JPH02272335A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To accurately measure a pressure without an influence of the change of temperature by arranging a heater in the vicinity of each pressure-sensitive element constituting a bridge circuit and detecting the ambient temperature of the pressure-sensitive element and controlling the current flowing to the heater to keep the temperature of the pressure-sensitive element constant. CONSTITUTION:When the ambient temperature falls, the resistance value of a temperature detecting diode 2 rises and a comparator input voltage gets lower than a reference voltage, and therefore, a signal in the high level is outputted from a comparator 3 and heaters H1 to H4 are operated to uniformly heat piezo elements P1 to P4. Thus, erroneous measurement of the pressure due to the variance of temperature characteristics of piezo resistance elements P1 to P4 is prevented. Meanwhile, when the ambient temperature rises, the resistance value of the temperature detecting diode 2 falls and the comparator input voltage gets higher than the reference voltage, and therefore, the output signal from the comparator 3 goes to the low level, and heaters H1 to H4 are not operated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to semiconductor pressure sensors, and particularly to temperature compensation thereof.

(Prior art) Semiconductor pressure sensors have been known in which a bridge circuit is configured with a pressure-sensitive element on a pressure-receiving diaphragm, and a pressure signal is extracted based on a change in the resistance value of the pressure-sensitive element due to distortion of the pressure-receiving diaphragm. , used as pressure (differential pressure) transmitters, acceleration sensors, etc.

However, since the characteristics of this type of semiconductor pressure sensor vary depending on the ambient temperature, it is necessary to perform temperature compensation.

FIG. 5 is a circuit diagram showing an example of temperature compensation in a conventional semiconductor pressure sensor.

As shown in the figure, the piezoresistive elements P1 to P4 are configured in a bridge shape on a pressure receiving diaphragm (not shown), and when pressure is applied, the resistance balance of the bridge is disrupted, causing the input of the differential amplifier 1 The voltage changes, and a signal corresponding to the change is output as a pressure signal.

The ambient temperature of the piezoresistive elements P1 to P4 is detected by a temperature detection diode 2, and a comparator 3 combines this temperature detection signal with a Zener diode 4 and resistors R1 and R.
2 is compared with a reference signal from a reference voltage source composed of 2.

When the temperature detection signal is lower than the reference signal, that is, when the ambient temperature is below the set temperature, the current control circuit 5 reduces the current flowing through each piezoresistive element P1 to P4. Moreover, when the ambient temperature becomes high and the temperature detection signal exceeds the reference signal, each piezoresistive element P1
~Increase the current flowing to P4.

In this way, each piezoresistive element P
Temperature compensation was achieved by adjusting the current flowing through P1 to P4 and changing the sensitivity of the buri and soji.

(Problem to be Solved by the Invention) However, according to the above conventional example, the piezoresistive element P
Since the sensitivities of 1 to P4 are not linear with respect to increases and decreases in current and vary depending on the individual elements, there is a problem in that measurement errors occur and accurate pressure n1 cannot be determined.

The present invention has been made in view of the conventional problems. The purpose is to provide a semiconductor pressure sensor that can always accurately determine pressure flPI without depending on temperature changes.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention configures a bridge circuit using a pressure-sensitive element on a pressure-receiving diaphragm, and reduces the resistance of the pressure-sensitive element due to distortion of the pressure-receiving diaphragm. In a semiconductor pressure sensor that extracts a pressure signal based on a value change, a heater is arranged near each pressure-sensitive element constituting the bridge circuit, and the ambient temperature of the pressure-sensitive element is detected to control the current flowing to the heater. The temperature of each pressure sensitive element is maintained constant.

Further, the sensor is characterized in that a circuit portion for controlling the current flowing through the heater is mounted within the sensor.

(Function) According to the present invention, the ambient temperature of the pressure sensitive element is detected, and when the detected temperature is below the reference temperature, the current flowing through the heater is increased, and when the detected temperature is above the reference temperature, the current flowing through the heater is decreased. . As a result, the temperature of the pressure-sensitive element is always kept constant, so that no error occurs in pressure measurement.

Furthermore, since the heater control circuit portion is mounted within the sensor, the influence of external noise and external temperature changes is reduced, allowing accurate control.

(Embodiment) FIG. 1 is a circuit diagram showing the electrical configuration of an embodiment of the present invention.
FIG. 2 is a sectional view showing the mechanical structure of the same embodiment, and FIG. 3 is an exploded perspective view thereof.

As shown in FIG. 1, piezoresistive elements P1 to P4 are configured in a bridge shape on a pressure receiving diaphragm (not shown), and when pressure is applied, the resistance balance of the bridge is disrupted and the differential amplifier 1 is The input terminal changes, and a signal corresponding to the change is output as a pressure signal.

The ambient temperature of the piezoresistive elements P1 to P4 is detected by the temperature detection diode 2, and this temperature detection signal is sent to the Zener diode 4 and the resistors R1 and R2 in the comparator 3.
It is compared with a reference signal of a reference voltage source consisting of .

In this embodiment, heaters H1 to H4 are provided close to each piezoresistive element P1 to P4, and piezoresistive element P
The heaters H1 to H4 operate depending on the ambient temperature of 1 to P4,
The temperatures of these piezoresistive elements P1 to P4 are always kept constant to avoid pressure measurement errors due to variations in temperature characteristics.

As shown in FIGS. 2 and 3, the mechanical configuration of the semiconductor pressure sensor of this embodiment includes a pedestal 8 that is incorporated into the container 6 via a pressure transmission shaft 7, and an adhesive bonded onto the pedestal 8. A pressure-receiving diaphragm 10 is connected to the pressure-receiving diaphragm 10 via an adhesive 9, and a heater-equipped film 11 is disposed close to the piezoresistive elements P1 to P4 formed on the pressure-receiving diaphragm 10.

Further, a control circuit 14 for controlling the current flowing through the heaters H1 to H4 shown in FIG. .

The pressure change signal output from the differential amplifier 1 is taken out from a signal extraction lead wire 13 buried in the container 6.

In the semiconductor pressure sensor having such a configuration, when the ambient temperature decreases, the resistance value of the temperature detection diode 2 increases, and the comparator input voltage becomes lower than the reference voltage. Therefore, a high level signal is output from the comparator 3, which activates each heater H1 to H4 and heats each piezoresistive element P1 to P4 to a uniform temperature. Therefore, it is possible to prevent erroneous pressure measurements due to variations in the temperature characteristics of the piezoresistive elements P1 to P4.

On the other hand, when the ambient temperature increases, the resistance value of the temperature detection diode 2 decreases, and the comparator input voltage becomes higher than the reference voltage. As a result, the output signal from the comparator 3 becomes low level, and the heaters H1 to H4 no longer operate.

In this way, according to this embodiment, the piezoresistive elements P1 to
Heaters H1 to H4 are arranged near P4, and the ambient temperature of piezoresistive elements P1 to P4 is detected. When the temperature falls below the reference temperature, each piezoresistive element P1 to P4 is uniformly heated by heaters H1 to H4. Since it is heated, it is possible to accurately determine 7fpI without causing pressure measurement errors due to variations in temperature characteristics.

Furthermore, since the heater control circuit is mounted on the pedestal 8 within the sensor, the effects of external noise and external temperature changes are reduced, allowing accurate control.

FIG. 4 is a sectional view showing the mechanical structure of another embodiment of the present invention.

This embodiment shows an example in which a heater H is wound around a pressure transmission shaft 7.

As in the first embodiment, the heater H is controlled by the control circuit 14 built into the base.

With this configuration, accurate pressure measurement is possible with a simpler configuration.

[Effects of the Invention] As described above, according to the present invention, accurate pressure measurement is possible without causing pressure measurement errors due to variations in temperature characteristics of pressure sensitive elements.

Furthermore, since the circuit portion that controls the heater is mounted within the sensor, it is less affected by external noise and external temperature changes, allowing for accurate control.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the electrical configuration of an embodiment of the present invention;
FIG. 2 is a sectional view showing the mechanical structure of the same embodiment, FIG. 3 is an exploded perspective view showing the same mechanical structure, and FIG. 4 is a sectional view showing the mechanical structure of another embodiment of the present invention. FIG. 5 is a circuit diagram showing the electrical configuration of a conventional example. 1... Differential amplifier 2... Temperature detection diode 3... Comparator 7... Pressure transmission shaft 8... Pedestal 10... Pressure receiving diaphragm 11... Film with heater 14... Heater Control circuits P1 to P4...Piezoresistance elements H1 to H4...Heater

Claims (2)

[Claims] (1) In a semiconductor pressure sensor in which a bridge circuit is formed by a pressure-sensitive element on a pressure-receiving diaphragm and a pressure signal is extracted based on a change in the resistance value of the pressure-sensitive element due to distortion of the pressure-receiving diaphragm, each sensor forming the bridge circuit A semiconductor pressure sensor comprising: a heater arranged near a pressure element, detecting the ambient temperature of the pressure sensing element, and controlling a current flowing through the heater to maintain a constant temperature of each pressure sensing element. (2) The semiconductor pressure sensor according to claim 1, wherein a circuit portion for controlling the current flowing through the heater is mounted within the sensor.