JP3331709B2 - Sensor signal processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing device such as an MRE sensor and a bar code reading linear image sensor.

[0002]

2. Description of the Related Art Conventionally, Japanese Patent Laying-Open No. 4-69986 discloses an apparatus for correcting the output level of an MRE sensor from an allowable range to an allowable range. The apparatus includes an amplifier for amplifying a sensor output signal, an upper threshold comparator for determining whether the output signal level of the amplifier has exceeded an upper threshold, and determining whether the output signal level of the amplifier has exceeded a lower threshold. A counter that counts down by inputting an upper limit detection signal from a comparator for a lower threshold and a counter that counts up by inputting a lower detection signal from the comparator for a lower threshold; A D / A converter that outputs an offset voltage (reference voltage) to the amplifier. That is, a threshold value for determining the upper and lower limits of the sensor signal level input to the waveform shaping circuit is provided, and when the sensor signal level exceeds the threshold value by the comparator, the count value of the counter is changed, and according to this count value, The output signal level of the amplifier is adjusted to fall within the above-mentioned upper and lower limits by changing the offset voltage signal (reference voltage signal) to be D / A converted and added to or subtracted from the sensor output signal.

[0003]

However, in the device disclosed in the above publication, the adjustment of the sensor signal is performed by a counter or a D / D converter.
Since the conversion is performed digitally using the A converter, the circuit scale becomes large, and the cost is increased.
Although the publication discloses that analog processing may be performed, the specific configuration is not mentioned at all and lacks specificity.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sensor signal processing device capable of keeping the amplitude of an amplified sensor signal within an allowable range with a simple configuration.

[0005]

According to the first aspect of the present invention, there is provided a sensor signal processing device in which the sensor signal is small and the sensor signal needs to be amplified by an amplifier before performing signal processing such as binarization. A first comparator for comparing an output value of the amplifier with a predetermined maximum value, and outputting a first signal when the output value of the amplifier is larger than a predetermined maximum value; Is compared with a predetermined minimum value, and a second comparator for outputting a second signal when the output value of the amplifier is smaller than the predetermined minimum value, and a reference voltage terminal of the amplifier. A capacitor, a discharging switching element that operates by a first signal from the first comparator to discharge the capacitor and reduce a reference voltage in an amplifier, and a second switching element from the second comparator. The sensor signal processing apparatus that includes a charge switching element for raising the reference voltage at the operating charging the capacitor amplifier as its gist at No..

According to a second aspect of the present invention, there is provided a sensor signal processing device which needs to amplify the sensor signal by an amplifier before performing signal processing such as binarization since the sensor signal is small, A capacitor connected to the reference voltage terminal of the amplifier, a leak diode for leaking the charge of the capacitor to the side where the charge is discharged, and comparing the output value of the amplifier with a predetermined minimum value, A sensor comprising: a comparator that outputs a signal when an output value is smaller than a predetermined minimum value; and a charging switching element that operates by a signal from the comparator to charge the capacitor and increase a reference voltage in an amplifier. The gist is a signal processing device.

According to a third aspect of the present invention, there is provided a sensor signal processing device which needs to amplify the sensor signal by an amplifier before performing signal processing such as binarization since the sensor signal is small, A capacitor connected to the reference voltage terminal of the amplifier, a leak diode that leaks current from a power supply to a side where the capacitor is charged, and comparing the output value of the amplifier with a predetermined maximum value,
A comparator that outputs a signal when the output value of the amplifier is larger than a predetermined maximum value, and a discharging switching element that operates by a signal from the comparator to discharge the capacitor and drop a reference voltage in the amplifier by a predetermined amount. The gist is a sensor signal processing device including

According to a fourth aspect of the present invention, in the sensor signal processing device according to any one of the first to third aspects, the capacitance of the capacitor is 100 PF or less, the switching element is a MOS transistor, and the amplifier is further provided. The gist of the present invention is that the sensor signal processing device is implemented as a one-chip MOS LSI by using a MOS transistor input amplifier.

[0009] The invention of claim 5, together with the external of the capacitor in the sensor signal processing apparatus according to any one of claims 1 to 3, the switching elements and by port over <br/> la transistor, Further, a gist of the present invention is a sensor signal processing device which is a one-chip bipolar LSI by using an amplifier having a bipolar transistor input as the amplifier.

[0010]

According to the first aspect of the present invention, the first comparator compares the output value of the amplifier with a predetermined maximum value, and outputs a first signal when the output value of the amplifier is larger than the predetermined maximum value. . The second comparator compares the output value of the amplifier with a predetermined minimum value, and outputs a second signal when the output value of the amplifier is smaller than the predetermined minimum value. The discharging switching element operates in response to the first signal from the first comparator to discharge the capacitor and lower the reference voltage in the amplifier. The charging switching element operates by the second signal from the second comparator to charge the capacitor and increase the reference voltage of the amplifier.

In this manner, the reference voltage in the amplifier is corrected by the analog circuit configuration, and the sensor signal is amplified by the amplifier using the reference voltage, and the amplitude of the amplified sensor signal falls within an allowable range.

According to a second aspect of the present invention, the leakage diode causes the charge of the capacitor to leak to the side where the charge is discharged. The comparator compares the output value of the amplifier with a predetermined minimum value, and outputs a signal when the output value of the amplifier is smaller than the predetermined minimum value. The charging switching element operates by a signal from the comparator to charge the capacitor and raise the reference voltage in the amplifier.

That is, when the output value of the amplifier is smaller than the minimum value by the comparator while the reference voltage of the amplifier is gradually decreased by causing the charge of the capacitor to leak to the side where the charge is discharged by the leakage diode, the capacitor is switched by the charging switching element. To raise the reference voltage at the amplifier. In this manner, the reference voltage at the amplifier is corrected by the analog circuit configuration, and the sensor signal is amplified by the amplifier using the reference voltage, and the amplitude of the amplified sensor signal falls within an allowable range.

According to a third aspect of the present invention, the leakage diode causes the current from the power supply to leak to the side where the capacitor is charged. The comparator compares the output value of the amplifier with a predetermined maximum value, and outputs a signal when the output value of the amplifier is larger than the predetermined maximum value. The discharging switching element operates in response to a signal from the comparator to discharge the capacitor and lower the reference voltage in the amplifier.

That is, when the output value of the amplifier is larger than the maximum value by the comparator while discharging the current from the power supply to the side where the capacitor is charged by the leak diode and gradually increasing the reference voltage of the amplifier, the switching for discharge is performed. The element causes the capacitor to discharge and the reference voltage at the amplifier to drop. In this manner, the reference voltage at the amplifier is corrected by the analog circuit configuration, and the sensor signal is amplified by the amplifier using the reference voltage, and the amplitude of the amplified sensor signal falls within an allowable range.

According to a fourth aspect of the present invention, there is provided the sensor signal processing device according to any one of the first to third aspects, wherein the one-chip MOS
LSI is implemented. According to a fifth aspect of the present invention, in the sensor signal processing device according to any one of the first to third aspects, a one-chip bipolar LSI is provided.

[0017]

【Example】

(First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a sensor signal processing device according to the present embodiment. The sensor signal processing device is a device for detecting the rotational position of the engine. As shown in FIG. 1, a gear 2 is fixed to a shaft 1 that rotates at a rotation speed of の with the rotation of the engine. The rotation angle sensor 3 is
It has a pair of MR elements 4A and 4B arranged opposite to the gear 2. The MR elements 4A and 4B are connected to a 5-volt power supply V _DD
Are connected in series to form a variable voltage dividing circuit (bridge). Then, the resistance values of the MR elements 4A and 4B change according to the change in the magnetic field direction accompanying the rotation of the gear 2. As a result, the voltage at the midpoint 5 of the MR elements 4A, 4B changes, and a voltage signal is output from the rotation angle sensor 3.

An operational amplifier 6 is connected to the midpoint 5 of the MR elements 4A and 4B, and the operational amplifier 6 converts the sensor output into impedance. The output terminal of the operational amplifier 6 is connected to the inverting input terminal of an amplifier 8 composed of an operational amplifier via a resistor 7 (2 KΩ in this embodiment). The output terminal of the amplifier 8 receives negative feedback via a resistor 9 (200 KΩ in this embodiment) and is connected to a waveform processing circuit 10. This waveform processing circuit 10 binarizes an input signal and outputs it. The operation range of the waveform processing circuit 10 is 0 to 5000 mV of the power supply voltage.

The output terminal of the amplifier 8 is connected to the non-inverting input terminal of the comparator 11 and the inverting input terminal of the comparator 12, respectively. Resistors 14, 15, and 16 are connected in series between the 5-volt power supply 13 and the ground, and a connection point a between the resistors 14 and 15 is connected to the comparator 1
1 inverting input terminal. Further, the resistor 15
A connection point b between the first and second terminals is connected to the non-inverting input terminal of the comparator 12.

A PMOS transistor 18, a resistor 19 (10 MΩ in this embodiment), a resistor 20 (10 MΩ in this embodiment) and an NMOS transistor 21 are connected in series between the power supply 17 and the ground. Further, a resistor 23 (1 KΩ in this embodiment) and a resistor 24 (1 KΩ in this embodiment) are connected in series between the power supply 22 and the ground. And a connection point c between the resistor 19 and the resistor 20;
A capacitor 25 (10 PF in this embodiment) is connected between a connection point d between the resistors 23 and 24.
The output terminal of the comparator 11 is an NMOS transistor 2
1 gate terminal. Comparator 1
The output terminal 2 is connected to the gate terminal of the PMOS transistor 18 via the inverter 26.

A connection point c between the resistors 19 and 20 is connected to the non-inverting input terminal of the operational amplifier 27. The output terminal of the operational amplifier 27 receives negative feedback,
It is connected to the non-inverting input terminal of the amplifier 8. That is,
The output voltage of the operational amplifier 27 becomes the reference voltage of the amplifier 8. The operational amplifier 27 is not always necessary.

Next, the operation of the sensor signal processing circuit thus configured will be described with reference to FIG. When the signal after the amplification of the sensor signal by the amplifier 8 becomes higher than the upper limit voltage PS (peak stop = 3.8 V) which is the potential at the connection point a in the comparator 11 (timing of t1 in FIG. 2), the comparator 11 The output DN becomes H level, and the NMOS transistor 21 turns on. as a result,
The capacitor 25 is discharged, the potential at the connection point c decreases,
The output of the operational amplifier 27 (the reference voltage of the amplifier 8) decreases. Then, at the moment when the output of the amplifier 8 falls and becomes equal to or lower than the upper limit voltage PS (timing of t2 in FIG. 2), NM
The OS transistor 21 turns off.

Conversely, when the signal after the amplification of the sensor signal by the amplifier 8 falls below the lower limit voltage BS (bottom stop = 0.2 V) which is the potential at the connection point b in the comparator 12 (t3 in FIG. 2). ), The output UP of the comparator 12 becomes H level, and the PMOS transistor 18 is turned on. As a result, the capacitor 25 is charged, the potential at the connection point c rises, and the output of the operational amplifier 27 (the reference voltage of the amplifier 8) also rises. Therefore, the amplifier 8
Instantaneously, the output of the PMOS transistor 18 rises above the lower limit voltage BS (at timing t4 in FIG. 2), the PMOS transistor 18 turns off.

As described above, the output of the amplifier 8 is automatically adjusted so as to oscillate within the range between the lower limit voltage BS and the upper limit voltage PS. Therefore, even if the midpoint offset of the rotation sensor 3 (MRE sensor) is ± 50 mV or more, the amplifier 8 can amplify 100 times so that the amplitude always falls between the lower limit voltage BS and the upper limit voltage PS.

That is, when the approach of the gear 2 is detected by the rotation sensor 3 (MRE sensor), the sensor applied voltage V _DD is 5
At V, the output signal of the sensor has an amplitude of only about 10 mV. In this state, since binarization cannot be performed with high angular accuracy, the signal is amplified about 100 times and the signal amplitude is set to 1000 mV.
I want to be around. Therefore, an amplifier 8 composed of an operational amplifier
Perform 100-fold amplification. The offset of the midpoint 5 of the variable voltage dividing circuit (bridge) of the MRE sensor is ± 50 mV due to the etching accuracy of the MRE thin film and the variation of the film thickness.
And big variation. If amplification is performed 100 times in this state, the offset becomes ± 5000 mV, which is larger than the power supply voltage, that is, the operation range of the waveform processing circuit 10 from 0 to 5000 mV, and the circuit does not operate. Therefore, this offset is canceled as described above.

The waveform processing circuit 10 is provided with
By adopting a circuit for storing a peak value and a bottom value and generating a threshold value and binarizing it, such as a sensor waveform processing circuit disclosed in 77671, a gear proximity type MRE capable of achieving an angular accuracy of ± 0.1 °. A sensor can be realized. In the circuit disclosed in the publication, the output signal after amplification of the sensor is passed through an amplifier with a large amplification factor and an amplifier with a small amplification factor, and the peak hold value of the output signal of the amplifier with a small amplification factor is set as a threshold value.
This is to binarize the output signal of the amplifier having a large amplification factor. In this circuit, if the waveform is within the allowable input range of the processing circuit (0 V to 4 V when the power supply voltage is 5 V), a binary pulse can be formed with a high degree of angular accuracy of ± 0, 1 °.

The rotation angle sensor 3 (MR elements 4A, 4A)
In these circuit configurations including B), CMOS-LS
All of them, including the capacitor 25, are integrated into one chip. In other words, to enable CMOS LSI,
The capacitor capacity is 10 PF to 100 PF.
Further, the on-resistance of the PMOS transistor 18 or the NMOS transistor 21 can be used as the 10MΩ charge / discharge resistors 19 and 20.

As described above, in this embodiment, the output value of the amplifier 8 is predetermined when the sensor signal needs to be amplified by the amplifier 8 before the binary signal processing is performed because the sensor signal is small. Comparing with the maximum value (3.8 V), when the output value of the amplifier 8 is larger than a predetermined maximum value (3.8 V), the comparator 11 (first comparator) that outputs the first signal, and the amplifier 8 Is compared with a predetermined minimum value (0.2 V), and when the output value of the amplifier 8 is smaller than the predetermined minimum value (0.2 V), the comparator 12 (second , A capacitor 25 connected to the reference voltage terminal of the amplifier 8, and an NMO that operates by the first signal from the comparator 11 to discharge the capacitor 25 and drop the reference voltage at the amplifier 8.
PM which operates by the S transistor 21 (discharge switching element) and the second signal from the comparator 12 to charge the capacitor 25 and raise the reference voltage in the amplifier 8
An OS transistor 18 (a switching element for charging). Therefore, the reference voltage in the amplifier 8 is corrected by the analog circuit configuration, and the sensor signal is amplified by the amplifier 8 using the reference voltage, and the amplitude of the amplified sensor signal falls within an allowable range (0 to 4 V).

If the adjustment of the sensor signal is performed digitally using a counter or a D / A converter as described above, the circuit scale is increased and the cost is increased. By performing the processing, the amplitude of the amplified sensor signal can be set within an allowable range with a simple configuration.

Further, since the circuit and the sensor for adjusting the sensor signal are formed as a one-chip LSI, the size can be reduced.
That is, in a digital processing circuit, the circuit scale becomes large and the chip size becomes large when integrated on one chip. However, in this embodiment, the chip size is reduced by using an analog circuit configuration. . (Second Embodiment) Next, a second embodiment will be described focusing on differences from the first embodiment.

In this embodiment, as shown in FIG. 3, only the lower limit is detected without detecting the upper limit of the amplified signal.
That is, a capacitor 29 is arranged between the PMOS transistor 18 and the ground, and a non-inverting input terminal of the operational amplifier 27 is connected to a connection point e between the PMOS transistor 18 and the capacitor 29. Furthermore, a leakage current generating diode 28 is arranged between the non-inverting input terminal of the operational amplifier 27 and the ground. Then, the reference current of the amplifier 8 is always decreased by the leak current generating diode 28, and the operation is performed only by detecting the lower limit. In this case, P ^- w
The leak current flowing to the ground can be positively utilized by using the diode 28 of the ell-N ⁺ diffusion.
That is, the circuit is designed to increase the reference voltage of the amplifier 8 only when the output of the amplifier 8 falls below the lower limit value BS by gradually lowering the potential of the capacitor 29 with an appropriate leak current. Just works
The output of the amplifier 8 can be kept within a certain range.

As described above, according to the present embodiment, the capacitor 29 connected to the reference voltage terminal of the amplifier 8, the diode 28 (leak diode) for leaking the charge of the capacitor 29 to the side where the charge is discharged, The comparator 12 compares the output value of the amplifier 8 with a predetermined minimum value (0.2 V), and outputs a signal when the output value of the amplifier 8 is smaller than the predetermined minimum value (0.2 V).
PMOS transistor 1 which operates by the signal from 2 to charge capacitor 29 and raise the reference voltage in amplifier 8
8 (switching element for charging). That is, the charge of the capacitor 29 is leaked to the side where the charge is discharged by the diode 28 (diode for leakage), and the amplifier 8
When the output value of the amplifier 8 is smaller than the minimum value (0.2 V) by the comparator 12 while gradually lowering the reference voltage, the capacitor 29 is charged by the PMOS transistor 18 (charging switching element), and the reference voltage of the amplifier 8 is reduced. To raise. In this manner, the reference voltage in the amplifier 8 is corrected by the analog circuit configuration, and the sensor signal is amplified by the amplifier 8 using the reference voltage, and the amplitude of the amplified sensor signal falls within an allowable range.

Further, the circuit and sensor for adjusting the sensor signal and the sensor are formed in a one-chip LSI, so that the size can be reduced. That is, in a digital processing circuit, the circuit scale becomes large and the chip size becomes large when integrated on one chip. However, in this embodiment, the chip size is reduced by using an analog circuit configuration. . (Third Embodiment) Next, a third embodiment will be described focusing on differences from the first embodiment.

In this embodiment, as shown in FIG. 4, only the upper limit is detected without detecting the lower limit of the amplified signal.
That is, the leakage current generating diode 32 is arranged between the power supply 30 and the capacitor 31 so that the reference voltage of the amplifier 8 always rises, and the amplifier 8 is operated only by detecting the upper limit. In this case, the diode 3 of P ^- well-N ⁺ diffusion
By using 2, the leak current flowing to the capacitor 31 side can be positively utilized. In other words, by always increasing the potential of the capacitor 31 little by little with an appropriate leakage current, the circuit can reduce the reference voltage of the amplifier 8 only when the output of the amplifier 8 exceeds the upper limit value PS and rises too much. Only by the operation described above, the output of the amplifier 8 can be kept within a certain range.

As described above, in this embodiment, the capacitor 31 connected to the reference voltage terminal of the amplifier 8 and the capacitor 3
1 is compared with a diode 32 (leakage diode) for leaking a current from the power supply 30 to the side where the electric charge is charged and the output value of the amplifier 8 with a predetermined maximum value (3.8 V). Output value is a predetermined maximum value (3.8V)
A comparator 11 that outputs a signal when it is larger than the threshold voltage, and an NMOS transistor 21 (discharge switching element) that operates in response to a signal from the comparator 11 to discharge the capacitor 31 and lower the reference voltage of the amplifier 8.
That is, while the current from the power supply 30 leaks to the side where the capacitor 31 is charged by the diode 32 (leakage diode), and the reference voltage of the amplifier 8 is gradually increased, the output value of the amplifier 8 becomes the maximum value by the comparator 11. (3.8V), the NMOS transistor 21
The capacitor 31 is discharged by the (switching element for discharging), and the reference voltage in the amplifier 8 is decreased. In this manner, the reference voltage in the amplifier 8 is corrected by the analog circuit configuration, and the sensor signal is amplified by the amplifier 8 using the reference voltage, and the amplitude of the amplified sensor signal falls within an allowable range.

Further, the circuit and the sensor for adjusting the sensor signal and the sensor are formed as one-chip LSI, so that the size can be reduced. That is, in a digital processing circuit, the circuit scale becomes large and the chip size becomes large when integrated on one chip. However, in this embodiment, the chip size is reduced by using an analog circuit configuration. .

It should be noted that the present invention is not limited to the above embodiments, but may be applied to, for example, a bar code reading linear image sensor or the like in addition to the MRE sensor.
Further, as a switching element for charging and discharging the capacitor, a bipolar transistor or a thyristor may be used in addition to a MOS transistor (FET).

Further, in each of the above embodiments, the capacitance of the capacitors 25, 29 and 31 is set to approximately 100 PF or less, and the switching element is the MOS transistor 1
8, 21 and the amplifier 8 is a MOS transistor input amplifier, so that a one-chip MOSL
SI can be achieved.

Further, in each of the above embodiments, the capacitors 25, 29, 31 are connected to an external large capacity (for example, 1000
0PF) and the switching element (1
The 8, 21) and by port over La transistors, further, the use of amplifiers of the amplifier 8 bipolar transistor input, can be one-chip bipolar LSI implementation.

[0041] Further, by 1-chip LSI by combining the MOS transistor and by port over La transistor may be a BiCMOS structure.

[0042]

As described in detail above, according to the first to third aspects of the present invention, the amplitude of the amplified sensor signal can be kept within an allowable range with a simple configuration. According to the present invention, MOS structure, exhibits excellent effects that can be easily single chip IC structure by port over la structure.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a sensor signal processing device according to a first embodiment.

FIG. 2 is a waveform chart for explaining the operation of the first embodiment.

FIG. 3 is a circuit diagram of a sensor signal processing device according to a second embodiment.

FIG. 4 is a circuit diagram of a sensor signal processing device according to a third embodiment.

[Explanation of symbols]

8 ... Amplifier, 11 ... Comparator as first comparator, 12 ... Comparator as second comparator, 18 ... PMOS transistor as switching element for charging, 21 ... N as switching element for discharging
MOS transistors, 25: capacitors, 28: diodes as leak diodes, 29: capacitors,
31: condenser, 32: diode as leak diode

Continuation of front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01P 3/488 G01D 5/245 102

Claims (5)

(57) [Claims] 1. A sensor signal processing apparatus which is required to amplify the sensor signal by an amplifier before performing signal processing such as binarization when the sensor signal is small, wherein the output value of the amplifier is And a first comparator that outputs a first signal when the output value of the amplifier is larger than a predetermined maximum value, and compares the output value of the amplifier with a predetermined minimum value. A second comparator that outputs a second signal when an output value of the amplifier is smaller than a predetermined minimum value; a capacitor connected to a reference voltage terminal of the amplifier; and a second comparator from the first comparator. A discharge switching element that operates by the signal of 1 and discharges the capacitor to lower the reference voltage in the amplifier; and the capacitor that operates by the second signal from the second comparator. Sensor signal processing apparatus characterized by comprising a charge switching element for raising the reference voltage at the charging and amplifier. 2. A sensor signal processing device which needs to amplify the sensor signal by an amplifier before performing signal processing such as binarization because the sensor signal is small, wherein a reference voltage of the amplifier is provided. A capacitor connected to the terminal, a leak diode that leaks the charge of the capacitor to the side where the charge is discharged, and comparing the output value of the amplifier with a predetermined minimum value, the output value of the amplifier is determined in advance. A sensor that outputs a signal when the value is smaller than the minimum value, and a charging switching element that operates by a signal from the comparator to charge the capacitor and increase a reference voltage in an amplifier. Signal processing device. 3. A sensor signal processing apparatus which is required to amplify the sensor signal by an amplifier before performing signal processing such as binarization because the sensor signal is small, wherein a reference voltage of the amplifier is provided. A capacitor connected to the terminal, a leakage diode for leaking current from a power supply to a side where the capacitor is charged, and comparing the output value of the amplifier with a predetermined maximum value to determine whether the output value of the amplifier is A comparator that outputs a signal when the signal is larger than a predetermined maximum value; and a discharge switching element that operates by a signal from the comparator to discharge the capacitor and drop a reference voltage in an amplifier by a predetermined amount. Characteristic sensor signal processing device. 4. A one- chip MOSL by setting the capacitance of the capacitor to 100 PF or less, using a MOS transistor as the switching element, and using an amplifier having a MOS transistor input as the amplifier.
4. The method according to claim 1, wherein the SI is used.
Item 7. The sensor signal processing device according to Item 1. 5. A with the external of said capacitor,
The switching element and by port over la transistor,
Further, by using an amplifier having a bipolar transistor input as the amplifier, a one-chip bipolar LSI
The sensor signal processing device according to any one of claims 1 to 3, wherein the sensor signal processing device is configured as: