JP2000315950A - A/d converter and controller using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an A/D converter that corrects an error given to an A/D conversion value of other sensor even when the wiring of a sensor connected to an amplifier circuit is broken and to provide a controller using it. SOLUTION: An amplifier circuit 70 is connected to at least one of a plurality of sensors, an output of sensors not connected to the amplifier circuit 70 or an output of the amplifier circuit 70 is selected and given to an input terminal for A/D conversion. In this case, a broken wire of a sensor 90 connected to the amplifier circuit 70 is detected and when the broken wire of the sensor is detected, as to other sensors 91 to 97 than the sensor 90 whose broken wire is detected, the A/D converter value after the broken wire is corrected on the basis of the A/D converter value before the broken wire for each sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an A / D converter for A / D converting a sensor input signal input via an amplifier circuit and a sensor input signal input without passing through an amplifier circuit, and an A / D converter for the A / D converter. The present invention relates to a control device using a D conversion device.

[0002]

2. Description of the Related Art As an example in which an A / D converter has a sensor connected via an amplifier circuit and a sensor connected without an amplifier circuit, for example, a circuit as shown in FIG. Can be considered.

[0003] In the processing device 10, a CPU 40, an A / D
The A / D converter 20 includes a multiplexer 30 and an A / D conversion processing unit 50. C
The PU 40 turns on any of the transistors Tr0, Tr1,..., Tr7 of the multiplexer 30 so that the A / D conversion processing unit 50
N0, AN1,..., AN7, sensors 90, 91,
, 97 are input and A / D converted, and then the CPU 40 executes a predetermined process.

[0004] The amplifier circuit 70 is connected between the sensor 90 and the port AN0. The diode D
0 and D1 are limiters for preventing a high voltage from being applied to the port AN0.

[0005]

When the sensor 90 is disconnected in the above configuration, the processing unit 10
Vin0 = (0−Vcc / 2) × (−Amp) + Vcc / 2 = Vcc × (Amp + 1) (1) Since the amplification factor Amp of Q1 is Amp> 1, Vin0> Vcc (2). At this time, assuming that the voltage drop of the diodes D0 and D1 is Vf (about 0.7 [V]), the emitter voltage Ve0 of Tr0 is as follows: Ve0 = Vcc + Vf (3) When the A / D conversion of the output signal Vsens1 of the sensor 91 is performed with the sensor 90 disconnected, Vd0 = V
Even if Tr0 is turned off as cc, the base-emitter voltage Vbe0 of Tr0 becomes Vbe0 = Ve0-Vb0 = Vcc + Vf-Vcc = Vf (4), and Tr0 is also turned on. At this time, a potential difference occurs between Vc0 and Vc1 (from Vc0 ≒ Vcc + Vf, Vc0
0> Vc1), and the current flows from AN0 to AN1.
Therefore, the voltage Vin1 of the port AN1 is
The output voltage of 1 is the voltage obtained by adding the voltage generated at the port AN0, and an error occurs when A / D conversion is performed. Similarly, an error occurs in the A / D conversion value of the sensor 92.

The present invention has been made in view of such a conventional problem, and corrects an error given to an A / D conversion value of another sensor when a sensor connected to an amplifier circuit is disconnected. It is an object of the present invention to provide an A / D conversion device capable of performing the above-mentioned operation and a control device using the same.

[0007]

According to a first aspect of the present invention, a plurality of sensors are connected to at least one of the plurality of sensors. At least one amplifying circuit for amplifying a sensor output signal and one input terminal, and selecting any one of the output of the sensor and the output of the amplifying circuit which is not connected to the amplifying circuit, and Connect analog /
A / D conversion means for performing digital conversion, disconnection detection means for detecting disconnection of the sensor connected to the amplifier circuit, and, if disconnection is detected, for each sensor other than the sensor for which disconnection is detected, An A / D converter having correction means for correcting the A / D conversion value after disconnection based on the A / D conversion value before disconnection.

According to a second aspect of the present invention, in the A / D converter according to the first aspect, when the disconnection is detected, the correction means detects a sensor other than the sensor that detected the disconnection. A difference between A / D conversion values before and after each disconnection is produced, and the A / D conversion value after the disconnection is corrected based on the calculated difference.

According to a third aspect of the present invention, a plurality of sensors, at least one amplifier circuit connected to at least one of the plurality of sensors and amplifying a sensor output signal, and one input terminal are provided. And selecting one of the output of the sensor and the output of the amplifier circuit that is not connected to the amplifier circuit and connecting the selected one to the input terminal,
A / D conversion means for performing digital conversion, storage means for storing the A / D conversion value in association with the type of sensor, and processing means for performing a predetermined operation based on the converted A / D conversion value And a disconnection detecting means for detecting disconnection of the sensor connected to the amplifier circuit, and when disconnection is detected, for sensors other than the sensor for which disconnection is detected,
A after disconnection based on the A / D conversion value before disconnection for each sensor
And a correction unit for correcting the / D conversion value.

According to a fourth aspect of the present invention, in the control device according to the third aspect, when the disconnection is detected, the correction means stores, for each sensor, a sensor other than the sensor in which the disconnection is detected. The difference between the A / D conversion values before and after the disconnection is produced, and the error of the A / D conversion value is corrected based on the calculated difference.

According to a fifth aspect of the present invention, in the apparatus according to any one of the first to fourth aspects, the disconnection detecting means is provided when there are a plurality of sensors connected to the amplifier circuit. For any one of the above, disconnection is detected.

According to a sixth aspect of the present invention, in the device according to the second or fourth aspect, the correction means calculates the calculated value from the A / D conversion value after the disconnection at predetermined intervals. It is characterized in that a value obtained by dividing the difference by a predetermined number is reduced.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an A / D converter according to the present invention and a control device using the same will be described in detail with reference to the accompanying drawings. FIG. 1 shows A according to the invention.
1 is a configuration diagram of an embodiment of a / D conversion device and a control device using the same.

First, the configuration will be described. The control device includes a processing device 10, sensors 90, 91,.
And a disconnection detection circuit 80.

The processing device 10 has a CPU 40, an A / D converter 20, and a storage device (memory) 60.

The A / D converter 20 includes a multiplexer 30
And an A / D conversion processing unit 50,
0 is the input port (AN0, AN1,
, AN7), and the switching transistors Tr0, Tr corresponding to each port.
,..., Tr7 are connected. Normal power supply voltage Vcc is supplied from CPU 40 to the base of these transistors.
(For example, 5 [V]) is applied and the transistor is in a non-conductive state. For example, when the output voltage of the sensor 91 is A / D-converted, the CPU 40
When a voltage of approximately 0 [V] is applied to the base of 0, only the transistor Tr0 becomes conductive, and the A / D conversion processing unit 50 performs A / D conversion.

The CPU 40 turns on each transistor one by one in order, and sets the Tr in a predetermined cycle.
It is programmed to repeat for 0, Tr1,..., Tr7.

The A / D conversion processing section 50 performs A / D conversion.
The converted A / D conversion value is sent to CPU 40 and stored in storage device 60 in association with each sensor.

The CPU 40 executes a predetermined process using the A / D converted value. The CPU 40 inputs the value stored in the storage device 60 and the value stored in the buffer / register of the A / D conversion processing unit 50.

Assuming that the output voltage of the sensor 90 is Vsens0 and the amplification factor of the operational amplifier Q1 is Amp (= R4 / R2), the voltage Vin0 input to the input port AN0 of the processing device 10 and the A / D converted voltage Vad0 are Vin0 = Vad0 = (Vsens0−Vcc / 2) × (−Amp) + Vcc / 2 (5) Further, the output voltage of the sensor 91 is set to Vsen.
s1, and the output voltage of the sensor 92 is Vsens2,
Input voltages Vin1 and Vin of input ports AN1 and AN2
2 and A / D converted Vad1 and Vad2 are respectively Vin1 = Vad1 = Vsens1 (6) Vin2 = Vad2 = Vsens2 (7)

Next, the disconnection detecting circuit 80 will be described. One end of the resistor R6 of the disconnection detection circuit 80 is connected to the sensor 90.
Connected to the output end of the The sensor output input from the resistor R6 is connected to the inverting input terminal of the operational amplifier Q2. The non-inverting input terminal is connected to the power supply voltage Vcc. The output terminal of the operational amplifier Q2 is connected to the CPU 40.

Next, the operation of the present embodiment will be described with reference to FIG. First, when detecting that the power has been turned on, the CPU 40 clears the abnormality determination processing counter Cnt_Ijo only once (sets Cnt_Ijo = 0) (see step S1).

Next, the input voltage Vin0 to the processing device 10
A / D converter 20 performs A / D conversion on A to D Vin7 to obtain A / D converted values Vad0 to Vad7 (see step S2).

Next, the CPU 40 determines whether the sensor 90 is disconnected. Output voltage Vopen of disconnection detection circuit 80 =
In the case of Vcc, the CPU 40 determines that the sensor 90 is normal (step S3: No). When it is determined that the sensor 90 is normal, the values of the A / D conversion values Vad0 to Vad7 are stored in the storage device 60 (see step S4).

The output voltage Vopen of the disconnection detecting circuit 80 =
If the value is 0, the CPU 40 determines that the sensor 90 is disconnected (step S3: Yes). When the disconnection is determined for the first time in this process, since Cnt_Ijo == 0 (step S5: Yes), the sensor 90 is determined as follows.
Of the A / D conversion values Vad1 to Vad7 of the other sensors 91 to 97 caused by the disconnection of d_Vad1 to d_V
ad7 is calculated (see step S6). d_Vad1 = Vad1-Vad1_1 d_Vad2 = Vad2-Vad2_1: d_Vad7 = Vad7-Vad7_1 (8)

Next, Cnt_Ijo = Cnt_Ijo + 1 (9) and 1 are added to the abnormality determination processing counter (see step S7).

If the current disconnection processing is the second or subsequent processing,
Since Cnt_Ijo> 1, Cnt_Ijo = 10
Until the value becomes 0, the process of the next step S10 is repeated (see steps S8 and S9).

In step S10, the other sensors 91 and 9 are disconnected by disconnection of the sensor 90 as described below.
, 97 are corrected. Vad1 = Vad1-d_Vad1 × Cnt_Ijo / 100 Vad2 = Vad2-d_Vad2 × Cnt_Ijo / 100: Vad7 = Vad7−d_Vad7 × Cnt_Ijo / 100 (10)

As described above, in this embodiment, the input of one A / D conversion processing unit 50 is switched by the multiplexer 30 to perform A / D conversion one by one, and the amplification circuit is used. 70 connected to the sensor 90 via the sensor 70 and sensors 91 to 91 connected without the amplifier 70
In the case of having the amplifier 97, the disconnection of the sensor 90 to which the amplifier circuit 20 is connected is detected, and the difference between A / D conversion values before and after the disconnection is calculated for the sensors 91 to 97 that do not pass through the amplifier circuit 70. Since the difference is subtracted from the A / D conversion value, it is possible to correct an error given to the A / D conversion values of the other sensors 91 to 97 when the sensor 90 to which the amplifier circuit 70 is connected is disconnected. This has the effect. Also,
Since the amount of change is gradually corrected in steps S8 and S9, a predetermined process or control executed using the A / D conversion value does not suddenly change due to the correction.

In the above embodiment, the amplification circuit 70
Is connected to only one of the sensors 90, but is not limited to this, and a plurality of sensors may be connected to the amplifier circuit. In this case, the disconnection detection circuit is 1
And it may be provided in any one of the sensors connected to the amplifier circuit.

[0031]

As described in detail above, according to the present invention, the amplifier circuit includes at least one of the plurality of sensors.
When one of the output of the sensor and the output of the amplifier circuit that is connected to one and not connected to the amplifier circuit is selected and connected to the input terminal to perform analog / digital conversion, the connection to the amplifier circuit is performed. When the disconnection is detected, the A / D of each sensor other than the sensor for which the disconnection was detected before disconnection is performed.
Since the A / D conversion value after disconnection is corrected based on the conversion value, it is possible to correct an error given to the A / D conversion value of another sensor when the sensor connected to the amplifier circuit is disconnected. There is an effect that it can be done.

When the correction is performed, the value obtained by dividing the difference calculated from the A / D conversion value after the disconnection by a predetermined number at every predetermined period is reduced, so that the correction is performed using the A / D conversion value. The predetermined processing and control to be performed are not suddenly changed by the correction.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of an A / D converter and a control device using the same according to the present invention.

FIG. 2 is a flowchart for explaining the operation of the present embodiment.

FIG. 3 is a configuration diagram of an embodiment of an A / D converter and a control device using the A / D converter according to the related art.

[Explanation of symbols]

Reference Signs List 10 processing device 20 A / D converter 30 multiplexer 40 CPU 50 A / D conversion processing unit 60 storage device (memory) 70 amplifying circuit 80 disconnection detecting circuit 90, 91, 92, 93, 94, 95, 96, 97
Sensors AN0, AN1, AN2, AN3, AN4, AN5, A
N6, AN7 port D0, D1 Diode Q1, Q2 Operational amplifier R1, R2, R3, R4, R5, R6, R7 Resistance Tr0, Tr1, Tr2, Tr3, Tr4, Tr5, T
r6, Tr7 switching transistor

Claims (6)

[Claims] 1. A plurality of sensors, at least one amplifying circuit connected to at least one of the plurality of sensors and amplifying a sensor output signal, and one input terminal, the plurality of sensors being connected to the amplifying circuit. A / D conversion means for selecting one of the output of the sensor and the output of the amplifier circuit and connecting to the input terminal to perform analog / digital conversion, and the sensor connected to the amplifier circuit A disconnection detecting means for detecting disconnection of the sensor, and, if a disconnection is detected, an A / D conversion value after the disconnection based on the A / D conversion value before disconnection for each sensor other than the sensor for which the disconnection is detected. An A / D conversion device, comprising: a correction unit configured to perform correction. 2. The A / D converter according to claim 1, wherein, when a disconnection is detected, the correction unit performs A / D conversion before and after the disconnection for each sensor other than the sensor for which the disconnection is detected. A / D which produces a value difference and corrects the A / D conversion value after disconnection based on the calculated difference.
Conversion device. 3. A plurality of sensors, at least one amplifying circuit connected to at least one of the plurality of sensors and amplifying a sensor output signal, and one input terminal, the plurality of sensors being connected to the amplifying circuit. A / D conversion means for selecting one of the output of the sensor and the output of the amplifier circuit and connecting to the input terminal to perform analog / digital conversion, and converting the A / D conversion value into a sensor. Storage means for storing the A / D converted value in association with the type of processing; processing means for performing a predetermined operation based on the converted A / D conversion value; and disconnection detection means for detecting disconnection of the sensor connected to the amplifier circuit. Correction means for correcting an A / D conversion value after disconnection based on an A / D conversion value before disconnection for each sensor other than the sensor for which disconnection is detected when disconnection is detected; Control device according to claim. 4. The control device according to claim 3, wherein, when a disconnection is detected, the correction unit performs A / D conversion before and after the disconnection stored for each sensor other than the sensor in which the disconnection is detected. A control device for producing a value difference and correcting an error of an A / D conversion value based on the calculated difference. 5. The apparatus according to claim 1, wherein said disconnection detecting means, when there are a plurality of sensors connected to said amplifier circuit, disconnects one of said sensors. An apparatus for detecting 6. The apparatus according to claim 2, wherein the correction unit subtracts a value obtained by dividing the calculated difference by a predetermined number from the A / D conversion value after the disconnection at predetermined intervals. An apparatus characterized in that: