JPS6399611A - Saw-tooth wave generating circuit - Google Patents

Abstract

PURPOSE:To obtain a saw-tooth wave output with a constant amplitude against the fluctuation of a frequency by detecting the peak value of a saw-tooth wave voltage, comparing it with the output of a reference power source circuit and changing a current charging a capacitor in an inverse proportion to that output. CONSTITUTION:A peak detection circuit 5 which detects the saw-tooth wave, a comparison amplifier circuit 6 which compares the output of the peak detection circuit 5 with the output of the reference power source circuit 7, and a current control circuit B which changes the current charging capacitor charged by an input voltage due to the output of the comparison amplifier circuit 6 are provided. The capacitor charges and discharges according to the low and high levels of an input pulse and generates the saw-tooth wave at its both sides. The peak detection circuit 5 detects the peak amplitude of these saw-tooth waves and the comparison amplifier circuit 6 compares the output of this detection with the output of the reference power source circuit. The output current of the current control circuit is increased and decreased in the inverse proportion to the output of the comparison amplifier circuit 6 and the amplitude of the saw-tooth waves is stabilized by changing the current charging the capacitor with the aid of this output.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a sawtooth wave generating circuit that can obtain an output with constant amplitude even when the frequency changes.

[Conventional technology]

FIG. 4 shows a conventional sawtooth wave generation circuit.

In this FIG. 4, the Noculus power is input to the pace of an NPN type transistor l, the emitter of the transistor l is grounded, the collector of the transistor l is connected to one end of the capacitor 3 via the resistor 2, and the output of the constant current circuit 17. , are connected to the input terminal of the buffer circuit 4.

One side of the capacitor 3 is grounded, the input terminal of the constant current circuit 170 is connected to a power supply, and the output terminal of the buffer circuit 4 is output from the output terminal as a sawtooth wave output.

Next, the operation will be explained. FIG. 5 shows the timing chart of FIG. 4. FIG. 5(a) shows the input waveform of the pulse signal, and FIG. 5(b) shows the output waveform of the t-threaded wave.

In FIG. 4, when the voltage input (FIG. 5(a)) is at a low V level, transistor 1 is off, the current of constant current circuit 17 flows to capacitor 3, and capacitor 3 is charged. .

Next, when the /-P pulse input becomes high level, transistor 1 is turned on, and the photoelectric charge transferred to capacitor 3 is
It is rapidly discharged through the resistor 2 and the transistor l'fc.

The resistor 2 is a current limiting resistor to prevent the transistor 1 from being destroyed due to an excessive current flowing through the transistor 1 due to the discharge current of the capacitor 3.

The buffer circuit 4 is a circuit for eliminating the influence of external circuits. Therefore, the photodischarge of the capacitor 3 is determined by the pulse input, and a sawtooth wave (FIG. 5(b)) is outputted from the buffer circuit 4.

[Problem that the invention seeks to solve]

Since the conventional sawtooth wave generation circuit is configured as described above, there is a problem in that when the cycle of the sawtooth wave input changes, the amplitude of the sawtooth wave output changes.

The present invention was made to solve these problems, and aims to provide a sawtooth wave generation circuit in which the amplitude of the sawtooth wave output is stable even when the cycle of the cell input changes.

[Means for solving the problem] A sawtooth wave generation circuit according to the present invention includes a peak detection circuit that detects a sawtooth wave, an IT comparison amplifier circuit that compares the output of the peak detection circuit and the output of a reference power supply circuit, A current control circuit is provided which changes the photocurrent of the capacitor photoelectrically generated by the input voltage based on the output of the comparison amplifier circuit.

[Effect]

In this invention, a capacitor is charged and discharged according to the low and high levels of the human power signal, generating a sawtooth wave at both ends of the capacitor, and detecting the peak and all peaks of the amplitude of this sawtooth wave with a detection circuit, and outputting the detection output. The output current of the current control circuit increases or decreases in inverse proportion to the output of the comparison amplifier circuit, and this output current changes the photocurrent of the capacitor, creating a sawtooth wave. stabilize the amplitude.

〔Example〕

Hereinafter, an embodiment of the sawtooth wave generation 1u path of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment. In FIG. 1, the same parts as in FIG. 4 will be described with the same reference numerals. In FIG. 1, the noise input input to the input terminal T1 is input to the transistor pace, the emitter of the transistor 1 is grounded, and the collector is connected to one end of the capacitor 3 via the resistor 2.
It is connected to the input end of the buffer circuit 4 and the output end of the current control circuit 8, and the other end of the capacitor 3 is grounded.

The output of the buffer circuit 4 is output as a sawtooth wave output to the output terminal T2, and is also applied to the input terminal of the peak detection circuit 5.

The output of the peak detection circuit 5 is applied to a comparison amplifier circuit 6, and the output of the reference power supply circuit 7 is also input to the comparison amplifier circuit 6.

This peak detection circuit 5 is configured, for example, as shown in FIG. and is grounded via a resistor 12.

Here, the explanation returns to FIG. 1. In FIG. 1, the comparison amplifier circuit 6 is composed of, for example, a low-cess filter and a differential amplifier circuit. The output of this comparison amplifier circuit 6 is sent to a current control circuit 8.

The current control circuit 8Vi controls the amplitude of the sawtooth p-wave voltage generated across the capacitor 30 at a constant level by changing the charging current of the capacitor 30, and thus the buffer circuit 4-
Peak detection circuit 5 - comparison amplifier circuit 6 - current control circuit 8 -
A loop of the buffer circuit 4 constitutes an AGC loop.

FIG. 3 is a circuit diagram showing a specific configuration of the current control circuit 8. As shown in FIG. In FIG. 3, a current control input output from a comparison amplifier circuit 6 is applied to an input terminal T5, and this input terminal T5 is connected to the pace of a transistor 16 via a Zener diode 13. ing.

The terminal of this transistor 16 is connected to the power supply terminal T6 via the resistor 14. Power supply terminal T6 is connected to the emitter of transistor 16 via resistor 15.

The collector of transistor 16 is connected to output terminal T7. This output terminal T7id is connected to one end of the capacitor 3 in FIG.

The Zener diode 13 and the resistor 14 level shift the input voltage to prevent saturation of the sawtooth wave when charging the capacitor 3 shown in FIG. 1, thereby improving the dynamic range of the current control circuit 8.

Next, the operation of this invention will be explained. 5(a) shows the timing of the sawtooth wave output, and FIG. 5(b) shows the timing of the sawtooth wave output.
) ) is low level, transistor 1 is off,
The capacitor 3 is photoelectrically charged by the output current of the current control circuit 8, and then when the nozzle input becomes high level, the transistor l is turned on, and the electric charge photoelectrically transferred to the capacitor 3 is transferred through the transistor 1 and the resistor 2. Discharge occurs rapidly.

This resistor 2 is a current limiting resistor for preventing the transistor 1 from being destroyed by the discharge current of the capacitor 3.

The buffer circuit 4 is a circuit that prevents the influence of the peak detection circuit 5 and external circuits. By charging and discharging the capacitor 3, a sawtooth wave is generated and output via the buffer circuit 4 (FIG. 5(b)).

・The output of the tsufa circuit 4 is output by the peak detection circuit 5,
The amplitude of the sawtooth wave is detected.

This peak detection circuit is as shown in Figure 2. In Figure 2, when the positive voltage of the output of the Gutufa circuit 4 is applied to the input terminal T3, the diode 10 is turned on, and the entire resistor 9 is turned on. When the voltage at the input terminal T3 decreases, the diode 10 is turned off and the capacitor 11 is discharged by the resistor 12. If the discharging time constant of the capacitor 11 is made sufficiently larger than the charging time constant of the capacitor 11, all peak values of the input will be detected.

The voltage detected by this peak detection circuit 5 is compared and amplified with the output voltage of a reference power supply circuit 7 by a comparison amplifier circuit 6 including a low-sos filter metal, and is applied to a current control circuit 8. This current control circuit 8 has a characteristic that the output current increases or decreases in inverse proportion to the input voltage, and this current control circuit 8 is controlled by the output of the comparison amplifier circuit 6 to change the current charging the capacitor 3. stabilizes the amplitude of the wave.

This current control circuit 8 has an input terminal T as shown in FIG.
5, the output of the comparison amplifier circuit 6 is added as an input, and the difference between the voltage obtained by adding the voltage of the Zener diode 13 to the input voltage of the input terminal T5, and the voltage between the pace and emitter of the transistor 16, and the power supply. It is the value obtained by dividing the voltage by the resistance value of the resistor 15, and the output current has a characteristic that it is inversely proportional to the input voltage.

Next, the case where the pulse period becomes longer will be explained.

Initially, the output current of the current control circuit 8 does not change and remains in the previous state, so the amplitude of the sawtooth wave output increases by the length of the charging period of the capacitor 3. When the amplitude of the sawtooth wave output increases, the output of the peak detection circuit 5 also increases, and the output of the comparison amplifier circuit 6 also increases.

Therefore, the output current of the current control circuit 8 decreases, and the amplitude of the sawtooth wave output changes more than it matches the output voltage of the reference power supply circuit 7.

Further, when the period of the A pulse input becomes shorter, the operation opposite to the above is performed, and the amplitude of the sawtooth wave output changes to match the output voltage of the reference power supply circuit 7, as in the above case.

As a result, even if the period of pulse input changes, the amplitude of the sawtooth wave remains constant due to the AGC looseness. At this time, the amplitude is determined by the output voltage of the reference power supply circuit 7.

〔Effect of the invention〕

As explained above, the present invention uses a peak detection circuit to detect the peak value of the sawtooth voltage generated across a capacitor that charges and discharges depending on the level of the input voltage, and the output of the peak detection circuit and the output of the reference power supply circuit. were compared using a comparison amplifier circuit, and the output of the current control circuit increased or decreased in inverse proportion to the output, changing the photocurrent in the capacitor, so that a sawtooth wave whose amplitude remained constant even when the frequency etc. changed. I get the output.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the sawtooth wave generation circuit of the present invention, FIG. 2 is a circuit diagram showing the configuration of a specific embodiment of the peak detection circuit in the above-mentioned sawtooth wave generation circuit, and FIG. , a circuit diagram showing the configuration of a specific embodiment of the current control circuit in the above sawtooth wave generation circuit, FIG. 4 is a circuit diagram of a conventional sawtooth wave generation circuit, and FIG. 5 is a circuit diagram of the conventional sawtooth wave generation circuit and the present invention. This is a timing chart of the generator circuit's human power and sawtooth wave output. DESCRIPTION OF SYMBOLS 1... Transistor, 2... Resistor, 3... Capacitor, 4... Buffer circuit, 5... Peak detection circuit, 6... Comparison amplifier circuit, 7... Reference power supply circuit, 8・
...Current control circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A capacitor that generates a sawtooth wave at both ends by charging or discharging according to the level of the input pulse, a peak detection circuit that detects the peak of the amplitude of this sawtooth wave, and a connection between the output of this peak detection circuit and the output of the reference power supply circuit. A sawtooth wave generation circuit comprising a comparison amplifier circuit for comparison, and a current control circuit that increases or decreases an output current in inverse proportion to the output of the comparison amplifier circuit to change the current charging the capacitor.