JPS59216320A - Saw tooth wave generating circuit - Google Patents

Abstract

PURPOSE:To generate a high-linearity saw tooth wave by charging temporarily the electric charge in a capacitor with a constant voltage and transferring this electric charge to another capacitor in steps with complementary switching of switches to integrate the electric charge. CONSTITUTION:When a pulse A having a period t2 is inputted to a monostable multivibrator 1, the monostable multivibrator 1 outputs a pulse B synchronously with the rise of this pulse A. In a time zone t1 when this pulse B is generated, the electric charge charged in a capacitor 2 is discharged to set the voltage at a terminal point C to zero as shown by a waveform C. Switches 8 and 9 are interlocked with each other as shown by waveforms E and F and are operated complimentarily, and an electric charge C2V0 is charged in a capacitor 7 by the power supply of a voltage V0 if the switch 8 is opened and the switch 9 is closed, and this charged electric charge is transferred to a capacitor 2 and the negative input terminal of an operational amplifier 6 otherwise.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sawtooth wave generating circuit that has a peak in synchronization with the period or inversion interval of an input pulse, and is particularly suitable for fc conversion without directly depending on capacitance and resistance values. The present invention relates to a sawtooth wave generation circuit designed as follows.

11th i! ! I is a diagram showing an example of a conventional sawtooth wave generation circuit.

First, the configuration of a conventional sawtooth wave generation circuit will be explained with reference to FIG. In FIG. 1, a monostable multivibrator 1 outputs a pulse B synchronized with the rising edge of an input pulse A. During the period when the pulse B is not generated, the transistor 4 is in an off state, and the capacitor 2 having a capacitance value C7 is charged by the power source VO via the resistor 3 of the resistor IR. Further, during the period in which the pulse B is generated, the transistor 4 is in an on state, and the electric charge stored in the capacitor 2 is discharged.

FIG. 2 is a waveform diagram for explaining the operation of the sawtooth wave generation circuit shown in FIG. 11.

Next, the operation of the sawtooth wave generating circuit shown in FIG. 1 will be explained with reference to FIG. The pulse A input to the monostable multivibrator 1 is 1 as shown in FIG.
The pulse B generated from the monostable multivibrator 1 in synchronization with the pulse A is also shown in Fig. 2 (
As shown in B), it has a period of t2. As mentioned above, during period t when pulse B is generated, capacitor 2 is discharged and the voltage at the 0 point becomes O, and during period 12-1 when pulse B is not generated, capacitor 2 is charged and becomes 0. The voltage at the point increases exponentially as shown in Figure 2, and reaches the peak value V in synchronization with the rise of the incident coverage A.
It becomes a sawtooth wave that reaches p.

The peak value Vp is given by the following equation, where the capacitance of the capacitor 2 is C1, the resistance value of the resistor 3 is R1, the voltage is R1, and the voltage is Vo.

Here, it is assumed that t2 is sufficiently larger than t1.

The slope of the sawtooth curve in FIG. 2(C) depends on the time constant -OR in equation (1), and if the period t2 is long, a large time constant is required. Therefore, a capacitor with a large capacity or a resistor with a high resistance value is required, and it is difficult to integrate the conventional sawtooth wave generating circuit shown in FIG. 1 into an IC.

Therefore, the main object of the present invention is to eliminate the above-mentioned drawbacks and to provide a sawtooth wave generation circuit suitable for IC implementation that does not directly depend on capacitance and resistance values.

To summarize, the present invention can be summarized as follows: the second capacitor is once charged with a charge using a constant voltage application means, and the operation of transferring the above-mentioned charge to the first capacitor by complementary opening and closing of the switch is repeated, and the first capacitor is then charged. By charging in stages, the generation of sawtooth waves is made independent of the time constant CR.

The objects and other objects and features of the present invention will become apparent from the detailed description given below with reference to the drawings.

FIG. 3 is a circuit diagram showing an embodiment of the present invention.

Next, the configuration of the embodiment shown in FIG. 3 will be explained. A monostable multivibrator 1 that generates a pulse synchronized with the rising edge of an input pulse is connected to an initial setting circuit 5 that includes a switch inside. During the time period when monostable multivibrator 1 is outputting pulses in response to input pulses,
The initial setting circuit 5 has a capacitance value C4 connected in parallel.
The electric charge of the capacitor 2 is discharged, and the voltage of the capacitor 2 is set to 0. Further, during the time period when the monostable multivibrator 1 is not outputting pulses, the above-mentioned discharging of the capacitor 2 is stopped. At the same time, the capacitor 2 is connected to the calculation itI.
It is connected in parallel with the IIM unit 6 to form an integrator.

The voltage at one terminal C point of this capacitor 2 is the integrated output of this integrator, that is, the output voltage of this embodiment.

On the other hand, a power supply with a constant voltage Vo is provided, and the switch 9
The capacitor 7 is connected to one terminal of the capacitor 7 having a capacitance value C2. Further, the above-mentioned terminal -D point of the capacitor 7 is simultaneously connected to the terminal on the opposite side of the above-mentioned 0 point of the capacitor 2 and the negative input terminal of the operational amplifier 6 via the switch 8 . The N-closers 8 and 9 complementarily control the time t based on the control signal from the switching control circuit 10.
.

It opens and closes at a cycle of .

FIG. 4 is a waveform diagram for explaining the embodiment shown in FIG. 3.

Next, the operation of the embodiment shown in FIG. 3 will be explained with reference to FIG. When the monostable multivibrator 1 receives a pulse A with a period t2 shown in FIG. 4 (A>), the monostable multivibrator 1 generates a pulse B shown in FIG. 4 (B) in synchronization with the rising edge of the pulse.
@Occur. The initial setting circuit 5 includes a switch therein, and during the time it+ when the pulse B is generated, the electric charge stored in the capacitor 2 is discharged and one side of the capacitor 2 is opened as shown in FIG. 4(C). Let the voltage at terminal C point be 0. In addition, the time period 12-1 in which pulse B is not generated.
In this case, the initial setting circuit 5 stops discharging the capacitor 2 described above. Switches 8 and 9 are shown in Fig. 4 (E) and (F).
), these are switches that open and close in a complementary manner in conjunction with each other, and when switch 8 is open and switch 9 is closed, the voltage Vo
The capacitor 7 is charged with an electric charge of C2VO by the power supply, and when the switch 8 closes and the switch 9 opens, the above-mentioned charge C2Vθ charged in the capacitor 7 is transferred to the negative input terminal of the capacitor 2 and the operational amplifier 6. .

During the period when the initial setting circuit 5 stops discharging the capacitor 2, the charge Q charged in the capacitor 7 is Q''C2Vo...(1) as described above, and this charge charges the operational amplifier 6. When transferred to the capacitor 2 via the capacitor 2, the charge on the 0 point side of the capacitor 2 becomes Q--C, V.
(2) becomes. Therefore, from equations (1) and (2), Vc
-C2/C+”V.

becomes.

Here, if the number of times the WM switch is closed after the voltage of capacitor 2 becomes O is N, the voltage VC (N) at the 0 point at N times is Vc (N) - Vo' N '' C2/ CI・
” (3).

The number of circuit closures in one cycle of the input pulse is 12/1.

Therefore, the peak value that Vc (N) takes in synchronization with one cycle of the input pulse is P = Vo -1z /j 6 ・Ct /C+
-(4).

Therefore, according to the above equation (4), the peak value Vp does not depend on the resistance value, but depends on the ratio of the switching period t of the switch 8.9 to the period t2 of the input pulse A, the capacitors 2, 7 The capacitance ratio C2/C, and [! It is determined by the ffi pressure Va, and therefore is not directly influenced by the capacitance value or resistance value.

By the way, in the above-mentioned embodiment, two switches 8 and 9 that open and close alternately are used, but for example, two fixed contacts and one switch are used.
So-called bipolar switchgear with two movable pieces 8.9
A similar effect can be obtained by using them as an integrated version.

As described above, according to the present invention, the second capacitor is once charged with a charge using a constant voltage, and the charge is transferred stepwise to the first capacitor by complementary opening and closing of the switch and integrated. Since the sawtooth wave is generated by the above, it is not linearly dependent on the capacitance value used, and therefore eight small capacitors can be used, and a sawtooth wave generation circuit that can be easily integrated into an IC can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a conventional sawtooth wave generating circuit. FIG. 2 is a waveform diagram for explaining the operation of a conventional sawtooth wave generating circuit. FIG. 3 is a circuit diagram of an embodiment of the present invention. FIG. 4 is a waveform diagram for explaining the operation of the embodiment shown in FIG. 3. In the figure, 1 is a monostable multivibrator, 2.7 is a capacitor, 3 is a resistor, 4 is a transistor, 5 is an initial setting circuit, 6 is an S-type amplifier, 8.9 is a switch, and 10 is a switching control means. . Agent Masuo Oiwa Figure 2 Figure 3 Figure 4

Claims (3)

[Claims] (1) A sawtooth wave generation circuit having a peak synchronized with the period or inversion interval of an input pulse, comprising: a first capacitor; and means for initializing the voltage of the first capacitor in synchronization with the input pulse; , a voltage applying means for applying a constant voltage, a second capacitor charged by the voltage applying means, an integrating means for receiving the electric charge of the second capacitor and charging the first capacitor, and the second capacitor. a sawtooth wave generating circuit, comprising: switching means for alternately connecting a capacitor of 1 to the voltage applying means and the integrating means; (2) The initial setting means lowers the voltage of the first capacitor in synchronization with the rising or falling edge of the input pulse.
A sawtooth wave generation circuit according to claim 1. (3) One end of the capacitor of WI2 is equivalently grounded, and the other end is connected to the first capacitor and the integrating means via the switching means. (4) The switching period of the switching means is