JPS62165420A - Attenuator circuit - Google Patents

Abstract

PURPOSE:To attain signal attenuation having resolution corresponding to the number of bits on a digital input by impressing an attenuated signal to a D/A converter as a reference signal and setting up a signal attenuation ratio on the basis of the digital input. CONSTITUTION:When a digital signal (0, 0, 1, 1, 0...) e.g. is inputted from a volume circuit 22 or a remote control receiver 23 to a control circuit 20, current Ix flowing into an inversional input terminal of an inversional amplifier 13 is expressed by (1/8+1/16), an amplified output voltage V0 is expressed by RIx, V0=(1/8+1/16)Vi is formed and the output of an attenuator circuit 11 is attenuated in accordance with the digital input. In this case, the circuit 11 impresses the attenuated signal as the reference signal of the D/A converter 14 and the attenuation ratio of a signal is set up by the digital input to the converter 14.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an attenuator circuit using a DA converter.

[Prior Art] Attenuator circuits used in the volume circuits of audio amplifiers and television receivers generally vary the resistance value of the resistor by sliding a contact on the resistor in conjunction with the volume knob. The configuration is such that Second
A conventional attenuator circuit 1 shown in the figure divides a power supply voltage E applied between terminals 2 and 3 by a contact 5 sliding on a resistor 4, and changes the mechanical position of the contact 5 into voltage. The configuration is such that the signal is converted into a change and supplied to the output circuit 6.

[Problem to be Solved by the Invention J The attenuator circuit 1 used in the above-mentioned conventional volume circuit, etc. is one of the few moving parts along with the switch, so it is prone to defects and has a short rotational life due to wear and tear of the resistor 4. The grease used to adjust the rotational torque of the volume knob may become deteriorated, causing noise, or in rare cases, the internal resin parts may become charged with static electricity, causing a clicking sound when rotating. There is Sara J
There is a problem in that the resolution is limited by the manufacturing precision of the resistor 4.

[Means for Solving the Problems] This invention solves the above problems, and uses a value obtained by multiplying a reference signal by a numerical value determined by a combination of reciprocals of powers of 2 according to digital human power. a DA converter that outputs an analog signal, an input circuit that inputs a signal to be attenuated as a reference signal to the DA converter, and a control that converts an external operation input into the digital input and supplies it to the DA converter. It is characterized in that it consists of means.

[Operation] This invention applies the signal to be attenuated as a reference signal to the DA converter, and sets the signal attenuation ratio by the digital input of the DA converter, thereby increasing the resolution according to the number of bits of the digital input. allows signal attenuation with

[Embodiment] An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a circuit diagram showing an embodiment of an attenuator circuit according to the present invention.

In FIG. 1, the attenuator circuit 11 uses a DA converter 14 consisting of an inverting amplifier 13 to which a ladder-type resistor circuit 12 is connected to a non-inverting input terminal. The structure is such that the attenuation is performed appropriately according to the digital input of the converter I4. Resistance circuit 1
2, n voltage dividing resistors I6 having a resistance value R are connected in series to the input circuit 15 of the signal to be attenuated, and each voltage dividing resistor 16
A shunt resistor 17 having a resistance value R is connected to both ends of the circuit in the form of a ladder. A voltage dividing resistor 18 having a resistance value of 2R is connected to the final nth stage shunt resistor 17. Therefore, in the resistor circuit I2, the combined resistance of the subsequent circuits with respect to the shunt resistor 17 is R, and equal current distribution is achieved at the connection point between the shunt resistor 17 and the voltage dividing resistor I6. .

On the other hand, each shunt resistor 17 is selectively connected to an inverting input terminal or a non-inverting input terminal of the inverting amplifier 13 by a switch 19, and n switches 1
9 is a digital input sent from the control circuit 20 (
B,,B,,,,.

Bn) is switched corresponding to each bit. Inverting amplifier 1
3, the non-inverting input terminal is grounded, and the resistance value of the feedback resistor 21 connecting the output terminal and the inverting input terminal is equal to the voltage dividing resistor 1.
Same as 6, it is R. Note that with respect to the signal voltage Vi applied to the input circuit I5, the input current ■ is V i /
This is expressed as I/R by the shunt resistor 17 at each stage.
2. I/4°1/8. It is divided as follows.

Here, a control circuit 20 that supplies digital signals to the DA converter 14 is connected to a touch input type volume circuit 22 and a remote control receiver 23.
2 or the output of the remote control receiver 23 is supplied to each switch 19, giving priority to the former. The touch input type volume circuit 22 has a plurality of pressure sensitive resistive elements 24a or touch sensors 24 arranged in a row horizontally, and the pressure sensitive resistive elements 24. Regarding a,
The touch force is determined based on the resistance change, and a double-encoded volume command is output.

The remote control receiver 23 receives the remote control command sent from the remote control transmitter 25, converts the volume command among the received various commands into a double-encoded volume command, and supplies the volume command to the control circuit 20. do. Note that the control circuit 20. Volume circuit 22 and remote control receiver 23
etc. constitute the control means.

Here, for example, a digital signal (0,
0, l, I, O, , , 0) are input. In this case, the current l flowing into the inverting input terminal of the inverting amplifier I3
x is expressed as (1/8 + 1/16)I. However, I=Vr/R. The output voltage VO of the inverting amplifier is
Since it is expressed as Rlx, V o = (1/8 +
1/] 6) The output of the attenuator circuit 11, V i, will be attenuated in accordance with the digital input.

In this way, the attenuator circuit II has a configuration in which the signal to be attenuated is applied as a shield quasi-signal to the DA converter 14, and the signal attenuation ratio is set by digital human power of the DA converter I4. Unlike conventional attenuator circuits 1, etc., which change the contact position of the contactor 5, which is a moving part, to produce a change in resistance, signal attenuation with a resolution corresponding to the number of bits of digital human power is possible. Furthermore, digital signals can be output directly from a circuit that can output digital signals, such as a touch input type volume circuit 22 or a remote control receiver 23 that receives remote control commands from a remote control transmitter 25. You can easily enter it via
It is suitable for volume control circuits for audio/video equipment, etc.

In the above embodiment, the DA converter is R-
It is not limited to the one using the 2R ladder resistance type resistance circuit 12, but may also use another type of resistance circuit, such as a weighted resistance type resistance circuit.In short, the reference signal is the sum of the reciprocals of powers of 2 according to the digital input. Any device that can be multiplied and output in analog form is sufficient.

[Effects of the Invention] As explained above, according to the present invention, a signal to be attenuated is applied as a reference signal to the DA converter, and the DA converter
Since the signal attenuation ratio is set by the digital input of the converter, unlike conventional attenuator circuits that change the contact position of a mechanically movable contactor to produce a change in resistance, the signal attenuation ratio can be set by the number of hits of the digital input. It is possible to attenuate the signal with appropriate resolution, and since it has no moving parts, it can maintain a long service life.Furthermore, the digital signal can receive remote control commands from a touch-powered volume circuit or a remote control transmitter. Since it can be easily inputted via a circuit that can directly output digital data, such as a remote control receiver, it has excellent effects, such as being suitable for volume control circuits for audio/video equipment.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of an attenuator circuit according to the present invention, and FIG. 2 is a circuit diagram showing an example of a conventional attenuator circuit. Il, , attenuator circuit, +4. ,,DA converter,
20. control circuit, 22. ,,Volume circuit, 23
．． ,,remote control receiver.

Claims (1)

[Claims] A DA converter whose analog output is a value obtained by multiplying a reference signal by a numerical value determined by a combination of reciprocals of powers of 2 according to the digital input, and a reference signal which outputs a signal to be attenuated for this DA converter. an attenuator circuit comprising an input circuit that inputs an input signal as an input signal, and a control means that converts an external operation input into the digital input signal and supplies the digital input signal to the DA converter.