JPH01255891A - Circuit for dimming luminous display device - Google Patents

Abstract

PURPOSE:To improve the visual recognizability by controlling the duty of the pulse width of a display turning-on/off signal, which is inputted to a drive circuit, based on the ambient brightness and processing it as the display turning-on/off signal thereafter. CONSTITUTION:After the pulse width of the display turning-on/off signal inputted to a drive circuit 11 is controlled to a proper duty in accordance with the ambient brightness of a luminous display device, this signal is processed as the normal display turning-on/off signal. Thus, the display is always dimmed in accordance with the ambient brightness, that is, the display is dimmed to a sufficient brightness against the brightness of the sunlight in the daytime to obtain the display of high visual recognizability, and the display is dimmed to a relative darkness at night to obtain the undazzled display according with the ambient darkness.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a drive circuit for a light emitting display device, and more particularly to a dimming circuit that can adjust display brightness according to ambient brightness. It is something.

[Conventional technology]

Conventionally, when using a light-emitting display device outdoors, the brightness of the surrounding area changes significantly between daytime and nighttime, so the display visibility of the light-emitting display device is increased by making the display brighter during the day. Also, since the surroundings are dark at night, if the display is too bright, it will be dazzling, and even a relatively dark display will not be sufficiently visible, so the display of the light emitting display device should be adjusted to be a little darker. There is.

[Problem to be solved by the invention] This adjustment can be done by, for example, switching the display brightness or darkness by specifying a time, or by comparing the surrounding brightness with a reference level using a light sensor. Since the display brightness and darkness is switched in two stages, a bright state and a dark state, there is no linearity in the brightness of the display by the light-emitting display device, and the balance with the surrounding brightness is poor, especially in the morning and evening. When the brightness of
The display contrast of the light-emitting display device may become low, and when it becomes dark even during the day due to weather events or abnormalities, the conventional switching of light and dark depending on the time cannot be used, and the display becomes too bright, causing halation. There were problems with visibility, such as making it difficult to see.

In view of the above points, the present invention adjusts the brightness of the display steplessly according to the surrounding brightness, so that even in the morning and evening or when the weather suddenly changes, the surrounding brightness at that time is always adjusted. The purpose is to provide a dimming circuit for a light emitting display device that can provide a highly visible display with appropriate contrast corresponding to the

[Means and actions for solving the problem] The above purpose is to
According to the present invention, in a drive circuit that causes a light emitting display device to perform a desired display using a display on/off signal, the display on/off signal to be input to the drive circuit has a pulse width based on the brightness around the display device. Dimming of a light-emitting display device in which the display of the light-emitting display device is dimmed according to the surrounding brightness by having the pulse width duty-controlled by a control circuit and then being processed as a display on/off signal. Achieved by circuit.

According to this invention, the display on/off signal that causes the light emitting display device to perform display is outputted to the normal display after the pulse width is appropriately duty-controlled by the pulse width control circuit in accordance with the brightness around the light emitting display device. Since it is processed as a display on/off signal, the display by the light emitting display device can always be dimmed to be bright enough to match the brightness of the surroundings, that is, to counter the brightness of sunlight during the day. This provides a display with high visibility, and by controlling the light to be relatively dark at night, a display that does not dazzle in accordance with the surrounding darkness can be obtained.Furthermore, even when the weather changes, such as in the morning or evening, This means that a display with appropriate contrast can always be obtained in accordance with the surrounding brightness at that time.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 shows an embodiment of a dimming circuit of a light emitting display device according to the present invention, and a dimming circuit 1o includes a drive circuit section 1.
1 and a pulse width control circuit section 21.

The drive circuit section 11 is composed of a driver 12 and an orgame 13 whose output terminal is connected to the enable input τ ball of the driver 12, and the driver 12 receives a data signal S.

A clock signal CL is input, and an OLED 14 is connected to its output as a light emitting display device whose display is to be dimmed by the dimming circuit 10. Therefore, in the drive circuit section 11, when an L level signal is input from the OR gate 13, the driver 12 operates, and when an H level signal is input, the driver 12 stops operating. ing.

In addition, in the case of illustration, multiple LEDs 14 are connected to the driver 12.
are connected to each output of , but the number is arbitrary.
Only one LED 14 may be provided.

The pulse width control circuit section 21 detects the brightness around the LED 14 as a current value using a phototransistor 22 disposed around the LED 14, and converts the detected current into a voltage value using a transistor 23. circuit 2
4, and the detection voltage from this ambient light detection circuit 24 is V/F.
It is composed of a dimming pulse variable circuit 2G which is converted into a pulse width by a conversion circuit 25, and a cough V/F conversion circuit 25.
The output of is connected to one input of the OR gate 13 via the inverter 27, and the display on/off signal is input to the other input of the OR gate 13.

The light control circuit of the present invention is configured as described above, and the LE
When making D14 emit light, the ambient light of the LED I4 enters the phototransistor 22 that constitutes the ambient light detection circuit 24 of the pulse width control circuit 21 of the main dimmer circuit 10, and as a result, the phototransistor 22 A collector current corresponding to the light will flow. By applying this collector current to the base of the transistor 23, a voltage corresponding to the amount of the incident light is generated between the emitter and collector of the transistor 23. By inputting this voltage as a control voltage to the V/F conversion circuit 25 of the dimming pulse variable circuit B26, the C/F conversion circuit 25 outputs a pulse signal with a frequency corresponding to the control voltage.

The pulse signal is input to one of the OR gates 13 of the drive circuit section 11 via the inverter 27. Therefore, the above-mentioned pulse signal and the display on/off signal from the non-oral display control circuit are input to the OR gate 13 of the drive circuit section 11, so that both the display on/off signal and the pulse signal are at L level. The output becomes L level only when .

Therefore, when the display on/off signal is an on signal or at a level, this causes the driver 12 to operate, and this driver 12 controls the pulse width of the LED 14 with the pulse signal based on the input data signal and clock signal. The voltage applied is applied, and the LED 14 is caused to emit light.

At this time, when the pulse signal applied to the EN input of the driver 12 is at the L level for a long time, the light emission display of the LED 14 is bright (and when the pulse signal is at the L level for a short time, the illumination display is bright).
The light emitting display of the ED 14 is dark, and the light is dimmed by 1 according to the duty system of the pulse width control circuit section 21.

[Effects of the Invention] As described above, according to the present invention, in a drive circuit that causes a light emitting display device to perform a desired display using a display on/off signal, the display on/off signal to be input to the drive circuit is applied to the display device. After the pulse width is duty-controlled by the pulse width control circuit based on the surrounding brightness,
Since the display of the light emitting display device is configured to be dimmed according to the surrounding brightness by being processed as a display on/off signal, the display of the light emitting display device always corresponds to the surrounding brightness. In other words, during the day, the light is dimmed sufficiently brightly to counter the brightness of sunlight, resulting in a highly visible display, and at night, the light is dimmed relatively dark, making it easier to see the surroundings. It is possible to obtain a display that does not dazzle according to the darkness, and even when there is a sudden change in the weather or in the morning or evening, a display with appropriate contrast can be obtained at all times according to the surrounding brightness at that time.

Thus, according to the present invention, by steplessly adjusting the brightness of the display according to the surrounding brightness, even in the morning and evening or when the weather suddenly changes, the display always corresponds to the surrounding brightness at that time. An extremely excellent light-emitting display device dimming circuit that can provide a highly visible display with a balanced and appropriate contrast can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing the configuration of an embodiment of a dimming circuit of a light emitting display device according to the present invention. 10...Dimmer circuit: 11...Drive circuit section;1
2... Driver; 13... Or gate; 14
...LED. 21... Pulse width control circuit section; 22... Phototransistor; 23... Transistor; 24... Ambient light detection circuit; 25... V/F conversion circuit; 26.
... Dimming pulse variable circuit; 27... Inverter.

Claims (1)

[Claims] (1) In a drive circuit that causes a light emitting display device to perform a desired display using a display on/off signal, the display on/off signal to be input to the drive circuit is pulsed by a pulse width control circuit based on the brightness around the display device. After the width is duty-controlled, the light emitting display device is processed as a display on/off signal, so that the display of the light emitting display device is dimmed according to the surrounding brightness.
Dimming circuit for light emitting display device.