JPS60202484A - Information display - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an information display device that displays information using a light emitting diode as a display element, and in particular, to easily maintain a constant integral value of a current flowing through the light emitting diode. The present invention relates to an information display device that can maintain a constant color mixture of different types of light emitting diodes.

[Prior art]

In an information display device using a light emitting diode as a display element, a current is passed through the light emitting diode to cause it to emit light and display information. When the voltage applied to the light emitting diode changes, the current flowing through the light emitting diode also changes, and the brightness changes accordingly.

On the other hand, in an information display device in which light emitting diodes with different emitting colors are arranged side by side to emit light and information is displayed using a mixed color, the luminous intensity of the light emitting diodes with different emitting colors changes as the current flowing through the light emitting diodes changes. However, the problem is that the balance of the mixed color is disrupted and the color tone changes. In particular, when light emitting diodes are made of different constituent materials, their current changes vary greatly.

An example of a limiting resistor connection circuit for a light emitting diode in a conventional information display device is shown in FIG. It is GAAtAS. R1 is a current limiting resistor connected in series with this red light emitting diode D1. D is a yellow light emitting diode, and its constituent material has the chemical symbol GAASP. R2 is a current limiting resistor connected in series with this yellow light emitting diode D. The series circuit of the current limiting resistor R□ and the red light emitting diode D1 and the series circuit of the current limiting resistor R8 and the yellow light emitting diode D are connected in parallel to the power source E. Note that vl is the voltage of the power supply E supplied to the light emitting diode.

In the circuit configured in this way, the current limiting resistor R1
and a current limiting resistor R2 supplies a current I of 20 mA to the red light emitting diode D1 and the yellow light emitting diode D2, respectively.
This red light emitting diode D
211 mA each for 1 and several color light emitting diode D2
Current 11. When I flows, the voltage is about 1.7, which is indicated by VB, respectively.
A voltage drop of approximately 2.2v occurs, designated v and v8.

When the voltage v1 of the power source E applied to the red light emitting diode D1 is 3V, the current limiting resistor R□ is a case of , and the voltage of the power source E applied to the yellow light emitting diode D When v1 is 3V, the current limiting resistor R8 has a value of 3-. Thus, the red and yellow light emitting diodes D1. The voltage generated when a current ■llll11 is passed through D is 1.7V, indicated by V, and 2.2V, indicated by V8, and its characteristics vary depending on the constituent materials. Furthermore, the voltage generated when current is passed through a light emitting diode has a characteristic that it remains approximately constant even if the current changes.

Here, when the voltage v0 of the power supply E applied to the red and yellow light emitting diodes D1+D2 decreases to 2.5V,
Comparing the currents 1lIl+ flowing through the red and yellow light-emitting diodes D, , D, respectively, the following are obtained, which are greatly reduced from 20 mA, and there is a large difference between the two.

The change in the current 11°4-□ when the voltage V□ of the power supply E changes is shown in Fig. 2, which is a characteristic diagram in which the horizontal axis represents the voltage and the m axis represents the current I. 2 Figure K
Oite, ■1' indicates av, v, l+ indicates 2.5V, I' indicates 29 mA, 11'' indicates 12.3 mA, I
B' indicates 7.5 mA.

As shown in the characteristics of Fig. 2, the voltage v0 of the power supply E is 3
When the current falls below V (vl'), the current ■1 becomes the current I,
However, when the voltage v1 of the power supply E becomes higher than 3V (V,'), the current ■ conversely.

becomes larger than the current ■1.

The characteristic of a light emitting diode is the current flowing through the light emitting diode on the horizontal axis. As shown in FIG. 3, which is a characteristic diagram in which the luminous intensity LI is plotted on the vertical axis, the luminous luminous intensity LI is the flowing current. Since it is proportional to , the difference in current is the difference in luminous intensity. That is, when the voltage vl of the power supply E supplied to the light emitting diode changes, the red light emitting diode D
0 and the yellow light emitting diode D is distorted, and the tone of the mixed color is distorted. Then, there is a problem in that the lower the voltage v0 of the power source E, the more intense the red color becomes, and the higher the voltage v1, the more intense the yellow color becomes.

To avoid this, there is a way to make the power supply E that supplies voltage to the light-emitting diodes a stabilized power supply, but in information display devices in which a large number of light-emitting diodes are mounted, the current capacity is large, the device is large, and This has the drawback that the circuit configuration becomes complicated and is not economical.

[Object and structure of the invention]

In view of the above points, the present invention has been made to solve such problems and eliminate such drawbacks, and its purpose is to stabilize the power source that supplies voltage to the light emitting diode by using complicated means such as stabilizing tS. With a simple configuration without using a light emitting diode, the luminous intensity of the light emitting diode can be kept constant even if the voltage applied to the light emitting diode changes, and
Even when light-emitting diodes of many different colors are mixed to emit light, the mixed color can be displayed without changing, and the brightness can be set to any desired brightness and can also be switched. Our purpose is to provide information display devices.

In order to achieve such an object, the present invention sets the value of the power supply voltage so that when the power supply voltage supplied to the light emitting diode is high, the pulse output time ratio is decreased, and when the power supply voltage is low, the pulse output time ratio is increased. A pulse generating circuit that changes the output time ratio of output pulses according to the pulse generation circuit, and a driving means that drives the two light emitting diodes based on the pulse output of the pulse generating circuit, and even if the power supply voltage changes l-, -
The integrated value of the current flowing through the light emitting diode can be kept constant.

〔Example〕

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

FIG. 4 is a block diagram showing an embodiment of the information display device according to the present invention, and only the parts necessary for explanation are shown.

In the figure, AC is an alternating current power supply, and DCP is this alternating current power supply A.
This is a DC power supply circuit that takes the output of C as an input and converts it into a DC power supply.The output terminal (+) on the ncpOilttj side of this DC power supply circuit is connected to the anode side of the red light emitting diode R・■, ED and the yellow light emitting diode Y−LEI). Connection 7- Yes. Note that this DC power supply circuit DCP is not a stabilized power supply, so when the voltage of the AC power supply AC changes, the DC voltage output between the positive output terminal ←) and the negative output terminal 0 corresponds to the change. ■.

is subject to change.

DCOl and DCO, respectively, are the above DC power supply circuit D.
This voltage controlled oscillator D is a voltage controlled oscillator whose oscillation frequency is controlled based on the input voltage of the CP output.
CP, , and DCP are usually commercially available as monolithic ICs, and can also be configured using operational amplifiers, etc., so that when the input voltage changes, the oscillation frequency corresponding to the change changes, that is, the input voltage decreases. and the oscillation frequency is increased, and when the input terminal increases, the oscillation frequency is lowered and each output terminal ov1. ov, respectively. Here, in each of the voltage controlled oscillators VCO1°VCO, the rate of change of the oscillation frequency with respect to a change in the input voltage and the oscillation frequency can be set individually. MMl and Dust are monomulti circuits that are powered by the outputs 8- of voltage-controlled oscillators CO1 and VCO, respectively, and when they receive oscillation signals from voltage-controlled oscillators VCO and VCO2, the rising edge of the signal It is configured to output a signal with a pulse width of a time set individually for each. SW
are interlocking switches that are provided in the monomulti circuit MM1゜゜, respectively, and constitute a circuit that switches the pulse output time ratio, and when the interlocking switch SW is "closed", the pulse width is narrowed and output. This interlocking switch SW is provided to adjust the brightness of the information display device to match the brightness of the surroundings at night.

Then, the voltage controlled oscillator VCO1 and the mono-multi circuit amount, and the voltage-controlled oscillator VCO, and the mono-multi circuit M
M and l respectively indicate red light emitting diode R-LED.
and a yellow light emitting diode (Y-IJr), which constitutes a pulse generation circuit that changes the output time ratio of the output pulse depending on the value of the power supply voltage supplied to the yellow light emitting diode (Y-IJr).

Ql and water are respectively controlled by the outputs of the monomulticircuit MMl and the monomulticircuit MM,a, and the red light emitting diode R-LKD and the yellow light emitting diode Y
- A transistor that forms a driving means for turning on and off the current supply path of the IJD, and the collector of this transistor Q1 is connected to the cathode side of the red light emitting diode R-LED via a switch SW and a current limiting resistor R in series. , the emitter is connected to the negative output terminal (c) of the DC power supply circuit DCP, and the base is connected to the output terminal O of the mono multi-circuit MM1.
It is connected to M. Further, the collector of the transistor Q2 is connected to the cathode side of the yellow light emitting diode Y-Lm via the switch SW2 and the current limiting resistor R3 in series, and the emitter is connected to the negative output terminal of the DC power supply circuit DCP (
), and the base is connected to the output terminal OM to the mono multi-circuit W.

Here, this switch SW and switch SW.

is a switch that controls the red light emitting diode R-LED and the yellow light emitting diode Y-LED to turn on and off, respectively.

Next, the operation of the embodiment shown in FIG. 4 will be explained with reference to the time chart shown in FIG.

This Fig. 5 is a time chart showing the operating waveforms of each part in Fig. 4, where (,) is the DC voltage V obtained between each output terminal (+), ← on the positive and negative sides of the DC power supply circuit DCP.
, (b) is a red light emitting diode R
- The waveform of the pulse current I8 flowing through the LED, (c) the output waveform of the output terminal OV1 of the voltage controlled oscillator vCO1, (d
) is the output waveform of the output terminal OM of the monomulti circuit MM1, (,) is the waveform of the pulse current ■ flowing through the yellow light emitting diode v-Lm, (f) is the output of the output terminal OV of the voltage controlled oscillator VCO, The waveform (g) shows the output waveform of the output terminal 0 to the mono multi-circuit (2).

And (a) is the area when the above DC voltage V is low,
(b) is the area when the above DC voltage V is the rated voltage, (
C) shows the region when the DC voltage v4 is high, and B) shows the period when the DC voltage v4 is the rated voltage and the interlock switch SW shown in FIG. 4 is in the "closed" dimming state.

First, the output of the AC power supply AC is input to the DC power supply circuit DCP, and when the voltage of the AC power supply AC changes, the output voltage is changed at the rate of change, and the output voltage of the positive and negative sides is changed. A DC voltage V is output between the output terminals ← and . This DC voltage V is the red light emitting diode R-LED and the yellow light emitting diode Y-LED.
and a voltage controlled oscillator VCQ.

Input to VCO. And this voltage controlled oscillator VC
O□, VCO increases the oscillation frequency when the input voltage decreases, lowers the oscillation frequency when the input voltage increases, and outputs an oscillation output to its output terminals Ov□, OV, respectively. Note that this voltage controlled oscillator vCO1 and voltage controlled oscillator vCO
2, as described above, the rate of change of the oscillation frequency with respect to the change in input voltage and the oscillation frequency can be set individually.

Next, FIG. 5(e) obtained at the output terminals Ovl, 0■ of the voltage controlled oscillators VCO□, VCO, respectively.
The oscillation outputs with the waveforms shown in (f) were input to the mono multi-circuits MM 1 , MM , l respectively, and the signals were individually set as shown in Fig. 5 (d) and (g) at the rising edge of the signal. A pulse signal with a pulse width of time t□t'l is outputted to each output terminal OMl+0M11, and each transistor Q+Q2 is operated by the pulse signal, and while the pulse signal is outputted, the transistor Q+ ,Qi+
conduction between the collector and emitter of each.

On the other hand, the switches sw, , sw, as mentioned above,
Red light emitting diode R-LH and yellow light emitting diode Y
- Controls the emission and extinction of the LEDs, and the resistor RByR4 is the current limiting resistor R1, respectively shown in FIG.
It is a limiting resistor corresponding to R2, and when the DC voltage V obtained at the output of the DC power supply circuit DCP is the rated voltage, the red light emitting diode 1 (-LED and the yellow light emitting diode Y-
The peak value (see Fig. 5(b) and (e)) of the pulse current ■8°■ flowing through each LED is kept constant.

Now, when the switches sw, , sw are "closed", the red light emitting diode R-LED and the yellow light emitting diode Y-LEI are turned on while the transistors Q1+Q2 are operating.
) are each supplied with a pulse current I8. I, will flow and pulse light will be emitted.

On the other hand, mono multi-circuit MM0. When the interlocking switches SW connected to MMB are "closed", the mono multi circuit Oboro and the mono multi circuit MM, l have their pulse widths as shown in Fig. 5(d) and (g), respectively. The output is narrowed to time t8 and time t as shown, and this is to adjust the brightness of the information display device to match the brightness of the surroundings at night.

Here, voltage controlled oscillator VCO□ and voltage controlled oscillator vC
The oscillation frequency of O1l is the red light emitting diode R-LED.
When the yellow light emitting diode Y-LE emits pulsed light, the state of light emission and extinction is set so high that it is difficult to distinguish between them due to an afterimage phenomenon in human vision.

Next, with reference to the time chart of FIG. 5, the state of the voltage and waveform of each part during periods (a), (b), (c), and (b) of each area will be explained.

First, during the period (A) shown in FIG. 5, the DC voltage V obtained between the output terminal (+) and (0) of the DC power supply circuit DCP is low as shown in FIG. Voltage controlled oscillator vco1.VCO2+7) Each output terminal ov,,
The ov8o output frequency increases as shown in FIG.
lGf, valley output terminal OM1. The OMB pulse output time ratio increases as shown in FIGS. 5(d) and (g). Therefore, although the peak value of the pulse current I8+4 is low as shown in Figure 5(b) and (e), since the time ratio of the pulse current I8+4 is large, the integrated value of the pulse current I8+4 is the rated voltage. It is equal to the integral value of the pulse current I8.I when the voltage controlled oscillator vCO□, VCO
Among the output frequencies of the two output terminals ovl and ov, as shown in Fig. 5(f), the reason why the output terminal Ov is higher is that the current is higher when the voltage is low as shown in Fig. 2 above. This is to correct the point where the values are different.
It is made larger than the LED to make the integral value of each pulse current constant.

Next, during the period ←) shown in Figure 5, the output terminal (G) of the DC power supply circuit DCP (DC voltage V obtained between 0) is due to the rated voltage as shown in Figure 5 (a). , voltage controlled oscillator vco□, VCO, +7) each output terminal ov1
．． ov.

The output frequency (see Fig. 5 (C), (,)) is lower than the output frequency during the period (A), and the pulse current I
,,I.

The same frequency is used to keep the integral value constant.

15- Note that in this example, the time t0 to t4 is t
The explanation is based on an example in which the ratio of mixed colors is set to be equal by setting l"tilt8=t4.
You can also change the ratio.

Next, in the period (c) shown in FIG. 5, the DC voltage V obtained between the output terminal ← and (c) of the DC power supply circuit DCP is high as shown in FIG. Voltage controlled oscillator VCO□, VCO, (7) each output terminal ov1. O
The output frequency of the monomulticircuit MM0.V and MM0. Each output terminal OM,, OM of MM.

The pulse output time ratio becomes small as shown in FIGS. 5(d) and (g). Therefore, the pulse current I8. I.

The wave height value of
The integral value of +I4 is the pulse current I8. at the rated voltage (see period (b) in FIG. 5). It is equal to the integral value of I.

Here, at the output frequency of each output terminal Ov1 +O"+1 of the voltage controlled oscillator VCO The reason why the current value is higher than that of the red light-emitting diode (R-Lil) is that, as shown in Fig. This is done by making the light emitting time ratio of the red light emitting diode RL]1ilT) larger than the light emitting time ratio of the forgiveness light emitting diodes Y, I, PIJ), and each pulse current
.

(2) This is to keep the integral value of .

Next, during the period shown in Figure 5), the output terminal (+) of the DC power supply circuit DCP (DC voltage v4 obtained between
is the rated voltage, the voltage controlled oscillator vco1. shown in FIGS. 5(e) and (f). VCO, O each output terminal Ov1.
The output frequency of Ov is the same as the period (b) shown in FIG.
M1. OM.

The output pulse width is as shown in Fig. 5(d) and (g) at time t8+t4 and time 1 in period (b), respectively.
1,1. (See Figures 5(d) and (g)) By configuring the output to be narrower, the output time ratio becomes smaller, and as a result, the pulse currents shown in Figures 5(b) and (=), respectively. I8. The integral value of I also becomes smaller. That is, this can be done by lowering the luminous intensity of the red light emitting diode R-LED and the yellow light emitting diode Y-Lil.

In this way, even if the power supply voltage supplied to the light emitting diode changes, the pulse generation circuit consisting of the voltage controlled oscillators vco, , vco2 and the mono-multi circuits MM, , MM changes the output pulse time ratio according to the power supply voltage. By pulse-driving the light emitting diode with the output pulse,
The integral value of the current flowing through the light emitting diodes can be easily kept constant, the mixed color of different types of light emitting diodes can be kept constant, and the light can be easily adjusted at night.

FIG. 6 is an explanatory diagram showing an example of arrangement of light emitting diodes.
I' = DR9 indicates red light emitting diode, DY1
~DY9 indicates a yellow light emitting diode. Each of these light emitting diodes is connected to the respective collectors of the transistors Ql and QlI shown in FIG. 4 through a switch and a current limiting resistor, and the switch connected to each light emitting diode is connected or By switching to a disconnector, the desired light emitting diode can be made to emit light, and any information within the range of this mounted light emitting diode can be displayed by changing the emitted color. By increasing the number of characters, it is possible to display arbitrary characters, figures, etc., and it is possible to maintain a constant brightness even if the human power supply voltage fluctuates.

Although the present invention has been described above using mechanical switches as the switches sw, sw, , sw2, the present invention is not limited thereto, and may be constructed using semiconductors such as transistors and 8CH. In addition, in the above explanation, the types of light emitting diodes were explained as two types, red and yellow, but the present invention is not limited to this, and other colors may be used, and there may be multiple types of light emitting diodes. Needless to say, it is possible.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, light is emitted by the output pulse of the pulse generation circuit that changes the output time ratio of the output pulse depending on the value of the power supply voltage supplied to the light emitting diode, without using complicated means. Simple 19-Pulse driving of a diode Even if the power supply voltage supplied to the light emitting diode changes, the light emitting diode can be driven in pulses by the output pulse of a pulse generation circuit that changes the output pulse time ratio according to the power supply voltage. This allows the integrated value of the current flowing through the light emitting diodes to be easily kept constant, the mixed color of different types of light emitting diodes to be kept constant, and the light control at night to be easily performed. So the practical effect is extremely dog.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an example of a limiting resistor connection of a light emitting diode to explain a conventional information display device, and Figs. 2 and 3 are a circuit diagram showing an example of a limiting resistor connection of a light emitting diode to explain the operation of Fig. 1. A characteristic diagram of current and a characteristic diagram of luminous intensity with respect to the current flowing through the light emitting diode, FIG. 4 is a configuration diagram showing an embodiment of the information display device according to the present invention,
FIG. 5 is a time chart for explaining the operation of the embodiment shown in FIG. 4, and FIG. 6 is an explanatory diagram showing an example of the arrangement of light emitting diodes. 2O- R-LED, DR, ~DRQ...Red light emitting diode, Y-LED, DY, ~DYII...Yellow light emitting diode, vCOvCO...Voltage controlled oscillator,
MM 1 , MMllll 2 ... Mono multi circuit, Q, IQ, ... Transistor, f3W, SWI + 5Wll ... Switch, DCP ... DC power supply circuit. Patent applicant Koito Kogyo Co., Ltd.

Claims (3)

[Claims] (1) In an information display device that displays information using a light emitting diode as a display element, when the power supply voltage supplied to the light emitting diode is high, the pulse output time ratio is decreased, and when the power supply voltage is low, the pulse output time ratio is increased. A pulse generating circuit that changes the output time ratio of output pulses depending on the value of the power supply voltage so that the power supply voltage changes, and a driving means that drives the light emitting diode based on the pulse output of the pulse generation circuit, the power supply voltage changing. An information display device characterized in that the integrated value of the current flowing through the light emitting diode can be kept constant even when the light emitting diode is in use. (2) Supply to the light emitting diode. A pulse generation circuit that changes the output time ratio of output pulses depending on the value of the power supply voltage is provided for each diode with different characteristics, so that the integral value of the current flowing through the light emitting diodes with different characteristics can be kept constant. An information display device according to claim 1, characterized in that: (3) The pulse generation circuit that changes the output time ratio of the output pulses depending on the value of the power source voltage supplied to the light emitting diode is characterized by being equipped with a circuit for switching the pulse output time ratio and having a dimming function. Claim 1
Information display device described in section.