JPH0524182Y2 - - Google Patents

Description

[Detailed explanation of the invention] [Technical field] This invention is an AC/DC device for detecting input signals of recorders, etc.
Concerning the conversion circuit, more specifically, when recording the signal under test on a recorder, etc., it is used for input signal detection to form a DC time signal from the signal under test to display the period during which the signal is being input. This relates to AC/DC conversion circuits.

[Technical background of the invention] Recording paper used in recorders, etc. is usually provided with scale lines at regular intervals along the feeding direction to indicate the time axis, and once the paper feeding speed is known, it is possible to The recording time of the signal waveform drawn in can be read. Recording of this signal waveform happens to start on the scale line and may end on the scale line, but generally recording starts between the scale lines and ends midway between the scale lines. In many cases, the record ends.

In the latter case, if the signal waveform to be recorded becomes complex, the time axis becomes difficult to read, so draw a straight line, for example, on one side of the recording paper as an auxiliary line for time reading from the start of recording the signal waveform to the end of recording. This is extremely convenient for the user in terms of waveform analysis. As mentioned above, the timing of turning on and off the time signal to draw this straight line needs to be aligned with the start and end of recording the signal waveform, but the higher the accuracy, the more the circuit that generates the time signal will need to be adjusted. The configuration becomes complicated, making it difficult to easily incorporate it into the input section of a recorder, a probe for signal pickup, etc. The above difficulties can be solved by converting this circuit into an IC, but
On the other hand, it is expensive, and is not preferred for products that are produced in small quantities and do not require very high precision.

[Purpose of the invention] This invention was devised in view of the above points, and its purpose is to provide a rectifier, a capacitor, a comparator, etc. for rectifying the signal under test to obtain a DC time signal voltage, and to have a simple configuration. The object of the present invention is to provide a low-cost AC/DC conversion circuit for input signal detection that has sufficient accuracy for practical use and does not require integration with an IC.

[Example] This invention will be described in detail below with reference to an example shown in the accompanying drawings.

Referring to Figure 1, for this input signal detection
The signal input side of the AC/DC conversion circuit is equipped with two input terminals 1 and 2, and the signal to be measured is applied from these input terminals 1 and 2 to a full-wave rectifier 4 via, for example, a current-limiting resistor 3. . A surge absorption circuit 5 using a varistor or the like is connected between the input terminals 1 and 2, and the surge voltage etc. superimposed on the signal under test are absorbed here.

A capacitor 6 or the like for compensating the dead area of the full-wave rectifier 4 is connected between both ends of the output side of the full-wave rectifier 4, and a photodiode for emitting light, for example, is connected via a current-limiting resistor 7. 8th grade is also connected. A phototransistor 9 and the like for converting the optical signal into an electrical signal is provided near the photodiode 8, and the electrical signal output from the phototransistor 9 is transferred to a transistor 10 for amplification and a transistor 10 for high frequency bypass. For example, the signal is applied to a comparator 12 provided for waveform shaping via a capacitor 11 or the like.

That is, the collector side of the phototransistor 9 is connected to the collector side of the transistor 10, and the emitter side thereof is connected to the base side of the transistor 10. This transistor 10
The emitter side of the transistor 10 is connected to a common wiring C (not shown), and the high frequency bypass capacitor 11 is connected between the collector and emitter of the transistor 10. The collector side of this transistor 10 is connected to one input terminal of the comparator 12, and a power supply voltage (+) Vcc is applied to this collector side via a resistor 13 for adjusting the amplification degree. Further, a predetermined threshold voltage (+) Vref is applied to the other input terminal of the comparator 12. The output signal from the comparator 12 is sent from an output terminal 14 to a recording section drive circuit (not shown) in the recorder main body.

The operation of the AC/DC conversion circuit for detecting input signals according to this invention will be explained below with reference to FIGS. 2 to 4. In FIG. 1, the same reference numerals A to H are given to the parts where the signal waveforms shown in A to E of FIG. 3 appear, respectively.

First, a brief principle explanation will be given with reference to FIG. 2. FIG. 2A shows a general example of the voltage applied to a rectifying element and the corresponding rectified output current. In above A, when a forward voltage is applied to the rectifying element, for example, from voltage O to E
It is known that the range up to E is a so-called dead area in which no rectifying action is performed, and that when this E is exceeded, a rectified current flows. Therefore, a signal voltage with a waveform as shown in FIG.
When E _O is added, the rectification action is not performed during time t, so the rectified output current has a waveform as shown by the solid line C. When this rectified output current is waveform-shaped by a comparator or the like, it becomes an intermittent rectangular waveform signal in which no output occurs during time t, as shown by the solid line in FIG.
In the circuit of this invention, a capacitor is connected to the output side of the rectifier, and its charging and discharging action is used to ensure that the waveform of the rectified output voltage does not fall below E′ as shown by the dotted line in C above. It is being done.
This eliminates the time t during which the output becomes zero, and also allows the threshold voltage for waveform shaping with the comparator to be set appropriately between O and this E'. As shown by , the DC signal voltage becomes a constant level with no discontinuities near time t.

Next, the operation of this input signal detection AC/DC conversion circuit will be explained with reference to FIG. Here, it is assumed that the voltage waveform of the signal to be measured has a sinusoidal waveform, for example, as shown in FIG. While this signal voltage is at input terminal 1 from time t _O to t ₁ ,
2, the output signal current from the full-wave rectifier 4 has a waveform as shown in FIG. In this embodiment, a capacitor 6 is connected to the output side of the full-wave rectifier 4.
is connected, the signal current waveform in B above actually becomes a signal voltage waveform as shown in C in the same figure, and the signal current waveform shown in B is connected to the photodiode 8 via the resistor 7.
added to. A current having a waveform similar to the signal voltage waveform shown in C above is passed through the photodiode 8, and an optical signal whose intensity changes in proportion to the change in the current waveform is emitted from the photodiode 8. This optical signal is converted into an electric signal by a phototransistor 9, and after being appropriately amplified via a transistor 10 as shown in d, is input to a comparator 12.

In the comparator 12, a threshold voltage is set lower than the voltage E'' shown in D above.
Vref has been added. The voltage of the signal to be measured inputted from the transistor 10 is waveform-shaped here, and a constant level DC signal voltage appears at the output terminal 14 as shown in FIG. This DC signal voltage is sent from this input signal detection AC/DC conversion circuit to the recorder body (not shown), and as shown in FIG. Recording paper 1 as 16
It is recorded on one side of 7.

In this case, in E of Figure 3 above, the rise time t ₂ of the DC signal voltage is the input time of the signal under test.
Although it lags slightly behind t ₀ , its fall time t ₃ also lags approximately the same amount as the time t ₁ when the signal under test turns off. Therefore, overall, the period from t ₀ to t ₁ during which the signal under test is input can be considered to be substantially equal to the period from t ₂ to t ₃ during which the DC signal voltage is formed. . Further, since the above-mentioned delay is so large that it can hardly be visually discerned on recording paper, it does not pose any particular problem in practice.

In this embodiment, the signal amplification degree is switched by the resistor 13 in response to switching of the level range of the signal to be measured on the recorder main body (not shown), so that the condition of Vref<E'' is always maintained. However, the level of Vref may be made variable to satisfy the above conditions.Also, although the above embodiment is explained for the case where the signal under test is a sinusoidal waveform, this input signal detection AC/
The DC conversion circuit can be applied to signals under measurement with waveforms different from sine waveforms without making any changes to the circuit.

[Effects of the invention] As explained above in detail, this AC/DC conversion circuit for input signal detection includes a full-wave rectifier 4 that detects the signal under test, and a full-wave rectifier 4 that uses its charge/discharge action to A capacitor 6 is provided for raising the lowest value of the rectified output voltage of No. 4 to a predetermined level E'. The rectified output voltage obtained by detecting the signal under test is applied to a photodiode 8 and a phototransistor 9.
A photocoupler consisting of a photocoupler and an amplifying transistor 10
The signal is sent to the comparator 12 via the circuit 12, etc., where it undergoes waveform shaping to form a DC signal voltage of a constant level. In this case, the threshold voltage Vref of the comparator 12 is set so that Vref<E'' with respect to the level E'' corresponding to the lowest level E'' of the rectified output voltage. The waveform of the DC signal voltage obtained by this method has no discontinuities, and the voltage level is flat and stable, making it suitable as a time signal for recorders, etc.The waveform of the signal to be measured is sinusoidal.
Even in cases other than waveforms, a flat and stable time signal can be obtained in the same way as described above, and the structure is simple and compact, so it can be installed in a narrow space.

[Brief explanation of the drawing]

The attached drawings all relate to embodiments of the AC/DC conversion circuit for input signal detection according to this invention, and FIG. 1 is a diagram of its circuit configuration, FIG. 2 is a diagram explaining the principle, and FIG. 3 is a signal waveform diagram of each part. FIG. 4 is an explanatory diagram showing an example of a signal to be measured and a time signal drawn on recording paper. In the figure, 4 is a full-wave rectifier, 6 is a capacitor, 8 is a photodiode, 9 is a phototransistor, and 12 is a comparator.

Claims (1)

[Scope of utility model registration claim] Turns on in synchronization with the input of the signal under test,
A DC signal voltage of a constant level that is turned off in synchronization with the disconnection of the input signal under test is formed from the signal under test, and the DC signal voltage is used to display the input period of the signal under test. An AC/DC conversion circuit for detecting an input signal that is sent out as a time signal, including a full-wave rectifier that detects the signal under test, and a pulsating signal voltage output from the full-wave rectifier, which is charged and discharged, a capacitor for boosting the minimum value of the pulsating signal voltage waveform to a predetermined level; and receiving the pulsating signal voltage whose minimum value has been boosted by the capacitor through a photocoupler at one input terminal. and a comparator to which a threshold voltage of a magnitude not exceeding the boosted voltage level is applied to the other input terminal, and the pulsating signal voltage is converted into a DC signal at a constant level via the comparator. An AC/DC conversion circuit for input signal detection characterized by waveform shaping into voltage.