JPH06213435A - Controller for combustion apparatus - Google Patents

Abstract

PURPOSE:To rationally correct an error occurring based on an offset voltage of an operational amplifier when an output voltage of a microvoltage output type sensor is amplified by the amplifier. CONSTITUTION:When a correction value write command signal generator 4 applies a first signal to a control circuit 3, the circuit 3 applies a specific input voltage Vin to an input of an operational amplifier 2. The circuit 2 also compares an actual output voltage present at the output of the amplifier 2 with a theoretical output voltage previously written in a ROM 7 corresponding to the specific voltage Vin to obtain correction data based on the error and stores it in an EEPROM 5. After the generator 4 stops outputting of the first signal, the circuit 3 obtains correction voltage data by considering correction data stored in the EEPROM 5 for the actual output voltage of the amplifier 2, and controls a combustion apparatus based on it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a combustion device used in a combustion device such as an automatic water heater, and more particularly, an operational amplifier (hereinafter abbreviated as an operational amplifier) which outputs various sensor outputs.
The present invention relates to an improvement for effectively correcting and using an error of the input data that may occur as a result of the amplification in a control device that is used as input data for controlling combustion equipment after being amplified by.

[0002]

2. Description of the Related Art For example, in an automatic water heater, a thermocouple or the like is used as a sensor for combustion detection or flame detection. And nowadays, microcomputers (generally,
A control circuit composed of a microcomputer (abbreviated as "microcomputer") performs necessary combustion device control according to the electromotive force of the thermocouple. However, since various sensors used for combustion control including such a thermocouple have an analog electric potential level of several mV to several tens of mV at most, A / D conversion of the sensor is performed. When used as input data in a control circuit such as a microcomputer, it is necessary to sandwich an operational amplifier between the sensor and the control circuit and first amplify the sensor output in the analog dimension.

FIG. 2 shows an example of a basic amplifier circuit in such a case, which is a well-known inverting amplification type sensor using an operational amplifier 2 and resistor networks R1 and R2, and a small voltage output type sensor such as a thermocouple. The output voltage Vin of 1 is theoretically amplified according to the following equation 1), and the amplified operational amplifier output voltage Vout
Is provided to the main control circuit 3 which is typically shown as "CPU" in the figure. That is, if the output voltage Vout at this theoretical value is expressed as Vout-theory, then Vout-theory = -Vin (R2 / R1).

However, as is well known, a so-called input offset voltage Voffset is expected in the operational amplifier 2, and if this is also taken into consideration, the operational amplifier output voltage (CPU
The realistic value Vout-actual of the input voltage) Vout is Vout-actual =-(Vin ± Voffset) (R2 / R1) ... 2).

However, there is no particular problem if the operational amplifier input voltage Vin given from the sensor 1 to the operational amplifier 2 is on the order of several V, but as described above, when the operational amplifier input voltage Vin is on the order of several mV to several tens of mV at most. Negative or positive error due to the presence of input offset voltage Voffset {V
offset (R2 / R1)} is a factor that cannot be ignored, and its compensation is indispensable especially in the control of the combustion equipment as the subject of the present invention. For example, if the output voltage of a thermocouple cannot be read accurately and the control circuit may make an incorrect judgment as to the presence or absence of flame, it may cause dangerous fuel such as gas, etc. This type of combustion equipment that handles events may not lead to serious situations. Therefore, conventionally, an error correction method as shown in FIG. 3 has been proposed.

The correction circuit 6 shown in FIG.
It is configured as a variable resistance circuit that divides cc, and biases the inverting input of the operational amplifier 2 toward the inverting input of the operational amplifier 2 in the direction that the input offset voltage Voffset that can occur between the positive-phase and negative-phase inputs of the operational amplifier 2 is equivalently approached to zero as much as possible. Is applied. The correction circuit based on such a voltage bias can be applied to other types of amplifier circuits that use operational amplifiers, for example, non-inverting amplifier circuits.

[0007]

The conventional correction method shown in FIG. 3 has some results. However, operational amplifier 2
The input offset voltage Voffset of is not uniform, and each has a considerable width. Therefore, the correction circuit 6
The adjustment work has to be done for each product (each control circuit), which is a very troublesome task, and it is difficult to make fine adjustments using a variable resistor, which is a small electromechanical component in the first place. . In addition, there is a possibility that the adjustment value may change later even though the adjustment is made due to the temperature characteristics of the variable resistance circuit portion.

Of course, some extremely high-grade operational amplifiers have a negligibly small input offset voltage even in the input voltage range of several mV.
Although the above problem can be solved by using such a device, such a model is extremely expensive, and it becomes a factor that hinders widespread use of the combustion equipment itself, which repels the product cost.

The present invention has been made under such circumstances, and even if an inexpensive operational amplifier is used, accurate correction can be performed with a simple operation and the influence of the input offset voltage can be sufficiently reduced. It is intended to provide a control device for an obtained combustion device.

[0010]

In order to achieve the above object, the present invention receives a control circuit which receives an analog output voltage of an operational amplifier for amplifying a minute voltage output of a sensor and converts the analog output voltage into digital data to perform various combustion controls. In contrast to (configurable by a microcomputer), the first non-volatile memory means in which the operational amplifier theoretical output voltage Vout-theory at a specific operational amplifier input voltage Vin is written with corresponding digital data, and the digital data is electrically supplied later. A writable second non-volatile memory means is coupled. A correction value write command signal generator is further coupled to the control circuit, and when the correction signal write command signal generator outputs a first signal indicating a write command, the control circuit provides the operational amplifier with the specific operational amplifier input voltage Vin. The operational amplifier output voltage Vout-ac actually obtained at the output of the operational amplifier
tual and the theoretical output voltage Vout-theory that should be obtained when the same specific operational amplifier input voltage Vin as described above is stored in the first non-volatile memory means and is applied to the operational amplifier.
Are compared with each other, and the comparison calculation data obtained based on the difference between them is written as correction data in the writable storage area of the second nonvolatile memory means. On the other hand, when the correction value write command signal generator outputs the second signal different from the above-mentioned first signal or does not output the first signal, the control circuit always or uses the sensor output. The actual operational amplifier output voltage V obtained at the output of the operational amplifier at the right time
For the out-actual, the combustion equipment is controlled based on the calibration voltage data obtained by adding the correction data written in the second nonvolatile memory means as described above.

In such a basic configuration of the present invention, the control circuit can be configured by the microcomputer as described above. In that case, the read-only ROM attached to the microcomputer is used as the first non-volatile memory means. it can. On the other hand, the second non-volatile memory means is an electrically rewritable non-volatile memory means (so-called EEPROM) external to the microcomputer, or after being provided as a product,
It can be a non-volatile memory means (PROM) that can be electrically written only once.

However, these are not limiting, and the first and second memory means are provided as the same part of the EEPR.
It may be OM or PROM. Further, when a plurality of minute voltage output type sensors are coupled to the control circuit, the present invention can be applied to some or all of them, and in this case, the operational amplifier is provided with a plurality dedicated to each sensor. Alternatively, a single operational amplifier can be shared by a plurality of sensors by inserting a multiplexer (switching switch means) or the like that receives a switching operation by a control circuit on the input side.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following is a description of the essential structure of a combustion device control apparatus constructed in accordance with the present invention with reference to FIG. 1. In this embodiment, as in the case described above, thermocouples, etc. A minute voltage output Vin, which is a sensing output from the sensor 1 required for controlling combustion equipment, is amplified by an operational amplifier 2 configured as an inverting amplification type by external resistors R1 and R2, and is output as an operational amplifier output voltage Vout. The case of being input to the control circuit 3 is illustrated. The control circuit 3 is assumed to be a microcomputer, as indicated by "CPU" in the drawings.

Particularly, in the one-chip microcomputer or CPU chip recently provided, a read-only memory (R
Since the OM) 7 is incorporated, in this embodiment, the R
The OM is used as the first non-volatile memory means 7 coupled to the control circuit 3, and in addition to this, it is similarly coupled to the control circuit 3, but is a component separate from the control circuit and is a second external component. An electrically rewritable EEPROM 5 is used as the non-volatile memory means 5.

First non-volatile memory means or ROM 7
When the input voltage Vin of a specific value is given to the operational amplifier 2, the theoretical output voltage Vout-theory that should be obtained at the output of the operational amplifier 2 according to the theoretical formula 1) already described.
Are written by corresponding digital data.
This theoretical data may be at least one, and may be plural for a plurality of input voltages Vin having different values, if necessary.

A correction value write command signal generator 4 is also connected to the control circuit 3. The generator can simply be configured to include a manual switch, the actuation of which produces a first signal, for example defined at a particular voltage level.

When this first signal is applied to the control circuit 3, the control circuit 3 enters a correction data value finding mode and RO
The operational amplifier input voltage Vin when the theoretical output voltage data written in M7 should be obtained is applied to the input of the operational amplifier 2. Then, at the output of the operational amplifier 2, the actual output voltage Vout-actual according to the above equation 2), which is generally affected by the offset voltage Voffset, appears.

However, the control circuit 3 outputs the operational amplifier output voltage Vout-actual actually obtained at the output of the operational amplifier 2 in this manner and the above-mentioned first non-volatile memory means 7.
The theoretical output voltage Vout-theory read from is calculated and compared, and the error data, for example, the error data that can be obtained by subtracting the above formula 1) from the above formula 2) is used as correction data in the second non-volatile memory means or the EEPROM 5. Store. When a plurality of theoretical output data are stored in the first nonvolatile memory means 7, the input voltage V for each of them is stored.
In is sequentially given to take in the error data, and if they are not the same, the reliability of the data is improved by appropriately performing an averaging process, and the resulting correction data is stored in the second non-volatile memory means 5.

In this way, the operational amplifier 2 used
If the correction data in which the offset voltage Voffset is also taken into consideration, the generation of the first signal from the correction value write command signal generator 4 is stopped or the second signal of a different form is generated. When the correction value write command signal generator 4 includes the manual switch as described above, the output potential level can be returned to the original value by returning the switch to the original value. It can be defined as the generation of a signal, and the first and second signals can be, for example, specific codewords.

In any case, based on this, when the control circuit 3 stops receiving the first signal or receives the second signal, thereafter, the control circuit always (generally at regular intervals),
Alternatively, when the output of the sensor 1 should be used, the correction data stored in the second non-volatile second memory means 5 is read from the output voltage Vout-actual actually obtained at the output of the operational amplifier 2, and addition / subtraction is performed. The calculation correction processing is performed according to the correction data, theoretical output voltage data or data that is as close as possible to the theoretical output voltage data is obtained as calibration voltage data, and the combustion equipment is controlled according to this data.

Modifications to the device of the above-mentioned embodiment according to the gist of the present invention are optional, for example, the second non-volatile memory means 5 is electrically incorporated at least once after being incorporated in the device. If it is writable, it will be used for that purpose.
It may be a ROM. Further, in the above-described embodiment, the theoretical value data is stored in the ROM 7 with the built-in CPU, but it can be changed so as to be stored in the EEPROM or PROM. In this case, as a result, the first and second non-volatile memory means referred to in the gist of the present invention can be the same as parts. The control circuit 3 is literally C
PU, that is, ROM that can be used as the first non-volatile memory means 7 when it has only a central processing unit
It goes without saying that the etc. will also be external. Further, the correction value write command signal generator 4 may be activated according to a specific program.

In this type of combustion control device,
Often multiple types of sensors are required, and for some or all of them, the present invention is equally applicable when there is a need for voltage amplification by an operational amplifier prior to data decoding as well. In this case, if a suitable input switching device such as a multiplexer (not shown) is inserted in the input of the operational amplifier 2 and the sensor is selected by the command of the control circuit 3, the operational amplifier can be calibrated according to the present invention. It is quite reasonable because it only requires a few.

[0023]

According to the present invention, in the combustion control device utilizing the sensor output amplified by the operational amplifier, the main control circuit corrects the error due to the presence of the input offset voltage of the operational amplifier, and thereafter, A value as close as possible to the theoretical output voltage of the operational amplifier corresponding to the value of the sensor output at any given time can be used as input data without any user intervention. Therefore, there is no need to use a variable resistor, which is an electromechanical component with many defects as in the past, and there is no risk of erroneous manual adjustment or fluctuations in the adjustment value due to temperature changes. Therefore, highly safe control can be performed. The manufacturing process will be dramatically simplified and streamlined.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a main part of a combustion device control apparatus configured according to the present invention.

FIG. 2 is an example of a general amplifier circuit configuration in the case of amplifying the voltage level of a minute voltage output type sensor by an operational amplifier and giving it to the control circuit.

FIG. 3 is an explanatory diagram of a conventional operational amplifier output voltage correction circuit.

[Explanation of symbols]

 1 sensor, 2 operational amplifier (opamp), 3 control circuit (CPU), 4 correction value write command signal generator, 5 second non-volatile memory means (EEPROM), 6 correction circuit, 7 first non-volatile memory means (ROM).

Claims (7)

[Claims] 1. A combustion apparatus having an operational amplifier for amplifying a minute voltage output from a sensor, and a control circuit for receiving an analog output voltage of the operational amplifier and converting the analog output voltage into digital data to perform various combustion controls. Control device;
First non-volatile memory means in which a theoretical output voltage to be obtained at the output of the operational amplifier when a specific input voltage is applied to the operational amplifier is written in the control circuit, and electrically writable And a second non-volatile memory means having a storage area, the control circuit supplying the operational amplifier with the specific input voltage when receiving the first signal from the correction value write command signal generator. Correction voltage is calculated by comparing the actual output voltage appearing at the output of the operational amplifier with the theoretical output voltage stored in the first non-volatile memory means with respect to the specific input voltage. While storing the correction data in the storage area of the non-volatile memory means, does not receive the first signal from the correction value write command signal generator or is different from the first signal. When receiving the second signal, the calibration voltage data is obtained by adding the correction data stored in the second nonvolatile memory means to the actual output voltage obtained at the output of the operational amplifier, A control device for a combustion device, which is configured to control the combustion device based on the calibration voltage data. 2. The control device for a combustion device according to claim 1, wherein the control circuit is a microcomputer. 3. The control device for a combustion device according to claim 2, wherein the first non-volatile memory means is a ROM attached to the microcomputer, and the second non-volatile memory means is the ROM. A control device for a combustion device, which is an EEPROM which is external to the microcomputer and is electrically rewritable. 4. The control device for a combustion device according to claim 2, wherein the first non-volatile memory means is a ROM attached to the microcomputer, and the second non-volatile memory means is the ROM. A control device for a combustion device, which is a PROM external to a microcomputer and capable of being electrically written only once. 5. The control device for a combustion device according to claim 1 or 2, wherein the first non-volatile memory means and the second non-volatile memory means are the same component. Control device for combustion equipment. 6. A control device for a combustion device according to claim 1, 2, 3, 4 or 5, wherein an input selector for receiving a switching command from the control circuit is provided at an input of the operational amplifier. A control device for a combustion device, wherein the output of the sensor commanded by the control circuit among the plurality of sensors connected to the input switch is selectively amplified by the operational amplifier. 7. The control device for a combustion device according to claim 1, 2, 3, 4, 5 or 6, wherein the correction value write command signal generator includes a manual switch, and A controller for combustion equipment, wherein the first signal is output.