JPH0769184B2 - Waveform shaping device for sensor output signal - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveform shaping device for a sensor output signal, and more particularly, a threshold value is changed according to the magnitude of the output signal, and the output value is changed according to the threshold value. The present invention relates to a sensor output signal waveform shaping device that shapes a signal waveform.

(Prior Art) In order to perform various controls of a rotating body, it is often the case that the angular position or the number of rotations of the rotating body is detected by a rotating body sensor, and the control is performed based on the detection result. When the rotating body is the camshaft of the engine, the detection result of the rotating body sensor is used for engine fuel injection control, ignition timing control, automatic transmission control, and the like.

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 the output signal into a pulse signal that takes either a low potential or a high potential. .

The waveform shaping of the output of the magnetic pickup sensor (hereinafter, simply referred to as a sensor), which is often used as the rotation sensor, will be described.

4 (a) and 4 (c) show the waveform of the sensor output signal,
The waveform after waveform shaping of this signal is shown in FIG.
It shows in (d). The same figures (a) and (b) show the respective waveforms when the rotating body is rotating at a low speed, and the same figures (c) and (d) show the respective waveforms when the rotating body is rotating at a high speed.

As shown in the drawing, the amplitude of the sensor output signal is small when the rotating body is in low rotation, and the amplitude of the sensor output signal is large when it is in high rotation. The threshold for waveform shaping is set to a negative potential near the "0" level when the rotation is low (hereinafter, the threshold is small), and the "0" level when the rotation is high. Is set to a negative potential away from (hereinafter, the threshold value is large).

In the figure, the output after shaping shifts to the low potential side “L” when the sensor output drops below the threshold value, and shifts to the high potential side “H” when the sensor output returns to “0” level. To do.

The threshold value is changed according to the number of rotations of the rotating body when induced noise from the ignition system or the like when the rotated detection body is an engine and when a plurality of sensors are arranged adjacent to each other. This is to prevent erroneous waveform shaping from being caused by mutual induced noises, and by influence 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 number of revolutions.

In the figure, the output signal of the sensor 1 becomes one input of the comparator 2. Then, the comparison result indicating whether this input is larger or smaller than the reference value (ground level in this conventional example) is output.

In response to the output from the comparator 2, the voltage setter 3 outputs a pulse signal in a voltage range equal to or lower than the rated voltage of the digital circuit 4 to the digital circuit 4. In the digital circuit 4,
Various digital processes are performed based on this pulse signal.

The constant voltage power source 5 is a circuit that creates 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 prior art, this constant voltage power source 5
Is configured to output a voltage of 5V.

The output of the voltage setting device 3 is input to the time constant circuit 7. The output of the time constant circuit 7 is the addition circuit 7a.
Is added to the sensor output signal and is input to the comparator 2 as a combined signal with the sensor output signal.

The output of the time constant circuit 7 is:
Since the pulse signals output from the voltage setting device 3 have large intervals, they are almost "0". On the other hand, when the rotating body rotates at high speed, a high output can be obtained because the interval between the pulse signals output from the voltage setting device 3 is small.

In this way, as the rotating body becomes higher in rotation, the comparator 2
Since the combined signal of the sensor output signal and the output of the time constant circuit 7 that is input to the signal becomes large, the reference value becomes relatively low. That is, the threshold becomes large.

(Problems to be Solved by the Invention) In the above-mentioned conventional technique, when the engine is started when the battery such as the vehicle, which is the main power source, is in an over-discharged state or in a low temperature state, the voltage of the battery sharply drops. I have something to do. In such a case, the output voltage of the constant voltage power source 5 may not maintain the constant voltage and may drop sharply.

Generally, the input voltage of the digital circuit 4 is the rated voltage ± 10
Even if it fluctuates in the range of about%, it operates normally. However,
If the power supply voltage of the voltage setting device 3 fluctuates to this extent, the following inconvenience occurs.

For example, when the crest value of the output pulse of the voltage setting device 3 decreases as the output voltage of the constant voltage power supply 5 decreases, the time constant circuit 7
Output decreases and the combined signal of the sensor output and the output of the time constant circuit 7 decreases. There is a problem that the threshold value becomes relatively small when the signal input to the comparator 2 becomes small.

An object of the present invention is to solve the above problems and to provide a waveform shaping device for a sensor output signal that can prevent adverse effects on a digital circuit due to erroneous waveform shaping when the main power supply voltage sharply drops.

(Means and Actions for Solving the Problem) In order to solve the above problems and achieve the object, the present invention provides a constant voltage power source for each of a voltage setting device and a digital circuit, and a constant voltage setting device for the voltage setting device. The output voltage of the voltage power supply
The first feature is that it is set lower than the output voltage of the constant voltage power supply for digital circuits.

Further, the present invention has a second feature in that it is provided with a voltage setter configured by a time constant circuit.

In the present invention having the above-mentioned first characteristic, the change amount of the output voltage when the input voltage of the constant voltage power supply for the voltage setting device is low is small, so that the output change amount of the voltage setting device is also suppressed to be small and malfunction does not occur. .

Further, according to the present invention having the second feature, when the input voltage of the constant voltage power supply for the voltage setting device is lowered, the amount of the input voltage reduction can be compensated by the function of the time constant circuit. Does not affect, and erroneous waveform shaping does not occur.

(Example) Below, the Example of this invention is described with reference to drawings.

FIG. 1 is a block diagram showing a first embodiment of the present invention.
In the figure, the same reference numerals as in FIG. 5 indicate the same or equivalent parts. In FIG. 1, the constant voltage power supply is divided into two, one of which is a voltage setting power supply 5a and the other is a digital circuit power supply 5b. And the output voltage of the voltage setter power supply 5a is
Each power supply was configured to have a value lower than the output voltage of the digital circuit power supply 5b.

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

When the main power supply 9 is, for example, a vehicle-mounted battery, the output of the comparator 2 should not be inverted because of a low voltage that is not affected by the voltage drop that occurs when the engine is started, or even if there is an effect, the effect is small. The voltage setting power supply 5a is configured so that a very low voltage is output.

In this way, even if the voltage of the main power supply 9 drops, the output voltage of the voltage setting device power supply 5a does not change, so the level of the output pulse of the voltage setting device 3 does not change, and therefore the output of the comparator 2 does not change, either.

Next, a second embodiment of the present invention will be described with reference to FIG.
In the figure, the same symbols as those in FIG. 1 indicate the same or equivalent parts.

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

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

In the second embodiment, when the output voltage of the constant voltage power supply 5 instantaneously drops due to the voltage drop of the main power supply 9, the charged electric charge of the capacitor C is changed to the voltage setting unit main body.
Since it is supplied to the voltage setting device 3a, the voltage applied to the voltage setting device main body 3a does not decrease much. Therefore, even if the voltage of the main power supply 9 drops, the output drop of the voltage setting device 3 is suppressed to a small level, and the operation is stabilized.

Next, a specific circuit example of the present invention is shown in FIG. In the figure, the output signal of the sensor 1 is input to the comparator 2 via the filter circuit 10. The time constant circuit 7 is composed of 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 source 5 is a voltage setting power source 5a,
Although an example has been shown in which it is provided separately from the digital circuit power supply 5b,
Also in this example, the same effect as in the case where one constant voltage power source is shared as the power source of the voltage setting device 3 and the digital circuit 4 as in the block diagram of FIG. 2 is obtained.

Battery 9 to voltage setting power supply 5a, digital circuit power supply 5b
And the power is supplied to the comparator 2. Digital circuit power supply
The output of 5b serves as a power source for the digital circuit 4 such as a microcomputer, and the output of the voltage setting power source 5a responds to the output of the comparator 2 and outputs a pulse signal to the digital circuit 4 (the voltage setting device 3 ( It consists 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 with respect 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. At the same time, this pulse signal is fed back to the input of the comparator 2 via the time constant circuit 7.

If the voltage of the battery 9 drops sharply, the voltage setter power supply
Although the output voltage of 5a also drops, if this sudden voltage drop is an instantaneous phenomenon, the capacitor C compensates for the voltage drop, and as a result, the high-potential side output of the pulse signal may drop. Absent.

As described above, in this embodiment, even if the voltage of the main power supply 9 drops, the voltage applied to the voltage setting device 3 does not change significantly. Therefore, in the waveform shaper in which the output of the voltage setting device 3 is fed back to the sensor output signal via the time constant circuit 7 and combined, and the threshold value is changed as a result, comparison is performed by the voltage fluctuation of the main power supply. The output of the device 2 does not reverse.

(Effects of the Invention) As is apparent from the above description, according to the present invention, even if the voltage of the main power supply drops momentarily, the sensor output signal is not erroneously shaped.

As a result, even when a high load is applied at the time of engine start, such as a vehicle-mounted power supply, and the voltage power supply drops sharply,
The waveform of the sensor output signal can be shaped without error.

[Brief description of drawings]

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 concrete circuit diagram of the second embodiment, and FIG. 4 is a sensor output signal waveform. FIG. 5 and a waveform diagram of this sensor output signal after shaping, and FIG. 5 is a block diagram showing a conventional technique. 1 ... Sensor, 2 ... Comparator, 3 ... Voltage setting device, 5 ...
… Constant voltage power supply, 5a …… Voltage setting power supply, 5b …… Digital circuit power supply, 7 …… Time constant circuit, 8 …… Rectifier

Claims (3)

[Claims] 1. A voltage setting device for forming a pulse signal having a binary level in a rated voltage range of a digital circuit in response to a result of comparison between a sensor output signal and a reference value, and an output of the voltage setting device. In a waveform shaping device for a sensor output signal, which is supplied to the digital circuit and is 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 set to the voltage setting. A constant voltage power supply for voltage setting to be supplied to the voltage setting device, wherein the voltage setting device includes a pull-up resistor and a capacitor connected between a power supply side terminal of the pull-up resistor and ground. Waveform shaping device for sensor output signal. 2. A constant voltage power source for a voltage setting device, which is different from the operating power source of the digital circuit, and a rectifier connected so as to conduct only from the constant voltage power source for the voltage setting device to the direction of the voltage setting device. 2. The waveform shaping device for the sensor output signal according to claim 1, wherein the voltage setting device is composed of a pull-up resistor and a capacitor connected between a power supply side terminal of the pull-up resistor and ground. . 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.