JPS636891Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a level adjustment circuit, and particularly to a level adjustment circuit suitable for use as a volume adjustment circuit in audio equipment.

[Conventional technology]

In audio equipment, for example, a receiver capable of receiving traffic information, when traffic information is being broadcast, even if another program source is being output to inform the listener, the information signal is output by switching this source. Ru. In such a case, the information signal must be output even when the volume in the volume adjustment circuit of the receiver is at zero.

FIG. 5 shows a circuit diagram of a conventional example of a level adjustment circuit as a volume adjustment circuit. In the figure, the first signal other than the information signal applied to input terminals IN1 and IN2 (hereinafter referred to as normal signal)
and an information signal as a second signal are selectively applied to one end of the variable resistor VR by switches S1 and S2, respectively. A resistor R1 is connected between the other end of the variable resistor VR and a reference potential, and a switch S3 which is inverted and interlocked with the switch S2 is connected in parallel to the resistor R1. A first or second signal output is derived from the sliding terminal of the variable resistor VR.

In this configuration, when the normal signal is input by closing the switch S1, the switch S2 is opened and the switch S3 is closed to short-circuit the resistor R3, and the output level of the normal signal is as shown in FIG. 6a. It is proportional to the volume rotation angle of the variable resistor VR, that is, the resistance value of the variable resistor VR.

On the other hand, switch S2 is closed (switch S1 is opened)
When an information signal is input by the switch S3, the switch S3 is opened, and the output level of the information signal changes from a predetermined level Vr at the minimum volume rotation angle in proportion to the volume rotation angle, as shown in FIG. 6b. Here, the predetermined level Vr is set by the resistor R1 to a value that allows the information signal to be sufficiently audible when the information signal is input when the volume rotation angle is the minimum, and is also generally used when inputting a normal signal. This approximately corresponds to the output level at the volume rotation angle position (near the X position in FIG. 6).

[Problem that the invention attempts to solve]

In such a conventional level adjustment circuit, for example, when the volume rotation angle is near the X position in FIG. 6, when an information signal is input, the output level changes by Vu. Therefore, even if the volume rotation angle is set to a position corresponding to a level that is easy to listen to, the output level suddenly increases due to the input of information signals, causing discomfort to the listener. .

[Means for solving problems]

The present invention has been made in order to solve the above-mentioned conventional problems, and its means include first and second signals being selectively applied to one end via first and second switch means, and a sliding switch being applied. a variable resistance element that derives the first or second signal output from a moving end; a voltage dividing circuit having one end connected to a reference potential point and a voltage dividing point connected to the other end of the variable resistance element; The third switch means is connected between the second signal and the other end of the voltage dividing circuit and operates in conjunction with the second switch means.

[Effect]

In the above means, when the first switch means is closed and the second and third switch means are each opened, the first signal output changes depending on the resistance value of the variable resistance element. In addition, the first
When the first switch means is opened and the second and third switch means are respectively closed, the second signal output changes from the minimum resistance value of the variable resistance element to the predetermined resistance value by the divided voltage of the voltage divider circuit. The output level remains approximately the same, and when the resistance value exceeds a predetermined resistance value, the output level changes depending on the resistance value of the variable resistance element.

[Example of idea]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of a level adjustment circuit according to the present invention, in which the same parts as in FIG. 5 are designated by the same symbols. In the figure, the input terminal IN2 to which the information signal (second signal) is applied
The configuration is the same as that of FIG. 1 except that a series connection circuit of a switch S4 (third switching means) and a resistor R2 is connected between the connection point of the variable resistor VR and the resistor R1. Switch S4 is Switch S2
(second switch means), and the resistance value of the resistor R1 is the variable resistor VR
The resistance value is set sufficiently smaller than the resistance value of .

In this configuration, when the normal signal (first signal) is input by closing the switch S1, the switch S2 is opened, and the switch S4 interlocked with this is also opened. Furthermore, since the resistance value of the resistor R1 is selected to be sufficiently small, the output level of the normal signal is proportional to the volume rotation angle of the variable resistor VR, that is, the resistance value of the variable resistor VR, as shown in FIG. 2a. On the other hand, when the information signal (second signal) is input by closing the switch S2, the switch S4 which is linked to the switch S2 is also closed, so the information signal is input to the variable resistance.
It is applied to one end of VR and also to the connection point between variable resistor VR and resistor R1 via resistor R2. The output signal based on the input signal applied to one end of the variable resistor VR is proportional to the volume rotation angle of the variable resistor VR, as shown in FIG. 2a, as in the case described above. Further, the output signal based on the input signal applied to the other end of the variable resistor VR via the resistor R2 is the second
As shown in FIG. b, when the volume rotation angle of the variable resistor VR is at its minimum, it decreases from a predetermined level Vr determined by the voltage division ratio of the resistors R1 and R2 in inverse proportion to the volume rotation angle. The input signals applied to both ends of the variable resistor VR are in phase, so the output signal is the root mean square value of each output as shown in Figure 2c, and when an information signal is input, the minimum resistance of the variable resistor VR is When the output level is approximately constant from the minimum value to the predetermined resistance value, that is, the volume rotation angle is at a position commonly used during normal signal input (near the X position in Figure 2), and the volume rotation angle is equal to or greater than the predetermined resistance value, the volume rotation angle changes. The output characteristic has an output level proportional to .

Therefore, even if an information signal is input in a volume rotation angle state near the X position, the information signal can be sufficiently heard because the output level is near the predetermined level Vr.

FIG. 3 is a circuit diagram of a second embodiment of the level adjustment circuit according to the present invention, in which parts equivalent to those in FIG. 1 are designated by the same reference numerals. In the above embodiment, since the variable resistor VR is connected in series with the resistor R1, the output does not become completely zero even when the volume rotation angle is zero. The value must be sufficiently low compared to the resistance value.

On the other hand, since the predetermined level Vr is determined by the voltage division ratio of the resistors R1 and R2, if the resistor R1 is a constant resistor, the resistance value of the resistor R2 must be set low accordingly. For this reason, the constant resistance R1+R2 acts as a load on the signal source, and unless the signal source has a sufficiently lower impedance than the resistors R1+R2, the output level may drop. Therefore, in this embodiment, in order to eliminate this problem, a buffer amplifier A whose input and output are in phase is connected between the voltage dividing circuit of resistors R1 and R2 and the input terminal IN2. This buffer amplifier A is used as an input terminal when inputting information signals.
By configuring it to be activated by the control signal applied to IN3, switch S4 can be omitted. It goes without saying that the switch S4 may be provided in series with the buffer amplifier A.

Figure 4 shows an application of the circuit in Figure 1 to a stereo circuit, where left and right stereo normal signals are supplied to input terminals IN1 (right) and IN2 (left), respectively, and are connected to each volume VR via switch S1. connected to one end of the Also, the information signal is input terminal IN2
is supplied to one end of each volume VR via switch S2, and is connected to one end of each volume VR via switch S2.
4. Connected to the other end of the volume VR via the resistor R2. A resistor R1 is connected between the other end of the volume VR and the reference potential. The operation and characteristics in FIG. 4 are the same as those in the embodiment shown in FIG. 1, and therefore their explanation will be omitted.

[Effect of idea]

As detailed above, according to the level adjustment circuit according to the present invention, the second signal can be output at a predetermined level even if the resistance value of the variable resistor is the minimum. Even if the second signal is applied when the resistance value is at the predetermined resistance value, the output signal can be output at a level close to the predetermined level, so that the listener will not feel uncomfortable. Furthermore, the output characteristics can be set arbitrarily depending on the purpose of use.

Therefore, such a level adjustment circuit is suitable for use as a volume adjustment circuit in a weather information receiver, a traffic information receiver, etc. that needs to warn or alert listeners.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a diagram for explaining the operation of Fig. 1, Fig. 3 is a circuit diagram showing another embodiment of the invention, and Fig. 4 is a diagram for explaining the operation of Fig. 1. Fig. 1 is a circuit diagram showing a third embodiment of the present invention applied to a stereo circuit, Fig. 5 is a circuit diagram of a conventional level adjustment circuit, and Fig. 6 is for explaining the operation of Fig. 5. This is a diagram. VR...Variable resistance, S1-S4...Switch,
A...batshua amp.

Claims (1)

[Claims for Utility Model Registration] (1) First and second signals are selectively applied to one end via first and second switch means, and the first or second signal is output from the sliding end. a voltage dividing circuit whose one end is connected to a reference potential point and whose voltage dividing point is connected to the other end of the variable resistance element, and the second signal and the other end of the voltage dividing circuit. a third switch means connected between said second switch means and interlocked with said second switch means;
When the first switch means is closed and the second and third switch means are opened, the first signal output changes according to the resistance value of the variable resistance element, and the first switch means is opened. However, when the second and third switch means are each closed, the second signal output changes at approximately the same output level from the minimum resistance value of the variable resistance element to the predetermined resistance value, and when the resistance value exceeds the predetermined resistance value. A level adjustment circuit characterized in that the level adjustment circuit is configured to change according to the resistance value of the variable resistance element. (2) The voltage dividing circuit includes a first resistor connected between the other end of the variable resistance element and the reference potential point, one end connected to the other end of the variable resistance element, and the other end connected to the first resistor. 3. The level adjustment circuit according to claim 1, further comprising a second resistor connected to the second signal through a switch means.