JP2746429B2 - Tone generation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION SUMMARY The present invention relates to a tone generating circuit, for the purpose of obtaining a good circuit efficient with less signal lines When forming an arbitrary waveform, a predetermined voltage V ₁ and V ₂ First to selectively connect
The partial pressure of the switch means, the output side and a predetermined resistor string a plurality of resistors are connected in series is connected between a terminal of the reference voltage V _0, the junction of the plurality of resistance of the first switching means A second switch means comprising a plurality of switches for outputting a voltage; and a control circuit for controlling the first and second switch means, and the second switch means extracts a divided voltage at each junction of the resistors. A tone generating circuit for generating a tone waveform by connecting the first switch means to one of predetermined voltages and sequentially switching a plurality of switches of the second switch means; The switch means is connected to the other of the predetermined voltages, and is controlled so as to sequentially switch a plurality of switches of the second switch means.

[Industrial applications]

The present invention relates to a tone generating circuit of a tone generator for generating a stepwise tone which is a basis for shaping an arbitrary vertically symmetrical waveform including a sine wave and the like.

[Conventional technology]

For molding a vertically symmetrical arbitrary waveform conventionally mainly sinusoidal like reference voltage, the reference voltage V _0, stepped waveform tone waveform with high voltages V ₁ and it is lower than the voltage V ₂ than it It is widely and generally performed to form a desired waveform by shaping the waveform later. FIG. 5 shows a conventional example of a tone generating circuit for producing the tone waveform.

Reference level V ₀ in FIG. 5, between the V higher level than _1, when the V ₂ and less than the level reference level greater than or equal _to V ₀ of the waveform (tone) of the high voltage V ₁ and the reference voltage V ₀ , A resistor string R ₁ composed of a plurality of resistors r _{1 to} r ₃
The voltage divided by the resistance division based on the combination of the above resistors r _{1 to} r ₃ from the connection point of each resistor
Extracted from S ₁ and S ₂ . On the other hand the reference level V ₀ below the waveform (tone) from a plurality of the resistance of the connecting point of the resistors r ₄ consisting ~r ₆ resistor string R ₂ provided between the low voltage V ₂ and the reference voltage V ₀ partial pressure obtained by resistance division based on the combination of the resistor r ₄ ~r ₆ is taken out from the switches S _3, S _4. Therefore, by controlling the ON-OFF operation of each of the switches S _{1 to} S _{4 in} a predetermined order by a control means such as a decoder, a predetermined step-like waveform, that is, a tone waveform, can be obtained from the output unit _VOUT . By shaping the waveform with an appropriate shaping circuit, an arbitrary vertically symmetrical waveform including a desired sine wave could be obtained.

[Problems to be solved by the invention]

However, in the conventional tone generating circuit as shown in FIG. 5, the symmetrical waveforms such as a sine wave to be obtained have the same magnitude of the output of each level, and have a vertical relationship with the reference level. Despite this, the control signals are required by the number of resistance divisions. Also, in order to shape the waveform, the same number of signal lines are required because the number of selection circuits is required as many as the output levels of the waveform. That is, in FIG. 5, four switches (S _{1 to} S ₄ ) are required, while four output levels are used for the waveform.

Therefore, in such a conventional tone generation circuit, not only the wiring becomes longer and the efficiency is reduced, but also when such a circuit is incorporated in an IC, the area of the chip becomes larger, which leads to a problem of an increase in cost.

[Means for Solving the Problems] The present invention employs the following technical configuration to achieve the above object. That is connected between the first switching means for selectively connecting a predetermined voltage V ₁ and V _2, the output side and a predetermined terminal of the reference voltage V ₀ which said first switch means, a plurality of resistors And a second switch means including a plurality of switches for outputting a divided voltage at each junction of the plurality of resistors;
And a control circuit for controlling the second switch means,
A tone generating circuit for generating a tone waveform by extracting a divided voltage at each junction of the resistor by the second switch means, wherein the control circuit sets the first switch means to one of the predetermined voltages; To switch the plurality of switches of the second switch means sequentially, and further connect the first switch means to the other of the predetermined voltages to sequentially switch the plurality of switches of the second switch means. Control as described above. Are symmetric vertically around the reference voltage V ₀ is the signal portion and a reference voltage level lower than the voltage level V ₂ signal portion having a having a reference voltage V ₀ level higher than the voltage level V ₁ was that is, in the present invention Paying attention to this, the resistor string for obtaining the divided voltage is provided only in one of the circuit for processing the signal in the portion higher than the reference voltage and the circuit for processing the signal in the portion lower than the reference voltage, and the number of output levels or less. , The same tone as in the related art can be formed.

[Action]

In the present invention, the voltage V ₁ higher than the reference voltage is used.
When low levels of the voltage V ₂ selected by one of the first switch means, is connected to a conventional manner of the resistor string, because you to sell desired partial pressures, between the conventional V ₁ and V _0, separately needed the resistor string between V ₂ and V ₀
Only _one R ₁ and R ₂ is needed. Therefore, the number of the selection circuits can be reduced to half the number of the conventional circuit + 1 by reducing the number of the resistor strings R to one. Therefore, the number of signal lines is also halved from the conventional one. It is understood that this is a more effective means as the number of waveform tones increases.

〔Example〕

Hereinafter, a tone generation circuit according to the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory view of the principle of the present invention, a terminal T ₀ of the reference voltage V ₀ for example, 0V is input, the reference voltage V ₀ from the high voltages V ₁
For example + 5V, and the terminal T ₂ which is lower voltage V ₂ for example -5V from the terminal T ₁ and the reference voltage V ₀ to be input is input is provided, the terminal T ₁ and T ₂ are selectively both terminal alternately and it is configured so that one through the first switching circuit S ₀ is connected to the resistor string R which is connected to the terminal T ₀ of the reference voltage to be connected.

Further, the resistor string R are those in which a plurality of resistors r ₁ ~r _n connected in series, each resistor r ₁ and r _2, r ₂ and r ₃ ... r _n-1
And r _n are connected to switches S ₁ and S ₂ for detecting the divided voltage.
... A second switch means S consisting of S _n-1 is provided.

Wherein each resistor r ₁ ~r _n constituting the resistor string R is preferably has the same resistance value, the number of Mata該resistor r ₁ is above the number of steps (reference voltage level required as a tone waveform Also, it is determined so as to correspond to (the lower number). The number of switches of the second switch means S is also determined according to the number of the resistors.

Also in the present invention are those which are program-controlled such that the first switching means S ₀ and the second switching means S is ON-OFF at a fixed sequence by a suitable control unit C, so that the desired Is output from the output _VOUT .

The tone waveform thus obtained can be shaped into a desired waveform by appropriate means in a later step.

Figure 2, there is shown one embodiment of a tone generating circuit according to the present invention, and the reference voltage V ₀ to 0V, low voltage V ₂ at + 5V reference high voltages V ₁ than voltage from -5V, also the waveform Is 4 and the resistance r constituting the resistance string R is 3
The number of switches constituting the second switch means for taking out the power distribution is two (S ₁ , S ₂ ). The resistors r constituting the resistor string R all have the same resistance value.

The node a of the resistor string R is It is.

Here, the first switch means S ₀ is controlled by the control means C.
Is connected to the terminal T ₁ and the switch of the second switch means S is
Switching is performed at predetermined time intervals in the order of S ₂ -S ₁ -S ₂ , and then the first switching means S ₀ is switched to the terminal T ₂ to switch the second switching means S to S ₂ -S ₁ -S as described above. _By switching in the order of _2, a symmetrical waveform is formed below the reference level, and a tone waveform as shown in FIG. 2 (b) is output from the output _VOUT . According to this embodiment, the number of signal lines and switches conventionally required four can be reduced to three. A circuit for controlling each switch means is not particularly limited, but a microcomputer or a decoder circuit can be used.
If the number of waveform steps is increased or a complicated waveform is desired to be obtained, the number of switches of the second switch means is increased, and the control program of the control circuit becomes more complicated.

Next, FIGS. 3 and 4 show more specific circuit configurations of the tone generation circuit according to the present invention.

FIG. 3 shows the first switch means S ₀ and the second switch means
1 shows a specific example of the configuration of the switch means S.

In FIG. 3, the terminal T ₁ of high voltages V ₁ than the reference voltage V ₀ is applied first switching means S voltage V ₂ is lower than the electronic switch S ₀₁ is connected also the reference voltage V ₀ which ₀ The same electronic switch S ₀₂ is connected to the applied terminal T ₂ , and both electronic switches S ₀₁ and S ₀₂ are alternately turned on and off by a signal applied to the control terminal D ₀ from a decoder described later. .

On the other hand, the output N of the first switch means S is connected to one end of a resistor string R composed of _three resistors r ₁ r ₂ r ₃ arranged in series, and the other end of the resistor string R is applied with a reference voltage V _0. It is connected to the terminal T ₀ that.

Note that the resistors r ₁ , r ₂ , and r ₃ constituting the resistor string R all have the same resistance value.

Further, the first switch S ₁ of the second switching means S is connected to a node unit a resistor r ₁ and r ₂ of the resistor string.

The partial pressure of the node part a is It is. The second switch S ₂ is a resistor of a resistor string.
It is connected to the node portion b of r ₂ and r _3. The partial pressure of the node b is It is. The switch S ₁ and S ₂ are sequentially ON-OFF in accordance with appropriate programs by the control signal of the decoder are connected individually to the control terminal D _1, D ₂ which control signal is applied in the decoder. The output of the second switch means S is AMP
Is output via.

FIG. 4 shows a specific example of the decoder circuit used in the present invention, in which three flip-flops (FF1,
FF2, FF3) and one inverter -INV.

The waveform diagram of the output _VOUT when the circuit of FIG. 3 is operated using the decoder of FIG. 4 is as shown in FIG. 4 (b).

In the embodiment has described the case r _1, r ₂ ... r _n are the same, these resistors may not be the same.

〔effect〕

As described above, according to the present invention, by using the same resistor string a plurality of times by the changeover switch, the number of selection circuits can be reduced to half the required number of conventional circuits + 1 by reducing the number of resistor strings to half that of the conventional one. Therefore, the effect of reducing the number of signal lines can be obtained, and the degree of integration of the integrated circuit can be increased, which greatly contributes to the cost reduction of the integrated circuit.

In addition, since the number of resistors used in the resistor string can be reduced, there is also an effect that there is no adverse effect due to variation between resistors.

The above effects of the present invention become more remarkable as the number of steps of the desired waveform increases.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention. FIG. 2 is a circuit diagram showing a specific example of the present invention. FIG. 3 is a diagram showing an example of the configuration of the switch means in a specific example of the present invention. FIG. 4 is a diagram showing an example of a decoder used in an embodiment of the present invention. FIG. 5 is a diagram showing an example of a conventional tone generating circuit. V ₀ …… Reference voltage, V ₁ …… Higher voltage than reference voltage, V ₂ ……
Low voltage, R ...... resistance string than the reference voltage, r _1, r ₂
... r _n ... resistors forming a resistor string, S ₀ ... first switch means, S ... second switch means, S ₁ , S ₂
... S _n ... Switches constituting second switch means, C.
... Control circuit of switch means, D ₀ ... Control input terminal of first switch means, D ₁ , D ₂ ... Control input terminals of second switch means, FF1, FF2, FF3 ... Flip-flop, INV ... …
Inverter.

Claims (1)

(57) [Claims] 1. A first selectively connecting the predetermined voltage V ₁ and V ₂
And switching means, which is connected between the output side and a predetermined terminal of the reference voltage V ₀ which first switching means, a resistor string connecting a plurality of resistors in series, each junction of a plurality of resistors And a control circuit for controlling the first and second switch means, wherein the second switch means outputs a divided voltage of each of the resistors. A tone generation circuit for extracting a divided voltage at a junction and generating a tone waveform, wherein the control circuit connects the first switch to one of the predetermined voltages, and the second switch A plurality of switches are sequentially switched, and further, the first switch is connected to the other of the predetermined voltages to control the plurality of switches of the second switch to be sequentially switched. Tone generator circuit to.