JPH034122A - Waveform shaping device for sensor output signal - Google Patents

Abstract

PURPOSE:To prevent an adverse effect on a digital circuit caused by erroneous wave shaping by providing a constant-voltage power source for setting voltage which supplies voltage lower than the power-supply voltage for operation of the digital circuit to a voltage setting device. CONSTITUTION:The constant-voltage power source is separated to a power source 5a for the voltage setting device and a power source 5b for the digital circuit, which are constituted so that the output voltage of the power source 5a may be lower than that of the power source 5b. In the case that a main power source 9 is an on-vehicle battery, the power source 5a is constituted so that is outputs such low voltage that it is not affected by the voltage drop which occurs at the time of starting an engine, or that the output of a comparator 2 is not inverted because the effect is small even if it is affected. Since the output voltage of the power source 5a does not change even if the voltage drop of the main power source 9 occurs, the level of the output pulse of the voltage setting device 3 is not changed, whereas the output of the comparator 2 does not changed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a waveform shaping device for a sensor output signal, and in particular, a threshold value is changed depending on the magnitude of the output signal, and the threshold value is used to adjust the output signal. The present invention relates to a sensor output signal waveform shaping device that shapes the waveform of a signal.

(Prior Art) In order to perform each FJ $1 all of a rotating body, the angular position or rotational speed of the rotating body is often detected by a rotating body sensor, and control is performed based on the detection result. When this rotating body is a camshaft of an engine, the detection result by the rotating body sensor is used for engine fuel injection control, ignition timing $ control, automatic transmission control, etc.

In order to use the output signal of the rotation sensor in a digital circuit such as a microcomputer, it is necessary to perform waveform shaping to convert this output signal into a pulse signal that has either a low potential or a high potential. .

Waveform shaping of the output of a magnetic pickup sensor (hereinafter simply referred to as a sensor), which is often used as the above-mentioned rotation sensor, will be explained.

4(a) and 4(C) show the waveform of the sensor output signal, and FIG. 4(b) shows the waveform after waveform shaping of this signal.

Shown in (d). Figures (a) and (b) show waveforms when the rotating body is rotating at a low speed, and Figures (c) and (d) show waveforms when the rotating body is rotating at a high speed.

As shown in the figure, when the rotating body rotates at low speed, the amplitude of the sensor output signal is small, and when the rotating body rotates at high speed, the amplitude of the sensor output signal becomes large. The threshold for waveform shaping is set to a negative potential close to the "O° level" for low rotations (hereinafter referred to as "small threshold value"), and the "O" level for high rotations. (
(Hereafter, the threshold is referred to as large).

In the figure, the output after shaping shifts to the low potential side "Lo" when the sensor output drops below the threshold, and shifts to the high potential side "H" when the sensor output returns to the "O" level. .

The reason why the threshold value is changed according to the rotation speed of the rotating body is because of induced noise from the ignition system when the detected rotating body is an engine, and when multiple sensors are arranged adjacently. This is to prevent erroneous waveform shaping from occurring due to the effects of mutually induced noise and the effects of output waveform distortion due to mechanical vibration in the high rotation range.

FIG. 5 shows a block diagram of a conventional device having a configuration suitable for performing waveform shaping by changing the threshold value according to the rotation speed.

In the figure, the output signal of sensor l becomes one input of comparator 2. Then, a comparison result is output as to whether this human power is larger or smaller than a reference value (ground level in this conventional example).

In response to the output from the comparator 2, a pulse signal in a voltage range below the rated voltage of the digital circuit 4 is output from the voltage setter 3 to the digital circuit 4.

The digital circuit 4 performs various digital processing based on this pulse signal.

The constant voltage power source 5 is a circuit that generates a power source for operating the digital circuit 4 and the voltage setting device 3 from a main power source 9 such as a battery. In the conventional technology, this constant voltage power supply 5
is configured to output a voltage of 5V.

Also, the previous 2? ! ! The output of the pressure setting device 3 is input to a time constant circuit 7. The output of the time constant circuit 7 is added to the sensor output signal in an adder circuit 7a, and is input to the comparator 2 as a composite signal with the sensor output signal.

When the rotating body is rotating at low speed, the output of the time constant circuit 7 is as follows.
Voltage setting′! Since the interval between the pulse signals output from S3 is large, the pulse signal is almost close to '0''.

On the other hand, when the rotating body rotates at a high speed, a high output can be obtained because the intervals between the pulse signals output from the voltage setting device 3 are small.

In this way, as the rotation of the rotating body increases, the comparator 2
Since the composite signal of the sensor output signal inputted to the sensor output signal and the output of the time constant circuit 7 becomes large, the reference value becomes relatively low. In other words, the threshold value becomes larger.

(Problem to be solved by the invention) In the above-mentioned conventional technology, when the engine is started when the main power source, such as an in-vehicle battery, is in an over-discharged state or in a low-temperature state, the voltage of the battery drops rapidly. There are things to do. In such a case, the output voltage of the constant voltage power supply '5 may not be able to maintain a constant voltage and may drop suddenly.

Generally, the input terminal of the digital circuit 4 has a rated voltage ±1
It operates normally even if it fluctuates within a range of about 0%. However, if the power supply voltage of the voltage setting device 3 fluctuates to this extent, the following problems occur.

For example, when the peak value of the output pulse of the voltage setter 3 decreases due to a decrease in the output voltage of the constant voltage voltage jij 5, the output of the time constant circuit 7 decreases, and the composite signal of the sensor output and the output of the time constant circuit 7 decreases. becomes smaller. There is a problem in that as the signal input to the comparator 2 becomes smaller, the threshold value becomes relatively smaller.

An object of the present invention is to provide a sensor output signal waveform shaping device that can solve the above-mentioned problems and prevent adverse effects on digital circuits due to erroneous waveform shaping when the main power supply voltage suddenly decreases.

(Means and effects for solving the problem) In order to solve the above problems and achieve the object, the present invention provides a constant voltage power supply for each of the voltage setting device and the digital circuit,
The first point is that the output voltage of the constant voltage power supply for the voltage setting device is set lower than the output voltage of the constant voltage power supply for the digital circuit.
It has the characteristics of

Further, the second feature of the present invention is that the voltage setting device constituted by a time constant circuit is made of brass.

In the present invention having the above-mentioned first feature, the amount of change in the output voltage when the input voltage of the constant voltage power supply for the voltage setting device decreases is small, so the amount of change in the output of the voltage setting device is also suppressed to a small value, thereby preventing malfunction. .

Furthermore, in the present invention having the second feature, when the input voltage of the constant voltage power supply for the voltage setting device decreases, this input terminal drop can be compensated for by the function of the time constant circuit, so that the output of the voltage setting device , and no erroneous waveform shaping occurs.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of the present invention.

In this figure, the same reference numerals as in FIG. 5 indicate the same or equivalent parts. In FIG. 1, the constant voltage power supply is separated into two parts, one of which is used as a voltage setting device power supply 5a and the other as a digital circuit power supply 5b.

Then, the output voltage of the voltage setting device power supply 5a is determined by the digital circuit f! Each power source was configured to have a lower value than the output voltage of the No. 11 source 5b.

The output of the digital circuit power supply 5b must be set so as to be able to supply the rated voltage (5V) for operating the digital circuit 4. On the other hand, the output of the voltage setting device 3 may be lower than the rated voltage of the digital circuit 4. Therefore, the output voltage of the voltage setter power supply 5a can be set lower than the output voltage of the digital circuit power supply 5b.

If the main power source 9 is a car battery, for example, the voltage is so low that it is not affected by the voltage drop that occurs when starting the engine, or even if there is an effect, the effect is small so that the output of the comparator 2 is not inverted. The voltage setter power supply 5a is configured so that a high voltage is output.

In this way, even if there is a voltage drop in the main power source 9, the output voltage of the voltage setter power source 5a does not change, so the level of the output pulse of the voltage setting 2i3 does not change, and therefore the output of the comparator 2 also does not change.

Next, a second embodiment of the present invention will be described with reference to FIG.

In this figure, the same reference numerals as in FIG. 1 indicate the same or equivalent parts.

In the figure, the output of a constant voltage power supply 5 is branched into two parts, one of which is supplied to a digital circuit 4 and the other to a voltage setting device 3 via a rectifier 8.

The voltage setting device 3 consists of a setting device main body 3a and a capacitor C attached in parallel to this main body 3a, and includes a kind of time constant circuit. The rectifier 8 is connected so that current flows only in the direction from the constant voltage power supply 5 to the voltage setting device 3.

Further, the output voltage of the constant voltage power supply is applied to the main body 3a of the voltage setting device 3 via the rectifier 8, and is also applied to the capacitor C, so that the capacitor C is charged.

In this m2 embodiment, when the output voltage of the constant voltage power supply 5 is reduced due to a decrease in the voltage of the main power supply 9, the charge of the capacitor C is supplied to the voltage setting device main body 3a. Therefore, the drop in the voltage applied to the voltage setting device main body 3a is small.

Therefore, even if the voltage of the main power supply 9 drops, the voltage setting W3
The output drop is suppressed to a small level, and stable operation is achieved.

Next, a specific circuit example of the present invention is shown in FIG.

In the figure, the output signal of sensor l is
0 to the comparator 2. A time constant circuit 7 is configured by the capacitor C1 and the resistor R2. The pull-up resistor R1 corresponds to the main body 3a of the voltage setting device 3, and the diode D1 corresponds to the rectifier 8.

In this circuit example, the constant voltage power supply 5 is provided separately into the voltage setting device base i5a and the digital circuit power supply 5b, but in this example as well, one constant voltage power supply is provided as shown in the block diagram of FIG. The same effect as when the voltage power source is shared as a power source for the voltage setting device 3 and the digital circuit 4 can be obtained.

Power is supplied from the battery 9 to the voltage setting S power supply 5a, the digital circuit power supply 5b, and the comparator 2.

The output of the digital circuit power supply 5b becomes a power supply for a digital circuit 4 such as a microcomputer, and the output of the voltage setting device power supply 5a is used to set a voltage for outputting a pulse signal to the digital circuit 4 in response to the output of the comparator 2. It becomes the power supply for the device 3 (consisting of pull-up resistor R1 and capacitor C).

In the circuit having such a configuration, the output level of the comparator 2 is determined according to the output signal of the sensor 1 relative to the reference voltage of the comparator 2. The output of the comparator 2, that is, the pulse signal, is input to the digital circuit 4. This pulse signal is simultaneously fed back to the input of the comparator 2 via the time constant circuit 7.

When the voltage of the battery 9 suddenly drops, the output voltage of the voltage setting device power supply 5a also drops, but if this sudden voltage drop is an instantaneous phenomenon, the capacitor C compensates for the voltage drop. As a result, the high potential side output of the pulse signal does not decrease.

As described above, in this embodiment, even if the voltage of the main power supply 9 decreases, the voltage applied to the voltage setting device 3 does not change significantly. Therefore, in a waveform shaper that feeds back the output of the voltage setting device 3 to the sensor output signal via the time constant circuit 7 and synthesizes it to change the threshold value, comparison is made based on voltage fluctuations of the main power supply. There is no possibility that the output of device 2 will be reversed.

(Effects of the Invention) As is clear from the above description, according to the present invention, even if a voltage drop in the main power supply momentarily occurs, the sensor output signal is not subjected to erroneous waveform shaping.

As a result, even when the power supply voltage drops suddenly due to a high load when starting the engine, such as with an on-board power supply,
It is possible to incorrectly shape the waveform of the sensor output signal.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the first embodiment of the present invention, Fig. 2 is a block diagram of the second embodiment, Fig. 3 is a specific circuit diagram of the second embodiment, and Fig. 4 is a sensor output signal waveform. The figure and the waveform diagram of the sensor output signal after shaping are block diagrams showing the prior art. DESCRIPTION OF SYMBOLS 1... Sensor, 2... Comparator, 3... Voltage setting device, 5... Constant voltage power supply, 5a... Voltage setting device power supply, 5
b...Digital circuit power supply, 7...Time constant circuit, 8.
・Rectifier diagram diagram

Claims (3)

[Claims] (1) It has a voltage setting device that forms a pulse signal having a binary level within the rated voltage range of the digital circuit in response to the comparison result between the sensor output signal and a reference value, and the output of this voltage setting device is connected to the digital circuit. In a waveform shaping device for a sensor output signal configured to be supplied to a circuit and superimposed on a sensor output signal via a time constant circuit, a voltage lower than an operating power supply voltage of the digital circuit is applied to the voltage setting device. A waveform shaping device for a sensor output signal, characterized by comprising a constant voltage power supply for setting a supply voltage. (2) A constant voltage power source for a voltage setting device that is separate from the operating power source of the digital circuit, and a rectifier connected so as to conduct only in the direction of the voltage setting device from the constant voltage power source for the voltage setting device, Claim 1, wherein the voltage setting device comprises a pull-up resistor and a capacitor connected between the power supply side terminal of the pull-up resistor and ground.
A waveform shaping device for a sensor output signal as described above. (3) The waveform shaping device for a sensor output signal according to claim 2, wherein the power supply for the voltage setting device is also used as an operating power supply for a digital circuit.