JPH05249907A - Display lighting system - Google Patents

Abstract

PURPOSE:To provide a display lighting system by which generation of heat is few on a display plane and flickering is not caused even if there exists vibration and brightness adjustment becomes easy. CONSTITUTION:A display lighting system is provided with an externally exposed display part, light-emitting diodes 17, 18 and 19 arranged so as to illuminate from inside of a device, PWM driving parts 31, 32 and 33 to carry out PWM driving on these diodes 17, 18 and 19 and a brightness variable control means 104 to control variably a duty ratio of a PWM signal for the PWM driving. Frequency of the PWM signal is selected to be high frequency in such a degree that flickering does not become a problem.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display illuminator suitable for use in, for example, an operation panel of a car audio system.

[0002]

2. Description of the Related Art Each operation key of an operation panel of an in-vehicle device such as a so-called car stereo is provided with a display pattern of characters, figures, symbols, etc. showing a function corresponding to the operation key, even at night or in a dark place. A lamp or a light emitting diode is used to illuminate these operation keys from the inside of the device so that the user can easily identify and operate them, so that the display pattern is exposed.

In the United States and European countries, it is obligatory that the brightness (brightness) of the display illumination on the operation panel must be continuously variable so that the brightness can be adjusted to the darkness close to the off state. There is. In the conventional brightness adjustment method, when a lamp is used as a lighting element, a method of direct current control (change in applied voltage) that controls the current flowing into the lamp Drives the lamp with a PWM signal and controls the duty ratio of the PWM signal The method of adjusting the brightness is used. Further, when the light emitting diode is used as an illuminating element, a direct current control method for controlling a current flowing into the light emitting diode is used.

[0004]

However, when a lamp is used as an illuminating element, there is a drawback that the operating conditions are limited because the temperature of the operation panel surface rises due to heat generation of the lamp. Further, in the case of the method of driving the lamp by PWM, since the lamp is driven, the frequency of the PWM signal cannot be increased, and it is necessary to drive the lamp at about 50 to 80 Hz. For this reason, there is a drawback in that the illumination flickers due to shaking of the vehicle while traveling. Furthermore, since the emitted light of the lamp is divergent light, there is a problem that the illumination light leaks to the adjacent key part when the operation key is made small. Therefore, the light shielding must be strictly performed, and the operation key is small. It has been difficult to make it multi-functional.

Further, in the case of direct current control of the light emitting diodes, the brightness when the current flowing into each of the light emitting diodes changes due to the variation in the current-to-luminance characteristics of the light emitting diodes. However, there was a defect that the brightness became uneven. Recently, in particular, in order to make the display illumination colorful, a plurality of light emitting diodes of different colors are often used, but light emitting diodes having different emission colors have a large difference in current-luminance characteristics.
The current situation is that uneven brightness cannot be avoided.

It is an object of the present invention to provide a display lighting device which can eliminate the above drawbacks.

[0007]

In order to solve the above-mentioned problems, the display lighting device according to the present invention has a display unit K1 exposed to the outside when the reference numerals of the embodiments described later are made to correspond to each other.
One or a plurality of light emitting diodes 17, 18, 19 arranged so as to illuminate from the inside of the device, and a PWM driving unit 3 for PWM driving the one or a plurality of light emitting diodes.
1, 32, 33 and a brightness variable control means 104 for variably controlling the duty ratio of the PWM signal for the PWM drive.
And is provided.

[0008]

According to the present invention having the above structure, the light emitting diode is PWM-driven. Then, by changing the duty ratio of the PWM signal by the brightness variable control means, the brightness of the light emitting diode can be changed and the brightness of the display section can be freely changed. When the light source for illumination is a light emitting diode, the heat generation is small and the PW having a relatively high frequency is used.
Since it can be driven by the M signal, it is possible to provide flicker-free illumination due to shaking while the vehicle is running. When a plurality of light emitting diodes are used, the duty ratio of the PWM signal is appropriately determined in advance for each light emitting diode, so that the display unit is illuminated with substantially the same brightness without causing uneven brightness. Similarly, when the emission colors are different, the uneven brightness due to the difference in color can be corrected by controlling the duty ratio of the PWM signal.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the display lighting device according to the present invention will be described below with reference to the drawings by taking the case of application to a car stereo as an example.

FIG. 2 shows an example of the operation panel surface of the car stereo of this example. In FIG. 2, 1 is a tape cassette insertion slot, 2 is a group of operation keys, 3 is an LCD display, 4 is an up-down key used for brightness adjustment of display illumination and other purposes. LCD display 3
When the car stereo is used in the radio receiver mode, the letters "AM" or "FM" and the reception frequency at that time are displayed as shown. In the tape play mode, the display 3 displays, for example, “TAP
The letter "E" is displayed.

The operation key group 2 is composed of a plurality of operation keys, and the plurality of keys K1, K2, K3 and the like among them are used as double function keys. That is, when the mode of use of the car stereo is the radio receiver mode, these keys K1, K2, K3 become tuning preset keys, and when these keys are pressed, they are preset corresponding to these keys. Broadcasting stations are automatically selected. When the car stereo is in the tape play mode, these keys K1, K2, K3 are used as a cassette eject key, a play key, a noise reduction selection key, and the like.

Each operation key of the operation key group 2 and the up / down key 4 are so-called self-illuminated. That is, the pressing portion / display plate of each key is illuminated from the back side from inside the device by the light source provided inside the device case of the car stereo. In the present invention, a light emitting diode is used as a light source for the illumination, and as will be described later, the PW
M drive. Since the light source is a light emitting diode, heat generated by display illumination on the operation panel surface is small.

Next, an example of the structure of the self-illuminating type illumination unit in the case of the double function key K1 will be described with reference to FIG. In FIG. 3, reference numeral 11 is a display plate that also serves as a pressing portion of the key K1. This display plate 11 is
In this example, as shown in FIG. 3B, the translucent white plate 12
Is formed by applying a black coating 13 having a light shielding property. On the display board 11, a portion of the display pattern 14 consisting of letters of a preset number as a preset channel selection key in the radio receiver mode, which is the first function of the key K1, and a tape player having a second function. Display pattern 1 consisting of function characters (character EJ representing eject key in the figure) as operation keys in mode
The black coating 13 is not applied to the portion 5 and the portion of the white plate 12 is left. Therefore, the display plate 11 is in a state in which white preset characters and letters as operation keys are formed on a black background. This display board 1
These display patterns 14 when illuminated from the backside of 1
Or, 15 will be displayed so as to stand out in the illumination color. The plate 12 may be a transparent plate and the display pattern portion such as characters and symbols may be colored in white.

The interior of the car stereo system is shown in FIGS. 3B and 3C.
As shown in FIG. 1, the light emitting diodes 1 as the illumination light sources corresponding to the characters 14 and 15 are respectively provided.
7 and 18 are provided on the printed circuit board 20. A PWM signal as a drive signal is supplied to the light emitting diodes 17 and 18 via a conductive pattern formed on the printed circuit board 20, and these are turned on at a predetermined brightness.

In this example, the light emitting diodes 17 and 1
In the case of No. 8, an emission color of orange is used. And
When the car stereo is in the radio receiver mode, the light emitting diode 17 is turned on, and the preset number display pattern 14 is illuminated in orange and displayed brightly.
When the car stereo is in the tape player mode, the light emitting diode 18 lights up and the function character (E
The display pattern 15 of J) is illuminated in orange and displayed brightly.

As shown in FIGS. 3A and 3B, the tip of a lens 16 serving as an operation display marker is provided at a substantially central portion of the display plate 11 in a protruding state. On the back side of the lens 16, as shown in FIG. 3B, for example, a light emitting diode 19 whose emission color is green is provided on the printed circuit board 20 as a light source for illumination of the operation display marker. Only when the key K1 is pressed by the user, the green light emitting diode 19 emits light, and the tip of the lens 16 as the operation display marker lights up in green.

In this case, in order to prevent the light emitted from each of the three light emitting diodes 17, 18, and 19 from leaking to a portion other than the portion to be illuminated, as shown in FIGS. Is surrounded by a light shielding plate 21. Since the light emitting diode has a large linearity of the emitted light, the structure of the light shielding plate 21 may be relatively simple. That is, even when a small key is used as a composite key, the display illumination of the one function display character is
The display illumination of other function display characters can be reliably separated.

The display plate 11 is also used as a pressing portion of the push key switch, and when this is pressed, the operation input signal set for the key is supplied to the key input decoder.

Other double function keys are also key K
It has the same configuration as 1. Further, other keys having substantially the same size as the key K1 are configured in substantially the same manner, but only two light-emitting diodes as a light source for illumination are used for the operation display marker and the single function display. Only necessary items such as installation are provided.

Next, the drive control system of the light emitting diode will be described with reference to FIG. FIG. 1 is a diagram for explanation, and is for explaining a state in which only the light emitting diodes 17, 18 and 19 for illumination of the above-mentioned key K1 are driven, and light emitting diodes for illumination of other keys are similar. It is driven by.

That is, in FIG. 1, reference numeral 100 denotes a PWM drive control circuit for a light emitting diode, which is composed of a microcomputer and is functionally equivalent to one provided with each means as shown in the drawing. That is, the PWM drive control circuit 100 includes the PWM signal generating means 101, 10
2, 103 and duty ratio control means 104
And a duty ratio setting decoder 105.

The PWM signal from the PWM signal generation circuit 101 is supplied to the light emitting diode 17 via the PWM drive circuit 31, and the light emitting diode 17 is supplied to this P signal.
It emits light with a brightness according to the duty ratio of the WM signal. Similarly, the PWM signal from the PWM signal generation circuit 102 is PW.
PWM to the light emitting diode 18 via the M drive circuit 32
The PWM signal from the signal generation circuit 103 is supplied to the light emitting diode 19 via the PWM drive circuit 33, and the light emitting diodes 18 and 19 emit light with the brightness according to the duty ratio of the PWM signal supplied thereto.

In this case, each PWM signal generation circuit 101,
The frequency of the PWM signal generated from 102 and 103 is 1
It is set to 50 Hz or higher. As a result, the flicker of the display illumination due to the shaking of the automobile while traveling is prevented. Further, the PW from each PWM signal generation circuit 101, 102, 103 at the time of the steady brightness of a predetermined brightness
The duty ratio of the M signal is determined by the light emitting diodes 17, 18,
When the current-luminance characteristics of 19 are different, they are not the same,
It is set according to the current-luminance characteristic of the light emitting diode driven by the PWM signal. As a result, even if there are variations in the brightness characteristics of the light emitting diodes, or even if the light emitting colors are different, it is possible to illuminate with the same brightness in the steady state.

The duty ratio control means 104 is
Each P from the PWM signal generating means 101, 102, 103
The duty ratio of the WM signal is controlled and the generation / stop of each PWM signal is controlled. Then, the operation signal of the operation key group 2 is supplied to the key input decoder 30 to decode which of the operation commands. Further, the operation signal of the up / down key 4 is supplied to the key input decoder 30 to detect whether it is up or down, and also detect the operation input amount. The decoded data of the key input decoder 30 is supplied to the duty ratio control means 104.

The duty ratio control means 104 is
The car stereo mode is detected from the decoded data of the operation signal of the operation key group 2 (including the mode selection key) from the key input decoder 30, and the light emitting diode to be turned on is determined according to the mode. 19
To turn on or off. The PWM signal generating means corresponding to the light emitting diode determined to be turned on by the duty ratio control means 104 is enabled, and the PWM signal is generated. Therefore, the light emitting diode driven by the PWM signal is turned on. The PWM signal generating means corresponding to the light emitting diode determined to be non-lighting is PW.
Generation of the M signal is stopped.

Further, the duty ratio control means 10
Reference numeral 4 determines the duty ratio of the PWM signal output from the PWM signal generating means 101, 102, 103 from the decoded data of the operation signal of the up / down key 4. For example, if the down key is kept pressed, the light emitting diodes that have been lit gradually become dark to the minimum value. The brightness change characteristic curve at this time is according to the setting data for each light emitting diode stored in the setting decoder 105. In this case, a plurality of luminance change characteristics are prepared in advance in the setting decoder 105, and it is possible for the user to select which change characteristic is to be used by inputting a setting code from the outside. For example, if the setting code is 4 bits, 16 kinds of brightness change characteristics can be selected for each light emitting diode. This makes it possible to avoid a difference in brightness change even if the light emitting diodes have different brightness change characteristics due to variations in light emitting diodes or differences in current-brightness change characteristics due to different color light emitting diodes. In addition, the brightness change control can be performed with a desired brightness change characteristic by inputting a setting code. Of course, all the light-emitting diodes for illumination for one key may be changed with the same brightness change characteristic.

Since the light emitting diode has a small light emitting surface unlike a lamp, in the case of a large key such as the key K4 or the key K5 in FIG. 2, only one light emitting diode is used for key illumination. In that case, uneven brightness occurs in the surface of the display plate, which is not preferable.

Therefore, in this example, in the case of these large keys, for example, as shown in FIG. 4, a plurality of light emitting diodes as light sources for illumination are used to avoid uneven brightness. In the case of the example of FIG. 4, three light emitting diodes 41, 42, 43 are provided at appropriate positions where uneven brightness does not occur. In this case, as shown in FIG. 5, the method of driving the plurality of light emitting diodes is as follows: the plurality of light emitting diodes 41, 42, 43 for the key K4, and the plurality of light emitting diodes 51, 52, for the key K5. 53,
Each connected in series, one transistor 44 and 5
4. In this case, the PWM signals for driving the illumination light sources for the keys K4 and K5 are supplied to the bases of the transistors 44 and 54, respectively.

When the lighting elements are connected in series as described above, in the case of a lamp, for example, one lamp requires about 8 V for lighting, and even if two lamps are connected in series, it becomes 1
It becomes 6 volts, and it cannot be driven for automobiles that normally use a 12 volt power source, but each light emitting diode can be about 1.4 volts, and even if three or more LEDs are connected in series, in a car stereo device, It can be driven sufficiently.
In this case, stable brightness can be obtained by causing the drive current of the light emitting diode to flow to the brightness saturation point.

The input of the adjustment signal for the brightness adjustment is not limited to the input by the up / down key, and the direct current voltage adjusted by the variable resistor may be A / D converted and input. , PWM signals may be input. Further, the input is not limited to the case where the key is provided on the operation panel, and the input may be made from the remote control device, for example.

The above example is the case where the present invention is applied to the display illumination device of the operation keys of the operation panel of the car stereo. However, the present invention is not limited to this example, the display illumination is required, and the brightness control is required. It is applicable to all necessary display lighting devices.

[0032]

As described above, according to the present invention, the light emitting diode is used as the light source for the display illumination, and the light emitting diode is driven by the PWM signal to control the brightness. Can be set to a high frequency, and a display illumination device that does not cause flicker even when a vehicle is running can be realized.

Further, by appropriately setting the duty ratio of the PWM signal for driving each light emitting diode, even if there is a variation in the light emitting brightness due to the difference in the light emitting color of the light emitting diodes, the substantially same brightness is obtained. Can be made to emit light, and visual balance can be easily achieved. Therefore, colorful display illumination using the different-color light emitting diodes can be performed without causing uneven brightness.

Further, by using the light emitting diode as the light source for illumination, the heat generation of the illumination unit can be reduced as compared with the lamp, and the influence of the heat generation on the circuit in the device can be reduced, and the user can It is possible to reduce the discomfort caused by the fever. Therefore, the display lighting device according to the present invention is less limited in terms of use, and the possibility of being used for various purposes is widened.

Further, since the light emitting diode having the feature that the emitted light has a large straight traveling property is used as the light source for illumination, it is easy to prevent the leakage light from wrapping around by using a relatively simple light shielding means. Even when a plurality of functions are displayed on one display board, the display pattern of the display characters of each function can be illuminated and displayed with good separability from the display patterns of other functions. ..

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a drive control circuit of a display lighting device according to the present invention.

FIG. 2 is a diagram showing a front panel of an example of an apparatus to which the present invention is applied.

FIG. 3 is a diagram showing a configuration example of a display illumination portion of some keys in the example of FIG.

FIG. 4 is a diagram showing a main part of another example of the display illumination device according to the present invention.

5 is a circuit diagram for explaining an example of a driving method of the illumination light source in the case of the example of FIG.

[Explanation of symbols]

 11 Display Board 12 Semi-transparent White Plate 13 Black Coating 14 First Function Display Character 15 Second Function Display Character 16 Lens 17, 18, 19 Light Emitting Diode 20 Printed Circuit Board 21 Shielding Plate 31, 32, 33 PWM Drive Circuit 101, 102, 103 PWM signal generating means 104 Duty ratio control means

Claims (2)

[Claims] 1. A one or a plurality of light emitting diodes arranged to illuminate a display unit exposed to the outside from the inside of the device, and a PWM drive unit for PWM-driving the one or a plurality of light emitting diodes. A display lighting device comprising: a luminance variable control means for variably controlling a duty ratio of a PWM signal for PWM driving. 2. A display plate portion, which is provided with a display pattern such as characters and symbols showing the first function and a display pattern showing the second function, and is exposed to the outside, and the display pattern of the display plate portion. A plurality of light emitting diodes arranged to illuminate from inside the device, a light shielding member for shielding between the light emitting diodes for illumination of each display pattern, and a light emitting diode for illumination of each display pattern A PWM drive section for PWM-driving each of them, a luminance variable control means for variably controlling the duty ratio of each PWM signal for the PWM drive, and lighting of the light-emitting diodes for illumination of each of the display patterns according to a display purpose function. And a display lighting device including lighting control means for controlling non-lighting.