JPH0921715A - Temperature compensation circuit for sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compensate for the nonlinearity of temperature characteristics accurately through a simple configuration. SOLUTION: Four resistors are arranged in bridge to constitute a semiconductor sensor element 11. A correction circuit 12 for temperature compensation is connected between a power supply and a resistor in the sensor element 11 on the power supply side or between the ground and a resistor arranged on the opposite side. The correction circuit 12 has temperature characteristics reverse to the output characteristics of a sensor circuit 10 provided with no correction circuit 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature compensating circuit for compensating the temperature characteristic of a sensor output.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 15, for example, a circuit of a semiconductor pressure sensor has a sensor element 1 composed of bridge resistors R1, R2, R3 and R4 formed in a silicon diaphragm, and a resistor R1 of the sensor element 1. , R2 and resistors R01 and R04 respectively connected between the constant voltage power supply and resistors R3 and R4 of the sensor element 1 and resistors R02 and R03 provided between the ground and the ground. Resistors R01-R04
Is smaller than the resistors R1 to R4 by two digits.
Further, in parallel with the resistors R3 and R4, the trimming resistor RP
3 and RP4 are provided, and the bridge balance and offset temperature characteristics are compensated by trimming. Further, as shown in FIG. 17, the output of the sensor element 1 is input to the operational amplifier 2, and a temperature sensitive resistor having a positive characteristic is incorporated in the negative feedback resistor RP to compensate for the negative sensitivity characteristic.

Further, as disclosed in Japanese Patent Publication No. 6-91265, a compensation circuit for compensating the temperature characteristic of sensitivity is provided in the operational amplifier input circuit so as to suppress the sensitivity temperature characteristic within a predetermined range. Things have been proposed.

[0004]

In the former case of the above-mentioned conventional technique, as shown in FIG. 17, the temperature characteristic of this pressure sensor has a non-linear curve having an inclination. This slope can be reduced to about 2% span by trimming RP3 and RP4, but the non-linearity is more than double the linearity error, as shown in FIG. It could not be made smaller. In the latter case of the above-mentioned conventional technique, the resistance of each bridge is not individually corrected, and sensitivity correction can be performed, but offset correction cannot be performed. Further, it is limited to the constant current circuit and cannot be used at a power source voltage as low as about 1.5V.

The present invention has been made in view of the above-mentioned problems of the prior art, and provides a temperature compensating circuit for a sensor, which is capable of accurately compensating the non-linearity of the temperature characteristic with a simple structure. The purpose is to

[0006]

According to the present invention, there is provided a semiconductor sensor element having four resistors formed in a bridge shape, between one of the resistors of the sensor element on the power source side and a power source, or , A temperature compensating correction circuit is provided between the resistor and the ground facing the resistor, and the characteristic of this compensating circuit is the temperature characteristic opposite to the output characteristic of the sensor circuit without the compensating circuit. It is a temperature compensation circuit for a sensor that has.

Further, according to the present invention, the thermistor used in the correction circuit has a temperature characteristic which cancels the temperature characteristic of the sensor circuit by using a positive temperature characteristic and a negative temperature characteristic. It is a thing. The thermistor is a surface-mounting type chip thermistor, and is mounted by laminating it on each other.

[0008]

According to the temperature compensating circuit for a sensor of the present invention, both the offset temperature characteristic and the temperature characteristic at the rated output can be accurately measured by attaching the temperature compensating correction circuit having the inverse characteristic to the sensor circuit. It can be corrected.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a temperature compensating circuit for a sensor according to a first embodiment of the present invention, in which a semiconductor pressure sensor circuit 10 is connected to a constant voltage power source (not shown). The semiconductor pressure sensor circuit 10 includes a sensor element 11 composed of bridge-shaped resistors R1, R2, R3 and R4 formed on a silicon diaphragm, and resistors R1 and R2 of the sensor element 11.
And resistors R01, R04 connected between the
And resistors R02 and R03 provided between the resistors R3 and R4 of the sensor element 11 and the ground, respectively. The resistances R01 to R04 are about 60Ω, which is two orders of magnitude smaller than the resistances R1 to R4 of about 6 KΩ. Further, trimming resistors RP3 and RP4 of about 600Ω are provided in parallel with the resistors R3 and R4, and by trimming,
Bridge balance and offset temperature characteristics are compensated.

A thermistor Rth1 is connected in parallel to the resistor R01 of the sensor element 11, and the temperature compensating circuit 12 is constituted by the resistor R01 and the thermistor Rth1. The characteristic of the correction circuit 12 is that the thermistor R
output characteristics of the sensor circuit 10 without th1
For example, it has a temperature characteristic opposite to that shown in FIG.

The thermistor Rth1 of the temperature compensating circuit for a semiconductor pressure sensor of this embodiment has a negative temperature characteristic.
A chip thermistor having 100Ω at B and a B constant of 2800 was used. The resistance value of the resistor R01 attached in parallel with the thermistor Rth1 is 100Ω, 80Ω, 60.
The total resistance value of the correction circuit 12 was measured using four types of Ω and 40 Ω. The result is, as shown in FIG.
When Rth1 is 100Ω, the temperature characteristic is the closest to the straight line. Here, the thermistor Rth1 and the resistor R01 forming the correction circuit 12 are appropriately selected according to the temperature characteristics of the sensor circuit. As parameters other than those shown in FIG. 2, the resistance value of the thermistor Rth1 and B
There is a constant, and the larger the thermistor resistance value and B constant, the greater the non-linearity of the temperature characteristics shown in FIG.

The temperature characteristic of the sensor circuit 10 is shown in FIG.
For the correction in the case of exhibiting the concave non-linearity as shown in (3), the thermistor th1 may be attached to the resistor R01, or the thermistor may be provided in parallel to R03. In addition, the sensor circuit 10
When correcting the temperature characteristic of the convex type of, the resistors R02, R0
It is good to attach an appropriate thermistor in parallel with 4.

According to the pressure sensor circuit of this embodiment, the offset temperature compensation and the temperature compensation at the rated output can be performed only by providing a predetermined thermistor Rth1 in parallel with one side of the resistor connected to the sensor element 11. It can be performed accurately and only needs to select an appropriate thermistor and resistor, the circuit is not complicated, and it is possible to inexpensively compensate for the one which was difficult to compensate in the conventional analog circuit.

Next, a second embodiment of the present invention will be described with reference to FIG.
It will be described with reference to FIG. Here, the same members as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, in addition to the correction circuit 12 in the first embodiment, a correction circuit 14 is provided in series with the correction circuit 12 between the resistors R2 and R02 of the sensor element 11. .
The correction circuit 14 includes a thermistor Rr in parallel with the resistor R21.
h2 and a resistor R22 in series therewith are provided.

According to this embodiment, as shown in FIG.
The correction circuit 12 makes a correction so that it is slightly convex upward, and a correction circuit 14 having a temperature characteristic symmetrical to this temperature characteristic is provided to further enhance the linearity of the sensor circuit 10.

Next, a third embodiment of the present invention will be described with reference to FIG. Here, the same members as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, the sensor circuit 1 driven by the constant voltage in the first embodiment is
0 is connected to a constant current circuit. Again,
Correction circuit 12 for correcting non-linearity on the constant current power supply 20 side
Is attached. Further, the position and the characteristic of the correction circuit 12 can be changed appropriately depending on the temperature characteristic of the sensor circuit 10 that is appropriately corrected.

Next, a fourth embodiment of the present invention will be described with reference to FIG. Here, the same members as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. This example is
The thermistors 31 and 32 are surface-mounted on the sensor element 30 provided with the sensor circuit 10 of the first embodiment. The thermistor 31 is an NTC thermistor having a negative temperature characteristic, and the thermistor 32 is a PTS thermistor having a positive temperature characteristic. The thermistors 31 and 32 have electrode portions on the front and back surfaces stacked on each other and are electrically connected in series. Lamination is performed using an adhesive and a conductive paint. The electrode on the front surface side of the thermistor 31 is wire-bonded to the electrode 38 of the sensor element 30 by the gold wire 33.
As shown in FIG. 6B, in the thermistor 32, the conductive paint 34 is applied to the electrodes on the back surface side and is connected to the electrodes of the sensor element 30, and the adhesive 3 is applied to the back surface around the conductive paint 34.
5 is applied and surely adhered to the sensor element 30.

According to the temperature compensating circuit for the sensor of this embodiment, the thermistors 31, 32 attached to the sensor element 30.
The installation space is small, and temperature compensation is possible. In particular, since the NTC thermistor 31 and the PTC thermistor 32 are laminated, the mounting space is small, and there is no temperature difference between them, so that temperature compensation can be performed accurately.

Next, a fifth embodiment of the present invention will be described with reference to FIG. Here, the same members as those in the fourth embodiment are designated by the same reference numerals, and the description thereof will be omitted. This example is
The thermistors 31 and 32 of the fourth embodiment are surface-mounted in parallel on the sensor element 30. Thermistor 31
Is a NTC thermistor having a negative temperature characteristic, and the thermistor 32 is a PTS thermistor having a positive temperature characteristic. The thermistors 31 and 32 are connected to each other by a flexible jumper jumper wire 36.
The second electrode and the bonding electrode 38 on the sensor element 30 are connected by a flexible jumper jumper wire 37.

According to the temperature compensating circuit for the sensor of this embodiment, the thermistors 31, 32 attached to the sensor element 30.
Can be appropriately selected, and mounting can be separately performed, and electrodes can be arbitrarily set such as copper foil or aluminum foil.

Next, a sixth embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. Here, the same members as those in the fourth embodiment are designated by the same reference numerals, and the description thereof will be omitted. In this embodiment, the thermistors 31 and 32 of the fourth embodiment are laminated via an aluminum plate 37, and the thermistor 3 is used.
2, a PTC thermistor 38 is provided in parallel with the thermistor 31 in series. The thermistor 38
The sensor element 30 is surface-mounted via the dummy pedestal 39.

Next, a sixth embodiment of the present invention will be described with reference to FIG.
0 and FIG. Here, the same members as those in the fourth embodiment are designated by the same reference numerals, and the description thereof will be omitted. This embodiment is the same as the thermistors 31 and 32 of the fourth embodiment.
The housing recess 4 of the circuit board 41 on which the sensor circuit is formed.
It is provided within 0. The thermistors 31 and 32 are accommodated in the accommodation recess 40 with a margin with respect to the inner wall,
The conductive elastic body 42 such as a metal piece urges the electrode on the front surface side toward the recess 40 so that it can be temporarily held. The elastic body 42 is connected to the upper electrode 44 of the sensor circuit of the circuit board 41 and also electrically connected to the electrode of the thermistor 31.
The elastic body 42 is for temporary fixing, and after the selection of the thermistors 31 and 32 is completed, the thermistor 3 is mounted by the solder reflow device.
Solder to one electrode. According to this embodiment, the surface of the circuit board 41 can be effectively used, and other elements can be mounted three-dimensionally. The elastic body 42 is
It can be sufficiently connected electrically and mechanically. It is also possible to connect using a conductive paint or the like.

As a pattern for mounting the temperature compensating circuit for sensor of the present invention on the mounting portion 42 of the circuit board 41 on which the resist is not applied, it is connected in parallel with another fixed resistor 50 as shown in FIG. Alternatively, as shown in FIG. 13, a plurality of thermistors may be connected in series and the thermistor row may be attached in parallel to the circuit. Also, FIG.
As shown in FIG. 4, each thermistor may be mounted in parallel with the circuit. In this case, the void 43 is formed by connecting with a conductive paint or solder to connect the circuits when the thermistor is not used, and the void 43 is formed by selecting any one of the four sides of the bridge circuit.

In the temperature compensating circuit for a sensor of the present invention, the type of the circuit board can be appropriately selected, and a printed board made of polyimide, glass epoxy resin or the like can be used. The sensor can be used not only as a pressure sensor but also as a magnetic sensor using an MR element, a sensor for humidity, gas, and the like. The shape of the thermistor may be a rectangular chip or a terminal.

[0025]

The temperature compensating circuit of the present invention can simultaneously perform offset temperature compensation and rated output temperature compensation in the compensation of the non-linearity of the temperature characteristic simply by selecting and connecting an appropriate thermistor. Moreover, it is possible to drive at a constant voltage with a low voltage, and it is possible to reduce the voltage of the battery power supply. Further, by preliminarily grasping the characteristics of the sensor element and selecting the optimum correction circuit, the performance of the sensor device can be greatly improved and the accuracy can be improved.

Further, by making the NTC thermistor and the PTC thermistor into chips and performing temperature compensation by combining the temperature characteristics, more accurate temperature compensation becomes possible. In addition, it is possible to reduce the space required and have a good followability with respect to the temperature change and a small variation.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment of a temperature compensation circuit of the present invention.

FIG. 2 is a graph showing characteristics of temperature and resistance value of the correction circuit according to the first embodiment of the present invention.

FIG. 3 is a circuit diagram of a second embodiment of the temperature compensation circuit of the present invention.

FIG. 4 is a graph showing characteristics of temperature and resistance of the correction circuit according to the second embodiment of the present invention.

FIG. 5 is a circuit diagram of a third embodiment of the temperature compensation circuit of the present invention.

FIG. 6 is a partial perspective view (a) showing a mounting example of a thermistor of a fourth embodiment of a temperature compensating circuit for a sensor of the present invention and a view (b) showing a back surface of the thermistor.

FIG. 7 is a partial perspective view showing a mounting example of the thermistor of the fifth embodiment of the temperature compensating circuit for sensor of the present invention.

FIG. 8 is a partial perspective view showing a mounting example of the thermistor of a sixth embodiment of the temperature compensating circuit for a sensor of the present invention.

FIG. 9 is a circuit diagram showing a mounting example of the thermistor of a sixth embodiment of the present invention.

FIG. 10 is a partial perspective view showing a mounting example of the thermistor of the seventh embodiment of the temperature compensating circuit for sensor of the present invention.

FIG. 11 is a partial perspective view showing a mounting substrate for a thermistor according to a seventh embodiment of the present invention.

FIG. 12 is a partial perspective view showing an example of mounting a thermistor of the temperature compensation circuit for a sensor of the present invention.

FIG. 13 is a partial perspective view showing another mounting example of the thermistor of the temperature compensation circuit for a sensor of the present invention.

FIG. 14 is a partial perspective view showing another mounting example of the thermistor of the temperature compensation circuit for a sensor of the present invention.

FIG. 15 is a circuit diagram of a conventional pressure sensor circuit.

FIG. 16 is a circuit diagram of an amplifier circuit of a conventional pressure sensor.

FIG. 17 is a graph showing temperature characteristics of a conventional pressure sensor.

[Explanation of symbols]

10 sensor circuit 11,30 sensor element 12,14 correction circuit R1, R2, R3, R4, R01, R02, R03, R
04 Resistance Rth1, Rth2 Thermistor 31 NTC Thermistor 32 PTC Thermistor

Claims (4)

[Claims] 1. A semiconductor sensor element in which four resistors are formed in a bridge shape, and one of the resistors of the sensor element on the power source side and a power source, or a resistor and a ground facing the resistor. And a correction circuit for temperature compensation is provided between the sensor and the sensor, and the characteristics of the correction circuit are opposite to the non-linearity of the output characteristics of the sensor circuit without the correction circuit. Temperature compensation circuit. 2. The correction circuit, which comprises a thermistor and a fixed resistor, has a temperature characteristic which is substantially symmetrical to the non-linearity of the output characteristic of the sensor element in the state where the correction circuit is not provided. The temperature compensation circuit for the sensor according to 1. 3. A thermistor used in the correction circuit, wherein a temperature characteristic that cancels the temperature characteristic of the sensor circuit is formed by using a positive temperature characteristic and a negative temperature characteristic. Alternatively, the temperature compensation circuit for the sensor according to the item 2. 4. The temperature compensating circuit for a sensor according to claim 3, wherein the thermistor is a surface mounting type chip thermistor and is mounted in a laminated manner.