JPH0416748B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a level meter, and particularly to a level meter that can switch and display two or more of various voltages or signal levels such as signal level and battery level in audio equipment and the like.

Generally, a level meter has been developed for displaying the signal level of communication equipment, audio equipment, etc., in which the light emitting parts of several light emitting diodes are lined up and the light emitting diodes emit light according to the measured level to display the level. . Furthermore, this type of level meter employs a method of switching and displaying two or more signal levels using one level meter. For example, in a radio cassette recorder, a level meter consisting of five light emitting diodes is used to check the recording level as well as the battery level.

In this case, the comparison levels of the comparators that drive each light emitting diode are set to A, B, C, D, and E in order, and a specific numerical example of each level is shown as follows: A=-
10dB (0.31x), B = -5dB (0.56x), C = 0dB (1
D = 3 dB (1.41 times), E = 6 dB (2 times). If a level meter with a level value corresponding to such signal level display is used as is for checking battery voltage, if the battery voltage level is set to display level E when the battery voltage level is sufficiently high, that voltage will be displayed. When the battery voltage reaches 1/2, level C is displayed, that is, a high level is displayed even though the battery is unusable, so it is not accurate as a battery check.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a level meter in which the comparison level to be set in the comparator can be changed depending on each object to be measured, and the level display can be optimized.

That is, the level meter of the present invention has a plurality of display elements (light emitting diodes 98, 100, 102, 104, 10) according to the number of level stages to be displayed.
6), the level meter displays the level by selectively operating each display element according to the level, including a constant voltage source 32 that generates a constant voltage, and a constant voltage source 32 that is connected to the constant voltage source according to the number of display elements. Correspondingly, a plurality of first voltage dividing elements (resistors 34, 36, 38, 4
0, 42, 44) are installed, a first voltage dividing circuit that divides the constant voltage generated by the constant voltage source to set a first comparison level, and a first voltage dividing circuit for each of the first voltage dividing elements. transistors 56, 58, 60, 62, 6
4 to the second voltage dividing element (resistors 46, 48, 5
0, 52, 54) are connected in parallel, and the first voltage dividing element and the second voltage dividing element are connected through the first transistor by conduction of the first transistor. a second voltage divider circuit that sets a second comparison level using a second voltage divider circuit; and a plurality of constant current sources 66, 68, which are installed corresponding to the first transistor and which supply base current to the first transistor. 70, 72, and 74 are connected in series to the constant current source, and depending on a level switching input applied to the base, the first transistor is cut off when conducting, and the first transistor is turned on when non-conducting. a second transistor 76, 78, 8 for switching and converting the first or second voltage divider circuit to the first or second comparison level;
0, 82, 84, the first comparison level or the second comparison level installed and switched corresponding to the display element, and the input voltage whose level should be displayed are compared to determine the magnitude of both. a plurality of comparators 18, 20, 22, 24, which generate outputs according to the relationship and cause operating current to flow through the corresponding display elements;
26.

In the level meter of the present invention, the first voltage dividing element includes resistors 34, 36, 38, 4
It can be configured with 0, 42, 44.

Further, in the level meter of the present invention, the second voltage dividing element includes resistors 46, 48, 50, 5
2, 54 or diode 108, 110, 11
2,114,116.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. FIG. 1 shows an embodiment of the level meter of the present invention. In the figure, an input to be measured is applied to an input terminal 2 from a signal source or a voltage source (not shown), and this input is converted to a DC level by a rectifier amplifier circuit 4. This rectifier amplifier circuit 4 includes an amplifier 6, a diode 8, and resistors 10 and 12.
and a smoothing capacitor 16 connected to an external terminal 14. That is, the input signal amplified by the amplifier 6 is rectified by the diode 8, smoothed by the capacitor 16, and converted to a DC level. This DC level output is applied to comparators 18, 20, 22, 24, and 26 that compare the DC level output to be displayed with a comparison level, and the level setting circuit 28 adjusts the level according to the number of levels to be displayed. It is compared with a set first or second comparison level.

The level setting circuit 28 sets the first and second comparison levels according to the number of levels to be displayed, and is configured to be able to change between the first and second comparison levels. In this case, each comparison level is changed into two types by switching the division and allocation using a switching input applied from the outside. That is, the constant voltage source 32 driven by the DC voltage Vcc applied to the power supply terminal 30 includes resistors 34, 36, 38, 4 as a plurality of first voltage dividing elements.
0, 42, and 44 are connected in series, and each resistor 36 to 44 has a resistor 46, 44 as a second voltage dividing element.
8, 50, 52, 54 are first transistors 56, 58, 60, 62, 6 as switching elements.
4 in parallel. That is, in order to set the first comparison level according to the number of levels to be displayed, a first voltage dividing circuit that divides the constant voltage of the constant voltage source 32 in stages includes resistors 34, 36, and 3.
8, 40, 42, 44 in series, and a transistor 56, 58, 60, 62 for each resistor 34, 36, 38, 40, 42, 44 of this first voltage dividing circuit. , 64, resistors 46, 48, 50, 52, 54 are connected in parallel through transistors 56, 58, 60, 62, 64.
Due to the conduction of the resistors 34, 36, 38, 40, 4
A second voltage dividing circuit for setting a second comparison level is constituted by a series-parallel circuit of resistors 2 and 44 and resistors 46, 48, 50, 52, and 54. A constant current source 66, 6 is connected to the base of each transistor 56 to 64.
8, 70, 72, 74 and the second for switching
The transistors 76, 78, 80, 82, and 84 are individually connected, and the bases of the transistors 76 to 84 are commonly connected to an input terminal 86 for switching input.
is formed.

Each output terminal 8 of the comparator 18 to 26 has a comparison level set by this level setting circuit 28.
Shipping diodes 98 to 106 are connected to 8 to 96 as display elements. That is, the light emitting diodes 98 to 106 are connected to the comparator 1.
The light is turned on when the power supply voltage Vcc is applied by reversing the operation of steps 8 to 26.

In the above configuration, when the input terminal 86 is maintained at a high level by the switching input, each transistor 76-84 becomes conductive, and the base of each transistor 56-64 is at a low level, so that each transistor 56-84 becomes conductive. 64 becomes non-conductive. In this state, each of the resistors 46 to 54 is electrically open to each of the resistors 34 to 44, and only the resistors 34 to 44 are connected in series to the output of the constant voltage source 32. As a result, the constant voltage source 3
The voltages formed at the connection points of the resistors 34 to 44 set the comparison levels of the comparators 18 to 26.

Additionally, when input terminal 86 is maintained low by the switching input, transistors 76-84 are non-conducting and constant current sources 66-7
The output current of 4 flows into the base of each transistor 56-64, and the output current of
4 transitions to a conductive state. As a result, each resistor 34
Resistors 46 to 54 are connected in parallel to resistors 46 to 44 via transistors 56 to 64, and the resistance value of the resistor ladder connected to constant voltage source 32 is changed. That is, the resistance value of each resistor 46 to 54 is set so that the comparison level set by the resistor 46 to 54 is logarithmic, and each resistor 46 to 54 is individually connected in parallel to this resistor 34 to 44. If the values are set so that the resistance values are the same in both cases, the comparison level set in each comparator 18 to 26 will be different from the above case because the division and distribution of the output voltage of the constant voltage source 32 will be changed. It will be changed to a different comparison level value.

With this configuration, by arbitrarily selecting the values of the resistors 34 to 54, it is possible to set and change the level according to the level of the object to be measured, and each comparison level can be set by the comparators 18 to 2.
6, one or more of the light emitting diodes can be caused to emit light according to the input signal level applied to the input terminal 2, and appropriate display can be performed depending on the object to be measured.

In this embodiment, resistors 46 to 54 and transistors 56 to 64 are used to change the comparison level, but the resistors 46 to 54 may be replaced with other voltage dividing elements, or diodes as shown in FIG. It is possible to obtain the same effect even if the transistor 56 is changed to 56 to 116.
64 may be constituted not only by electronic switches but also by mechanical switching elements such as relays. Further, in each embodiment, the resistors 46 to 54 or diodes 108 to 116 as voltage dividing elements are connected to each resistor 46 to 54, but in this way, voltage dividing elements are connected in parallel to all the resistors. Alternatively, a voltage dividing element may be connected in parallel to one or more of the resistors.

Furthermore, in each embodiment, two types of level changes have been described, but if the number of voltage dividing elements and switching elements connected in parallel for level changes is increased to a plurality of levels, it is possible to display a plurality of different levels by switching control. can. In this case, according to the embodiment described above, it is necessary to provide each switching element with a constant current source and a switching transistor as a switching circuit.

As explained above, according to the present invention, the following effects can be obtained.

(a) Since the first or second comparison level to be set in the comparator can be changed by the level switching input, the first or second comparison level to be set in the comparator
Alternatively, the second comparison level can be selected and set, and the level display can be optimized.

(b) A first voltage dividing element constituting a first voltage dividing circuit that sets a first comparison level according to the number of levels to be displayed is connected to a second voltage dividing element via a first transistor. are connected in parallel to form a second voltage divider circuit, a constant current source is installed individually for the first transistor, and the base current is individually supplied to the first transistor using the second transistor. Therefore, the level of the first or second comparison level can be changed without malfunction, and as a result, the reliability of level display can be improved, and integration can be easily achieved.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a level meter according to the invention, and FIG. 2 is a circuit diagram showing another embodiment of the invention. 18, 20, 22, 24, 26... Comparator, 28... Level setting circuit, 32... Constant voltage source, 34, 36, 38, 40, 42, 44... Resistor (first voltage dividing element), 46, 48, 50, 52,
54...Resistor (second voltage dividing element), 56, 58,
60, 62, 64...first transistor, 6
6, 68, 70, 72, 74...constant current source, 7
6, 78, 80, 82, 84... second transistor, 98, 100, 102, 104, 106...
...Light emitting diode (display element), 108, 110,
112, 114, 116...Diode (second voltage dividing element).

Claims (1)

[Claims] 1. A level meter that is equipped with a plurality of display elements according to the number of levels to be displayed, and that displays the level by selectively operating each display element according to the level, comprising: A constant voltage source generated, a plurality of first voltage dividing elements corresponding to the number of display elements are installed on this constant voltage source, and the constant voltage generated by the constant voltage source is divided to perform a first comparison. A first voltage dividing circuit that sets a level, and a second voltage dividing element are connected in parallel via a first transistor for each of the first voltage dividing elements, and when the first transistor is conductive, a second voltage dividing circuit that sets a second comparison level using a parallel circuit of the first voltage dividing element and the second voltage dividing element connected through the first transistor; and the first transistor. was installed in response to
a plurality of constant current sources to supply base current to the first transistor; and a plurality of constant current sources connected in series to the constant current sources, and the first
When the transistor is in a cut-off state and non-conducting, the first transistor is turned off.
the first or second voltage divider circuit to conduct the first or second voltage divider circuit.
a second transistor for changing the comparison level to the first comparison level or the second comparison level installed corresponding to the display element and switched, and an input voltage whose level is to be displayed. A level meter comprising: a plurality of comparators that generate an output according to the magnitude relationship between the two and cause an operating current to flow through the corresponding display element. 2. The level meter according to claim 1, wherein the first voltage dividing element is composed of a resistor. 3. Claim 1, wherein the second voltage dividing element is composed of a resistor or a diode.
Level meter as described in section.