JP2524386B2 - Pseudo trapezoidal wave generation circuit - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a pseudo trapezoidal wave generation circuit, and more particularly to a circuit for obtaining a voltage signal that changes substantially linearly.

[Prior art] With the development of semiconductor technology, ICs for controlling various devices,
LSI etc. have come to be used. The operation of a video tape recorder or the like is controlled by a built-in microcomputer or the like. When the current is controlled by such a microcomputer or the like, the control signal is an ON / OFF signal, and the control is basically based on a rectangular wave. However, in the case of supplying a current to the coil, if the current rises and falls by a rectangular wave, the current change may be too large, which may be inconvenient.

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

Therefore, conventionally, there has been a demand for gradually rising and falling a rectangular wave, and this is normally achieved by using a capacitor. That is, a capacitor is connected to the current supply circuit, and when the rectangular wave rises and falls, charge and discharge of this capacitor are used to gradually change the voltage.

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

The present invention has been made to solve the above problems, and provides a pseudo trapezoidal wave generation circuit that obtains a voltage signal that linearly changes without increasing the capacitance of a capacitor. With the goal.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention utilizes a charge of a capacitor to rewrite a control signal of a video device, and outputs a pseudo-trapezoidal wave that linearly increases a waveform. A pulse generator for generating a plurality of pulse signals having different repetition periods, a counter for outputting a sequentially increasing count value, a plurality of pulse signals for receiving the pulse signals, and superimposing them on each other to count each of the counters. A signal having a duty ratio corresponding to the value is generated, and a signal whose duty ratio is sequentially increased according to the increase of the count value is obtained, and a synthesis circuit for converting this into a voltage signal and outputting the voltage signal, a resistor connected in series, and An integrating circuit that has a capacitor and integrates a voltage signal input from the synthesizing circuit; It is characterized in that the CR time constant in the integrator circuit is corrected to obtain a pseudo trapezoidal wave whose voltage changes linearly in the slope portion from the integrator circuit.

[Operation] The pulse generator supplies a plurality of pulse signals having different repetition periods to the combining circuit. Then, the synthesizing circuit synthesizes the signals in which the plurality of types of pulse signals are sequentially superimposed at a predetermined frequency to sequentially increase the duty ratio. Then, the signal in which the duty ratio is sequentially increased is converted into a voltage signal and supplied to the integration circuit.

The integrator circuit integrates this voltage signal and outputs a voltage signal in which the voltage sequentially rises.Here, the output from the combiner circuit corrects the CR time constant in the integrator circuit, and the integration result becomes linear. Is set to. Therefore, a pseudo trapezoidal wave whose voltage changes linearly can be obtained here.

[Embodiment] Next, a pseudo trapezoidal wave generation circuit according to the present invention will be described with reference to the drawings.

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

That is, (B) is a signal that does not overlap with (A) where it is on and has a duty ratio of 25%.
(C) is a pulse signal whose ON position does not overlap with either (A) or (B) and has a duty ratio of 12.5%. In (D), the ON locations are (A), (B), and (C).
Is a pulse signal that does not overlap with any of the above and has a duty ratio of 6.25%. Then, in (E), the duty ratio is further reduced to 1/2 in the same manner. In this example, these 5 steps of signals are used, and 16 pulses make 1
A cycle is formed. Note that the number of steps can be determined as necessary, and the number of steps can be increased or decreased as necessary. Further, the generation of such a signal can be achieved by an operation similar to that of frequency division.

Then, the synthesizing circuit 12 superimposes a plurality of types of supplied signals at a predetermined frequency, and this frequency is determined by the signal from the counter 14. That is, as shown in FIG. 3, the pulse signal supplied from the pulse generator 10 is sequentially superposed on the output from the counter 14 to generate a signal whose duty ratio sequentially increases. In the example of FIG. 3, a signal with a duty ratio of 0 is associated with the count value “00000”, a signal with a duty ratio of 3.125% is associated with “00001” of FIG. The signal with the duty ratio of 6.25% in FIG. 2D, “00011”, is shown in FIG.
A signal having a duty ratio of 9.375% in which (D) is superimposed is associated, and a signal having a duty ratio of 12.5% in FIG. 2C is associated with the count value "00100". And in the same way, "00101", "00110", "00111", "01000",
..., "10111", "11001", "11010", "11011",
A signal is generated in which the duty ratio increases in sequence by 3.125%, such as "11100", "11101", and "11110", and the count value "1"
At “1111”, the signal becomes a duty ratio of 96.847%, and one cycle is completed. The count value of the counter 14 is calculated by counting the TRIG signal supplied here.

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

The output signal of the synthesizing circuit 12 is input to the integrating circuit 16.
The integrating circuit 16 is composed of a resistor R and a capacitor C connected in series, one end of the resistor R is connected to the synthesizing circuit 12, and the other end of the capacitor C is grounded. And
The integrated voltage is output from the connection between the resistor R and the capacitor C. Since it is difficult to store the capacitor C inside the IC, the capacitor C is provided outside the IC and is connected through the terminal T ₁ .

In such an integrating circuit 16, when a voltage signal whose duty ratio is sequentially increased at a predetermined timing is input from the synthesizing circuit 12, this is integrated and output as a gradually increasing voltage signal.

The output terminal of the integrating circuit is connected to the buffer 18, and the output of 16 of the integrating circuit is smoothed and amplified here and output from the output terminal T ₂ to the outside of the IC. 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, the linearly rising portion of the trapezoidal wave can be formed by outputting the gradually increasing voltage signal from the combining circuit 12 according to the output value of the counter 14.

Here, in this example, two combining circuits 12, a counter 14, an integrating circuit 16, a buffer 18, etc. are provided in parallel, and a portion where the voltage value of the trapezoidal wave rises and a portion where the trapezoidal wave voltage value falls are formed separately. ing.

That is, the counter 14a has the above-mentioned count value "00000".
To "11111", and the counter 14b counts from "11111" to "00000". Then, at each point of the TRIG signals supplied to the counters 14a and 14b, a trapezoidal wave is obtained by controlling the values of the counters 14a and 14b as follows.

The counters 14a and 14b both have a count value of "00000" in the initial state. And the counter 14a
A trigger is received at the TRIG signal point a, and the counter value "1111
Count up to 1 "as above. Then, after the count value becomes "11111", this value is held.

Then, a trigger is received at the TRIG signal point b after a certain period of time, the count value of the counter 14a is reset to "00000", the count value of the counter 14b is set to "11111", and the value of is held. Furthermore, after a certain period of time,
When the TRIG signal point c is reached, a trigger is received here and the counter
14b starts counting down. Then, the countdown is performed until the count value becomes "00000", and then the count value "00000" is held.

In this way, the counters 14a and 14b respectively output a predetermined linearly changing rising waveform and falling waveform.
Since the combining circuits 12a and 12b combine the signals from the pulse generator 10 according to the count value supplied in this way, trapezoidal waves as shown in FIG. 4 are output from the output terminals T _2a and T _2b . Is output.

As described above, according to the circuit of this embodiment, it is possible to obtain a trapezoidal wave whose voltage changes linearly, and to supply a current of a predetermined change to the coil and the like. Further, by changing the gain of the counter 14, it is possible to control the degree of increase in the ON output of the voltage signal output from the combining circuit 12. Therefore, it is not necessary to change the capacitance of the capacitor C, and the rising slope can be changed. As a result, the capacitance of the capacitor may be small even when a voltage signal with a small slope is obtained.

[Effects of the Invention] As described above, according to the pseudo trapezoidal wave generation circuit of the present invention, it is possible to obtain a trapezoidal wave whose slope is almost linear, and it is possible to effectively reduce the shock when the voltage changes. . Further, the slope of the voltage change can be adjusted by adjusting the frequency of superposition in the synthesis circuit, and it is not necessary to change the capacitance of the capacitor.

[Brief description of drawings]

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 a pulse generator 10 in the same embodiment, and FIG. 3 is a synthesis circuit in the same embodiment. FIG. 4 is a waveform diagram of a signal generated by 12 and FIG. 4 is a waveform diagram of an output signal at the output terminals T _2a and T _2b . 10 …… Pulse generator 12 …… Synthesis circuit 14 …… Counter 16 …… Integrator circuit 18 …… Buffer R …… Resistance C …… Capacitor

Claims (1)

(57) [Claims] 1. A pseudo trapezoidal wave generation circuit which outputs a linearly increasing waveform by utilizing charging of a capacitor to rewrite a control signal of a video device, wherein a plurality of pulse signals having different repetition periods are generated. A pulse generator that generates a counter, a counter that outputs a sequentially increasing count value, receives the plurality of pulse signals, and superimposes these pulse signals to generate a signal of a duty ratio corresponding to each count value of the counter, It has a combination circuit that obtains a signal whose duty ratio gradually increases in accordance with the increase, and that converts this into a voltage signal and outputs it, and a resistor and capacitor that are connected in series, and integrates the voltage signal input from the combination circuit. Integrating circuit that performs the correction of the CR time constant in the integrating circuit by the output of the combining circuit. Quasi trapezoidal wave generating circuit, wherein a voltage to obtain a pseudo-trapezoidal waveform which varies linearly in the inclined portion.