime brightness adjustment, so they display speed, fuel amount, etc. at the same brightness on both bright, sunny days and dim, cloudy days, which consumes unnecessary power. Furthermore, the lights were too bright during the dimly lit daytime, causing excessive eye fatigue for drivers.

The present invention was made to eliminate the above-mentioned drawbacks, and provides a display dimming device that can adjust the brightness from the maximum brightness inherent to the display to a predetermined brightness, for example, 0 brightness, according to the surrounding brightness even during the day. It is intended to.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. In FIG. 1, 1 is an on-vehicle battery, 2 is an ignition switch, 3 is a lighting switch, 4 is a lamp such as a small lamp or headlamp connected to the battery 1 via the lighting switch 3, and 5 is a lighting switch 3. 6 is a day/night switching circuit which inputs the output signal (day/night detection signal) of _the judgment circuit 5.
It consists of a transistor _TR1 that is off during the day and on at night. 7 is the above battery 1
A display means that is illuminated or emits light with a brightness proportional to the electric power supplied from the ignition switch 2 through the ignition switch 2, and 8 controls the duty ratio of the output pulse manually by adjusting the volume or by detecting the brightness in the vehicle interior. A waveform generating section configured to be automatically changed by a light receiving element; 9 an inverting circuit consisting of a transistor TR ₄ for inverting and amplifying the output signal from the waveform generating section 8; 10 a display means 7 as a load; In this power adjustment circuit, a transistor TR ₂ whose base is connected to the collector of a transistor TR ₁ and a transistor TR ₅ whose base is connected to the collector of a transistor TR ₄ are connected in series, and further a transistor TR ₂ is connected in series.
Zener diode between the collector and emitter of
Consists of D ₁ connected. Note that the Zener diode _D1 has a Zener voltage of, for example, 1/ _2V0 , which is half of the battery voltage _V0 .

The operation of this embodiment during daytime will be explained. When the ignition switch 2 is closed and the lighting switch 3 is open, the transistor TR ₁
is in the off state, which causes transistor TR ₂
turns on only when transistor _TR5 is on. In addition, since the transistor TR ₄ alternately repeats the on and off state by the pulse whose duty ratio can be changed from 0 to 100% supplied from the waveform generator 8, the transistor TR ₅ also repeats the on and off state alternately. There is. Therefore, the voltage waveform at point A (collector of transistor TR ₂ ) alternates between +V ₀ and 0 as shown in FIG. Since the power in the shaded area in FIG. 2A is continuously changed from 0 to 100% and is supplied to the display means 7, the brightness ratio (brightness relative to the maximum brightness) of the display means 7 is changed during the daytime as shown in FIG. Like the linear characteristic, it can be changed in inverse proportion to the light attenuation rate (for example, how much the volume of the waveform generator 8 is throttled).

Next, the operation at night will be explained. When the ignition switch 2 and the lighting switch 3 are closed, the transistor _TR1 is turned on, so the transistor _TR2 is turned off. Here, the transistor TR ₄ alternately repeats on and off states by the pulses supplied from the waveform generator 8, and as a result, the transistor TR ₅ repeats the on and off states alternately, as shown in FIG. 2B. As shown, the lowest potential at point A is limited to the Zener voltage (for example, +1/2V) of the Zener diode _D1 , and the display means 7 is supplied with the power shown in the shaded area in FIG. 2B. The brightness rate varies from 50% brightness rate to 0% as shown in the linear characteristic at night shown in Figure 3.
can be changed in inverse proportion to the attenuation rate.

In the above embodiments, daytime refers to a time when the brightness does not require lighting the small lamp or headlamp, and night refers to a time when the brightness is necessary. Further, in the above embodiment, the load of the power adjustment circuit 10 is the display means 7, but it may be an illumination means that illuminates the display.

As explained above, according to the present invention, there is provided a waveform generator 8 that can arbitrarily select the duty ratio of the output pulse, a determination circuit 5 that distinguishes and detects day and night, and a waveform generator that generates the waveform based on the day/night detection signal from the determination circuit. A power adjustment circuit 10 that outputs a power ratio with respect to a duty ratio of an output signal from a generating section 8 at nighttime that is smaller than that during daytime, and a display means that lights up and displays a display at a brightness based on the signal from the power adjustment circuit. 7, the power adjustment circuit 10 includes a switching element TR 5 that turns on and off in response to an output pulse from the waveform generator 8, and a switching element TR ₅ that is connected in series with the switching element and the display means 7 to perform the determination. When a day/night detection signal is supplied from the circuit 5 and the switching element TR ₅ is turned on or off, two types of constant voltage power with different voltage values are displayed on the display means 7 depending on the state of the day/night detection signal. The display brightness control circuit is characterized by comprising constant voltage circuits D ₁ , TR ₂ , and 1 that supply pulsed voltage, so that the display brightness of digital instruments can be adjusted arbitrarily depending on the surrounding brightness. This allows users to freely adjust the settings according to their own preferences or physical conditions such as eye fatigue, and has the advantage of eliminating unnecessary power consumption during the day. Furthermore, since a constant voltage is supplied to the display means, a plurality of display means can be connected in parallel, so that the circuit can be shared regardless of the number of display means.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a dimming circuit of a display device showing one embodiment of the present invention, Fig. 2 A and B are voltage waveform diagrams at point A of the circuit shown in Fig. 1, and Fig. 3 is a diagram of the voltage waveform at point A of the circuit shown in Fig. 1. FIG. 3 is a characteristic diagram of the circuit shown in FIG. 5... Judgment circuit, 7... Display means, 8... Waveform generator, 10... Power adjustment circuit.

Claims (1)

[Scope of utility model registration request] A waveform generator 8 that can arbitrarily select the duty ratio of the output pulse, a determination circuit 5 that distinguishes and detects day and night, and a duty ratio of the output signal from the waveform generator 8 based on the day/night detection signal from the determination circuit. The power adjustment circuit 10 includes a power adjustment circuit 10 that outputs a power ratio smaller than that of the daytime at night, and a display means 7 that lights up and displays a display with a brightness based on a signal from the power adjustment circuit.
is a switching element TR ₅ which is turned on and off in response to an output pulse from the waveform generator 8, and is connected in series to the switching element and the display means 7, and is supplied with a day/night detection signal from the determination circuit 5; and a constant voltage circuit D that supplies two types of constant voltage power having different voltage values to the display means 7 in pulse form according to the state of the day/night detection signal when the switching element TR ₅ is turned on or off. ₁ , TR ₂ ,
1. A dimming circuit for a display device comprising: