JPS5825349Y2 - Muting device for meter circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a muting device for meter circuits, such as deviation meters, signal meters or VU meters.

Conventionally, a muting device is provided in a meter circuit in order to prevent the meter from swinging abnormally due to an electric shock when a power switch is turned on.

As shown in Figure 1a, this muting device consists of a diode 2 with the output of a negative feedback amplifier 1 connected in the forward direction, and a meter 3 connected in series, and a muting device 4 connected in parallel to the ground-meter 3. However, in a transient state when the power switch is turned on, the input of the meter 3 is grounded, and after reaching a steady state, the meter 3 is activated to prevent abnormal swing of the meter 3.

In addition, as shown in Figure 1, a diode 2 with the output of the negative feedback amplifier 1 connected in the forward direction and a meter 3 are connected in series through a switch 5 and grounded. Various muting devices were provided, such as turning off the switch 5 to disconnect the meter 3, and turning on the switch 5 to operate the meter 3 after reaching a steady state to prevent abnormal swings of the meter 3.

However, constructing the above circuit requires transistors or relays for the muting device, making the circuit complex and expensive.

The present invention has been made in consideration of the above, and an object of the present invention is to provide a muting device for a meter circuit that has a simple circuit configuration and prevents abnormal swing of the meter during a transient state such as when a power switch is turned on.

According to the present invention, this purpose is to connect a meter circuit through a diode to the output of a negative feedback amplifier, and
This is achieved by including a circuit that applies a voltage only for a predetermined period to the negative feedback input terminal of the negative feedback amplifier, and by reverse biasing the diode only while the voltage is being applied to prevent the meter from swinging.

Next, embodiments of the present invention will be described based on the drawings.

FIG. 2 shows a circuit diagram of an embodiment of the present invention.

In FIG. 2, 1 indicates a negative feedback amplifier, 6 indicates the input terminal of the negative feedback amplifier 1, and 1 also indicates the negative feedback input terminal.
Similarly, numerals 8 and 8 respectively indicate output terminals.

Output terminal 8 has diode 2 and meter 3 connected in the forward direction.
are connected in series, and the other end of the meter 3 is grounded.

Further, the output terminal 3 is connected to the negative feedback input terminal 7 through the negative feedback resistor R1, and the negative feedback input terminal 7 is grounded through the negative feedback resistor R2.

On the other hand, the output terminal B of the power supply circuit 9 has a capacitor C and a resistor R.
Ground through a series circuit with 4.

A connection point A between the capacitor C and the resistor R4 is connected to the negative feedback input terminal 7 through the terminal Vc and a series circuit of the diode 10 and the resistor R3 in the forward direction.

In the circuit configured as above, the voltage applied to the input terminal IN of the amplifier 1 and the voltage appearing at the output terminal 8 are in phase, and when the power switch 16 of the power supply circuit 9 is turned on, Capacitor C1 is connected by output terminal B of power supply circuit 9.
A current flows through the diode 10 and the resistor R3s R2, a voltage is applied to the negative feedback terminal 7, the voltage at the output terminal 8 moves to the negative side, the diode 2 is reverse biased, and the meter 3 does not swing.

Next, as time passes, the current flowing through the capacitor C1 diode 10 and resistor R3*R2 is attenuated by a time constant determined by capacitor C1 diode 10, resistor R25, R3 and R4.
When the potential at the connection point A is lowered, the voltage applied to the negative feedback input terminal 7 through the resistor R3 decreases to zero.

As a result, diode 2 becomes forward biased and meter 3
works normally.

As explained above, in this embodiment, when the power switch of the power supply circuit is turned on, voltage is applied to the negative feedback input terminal of the negative feedback amplifier for only a certain period of time, so that the meter circuit is turned off for a certain period of time. The distance meter does not swing abnormally.

The predetermined period of time can be arbitrarily selected depending on the time constant of the circuitry connected between the power supply circuit and the negative feedback input terminal.

FIG. 3 shows another embodiment of the present invention.

This embodiment is an example of a deviation meter circuit.

The same components as in FIG. 2 are given the same reference numerals.

As shown in FIG. 3, the negative feedback amplifier 1 is connected to a diode 2 and a deviation meter 3, and a diode 10 and resistors R1 and R are connected to each other for applying voltage to the negative feedback input terminal 7.
2 and R3 are identical to the embodiment of FIG.

On the other hand, 11 is a high frequency amplification circuit, 13 is a discriminator, and 14 is a stereo demodulation circuit.
It constitutes an M stereo tuner.

Now, a NAND circuit 15 is provided which receives a 10.7 MH2 signal from the intermediate frequency amplification circuit 12 and a DC voltage from the discriminator 13, and applies a voltage from the output terminal of the NAND circuit 15 to the negative feedback input terminal 7. is connected to terminal Vc.

In this circuit, the voltage output from the intermediate frequency amplification circuit to the NAND circuit is the muting voltage of a muting circuit used in a normal 1M stereo tuner.

When a radio wave is received, the muting gummy pressure and the DC signal voltage from the discriminator 13 are applied to the NAND circuit 1.
Since the NAND circuit 15 does not generate an output, no voltage is applied to the terminal Vc, and the deviation meter 3 operates normally.

When radio waves are not being received and there is noise, NAN is the opposite of when radio waves are being received.
There is no input to the D circuit 15, and the NAND circuit 15 generates a voltage, which is applied to the terminal Vc and moves the voltage at the output terminal 8 to the negative side, making the diode 2 reverse biased and the deviation meter 3 not swinging.

As explained above, in this embodiment, the muting output of the conventional 1M stereo tuner is used, the deviation meter is operated normally when receiving radio waves, and the deviation meter is disconnected when there is noise.
I can't shake it.

As explained above, according to the present invention, the diode of the meter circuit is cut off during the transient state when the power supply circuit is turned on, when the 1M stereo tuner is operating, etc.
By muting the meter circuit, abnormal swings of the meter can be prevented.

The second circuit is made up of passive elements, has a simple circuit configuration, and is less expensive than devices with conventional circuit configurations.

[Brief explanation of drawings]

1A and 1B are block diagrams of a conventional muting device for a meter circuit, FIG. 2 is a circuit diagram of one embodiment of the present invention, and FIG. 3 is a circuit diagram of another embodiment of the present invention. 1; Negative feedback amplifier, 2 and 10: Diode, 3; Meter, C; Capacitor, R1mR2pR3 and R4:
Resistor, 15: NAND circuit.

Claims (1)

[Scope of utility model registration request] A meter circuit is connected to a meter through a diode to the output of an amplifier, and a bias circuit is provided in front of the diode, and the bias circuit reverse biases the diode only for a predetermined period of time to prevent the meter from swinging. A muting device for meter circuits.