JPH0258919A - Pseudo trapezoidal wave generating circuit - Google Patents

Abstract

PURPOSE:To eliminate the need for the change of the capacity of a capacitor by correcting a CR time constant in an integrating circuit with an output in a synthesizing circuit and obtaining a pseudo trapezoidal wave, in which the voltage is linearly changed in the inclined part, from the integration circuit. CONSTITUTION:A pulse generator 10 supplies plural pulse signals different in repeating periods to a synthesizing circuit 12, the synthesizing circuit 12 synthesizes the signal in which a duty ratio is successively raised, the signal is converted to a voltage signal, and it is supplied to an integration circuit 16. The integration, circuit 16 integrates the voltage signal, it outputs the voltage signal in which the voltage is boosted successively, and here, since the output from the synthesizing circuit 12 is set so that an integration result can be made linear by correcting the CR time constant in the integration circuit 16, the pseudo trapezoidal wave, in which the voltage is linearly changed, can be obtained. Thus, the shock at the time of a voltage change can be effectively released, and even at the time of obtaining the voltage signal with a small inclination, the capacity of the capacitor is made sufficient to be small.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a pseudo-trapezoidal wave generation circuit, particularly a circuit for obtaining a voltage signal that changes approximately linearly.

[Conventional technology] With the development of semiconductor technology, IC,
, LSI, etc. are now being used.

For example, even in a video tape recorder, the operation is controlled by a built-in microcomputer or the like. When controlling the current using such a microcomputer, the control signal is an on/off signal, and control is basically based on a rectangular wave. However, when supplying current to a coil, if the current rises and falls using a rectangular wave, the current changes are too large, which may be inconvenient.

For example, when a cue signal is included in a control signal written on a control track of a video tape, and when this cue signal is rewritten, it is necessary to gradually rise and fall. This is because only a part of the Mi signal is rewritten, so that there is no difference in level at the start and end.

Therefore, there has been a demand in the past for the rise and fall of a rectangular wave to occur gradually, and this is usually accomplished using a capacitor. That is, a capacitor is connected to the current supply circuit, and the voltage is gradually changed by using charging and discharging of the capacitor at the rise and fall of a rectangular wave.

[Problems to be Solved by the Invention] However, when such charging and discharging of a capacitor is used, the voltage change becomes exponential. Therefore,
The voltage change at the start of the change will be quite large. Therefore, in order to make this change smoother and more linear, it is necessary to use a capacitor with a large time constant, that is, a capacitor with a large capacitance. When a capacitor with a large capacity is used, there are problems in that it is large in size, difficult to integrate, and takes too long to reach a steady state.

The present invention has been made to solve these problems, and it is an object of the present invention to provide a pseudo-trapezoidal wave generation circuit that obtains a voltage signal that changes in a predetermined linear manner without increasing the capacitance of the capacitor. With the goal.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a pseudo-trapezoidal wave generation circuit that outputs a linearly increasing waveform by using charging of a capacitor, and which generates a pseudo-trapezoidal waveform with a different repetition period. A pulse generator that generates multiple pulse signals, receives these multiple pulse signals, and sequentially superimposes them at a predetermined frequency to obtain a signal whose duty ratio increases sequentially, and converts this into a voltage signal and outputs it. and an integrating circuit that has a resistor and a capacitor connected in series and integrates a voltage signal input from the combining circuit, and the CR time constant of the integrating circuit is determined by the output of the combining circuit. It is characterized in that a quasi-trapezoidal wave in which the voltage changes linearly at its slope portion is obtained from the integrating circuit.

[Operation] The pulse generator supplies pulse signals with different numbers of repetition cycles to the synthesis circuit. And this synthesis circuit is
These plural types of pulse signals are sequentially superimposed at a predetermined frequency to synthesize signals whose duty ratios increase sequentially. Then, this signal whose duty ratio sequentially increases is converted into a voltage signal and supplied to the integrating circuit.

The integrating circuit integrates this voltage signal and outputs a voltage signal whose voltage increases sequentially. Here, the output from the synthesizing circuit corrects the CR time constant in the integrating circuit so that the integration result is linear. It is set to be. Therefore, a pseudo-trapezoidal wave in which the voltage changes linearly can be obtained here.

[Embodiment] Next, a pseudo trapezoidal wave generating circuit according to the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the overall configuration of a pseudo trapezoidal wave generation circuit according to the present invention, in which a pulse generator 10 generates a plurality of types of pulse signals with different repetition periods and supplies them to a synthesis circuit 12. . Here, in this example, the pulse generator generates pulses as shown in FIG. 2 by pulse width modulation. That is, the following signals are generated based on the pulses having a frequency of about 3.5 MHz and a duty ratio of 50% as shown in FIG. 2(A).

That is, (B) is a signal in which the ON positions do not overlap with (A) and the duty ratio is 25%.

(C) is a pulse signal whose ON location does not overlap with either (A) or (B) and whose duty ratio is 12.5%. In (D), the on positions are (A), (B), (
Does not overlap with any of C) and has a duty ratio of 6.2
This is a pulse signal of 5%. And (E) is similar, but the duty ratio is further reduced to 1/2. In this example, this five-stage signal is used, and one cycle is formed by 16 pulses. Note that the number of stages can be determined as necessary, and the number of stages can be increased or decreased as necessary. Further, generation of such a signal can be achieved by an operation similar to frequency division.

Then, the combining circuit 12 superimposes the supplied plural types of signals at a predetermined frequency, and this frequency is determined by the signal from the counter 14. That is, as shown in FIG.
The pulse signals supplied from the controller are sequentially superimposed to generate a signal whose duty ratio increases sequentially. In the example of FIG. 3, for the count value r00000J, a signal with a duty ratio of 0, ro
Duty ratio of 3.1 in Fig. 2 (E) for 000 N
25% signal is responded, count value ro 0010J
In contrast, the signal with a duty ratio of 6.25% in Fig. 2 (D),
A signal with a duty ratio of 9.375% obtained by superimposing Fig. 2 (E) and CD) on rooolJ corresponds to a signal with a duty ratio of 1 in Fig. 2 (C) for the count value "00100J".
A signal of 2.5% is supported. Then, similarly, roolON, ro 0110J, "00111J, r
o 1000J, ... "10111J, rll
oolJ, rl 1010J, "11011", rll
looJ, rl 1101J, rl 1110J, and a signal in which the duty ratio increases by 3.125% is generated, and at the count value [11111J, the duty ratio is 96.
One cycle ends with a signal of 847%. Note that the count value in the counter 14 is determined by the TR supplied here.
This is done by counting IG signals.

In this way, a signal whose duty ratio increases sequentially according to the count value of the counter 14 is generated in the synthesis circuit 12a. The synthesis circuit 12 then outputs the signal generated in this manner as an analog voltage signal.

The output signal of the combining circuit 12 is input to the integrating circuit 16. This integrating circuit 16 consists of a resistor R and a capacitor C connected in series.
The other end of capacitor C is grounded.

Then, the integrated voltage is output from the connection between the resistor R and the capacitor C.

Note that since it is difficult to accommodate the capacitor C inside the IC, it is provided outside the IC and connected via the terminal Tt.

In such an integrating circuit 16, when a voltage signal whose duty ratio increases sequentially at a predetermined timing is manually inputted from the combining circuit 12, this is integrated and outputted as a gradually increasing voltage signal.

The output terminal of the integrating circuit is connected to a buffer 18, and the 16 outputs of the integrating circuit are smoothed and amplified here and outputted from the output terminal T2 to the outside of the IC. Note that the transmission gate G is for controlling the output of the voltage signal, and prohibits the output during reproduction.

As described above, according to the present invention, by outputting a voltage signal that gradually increases from the combining circuit 12 in accordance with the output value of the counter 14, it is possible to form a linearly increasing portion of the trapezoidal wave.

In this example, two synthesis circuits 12, two counters 14, two integration circuits 16, two buffers 18, etc. are provided in parallel to form separate sections where the voltage value of the trapezoidal wave increases and decreases. ing.

That is, the counter 14a has the above-mentioned count value r000.
00J to rl 1111J, and the counter 14b counts from the count value rl 1111'' to ro 0
Count to 000J. And counter 14a
, 14b, a trapezoidal wave is generated by controlling the values of the counters 14a and 14b as follows.

Both counters 14a and 14b have a count value of ro 0000J in their initial states.

Then, the counter 14a receives a trigger at the TRIG signal point a, and counts up twice until the counter value rl 1111J. And the count value is r
After reaching l 111 N, this value is held.

Then, a trigger is received at the TRIG signal point after a certain period of time has elapsed, and the count value of the counter 14a becomes ro 00.
00J, and the count value of the counter 14b is set to rl 111 N and holds the value. Further, after a certain period of time has elapsed, the counter 14b receives a trigger at the TRIG signal point signal point sum and starts counting down. Then, the countdown is performed until the count value reaches ro 0000J, and then the count value becomes ``0''.
Holds 0000J.

In this way, the counters 14a and 14b each output predetermined rising waveforms and falling waveforms that change linearly. Then, the synthesis circuits 12a and 12b output the pulse generator 10 according to the count value supplied in this way.
In order to synthesize the signals from the output terminals T and T2b, a trapezoidal wave as shown in FIG. 4a is output from the output terminals T and T2b.

As described above, according to the circuit of this embodiment, a trapezoidal wave in which the voltage changes linearly can be obtained, and a current of a predetermined change can be supplied to the coil or the like. Further, by changing the gain in the counter 14, the degree of increase in the ON output of the voltage signal output from the combining circuit 12 can be controlled. Therefore, there is no need to change the capacitance of the capacitor C, and the slope of the rise can be changed. As a result, even when obtaining a voltage with a small slope (No. 8), the capacity of the capacitor may be small.

[Effects of the Invention] As explained above, according to the pseudo-trapezoidal wave generation circuit according to the present invention, a trapezoidal wave whose slope is substantially straight can be obtained, and shocks caused by voltage changes can be effectively alleviated. . Furthermore, the slope of voltage change can be adjusted by adjusting the frequency of folding in the synthesis circuit, and there is no need to change the capacitance of the capacitor.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a pseudo trapezoidal wave generation circuit according to an embodiment of the present invention, FIG. 2 is a waveform diagram of a signal generated by the pulse generator 10 in the embodiment, and FIG. 3 is a synthesis circuit in the embodiment. 12 is a waveform diagram of the signal generated, and FIG. 4 is a waveform diagram of the output signal at the output terminals T2a' and 2b. 10...Pulse generator 12...Synthesizing circuit 14...Counter 16...Integrator Circuit 18... Buffer R... Resistor C... Capacitor

Claims (1)

[Claims] (1) A pseudo-trapezoidal wave generation circuit that outputs a linearly increasing waveform using charging of a capacitor, which includes a pulse generator that generates multiple pulse signals with different repetition periods, and a pulse generator that generates multiple pulse signals with different repetition periods; a synthesis circuit that sequentially superimposes these signals at a predetermined frequency to obtain a signal whose duty ratio increases sequentially, converts it into a voltage signal, and outputs it; and a synthesis circuit that includes a resistor and a capacitor connected in series. an integrating circuit that integrates a voltage signal input from the integrating circuit, and an output from the combining circuit corrects the CR time constant in the integrating circuit, and a pseudo-simulator in which the voltage from the integrating circuit changes linearly in its slope part. A pseudo-trapezoidal wave generation circuit characterized by obtaining a trapezoidal wave.