JPH0830224A - 2-color emission type graphic display - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce the number of parts by eliminating the conversion driver used in the conventional device for converting the polarity of the control signal of the decoder driver. A display unit 2 in which anodes of one light emitting color light emitting diode R and another light emitting color light emitting diode G are commonly connected for each display element of the display unit 2 and is turned on in response to a graphic display signal.
A decoder driver 3 for outputting a control signal consisting of a power supply voltage to a common contact of the anodes of one light emitting color light emitting diode R and another light emitting color light emitting diode G, and one light emitting color light emitting diode of each display element of the display unit 2 which is lit or The emission color selection circuit 5 outputs a control signal composed of a ground voltage to the cathode of the other emission color light emitting diode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-color light emitting type graphic display mounted on a control panel or the like to display a graphic such as an arbitrary number or character in two colors, for example, red and green.

[0002]

2. Description of the Related Art As a two-color light emitting type graphic display device of this type,
A two-color light emitting type number display using red and green light emitting diodes is well known. 3A and 3B show a general structure of a two-color light emitting type number display, where FIG. 3A is a perspective view and FIG.
It is a block diagram of the display part of. In FIG. 3A, the two-color light emitting type number display is provided with the display unit 2 on the front surface of the case 1,
The control circuit of the display unit 2 is housed inside the case 1. As shown in FIG. 3B, the display unit 2 includes a red light emitting diode R (R _a , R _b , ... R _g ) and a green light emitting diode G (G _a , G _b , ... G _g ), respectively. Consisting of 7
..G, and a decimal point DP indicating the number of digits consisting of the red light emitting diode R ( _RDP ) and the green light emitting diode G ( _GDP ), for a total of eight display elements. Composed.

One or a plurality of this two-color light emitting type number display
Place several pieces side-by-side to create a number segment or decimal
Red or green light emitting diode of each display element of point
By selecting the mode and turning it on, you can select any value in two colors.
Can be displayed. FIG. 4 shows a conventional example of a two-color light emitting type number display.
It is a circuit diagram. In FIG. 4, each display element of the display unit 2,
That is, the numerical segments a, b, ...
Int DP red light emitting diode R (R_a, R_b・ ・ ・
・ R_g, R_DP) And a green light emitting diode G (G_a, G
_b・ ・ ・ G_g, G_DP) Is the cursor for each display element
Connected in common. And the two-color light emitting type number display is
The display unit 2 and the 4-bit number display signals A to D are input,
For each display element a, b, ...
On the other hand, a control signal V composed of the power supply voltage of the power supply terminal V_a, V
_b・ ・ ・ V_g, V_DPDecoder driver 3 that outputs
And the power supply voltage of the power supply terminal V of this decoder driver 3
Control signal V_a, V_b・ ・ ・ V_g, V_DPThe ground end
Control signal E consisting of the ground voltage of the child E_a, E_b・ ・ ・ E
_g, E_DPAnd each control signal E_a, E_b・ ・ ・
E_g, E_DPThrough the current limiting resistor 6 in each table of the display unit 2.
Red light-emitting diode R of display elements a, b, ...
And at the common connection point of the cathodes of the green light emitting diode G
The conversion driver 4 for outputting and its collector are power terminals V
In addition, the emitter is a red light emitting diode of each display element of the display unit 2.
Iodo R (R_a, R _b・ ・ ・ R_g, R_DP) Anno
The base is the resistor 54 and the emission color selection signal switch.
It is connected to the ground terminal E via the switch 55 and its base
51 with a resistor 52 connected between the collector and the collector
And its collector emits green light of each display element of the display unit 2.
Diode G (G_a, G_b・ ・ ・ G_g, G_DP) Ano
Its emitter to the power supply terminal V and its base to
Transistor 53 connected to the base of transistor 51
And a light emission color selection circuit 5 including.

The operation of this two-color type display is as follows.
Is. 4-bit number display signal A to the decoder driver 3
Table in which ~ D is input and lights up corresponding to this number display signal
Control signal consisting of power supply voltage for display element of display
V_a, V_b・ ・ ・ V_g, V_DPIs output. This control signal
No. is a conversion driver 4 and a control signal E consisting of a ground voltage._a,
E _b・ ・ ・ E_g, E_DPConverted into the respective current limiting resistors
Red light emitting diode R and green of each display element via 6
Output to the common connection point of the cathodes of the color light emitting diodes G
It On the other hand, the switch for the emission color selection signal of the emission color selection circuit 5
When switch 55 is turned off, transistor 51 turns on and emits red light.
The anode for the photo diode R is connected to the emission color selection signal switch.
When the switch 55 is turned on, the transistor 53 is turned on and green.
From the power supply voltage to the anode of the color LED G
Is output.

Here, for example, when the numeral 1 is displayed in red, a 4-bit number display signal indicating 1 is input to the decoder driver 3 and the light emission color selection signal switch 55 of the light emission color selection circuit 5 is turned off. To do. Then, the decoder driver 3 outputs the control signals V _b and V _c composed of the power supply voltage, and the control signal is converted into the control signals E _b and E _c composed of the ground voltage by the conversion driver 4 and the red light emitting diodes R _b and R _{b. A} control signal consisting of a ground voltage is applied to the cathode of _c , and a control signal consisting of a power supply voltage is applied from the emission color selection circuit 5 to the anodes of the red light emitting diodes R _b and R _c . Therefore, these red light emitting diodes _Rb and _Rc are turned on and the numeral 1 is displayed in red.

[0006]

The above-mentioned two-color light emitting type number display requires a conversion driver for converting a control signal consisting of a power supply voltage output from the decoder driver into a control signal consisting of a ground voltage. The large number of parts causes a cost increase. Further, for the transistors 51 and 53 of the emission color selection circuit 5, it is necessary to select an expensive transistor with a small variation in the current amplification factor h _fe , as described below, which causes a cost increase as described above. Has become. That is, the emitter currents of the transistors 51 and 53 of the emission color selection circuit 5 are current values obtained by multiplying these base currents by the current amplification factor h _fe , and when the current amplification factor h _fe varies, each light emitting diode is energized. The generated current varies, and the brightness thereof varies. This variation in brightness appears as a variation in the brightness of the light emitting diode between products, especially when mass-produced (note that the base current of these transistors 51 and 53 is increased and the current amplification factor h _fe is almost constant). However, in order to increase the base current, the resistors 52 and 5 of the emission color selection circuit 5 are used.
It is necessary to lower the resistance value of No. 4, but if the resistance values of these resistors 52 and 54 are lowered, the switch 5 for the emission color selection signal
When 5 is turned on, the ground current flowing through the resistor 54 increases, and this ground current risks damaging the transistors 51 and 53).

Further, the red light emitting diode R and the green light emitting diode G have different lighting voltages, the red light emitting diode R has a low lighting voltage and thus has high brightness, and the green light emitting diode G has a high lighting voltage and therefore has low brightness. Therefore this 2
The color-emission-type number display has a problem that the brightness when displaying in red is different from the brightness when displaying in green. An object of the present invention is to eliminate the conversion driver required in the conventional device, reduce the number of components, and prevent the variation in the brightness of each light emitting diode due to the variation in the current amplification factor of the transistor of the emission color selection circuit. It is an object of the present invention to provide a two-color light emitting type graphic display capable of adjusting the brightness of light emitting diodes of different colors to be equal.

[0008]

In order to achieve the above-mentioned object, a two-color light emitting type graphic display of the present invention comprises a plurality of display elements provided with light emitting diodes corresponding to two different colors. A two-color light emitting type graphic display for displaying an arbitrary graphic in two colors by selecting one of the light emitting color light emitting diodes or the other light emitting color light emitting diode of these display elements to light up is provided with a display unit. A display unit in which the anodes of the light emitting diodes of the display elements are commonly connected to each display element, and a light emitting diode of one of the display colors of the display element of the display unit that receives a graphic display signal and lights up in response to the graphic display signal, A decoder driver that outputs a control signal composed of a power supply voltage and a light emission color selection signal are input to a common connection point of the anodes of the other light emission color light emitting diodes. Constituting a light emitting color selection circuit for outputting a control signal consisting of one of the cathode to the ground voltage of the light-emitting color light emitting diode or other light-emitting color light emitting diodes of the display elements corresponding to the display unit. In the light emitting color selection circuit, for example, the collector is a ground terminal, the emitter is a cathode of one light emitting color light emitting diode of each display element of the display unit, and the base is a ground terminal via a light emitting color selection signal switch. Connected to the first transistor, the collector of which is the cathode of the other light emitting color light emitting diode of each display element of the display unit, the emitter of which is the ground terminal, and the base of which is the base of the first transistor and the first transistor. The second transistor is connected to the power supply terminal through the resistor. Furthermore, the second of this emission color selection
It is preferable to insert a second resistor between the connection point between the base of the transistor and the switch for the emission color selection signal and the base of the first transistor.

[0009]

In the two-color light emitting type graphic display of the present invention, the anode of the light emitting diode of each display element of the display section is commonly connected to each display element, and the power supply voltage output from the decoder driver to the lighted display element. The control signal consisting of each of the display elements is output to the common connection point of the anodes of one light emitting color light emitting diode and the other light emitting color light emitting diode, and the light emitting color selecting circuit outputs one of the light emitting color light emitting diodes of each display element. Alternatively, since the control signal consisting of the ground voltage is output to the cathode of the other light emitting color light emitting diode, the control signal consisting of the power supply voltage is output from the decoder driver to the display element, and the light emitting color selection circuit outputs the ground voltage to the display element. Is output.

Further, in the light emission color selection circuit, its collector is a ground terminal, its emitter is a cathode of one light emission color light emitting diode of each display element of the display section, and its base is a ground terminal via a light emission color selection signal switch. First connected to
And its collector to the cathode of the other light emitting color light emitting diode of each display element of the display unit, its emitter to the ground terminal, and its base to the power supply terminal via the base of the first transistor and the first resistor. It is composed of a second transistor connected, and when the switch for the emission color selection signal is turned on, the ground current flowing through the first resistor is prevented from flowing to these transistors and damage to these transistors is prevented. 1 can be reduced to increase the base current of these transistors to operate in a saturated state where the current amplification factor is almost constant, and the variation in the luminance of each light emitting diode due to the variation in the current amplification factor of these transistors. Disappears.

Furthermore, in this light emission color selection circuit, the second resistor is inserted between the connection point of the base of the second transistor and the switch for the light emission color selection signal and the base of the first transistor. By adjusting the resistance value of the inserted second resistor, the base current of the first transistor can be limited, and the emitter current, that is, the current flowing through the one-emission color light-emitting diode can be limited. By using a red light emitting diode having a high brightness as the diode and a green light emitting diode having another light emission color as the green light emitting diode having a low brightness, the brightness can be adjusted to be equal to each other.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram of a two-color light emitting type number display showing an embodiment of the two-color light emitting type display of the present invention. In FIG. 1, each display element of the display unit 2, that is, the numerical segments a, b, ... G and the red light emitting diode R (R _a , R _b , ... R _g , R _DP ) of the decimal point DP and the green color. Light emitting diode G (G _a , G _b , ... G _g , G _DP ).
Connects their anodes in common for each display element. The two-color light emitting type number display receives the display section 2 and the 4-bit number display signals A to D, and the red light emitting diode of each display element of the display section 2 which lights up corresponding to the number display signal. control signal V _a to the common connection point of the R and the green light emitting diode G consisting supply voltage of the power supply terminal V, V _b, ··· V
Decoder driver 3 that outputs _g and V _DP through current limiting resistance 6, its collector to ground terminal E, its emitter to the cathode of red light emitting diode R of each display element of display unit 2, and its base to light emission. Color selection signal switch 5
The transistor 53 connected to the ground terminal E via the transistor 5, and its collector is the cathode of the green light emitting diode G of each display element of the display unit 2, and its emitter is the ground terminal E.
Of the transistor 51 whose base is connected to the power supply terminal V through the base of the transistor 53 and the resistor 56.
And a light emission color selection circuit 5 including.

The operation of this two-color light emitting type number display is as follows. 4-bit number display signal A to the decoder driver 3
To D are input, and control signals V _a , V _b , ... V _g , V _DP composed of power supply voltages are output to the display elements of the display unit that are turned on in response to the number display signals. This control signal is output to the common connection point of the anodes of the red light emitting diode R and the green light emitting diode G of each display element via the current limiting resistor 6. On the other hand, when the light emission color selection signal switch 55 of the light emission color selection circuit 5 is turned on, the transistor 53 is turned on and the cathode of the red light emitting diode R is
When the light emission color selection signal switch 55 is turned off, the transistor 51 is turned on and the control signal composed of the ground voltage is output to the cathode of the green light emitting diode G.

Here, for example, when the numeral 1 is displayed in red, a 4-bit number display signal indicating 1 is input to the decoder driver 3 and the light emission color selection signal switch 55 of the light emission color selection circuit 5 is turned on. To do so. Then, the decoder driver 3 outputs the control signals V _b and V _c of the power supply voltage, the control signals of the power supply voltage are applied to the anodes of the red light emitting diodes R _b and R _c , and the emission color selection circuit 5 outputs the control signals. Red light emitting diodes R _b and R
_A control signal consisting of a ground voltage is applied to the cathode of _c . Therefore, these red light emitting diodes R _b and R _c
Lights up and the number 1 is displayed in red.

In this two-color light emitting type number display, the conversion driver 4 for converting the control signal composed of the power supply voltage of the decoder driver 3 into the control signal composed of the ground voltage, which is required in the conventional device shown in FIG. 4, is unnecessary. Therefore, the number of parts is reduced. Further, the resistance value of the resistor 56 of the emission color selection circuit 5 is reduced to increase the base current of the transistor 51 or 53, and the transistors 51 and 53 are used in a saturated state where the current amplification factor h _fe is substantially constant. As a result, even if the current amplification factors h _fe of these transistors 51 are varied, the currents supplied to the respective light emitting diodes are substantially constant, and variations in their luminance are prevented (in the emission color selection circuit 5, the emission color selection circuit 5 is selected). When the signal switch 55 is turned on, the ground current flowing through the resistor 56 does not flow through the transistors 51 and 53, but directly flows into the ground terminal E, so there is no risk of damaging the transistor 51 or 53 even if the resistance value of the resistor 56 is lowered. ). As a result, the luminance of the light emitting diode of each product can be made substantially constant, especially when mass-produced.

FIG. 2 is a circuit diagram of a two-color light emitting type number display showing a different embodiment of the present invention. The difference between this embodiment shown in FIG. 2 and the embodiment shown in FIG.
The resistor 57 is interposed between the connection point of the base of the above-mentioned and the switch 55 for the emission color selection signal and the base of the transistor 53. In this embodiment, by adjusting the resistance value of the inserted resistor 57, the base current of the transistor 53 is limited, and the emitter current thereof, that is, the current flowing through the red light emitting diode R is limited so that the green light emitting diode of low brightness is obtained. It is possible to adjust so that the brightness of G and the brightness of the red light emitting diode R having high brightness are substantially equal. Other operations are similar to those of the embodiment shown in FIG.

[0017]

In the two-color light emitting type graphic display device of the present invention, the number of parts is reduced, and when the products are mass-produced, the brightness of the light emitting diodes of each product is substantially constant, and the brightness of the light emitting diodes of different colors is equal. Since it can be adjusted as described above, a low-cost, high-performance two-color light emitting type graphic display can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a two-color light emitting type number display showing an embodiment of a two-color light emitting type graphic display of the present invention.

FIG. 2 is a circuit diagram of a two-color light emitting type number display showing a different embodiment of the two-color light emitting type graphic display of the present invention.

FIG. 3 shows a general structure of a two-color light emitting type number display,
(A) is a perspective view, (b) is a block diagram of the display part of (a)

FIG. 4 is a circuit diagram showing a conventional example of a two-color light emitting type number display.

[Explanation of reference numerals] 2 display unit 3 decoder driver 5 light emission color selection circuit 51 second transistor 53 first transistor 55 light emission color selection signal switch 56 first resistor 57 second resistor R red light emitting diode (one of Emitting color light emitting diode) G Green light emitting diode (other light emitting color light emitting diode)

Claims (3)

[Claims] 1. A display unit comprising a plurality of display elements provided with light emitting diodes corresponding to two different colors,
In the two-color light emitting type graphic display device for displaying an arbitrary graphic in two colors by selecting one of the light emitting color light emitting diodes or the other light emitting color light emitting diode of these display elements to light up, the light emitting diode of each display element Of which the anode of is commonly connected to each display element and the display element of the display section which receives the graphic display signal and lights up in response to this graphic display signal. A decoder driver that outputs a control signal composed of a power supply voltage to a common connection point of the anodes of the diodes,
A light emission color selection signal is input, and in response to this light emission color selection signal, a light emission color that outputs a control signal consisting of a ground voltage to the cathode of one light emission color light emitting diode or the other light emission color light emitting diode of each display element of the display section. A two-color light emitting type graphic display comprising a selection circuit. 2. The two-color light emitting type graphic display device according to claim 1, wherein in the light emitting color selection circuit, the collector is a ground terminal and the emitter is one light emitting color light emitting diode of each display element of the display section. The first transistor whose base is connected to the ground terminal through the switch for the emission color selection signal to the cathode, and its collector to the cathode of the other emission color light emitting diode of each display element of the display section, and its emitter to the ground A two-color light emitting type graphic display characterized in that a terminal is composed of a base of the first transistor and a second transistor connected to a power supply terminal through a first resistor. 3. The two-color light emitting type graphic display device according to claim 2, wherein the base of the second transistor of the light emitting color selecting circuit, the connection point of the light emitting color selecting signal switch and the base of the first transistor. A two-color light emitting type graphic display device having a second resistor interposed therebetween.