JPS6236145Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a level display circuit that displays the level of an input signal using a plurality of light emitting elements.

Conventionally, as a display device for displaying the levels of various signals, in addition to so-called voltmeters or oscilloscopes, a plurality of light emitting elements such as LEDs (light emitting diodes) are arranged in parallel, and the signal levels are displayed as bar graphs or lighting positions ( 2. Description of the Related Art A display device is known that displays steps using a dot display. FIG. 1 shows an example of this type of display device, in which the level of an input signal applied to an input terminal 1 is transmitted via a display driver 2 to five LEDs 3-1 to 3-5.
It is now displayed as a bar graph. In this case, the display driver 2 uses the reference voltages V ₁ to V ₂ (V ₁ <V ₂ <V ₃ <V ₄ <V ₅ ) as shown in FIG.
are applied to five comparison circuits 4-1 to 4-
5. For example, when an input signal voltage V _io of V ₂ <V _io <V ₃ is applied to input terminal 1,
Each output terminal of the comparator circuits 4-1 and 4-2 is at zero level, and the LEDs 3-1 and 3-2 are turned on. That is, the relationship between the lighting states of the LEDs 3-1 to 3-5 and the input signal voltage _Vio is illustrated in FIG. 3.

By the way, in the case of this display device, since the level is displayed stepwise according to the level of the input signal, it is particularly important that the input signal level is a voltage between the threshold values of each step (i.e., the voltages V ₁ to V ₅ ). In some cases, the disadvantage is that the input signal level cannot be accurately displayed.

This invention was made to eliminate such drawbacks, and by superimposing an AC bias signal whose waveform instantaneous value continuously increases or decreases over almost the entire period of each cycle on the input signal or reference voltage, The above-mentioned voltage between the thresholds can also be displayed based on the degree of brightness and darkness of the light emitting element.

Hereinafter, embodiments of this invention will be described with reference to the drawings. FIG. 4 is a circuit diagram showing the configuration of the level display circuit according to this invention. In this figure, an input signal applied to an input terminal 11 is passed through a resistor 12, and then an AC signal is supplied via a capacitor 13. A bias signal is superimposed and supplied to one input terminal of each of comparison circuits 14-1 to 14-5. The AC bias signal may be any periodic signal such as a sine wave, triangular wave, or sawtooth wave, that is, an AC voltage signal whose waveform instantaneous value continuously increases or decreases over approximately the entire period of each cycle. , and the frequency can be appropriately selected as long as it is not an extremely low or high frequency (for example, a commercial frequency of 60 Hz). Note that the level will be described later. Reference voltages V ₁ to V ₅ (V ₁ <V ₂ <V ₃ <V ₄ <V ₅ ) are applied to the other input terminals of each of the comparison circuits 14-1 to 14-5.
are supplied respectively. These reference voltages V ₁ to
V ₅ is the constant voltage Vref supplied to terminal 15.
It is made by dividing it by resistors 16-1 to 16-5 (each resistance value R) of equal value,
Therefore, between each reference voltage, V ₁ = V ₂ − _{V 1} = V ₃ − _{V 2} = V ₄ − V ₃ = V ₅ − V ₄ = V ₀
…(1) The following relationship has been established. And the comparison circuit 14
The respective outputs of -1 to 14-5 are supplied to the respective cathodes of LEDs 17-1 to 17-5 (light emitting elements). These LED17-1 to 1
7-5 are arranged in a line and used to display the level of the input signal supplied to the input terminal 11 in a bar graph. Further, the positive voltage obtained at the positive power supply terminal 18 is supplied to each anode of the LEDs 17-1 to 17-5.

Next, the operation of the circuit having the above configuration will be explained. First, the AC bias signal is assumed to be a sine wave AC signal whose peak value V _p -p satisfies V _p -p < V ₀ (see equation (1) above). When a voltage V _io approximately halfway between the reference voltages V ₂ and V ₃ is applied to the input terminal 11, for example _, as shown in FIG. are superimposed to form the signal shown in FIG. Each instantaneous value of this signal (the signal shown in FIG. 5B) is always between the reference voltages V ₂ and V ₃ , and therefore
While each output of comparator circuit 14 becomes zero level,
-3, 14-4, and 14-5 outputs have a positive voltage level. (This positive voltage level is the level of the positive power supply voltage supplied to the comparison circuits 14-1 to 14-5.) As a result, as shown in FIG. It will be fully lit. On the other hand, LED17-3, 17-4, 17
-5 is in an off state.

Next, when an input signal having a voltage value V shown in FIG. 5D is applied to the input terminal 11, one input terminal of each of the comparison circuits 14-1 to 14-5 is applied as shown in FIG. The signal indicated is applied. Since the instantaneous value of this signal is always larger than the reference voltages V ₁ and V ₂ , each output of the comparator circuits 14-1 and 14-2 becomes zero level, and both the LEDs 17-1 and 17-2 are completely lit. . On the other hand, since the relative magnitude of the signals supplied to each input terminal of the comparison circuit 14-3 changes alternately at the same period as the AC bias signal, the output of the comparison circuit 14 becomes zero at the same period as the AC bias signal. level or positive voltage level (in this case, the time at zero level and the time at positive voltage level are equal), therefore LED 17-3 will repeatedly turn on and off at the above cycle. . That is, when looking at the LED 17-3 with the naked eye, it appears to be lit at about half the brightness of when it is fully lit. In addition, LED17-4, 17
-5 is turned off. Further, the lighting/unlighting states of the LEDs 17-1 to 17-5 are shown in FIG.

For example, when the input signal voltage applied to the input terminal 11 is the voltage shown in FIG.
The signal shown in FIG.
As shown in Figure 5, LED17-1, 17-
2 is fully lit, LED 17-3 is lit with even weaker brightness compared to the case shown in Figure 5 above,
LEDs 17-4 and 17-5 go off.

In this way, even if the input signal voltage is an intermediate value between the reference voltages _V1 to _V5 , the circuit shown in FIG.
The input signal voltage can be displayed with each brightness of 7-5. Then, the peak value V _p -p of the AC bias signal mentioned above is V _p -
The display characteristics when p<V ₀ are illustrated in FIG. 6. In this figure, the broken line indicates the display characteristics of the conventional display device (characteristics shown in Figure 3).
It shows. This figure 6 shows that, for example, when the input signal voltage V _io is the value V _a , the LEDs 17-1 and 17-2 are completely lit, and when it is between the values V _a and V _b , the above state continues, and the value When it reaches V _b , LED17
-3 indicates that it starts to light up.

Next, the peak value V _p −p of the AC bias signal
FIG. 7 shows the display characteristics when V _p -p=V ₀ . In this case, for example, the input signal voltage V _io is the value V _a
At the same time that LED 17-2 becomes fully lit, LED 17-3 begins to light.
Therefore, the display characteristic becomes a straight line as shown in the figure.

Figure 8 shows the peak value V _p -p of the AC bias signal.
indicates the display characteristics when V _p -p>V ₀ ,
In this case, for example, the input signal voltage V _io becomes the value V _a
LED17-3 before LED17-2 lights up completely.
will begin to light up, resulting in a refracted characteristic as shown in the figure.

Next, a second embodiment of this invention will be described. FIG. 9 shows the configuration of a level display circuit that is a second embodiment of this invention. In this figure, parts corresponding to the circuit shown in FIG. 4 are given the same reference numerals. . The circuit shown in this figure is the fourth
The difference from the circuit shown in the figure is that a resistor 20 is inserted between the terminal 15 and the resistor 16-5;
0 and the resistor 16-5 is supplied with an AC bias signal. That is, in the case of the circuit shown in FIG. 9, the AC bias signal is not superimposed on the input signal, but the AC bias signal is superimposed on the reference voltages _V1 to _V5 . In this case as well, the signal (input signal) supplied to one input terminal of each of the comparator circuits 14-1 to 14-5 and the signal (reference voltage) supplied to the other input terminal become an AC bias signal. Therefore, the circuit changes relatively over time, and therefore has exactly the same effect as the circuit shown in FIG.

FIG. 10 shows a third embodiment of this invention, and the level display circuit shown in this figure shows a dot display (of the corresponding level) instead of the bar graph display in the first and second embodiments. The input signal level is displayed using a method in which only the indicator (LED) is lit. That is,
In FIG. 10, an input signal obtained at an input terminal 30 passes through a resistor 31, and then an AC bias signal supplied via a capacitor 33 is superimposed on the input signal. Then, the signal on which this AC bias signal is superimposed is transmitted to the comparator circuits 32-1, 32-3, 32-5, 32-
Comparator circuits 32-2, 32-4, 32-6, 32-8, 32
-9 to each other input terminal. Also, comparison circuits 32-1, 32-3, 32-
The ground potential and the reference voltages V ₁₁ , V ₁₃ , V ₁₅ are respectively supplied to the other input terminals of the comparison circuits 32-2, 32-4, 32-6, 32-8, 3
Each one of the input terminals of 2-9 has a reference voltage.
V ₁₂ , V ₁₄ , V ₁₆ , V ₁₈ , and V ₁₇ are supplied. Note that these reference voltages V ₁₁ to V ₁₈
(V ₁₁ < V ₁₂ < V ₁₃ < V ₁₄ < V ₁₅ V ₁₆ < V ₁₇ < V ₁₈ ), the constant voltage Vref applied to the terminal 35 is expressed by the resistors 34-1 to 34-9 (the resistance value is (both are assumed to be equal). That is, V ₁₂ −V ₁₁ = V ₁₃ −V ₁₂ = V ₁₄ −V ₁₃ =
They have the following relationship: V ₁₅ −V ₁₄ = V ₁₆ −V ₁₅ = V ₁₇ −V ₁₆ = V ₁₈ −V ₁₇ = V ₀ . The comparison circuit 32-1, 3
Each output of 2-2 is sent to a NAND circuit 36-1, and each output of comparison circuits 32-3 and 32-4 is sent to a NAND circuit 36.
-2, each output of the comparison circuits 32-5, 32-6 is sent to the NAND circuit 36-3, and the comparison circuits 32-7,
32-8 are respectively supplied to NAND circuits 36-4, and NAND circuits 36-1 to 36-4.
and each output of the comparator circuit 32-9 is LED3.
7-1 to 37-5 (light emitting elements) are driven. In addition, LED37-1 to 37-
A positive voltage is supplied to each anode of 5 from a positive power supply terminal 38.

In the above configuration, if the AC bias signal is a sine wave AC whose peak voltage V _p -p is, for example, V _p -p<2V ₀ , the display characteristics will be as shown in FIG. In this figure, the broken line indicates the characteristics of a conventional display device using dot display. and,
In the level display circuit shown in FIG. 10, the LED
The input signal level can be displayed by the brightness of 37-1 to 37-5. Further, by changing the value of the peak voltage V _p -p of the AC bias signal, the display characteristics can be changed.
Note that the AC bias signal may be supplied to the connection point between the resistors 34-8 and 34-9 as shown by the broken line in FIG. In this case, the reference voltage V ₁₁
An AC bias signal is superimposed on V18 to _V18 . Further, in the above embodiments, the number of LEDs is five in each case, but this is not limited to five and can be configured using a large number of LEDs.

As explained above, according to this invention, since an AC bias signal whose waveform instantaneous value continuously increases or decreases over almost the entire period of each cycle is superimposed on the input signal or reference voltage, the difference between the reference voltage and The signal level of the light emitting element can also be displayed by the degree of brightness of the light emitting element. In addition, the circuit can be configured easily and inexpensively, the characteristics of light intensity changes of the light emitting elements can be easily controlled, and the conventional step display drive circuit can be used as is, providing various advantages. It is suitable for this type of display circuit.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of a display device using conventional step display, Fig. 2 is a circuit diagram showing details of the display device shown in Fig. 1, and Fig. 3 is a display characteristic of the display device shown in Fig. 1. FIG. 4 is a circuit diagram showing the first embodiment of the invention, and FIGS. Figures 6 to 8 are all 4th
FIG. 9 shows the display characteristics of the first embodiment shown in FIG.
The figure is a circuit diagram showing a second embodiment of this invention.
FIG. 0 is a circuit diagram showing a third embodiment of this invention, and FIG. 11 is a diagram showing display characteristics of the third embodiment shown in FIG. 14-1 to 14-5, 32-1 to 32-9...
Comparison circuit, 17-1 to 17-5, 37-1 to 37
-5...Light emitting element (LED).

Claims (1)

[Scope of utility model registration request] It has a plurality of comparator circuits to which a common input signal is supplied, each of which is supplied with a different reference voltage, and a plurality of light emitting elements driven by the outputs of these comparator circuits, and the level of the input signal is determined by the level of the input signal. In the level display circuit configured to display the number of light emitting elements or the lighting position of the light emitting elements, the instantaneous waveform value of the input signal or the reference voltage continuously increases or decreases over substantially the entire period of each cycle. By superimposing alternating current voltages and changing the input signal level change between the reference voltages and changing the lighting period width of the light emitting element, it is possible to continuously display the degree of light emission brightness of the light emitting element. A level display circuit characterized by: