JPS5842968B2 - Astable oscillator control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control circuit capable of extracting only one pulse from an astable multi-by-break that has started oscillation.

Conventional oscillators for generating repeat tones in electronic musical instruments use an unstable multivibrator, and control musical tones by extracting pulses from the multivibrator, which starts oscillating when a key is pressed.

That is, as shown in FIG. 1, a known unstable multivibrator is constructed from the first transistor Q1, the second transistor Q2, capacitors C1 and C2, and resistive elements, and from the bases of both transistors, resistive elements R1 and R2 and diodes are connected. D0. An oscillator is used in which a terminal commonly connected to D2 is used as an output terminal, and a transistor Q3 serving as a switching element is connected to the base terminal of a second transistor Q2.

If, for example, a negative voltage is suddenly applied to the base of the transistor Q3 as a control signal from an external source by closing a key switch corresponding to a key press, the transistor Q3 is turned off, and until now the base of the second transistor Q2 has been grounded. The multivibrator, which had stopped oscillating, starts oscillating.

Then, the pulse generated at the base electrode was taken out through resistive elements/diodes R1/Dl and R2/D2 to control musical tones.

Due to its characteristics, an unstable multivibrator connects pulse generation while the key switch is closed, but when a key is released immediately after being pressed in a staccato playing style, even if only one pulse is desired to be output from the output terminal, both transistors naturally generate pulses. A pulse output is obtained one by one, which is unfavorable in terms of performance and hearing.

In the time chart shown in FIG. 2, FIG. 2A shows the input voltage to the base of the transistor Q3 as the key switch opens and closes, and FIG. 2B shows the pulse output from the output terminal.

When the key switch is closed at time T1 and opened at time T1, the pulse outputs become Pl and P2.

In this case, an undesired pulse P2 is generated at time T2,
Even if the key switch is newly closed at time T3, the pulse P
3 cannot be obtained immediately and occurs at time T4.

It is an object of the invention to provide an astable oscillator control circuit which, if desired, can extract only one pulse from an astable multi-by-break that has started oscillating in a circuit as described above.

Hereinafter, an embodiment in which the present invention is applied to an oscillator for generating repeat tones of an electronic musical instrument will be described in detail with reference to FIG.

In FIG. 3, Ql, Q2. Q3. R1, R2, Dl.

D2. C1 and C2 are the same as in FIG.

D3゜Q4 indicates a diode and a transistor constituting the bypass element in the present invention, one end of which is connected to the second transistor Q.
The transistor Q4 is connected to the connection point between the resistive element R2 and the diode D2 of the base circuit No. 2, and the opposite side of the transistor Q4 from the diode D3 is connected to the power supply terminal B (the ground point for the output pulse).

When no key is pressed and the key switch is open, there is no signal at the key switch output terminal, and both transistors Q3 and Q4 are turned on.

At time T as shown in FIG. 2A.

When the key switch is closed, transistors Q3-Q4
turns OFF, the multi-by-break starts oscillating, and one pulse PP is generated via the diode D□ as shown in FIG. 2C.

Then, when the key switch is opened at time T1 when the pulse PP1 is generated, the pulse (referred to as PP2) generated at the base of the transistor Q2 is transmitted to the transistor Q3. Since Q is ON, diode D3
The pulse PP2 is bypassed through the transistor Q4 and the transistor Q4.
It does not appear on the pulse output terminal.

Then, when the key switch is closed at time T3, a pulse PP3 is generated immediately, and when the key switch continues to be closed at time T, a pulse PP4 is generated.

A multi-by-break oscillation/stop judgment signal is applied to the transistor Q3, which serves as an opening/closing element for the multi-by-break circuit operation, through a transistor Q4 among the bypass elements.

In this way, according to the present invention, an undesired pulse is not generated at the output terminal by a simple additional circuit, and the multivib break starts oscillating immediately when the key switch is closed. Therefore, when applied to an electronic musical instrument, for example, when playing a staccato This is an effective control circuit that can reliably produce repeat tones and the like using desired pulses even when keys are pressed.

[Brief explanation of drawings]

FIG. 1 shows a conventional unstable multi-by-break control circuit, and FIG. 2 shows a time chart for explaining the operation. FIG. 3 is a circuit diagram showing one embodiment of the present invention. Ql...First transistor, Q2...
Second transistor, Q3...Switching element, Dl,
D2. D3...Diode, R,, R2...
...Resistance element, Q4...Transistor.

Claims (1)

[Claims] 1. The terminals commonly connected from the bases of the first and second transistors constituting the unstable multivibrator through respective resistive elements and diodes are used as pulse output terminals,
In an unstable oscillator control circuit having a switching element connected to the base of the second transistor and controlling oscillation/stop of the multi-by-break by applying an external control signal, a connection point between the resistive element and the diode of the base circuit of the second transistor; and a bypass element for the pulse output, which is connected between an equivalent ground point and to which an external control signal for controlling oscillation and stopping of the multivibrator is applied, and the switching element is controlled to open and close at the same time as the bypass element. An astable oscillator control circuit, characterized in that the control signal is applied through the bypass element so that the control signal is applied to the non-stable oscillator control circuit.