JPS5836360B2 - Shingoubunshiyu Cairo - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal frequency dividing circuit that is effective for dividing the frequency of a sound source signal of an electronic musical instrument.

It has been well known that a sawtooth wave or a staircase wave is more desirable as a waveform containing even harmonic components not included in a rectangular wave as a sound source signal for an electronic musical instrument or the like.

On the other hand, in the case of a staircase wave, higher even-order harmonic components are missing depending on the number of steps, but if this missing component is made to be above the upper limit of the audible frequency, it is effectively a sawtooth wave. It has the same sound quality effect.

The reason why these sawtooth waves or staircase waves are not often used in practice is that frequency division of these waveforms is difficult or requires extremely complicated circuitry, making it expensive.

The present invention provides a circuit system that facilitates integration of these signal waveform frequency divisions into integrated circuits (ICs) or LSIs.

The main components of the present invention are a series-connected rectangular wave frequency divider group, an R2R resistance network, and a switch group, and the range of required resistance values is extremely narrow. It is easy to obtain, and other circuit elements do not require particularly high precision.

Hereinafter, the present invention will be explained in detail using examples.

FIG. 1 shows an embodiment of the present invention.

The case where the input signal has a sawtooth waveform will be described below, but the same applies to cases where the input signal is a staircase wave or the like.

In the figure, 2 to 5 are frequency dividers, 6 is a sawtooth current wave input terminal, 7 to 11 are constant current sources, 12 to 16 are electronic switches,
17, 18, 20, 22, 24 are resistors with resistance value R, 1
9, 21, 23, and 25 are resistors with a resistance value of 2R, 1 is an input terminal for a rectangular wave signal, and 26 is an output terminal for a frequency-divided sawtooth wave.

The signal supplied to terminal 1 is a rectangular wave signal that is synchronized with the sawtooth wave applied to terminal 6 and has a repetition frequency half that of the sawtooth wave, and is a signal obtained by dividing the input signal at terminal 60 with a single-stage frequency divider. It is convenient to input this into terminal 1.

In this case, since a sawtooth wave current source is applied to terminal 6, it is also possible to insert a series resistor into terminal 6 and take out the voltage across it to a differential amplifier, or alternatively, The trigger signal taken out from the middle of the sawtooth wave current generating circuit supplied to the circuit 6 may be frequency-divided and used.

When the input signal to the terminal 60 is shown in FIG. 2a, the signal at the terminal 1 is shown in FIG. 2b.

Terminal 6 has an amplitude ■ as shown in Figure 3a.

A sawtooth wave current of is applied, while constant current sources 7 to 1
The current value of 1 is also set to ■o.

The current flowing through the R-2R resistor network via switches 12 and 13 is a square wave current as shown in FIGS. 3b and 3d, respectively.

Therefore, the current supplied to the R-2R resistor network via switches 14-16 is also a similar square wave, with periods twice, four times, and eight times, respectively.

Now, R-2R is connected via terminal 6 and switches 12 to 16.
Let the current supplied to the resistor network be 1(t), , respectively.
■If 2(t)5゜Ia(tt), the voltage at terminal 26 V
.

UT(j) is expressed by the following equation. I t(t) ~ Ia(
The amplitude of t) is ■.

Because ■. The amplitude of UT(t) is ■.

It becomes R. This situation is shown in FIGS. 3c and 3e.

FIG. 3C shows an example of combining one stage of rectangular waves and a sawtooth wave, and FIG. 3e shows an example of combining two stages of rectangular waves and sawtooth waves.

As can be seen from FIGS. 3c and 3e and the first equation, according to this configuration, the amplitude I is always constant regardless of the number of frequency division stages.

There is a big advantage that an output of R can be obtained.

In the embodiment shown in FIG. 1, the resistor 25 is 2R, but it may be R, or generally any value r.

The reason for this will be explained. Now, assuming that switches 12 to 15 are open, switch 16 is closed, and input terminal 6 is open, the resistance value between switch 16 and ground is equal to resistance 1.
It is a parallel resistance of the combined resistance value 2R of 1 to 24 and the resistance value r of the resistor 25, and therefore, the voltage V1 of the output terminal 26 is as follows.

Next, only the switch 15 is closed, and the other switches 12 to 1 are closed.
Assuming that 4 and 16 are open and the input terminal 6 is open as described above, the resistance value between the switch 15 and the ground is the combined resistance value 2R of the resistors 17 to 22, the resistance value 2R of the resistor 23, There are three parallel resistances of resistors 24 and 250 series resistance values (R + r), and the voltage V2 at the output terminal 26 is as follows.

As is clear from comparing v1 and V2 above, the output from constant current source 11 is always twice the output from constant current source 10, and this ratio is always constant regardless of the resistance value r of resistor 25. It is maintained.

Note that such an operation is similarly performed when the plurality of switches 12 to 16 are closed and an input is applied to the input terminal 6.

Another embodiment of the invention is shown in FIG.

Terminal 101 is a sawtooth wave voltage signal input terminal, terminal 102 is a constant voltage input terminal, terminal 103 is a rectangular wave signal input terminal, 104 -
107 is a rectangular wave frequency divider, 108 to 112 are electronic switches, 113, 114, 116, [8, 120, 122 are each a resistor with a resistance value of 2R, 115, 11 7, 119
, 121 are resistors each having a resistance value R, 123 is a frequency-divided sawtooth output terminal, and 124 is a reset signal input terminal.

The rectangular wave supplied to the terminal 103 is a rectangular wave signal that is synchronized with the sawtooth wave of the terminal 101 and has a repetition frequency that is half that of the sawtooth wave. Input to terminal 103.

Terminal 10 when the human input signal at terminal 101 is shown in Figure 5a
3 is shown in FIG. 5b.

The terminal 101 has an amplitude V as shown in FIG. 6a.

A sawtooth wave is applied to the terminal 102, and the same amplitude value ■ as the above amplitude value is applied to the terminal 102.

A constant voltage is applied. ** Therefore switch 10
The voltages applied to the upper ends of resistors 114 and 116 via resistors 8 and 109 are rectangular wave voltages as shown in FIGS. 6b and 6d, respectively.

Therefore, resistors 118 and 12 are connected via switches 110 to 112.
Similarly, the voltage applied to the upper end of 0,122 has an amplitude of V.

It is a rectangular wave with a period of 2 times, 4 times, and 8 times, respectively.

Resistor 1 via terminal 101 and switches 108 to 112
The voltages supplied to the upper ends of 14, 116, 118, 120, and 122 are respectively V1(t) j ■2(t) +V
3('t)j V4(t)fu■5(t)fu■6 (t)
Then, the voltage at terminal 123 is V.

UT(jJ is expressed by the following formula.v1(t)~”a(
The amplitude of t) is V.

Therefore, the amplitude of VOUT(j) is also V.

bawl. Figure 6C shows an example of sawtooth % frequency division by combining one stage of rectangular wave and sawtooth wave, and Figure 6e shows an example of sawtooth wave by combining two stages of rectangular wave and sawtooth wave. Examples of K frequency division are shown below.

The example of FIG. 4 and equation (2) is a case of y32 division of a sawtooth wave by combining five stages of rectangular waves and a sawtooth wave.
The amplitude V in the same manner as in Figure e.

It will be understood that a sawtooth waveform of .

One of the features of this circuit is that the amplitude is always constant regardless of the number of division stages.

A sawtooth wave output can be obtained.

Terminal 124 is a reset input terminal, and is used to match the phase with other frequency dividing circuit groups that are operated at the same time.

Although the above explanation has been made for the case where the input signal is a sawtooth wave, it is easily understood that the frequency division is performed by the same operation even when the input signal is a staircase wave.

In this case, since the deletion of high-order even-numbered harmonics in the frequency-divided signal has a constant frequency regardless of the number of division stages, it is necessary to ensure that this deletion component in the original signal is above the upper limit of the audible frequency. If you do this, you will get a sound quality effect that is no different from a sawtooth wave.

In addition, the resistance value of the high-precision resistor required for the resistor network of the present invention is only two types, R and 2R, and 2R is the 2nd value of R.
Since it can be easily realized by connecting two resistors in series, it can be said that it is essentially one type of resistor.

This is extremely advantageous when mass producing the circuit.

That is, when this circuit is constructed from individual components, resistors made from the same material and manufactured in the same lot can be used, and resistors with little variation in characteristics and uniform temperature coefficients can be obtained and used at low prices.

Furthermore, when this circuit is configured as an integrated circuit, the shapes, dimensions, directions within the chip, etc. of the resistive elements can be made uniform, and as a result, elements with uniform characteristics can be realized with extremely high precision.

It goes without saying that the present invention is not limited to only sawtooth waves and staircase waves, but can also be applied to frequency division of waveforms similar to these.

As described in the second aspect, the present invention can provide a signal frequency dividing circuit that is extremely effective for dividing the frequency of a sound source signal of an electronic musical instrument.

[Brief explanation of drawings]

Figure 1 is a wiring diagram of a signal frequency divider circuit in an embodiment of the present invention, Figure 2 is a waveform diagram of the circuit in Figure 1, and Figure 3 is a waveform diagram for explaining the operation of the circuit in Figure 1. , FIG. 4 is a circuit diagram showing another embodiment of the present invention, FIG. 5 is a waveform diagram of the circuit of FIG. 4, and FIG. 6 is a waveform diagram for explaining the operation of the circuit of FIG. 4. . 1... Square wave signal input terminal, 2-5...
・Frequency divider, 6...Sawtooth wave signal manual terminal, 7~1
1...゜Constant current source, 12-16...Switch, 17-25...Resistor, 26...
・Output terminal.

Claims (1)

[Claims] 1. An original signal source that generates a sawtooth wave or staircase wave original signal, a square wave signal source that generates one or more rectangular wave signals with a repetition period that is an even multiple of the original signal, and a constant current source or constant current source. Opening/closing is controlled by a voltage source and the above rectangular wave signal,
a switch that derives the output of the constant current source or the constant voltage source in the form of a rectangular wave with a period corresponding to the period of the rectangular wave signal;
a resistor network for adding the original signal and the rectangular wave output of the switch; A signal frequency dividing circuit characterized in that the weight of the rectangular wave output is added as 1, 2, 4, . . . to the weight of 1 of the original signal.