Method and circuit for correcting sensor temperature dependency characteristic

Abstract

A method and circuit for preventing an output signal, which has been corrected through digital correction or analog correction, from deviating from a target value and for preventing power supply noise and power consumption from increasing. A sensor amplification circuit receives output of a sensor as an input signal. Correction points are set at predetermined temperature intervals. The sensor amplification circuit performs digital correction for correcting the input signal with correction data set for each correction point. Further, the sensor amplification circuit performs a second correction for correcting the input signal between the correction points with gradient data calculated from the correction data for two of the correction points that are adjacent to each other.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

FIG. 1 is a schematic circuit diagram showing a sensor amplification circuit including a digital correction function in the prior art;

FIG. 2 is a schematic graph showing the output characteristic of the prior art sensor amplification circuit;

FIG. 3 is a schematic block circuit diagram showing a sensor amplification circuit including an analog correction function in the prior art;

FIG. 4( a) is a graph showing the relationship between the temperature and the output voltage of the sensor shown in FIG. 3;

FIG. 4( b) is a graph schematically showing the relationship between the temperature and temperature dependent voltage, which is supplied to the analog correction amplifier shown in FIG. 3;

FIG. 4( c) is a graph showing the relationship between the temperature and reference voltage in FIG. 3;

FIG. 4( d) is a graph schematically showing the relationship between the temperature and output voltage of the output-stage amplifier shown in FIG. 3;

FIG. 4( e) is a graph schematically showing the relationship between the temperature and the output voltage of the analog correction amplifier shown in FIG. 3;

FIG. 5 is a graph schematically showing the output characteristic of the sensor amplification circuit of FIG. 3;

FIG. 6 is a schematic block circuit diagram showing a sensor amplification circuit according to a first embodiment of the present invention;

FIG. 7 is a schematic block circuit diagram showing part of the sensor amplification circuit of FIG. 6;

FIG. 8 is a graph schematically showing the output characteristic of the sensor amplification circuit of FIG. 6;

FIG. 9 is a table showing the correction data stored in a memory device shown in FIG. 7;

FIG. 10 is a table showing gradient data calculated by a gradient calculation circuit shown in FIG. 7;

FIG. 11 is a graph obtained through a correction process according to a second embodiment of the present invention;

FIG. 12 is a table showing the correction data used at each correction point of FIG. 11;

FIG. 13 is a table showing the gradient data used at each correction point of FIG. 11;

FIG. 14 is a graph obtained through a correction process according to a third embodiment of the present invention;

FIG. 15 is a schematic block diagram showing a control circuit of a sensor amplification circuit according to a fourth embodiment of the present invention;

FIG. 16 is a table used by a determination unit shown in FIG. 15 in a determination process; and

FIG. 17 is a schematic block diagram showing a control circuit according to a fifth embodiment of the present invention.

Claims

1. A method for correcting an input signal having a temperature dependent characteristic, the method comprising: setting correction data for each of a plurality of correction points set at a predetermined temperature interval;performing a first correction for correcting the input signal with the correction data;calculating gradient data between two of the correction points that are adjacent to each other from the correction data for each of the two adjacent correction points; andperforming a second correction for correcting the input signal with the gradient data.

2. The method according to claim 1, wherein said setting the correction data includes changing the predetermined temperature interval between the two adjacent correction points in accordance with the temperature dependency characteristic of the input signal.

3. The method according to claim 1, further comprising: comparing the correction data for a given correction point with the correction data for at least one of two correction points adjacent to the given correction point;repeating said comparing for each correction point; anddetermining whether the first correction or the second correction is necessary based on the comparison.

4. The method according to claim 1, further comprising: comparing the correction data for each of the correction points with the correction data for each of two correction points adjacent to that correction point and determining whether the first correction or the second correction is necessary for each correction point based on the comparison; andperforming the first correction or the second correction based on the determination.

5. The method according to claim 1, further comprising: generating an output signal having a predetermined characteristic curve by amplifying the input signal;wherein said performing a first correction includes changing the characteristic curve of the output signal by correcting the input signal based on the correction data so that the characteristic curve converges to a predetermined target value regardless of temperature; andwherein said performing a second correction includes changing the characteristic curve of the output signal by correcting the input signal based on the gradient data so that the characteristic curve converges to a predetermined target value regardless of temperature.

6. A correction circuit for correcting an input signal having a temperature dependent characteristic, the correction circuit comprising: a memory device for storing correction data for each of a plurality of correction points set at a predetermined temperature interval;a first correction circuit for correcting the input signal at each correction point based on the correction data corresponding to each correction point;a second correction circuit for correcting the input signal between two of the correction points that are adjacent to each other based on gradient data calculated from the correction data for each of the two adjacent correction points;a sensor for detecting temperature; anda control circuit for reading the correction data corresponding to the temperature detected by the temperature sensor from the memory device and controlling operation of the first correction circuit and the second correction circuit based on the correction data.

7. The correction circuit according to claim 6, wherein the predetermined temperature interval between the two adjacent correction points is changed in accordance with the temperature dependency characteristic of the input signal.

8. The correction circuit according to claim 6, wherein the control circuit includes: a determination unit for comparing the correction data for a given correction point with the correction data for at least one of two correction points adjacent to the given correction point and for determining whether correction with the first correction circuit or the second correction circuit is necessary based on the comparison, wherein the determination unit repeats said comparing for each correction point.

9. The correction circuit according to claim 6, further comprising: a determination unit for comparing the correction data for each of the correction points with the correction data for each of two correction points adjacent to that correction point, determining whether correction with the first correction circuit or the second correction circuit is necessary for each correction point based on the comparison, and storing the determination in the memory device; andwherein the control circuit controls operation of the first correction circuit and second correction circuit based on the determination.

10. The correction circuit according to claim 6, further comprising: an amplification circuit unit, including the first correction circuit and the second correction circuit, for correcting the input signal with the first correction circuit and the second correction circuit to generate an output signal having a predetermined characteristic curve;wherein the first correction circuit adjusts gain and offset voltage of the amplification circuit unit based on the correction data so that the characteristic curve of the output signal converges to a predetermined target value regardless of the temperature; andwherein the second correction circuit adjusts the gain and the offset voltage of the amplification circuit unit based on the gradient data so that the characteristic curve of the output signal converges to a predetermined target value regardless of the temperature.

11. The correction circuit according to claim 6, wherein the correction circuit is connected to a sensor and receives an output signal of the sensor as the input signal.