JPS59206771A - Level meter circuit - Google Patents

Abstract

PURPOSE:To execute uniform display corresponding to an input signal level by connecting a driving circuit for supplying driving current corresponding to the input signal level to a display element, detecting the output of the driving circuit, and feeding back the detected signal as a control input suppressing the input signal level. CONSTITUTION:An input signal to be displayed at its level is supplied to an input terminal 4 connected to a pre-amplifier 2. An output from the amplifier 2 is supplied to an output terminal 6 and the driving circuit 8 through a resistor (R) 5. The output side of the circuit 8 is connected to an output terminal 9 and a light emitting diode 12 is connected to the terminal 9 through a capacitor (C) 10 and an R11. A detecting circuit 14 is connected to the output side of the circuit 8 and the circuit 14 is provided with a diode 16 for detection and a smoothing circuit consisting of an R18 and a C20. A DC output obtained by the circuit 14 is applied as a control input of a volume circuit 22 and the output of the circuit is fed back to the input side of the circuit 8. Thus, the dynamic range of the display level can be increased and visually uniform display corresponding to the input signal level can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a level meter circuit, and more particularly to a level meter circuit that displays a signal level on a meter.

Conventionally, in various audio devices, a level making circuit used to display a signal level uses a linear amplifier or a logarithmic compression amplifier to drive a display element such as an indicator or a light emitting diode.

Such a circuit has drawbacks such as a small dynamic range of meter readings and a narrow display range.

An object of the present invention is to provide a level meter circuit that can expand the dynamic range of instructions and display uniformly from small levels to large levels.

The present invention includes a drive circuit that supplies a drive current corresponding to an input signal level to a display element, a detection circuit that detects and smoothes the output of this drive circuit, and uses the output of this detection circuit as a control input to drive the drive circuit. The device is characterized by comprising a volume circuit that suppresses the input signal level applied to the circuit.

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 circuit of the present invention. A preamplifier 2 is installed at the front stage of this level making circuit, and an input signal to be used for level display is applied to an input terminal 4 formed in the preamplifier 2. An output terminal 6 is formed on the output side of the preamplifier 2 to take out the output of the preamplifier 2 via a resistor 5, and an output terminal 6 is formed on the output side of the preamplifier 2 to take out the output of the preamplifier 2 via a resistor 5. A drive circuit 8 is installed. An output terminal 9 is formed on the output side of this drive circuit 8,
In this embodiment, a light emitting diode 12 is connected between the output terminal 9 and the reference potential point via a coupling capacitor 10 and a current limiting resistor 11, with its cathode at the reference potential point 1u11. . A charging resistor 13 is connected between the anode of the light emitting diode 12 and a reference potential point.

Furthermore, a detection circuit 14 is installed on the output side of the drive circuit 8 to detect the drive output. That is, a diode 16 for detecting the output of the drive circuit 8 is installed in the detection circuit 14, and a resistor 18 and a capacitor 20 are connected between the cathode of the diode 16 and a reference potential point to form a smoothing circuit. .

The DC output obtained by this detection circuit 14 becomes the control power of a volume circuit 22, and the output of this volume circuit 22 is connected to the input section of the drive 1 path 8. That is,
The impedance of the volume circuit 22 is changed based on the control input obtained by peak-detecting the output of the drive circuit 8,
The input signal level applied to the drive circuit 8 is suppressed in accordance with the human strength level.

The operation will be explained based on the above configuration. Input terminal 4
The input signal applied to is amplified by a preamplifier 2, then taken out from an output terminal 6 via a resistor 5, and is applied to a speaker or the like via a power amplifier (not shown).

On the other hand, the signal input given to the drive circuit 8 is returned to a drive signal according to its level, and this drive current is transmitted to the output terminal 9.
is applied to the light emitting diode 12 from the light emitting diode 1
2 emits light in response to an input signal. Here, when the input signal level is small, the detection circuit 14 and the volume circuit 2
2, and the light emitting diode 12 can be caused to emit light according to the signal level by the output of the drive circuit 8.

In addition, when the input signal level becomes extremely high, the output of the drive circuit 8 is detected by the detection circuit 14, and the control signal level given by this detection output is used to control the volume circuit 2.
2 is controlled, the input signal level applied to the drive circuit 8 is suppressed.

FIG. 2 shows the operating characteristics in this case, and shows the output voltage Vo generated at the output terminal 9 with respect to the input signal level VIN. Range A indicates a case where the input signal level is small, and range B indicates a state in which the volume circuit 22 suppresses the signal level when the input signal level exceeds a certain value.

Here, the resistance value of the resistor 5 is R, the output impedance of the volume circuit 22 is RO1, the amplification gain of the drive circuit 8 is Av
Then, the output voltage ■0 is given by the following equation. That is, Vo=V+N・Av−Ro/(Ro+R
).

Therefore, the response level and compression ratio can be determined each time the sensitivity of the detection or volume circuit 22 is changed.

The response is determined by the time constant T(-C-R), which is the product of the resistor 18 and capacitor 20 that constitute the smoothing circuit, so the resistance value of the resistor 18 or the capacitor 20
By changing the capacity of , a desired response speed can be obtained.

With this configuration, it is possible to increase the dynamic range of the display level, and it is possible to obtain a visually uniform display state according to the input signal level from a minute level to a large level. Since noise and signals are distinguished, it is possible to display only signals at a commercial level more responsively than surrounding noise. Moreover, even when a high level signal arrives, the display of the display element is not saturated and a stable state can be obtained. For example, when installed in various electronic devices, it is possible to avoid the effects of continuous noise such as motor noise and hum, and to display only signal components.

Furthermore, the slope of range A shown in FIG.
For example, the angle can be adjusted to any desired angle by adjusting the operating current, that is, the gain, of a differential amplifier configured as an internal circuit of 2.

Although the embodiment has been described using a light emitting diode as an example of a display element, the same effect can be expected even if an indicator is used as a display element.

As explained above, according to the present invention, it is possible to obtain a visually uniform display according to the input signal level, and moreover, it is possible to display the signal level at a relative level that is in line with surrounding noise. It is possible to display the level.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the level meter circuit of the present invention, and FIG. 2 is an explanatory diagram showing its operating characteristics. 8... Drive circuit, 12... Light emitting diode as a display element, 14... Detection circuit, 22... Volume circuit.

Claims (1)

[Claims] A drive circuit that supplies a drive current corresponding to the input signal level to the display element, a detection circuit that detects and smoothes the output of this drive circuit, and outputs the output of this detection circuit as a control input that is applied to the drive circuit. A level making circuit comprising a volume circuit that suppresses an input signal level.