JPS6268311A - Electronic volume circuit - Google Patents

Abstract

PURPOSE:To obtain an electronic volume circuit with less effect of a click tone in switching a semiconductor switch constituting a switching circuit by using the switching circuit so as to select input terminals of an R-2R ladder type resistance network. CONSTITUTION:An input signal inputted from the switch element selected by a digital control signal is inputted to the next R-2R ladder type resistance network 7. In the R-2R ladder type resistance network 7, the attenuation is decided by an input terminal to which the input signal is inputted and various attenuations are obtained by combining the input terminals. In switching a semiconductor switch constituting a switching circuit 6, the noise generated due to the inter-electrode capacitance of the semiconductor switch element is inputted and the noise is attenuated also by the R-2R ladder type resistance network 7 the same as the input signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electronic volume circuit that can be used for digitally controlled volume adjustment or sound quality adjustment (frequency characteristic control) of consumer equipment.

Conventional technology In recent years, in order to respond to miniaturization and higher performance in the field of consumer electronics, electronic control using digital control technology has been implemented, and audio systems that are easier to use for consumers have been developed. It's coming.

Hereinafter, a conventional digitally controlled electronic volume circuit closely related to the present invention will be explained with reference to the drawings.

FIG. 4 shows a configuration diagram of a conventional digitally controlled electronic volume circuit. In FIG. 4, 1 is an input terminal, and 2 is an R-2R ladder resistor network. Reference numeral 3 denotes a switching circuit composed of a group of analog switches, such as MO3 type FETs. Reference numeral 4 denotes an adder circuit composed of an operational amplifier and the like having a feedback resistor Rfll. 5 is an output terminal.

The operation of the digitally controlled electronic volume circuit configured as described above will be explained below.

First, the input signal that operates with the current source is input to the R-2R ladder resistor network 2, and the output current obtained from each terminal of the R-2R ladder resistor network 2 is controlled by an external digital control signal. It is selected by the circuit 3 and converted into a voltage by the next adding circuit 4. R-2
The output current obtained from each terminal of R ladder resistor 2 becomes half of that of the input terminal as it moves away from input terminal 1. In other words, the output current of the nth stage is (1/1/2) of the input terminal.
2) Therefore, any amount of attenuation can be obtained by independently controlling each switch element included in the switching circuit 3.

Problems to be Solved by the Invention However, in the above configuration, when the semiconductor switch such as the MO3 type FET that constitutes the switching circuit 3 switches, due to the interelectrode capacitance of the semiconductor switch element,
Since the noise resulting from the differentiation of the digital control signal is applied to the output signal, there is a problem in that when attempting to change the volume using the electronic volume circuit configured as described above, this noise will be generated as a click sound. Ta.

In view of the above-mentioned problems, the present invention provides an electronic volume circuit that is less affected by click sounds caused by the interelectrode capacitance of semiconductor switching elements.

Means for Solving the Problems In order to solve the above problems, the electronic volume circuit of the present invention, when attenuating the level of an input signal to an arbitrary value,
Consisting of a switching circuit that selects the input terminal corresponding to that value using a digital control signal, and a resistor that is supplied with an input signal from this switching circuit and has a resistance ratio of 1:2 to attenuate the level to an arbitrary value. R-2R ladder-shaped resistor network, and a signal is extracted from the output of this R-2R ladder-shaped resistor network. i amplifier circuit.

According to the above-described structure, the present invention is capable of attenuating the noise signal generated by differentiating the digital control signal caused by the capacitance between the electrodes of the semiconductor switching element at the same level as the input signal (also attenuated by the R-2R ladder resistor network). Therefore, the influence of the click noise generated due to the interelectrode capacitance of the semiconductor switching element is reduced.

Example Below, regarding an electronic volume circuit according to an example of the present invention,
This will be explained with reference to the drawings.

FIG. 1 shows a configuration diagram of an electronic volume circuit according to an embodiment of the present invention. In FIG. 1, 6 is a switching circuit composed of a group of analog switches, such as MO3 type FETs, and 7 is an R-2R ladder resistor network.

The operation of the electronic volume circuit configured as described above will be explained below.

First, the input signal that operates as a current source is, for example, a 3d
When it is desired to obtain the attenuation amount of B and B, the switch elements selected at the back of each switch element of the switching circuit 6 are supplied to the input terminal as shown in FIG. In addition, in FIG. 3, a white circle is a switch element to be selected, and G is a switch element connected to a ground point. At this time, the unselected switch elements among the switch elements of the switching circuit 6 are connected to the ground point. In other words, when trying to obtain an attenuation of 9 dB, for example, 6-2.6-4.6-5 of each switching element of the switching circuit 6
It is sufficient to select each switch element, supply an input signal to these switch elements, and connect a ground point to the other switch elements. The input signal inputted from the switch element selected by the digital control signal in this manner is inputted to the next R-2R ladder-shaped resistance line 7. This R-2R
The amount of attenuation of the ladder resistor m7 is determined by the input terminal to which the input signal is input. For example, when input to the first stage input terminal, an attenuation of 6 dB is obtained, and various attenuations can be obtained by combining the input terminals of the R-2R ladder resistor network 7. At this time, the input terminal of the rl-2R ladder resistor network 7 receives not only the input signal but also the noise generated due to the capacitance between the electrodes of the semiconductor switch elements when the semiconductor switches constituting the switching circuit 6 are switched. However, in the configuration of this embodiment, this noise is also attenuated by the R-2R ladder resistor network 7 in the same way as the human input signal. The human input signal attenuated by the R-2R ladder resistor network 7 is output after being converted into a voltage by the adder circuit 5 having the next feedback resistor R11. Therefore, any amount of attenuation can be obtained by combining the switching elements of the switching circuit 6.

As described above, according to this embodiment, by using the method of selecting the input terminal of the R-2R ladder resistor network 7 by the switching circuit 6, Therefore, it is possible to obtain an electronic volume circuit that is less affected by click noise.

In the above embodiment, it is assumed that the input signal operates as a current source, but by using a buffer amplifier circuit as shown in FIG. 2 in the adder circuit 4 of FIG. An electronic volume circuit having the following effects can be obtained.

Further, although the switching elements are selected as shown in FIG. 3 in order to obtain an attenuation amount of 3 dB steps, other combinations are also possible.

Effects of the Invention As described above, the present invention provides R
- Since the method of selecting the input terminal of the 2R ladder resistor network is used, when the semiconductor switch that constitutes the switching circuit is switched, the click sound generated due to the capacitance between the electrodes of the semiconductor switch element is suppressed. An excellent effect is obtained in that an electronic volume circuit with little influence can be obtained.

[Brief explanation of drawings]

Fig. 1 is a wiring diagram of an electronic volume circuit according to an embodiment of the present invention, Fig. 2 is a wiring diagram of a buffer amplifier circuit used for amplification in which the input signal operates as a voltage source, and Fig. 3 is attenuation in 3 dB steps. FIG. 4 is a wiring diagram of a conventional digitally controlled electronic volume circuit. l...Input terminal, 2.7...R-2R
Ladder-shaped abrasive net, 3, 6... Switching circuit, 4... Addition circuit, 5... Output terminal. Name of agent: Patent attorney Toshio Nakao (1 person) Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A switching circuit that uses a digital control signal to select an input terminal corresponding to an arbitrary value at which the level of the input signal is to be attenuated; An electronic volume comprising: an R-2R ladder-shaped resistance network composed of resistors having a resistance ratio of 1:2; and a buffer amplifier circuit that extracts a signal from the output of the R-2R ladder-shaped resistance network. circuit.