JP3735494B2 - Temperature detection circuit - Google Patents

Description

領域Ｃでは、

となる。
【００４３】
各領域を判別するための閾値は、２つ必要となるので、領域Ａと領域Ｂの判別をＶｔｈＡＢ、領域Ｂと領域Ｃの判別をＶｔｈＢＣとすると、

に設定すればよい。
【００４４】
図５は複数の温度センサ１１、１２を入力とした第二の実施例を示したものである。
【００４５】
ここでは２つの温度センサ１１、１２を入力とするが、３つ以上の温度センサを用いる場合でも同様の回路構成となる。
【００４６】
図５において、温度センサ１１、１２はそれぞれ抵抗２１、２２と直列に接続し、それぞれ正負電源に接続する。
【００４７】
また、それぞれの接続点電圧をＶｉｎ１、Ｖｉｎ２とする。
【００４８】
比較部３からＡＤ変換器６までの構成は図１の構成と同様であるが、基準電圧回路出力Ｖｔｈ３０、３１は各温度センサの検出温度に合わせて設定する。
【００４９】
図６はセンサ温度に対する検出温度の変化と、本構成の回路における出力電圧Ｖｏｕｔの例である。
【００５０】
図７は領域Ｄ、Ｅ、Ｆ、Ｇの各場合の回路状態を簡略化したものである。
【００５１】
図３の場合と同様、比較回路３０、３１はそれぞれスイツチと置き換えることができる。
【００５２】
センサ１１の２つの状態（Ｄ、Ｅ）とセンサ１２の２つの状態（Ｆ、Ｇ）があるため、Ｖｏｕｔは４レベルの出力となる。
【００５３】
それぞれを組み合わせたときの電圧をＶｏｕｔＤＦ、ＶｏｕｔＤＧ、ＶｏｕｔＥＦ、ＶｏｕｔＥＧとすると、

となる。
【００５４】
各状態を判別するための閾値は３つ必要となるので、組合せ（Ｄ＆Ｆ）と（Ｄ＆Ｇ）の判別をＶｔｈＤＦＤＧ、組合せ（Ｄ＆Ｇ）と（Ｅ＆Ｆ）の判別をＶｔｈＤＧＥＦ、組合せ（Ｅ＆Ｆ）と（Ｅ＆Ｇ）の判別をＶｔｈＥＦＥＧとすると、

に設定すればよい。
【００５５】
図８は、図５の実施例に対し、比較部３の出力を絶縁回路で構成した第３の実施例である。
【００５６】
図５に対し、比較器３００及び３１０の出力側にフォトカプラ発光素子用電流制限抵抗３０３及び３１３を接続し、さらにフォトカプラ３０４及び３１４の発光側端子に接続する。ここで、センサ回路部と比較部およびフォトカプラの発光側電源端子は共通電源Ｖ１及びＧ１とする。
【００５７】
抵抗５を接続する電源は、共通電源Ｖ１及びＧ１とは絶縁された電源Ｖ２ーＧ２側に接続する。
【００５８】
フォトカプラ３０４及び３１４の出力端子は一方を抵抗回路部４に接続し、他方をＧ２に接続する。
【００５９】
また、ＡＤ変換器６には、電圧リファレンスＡＶｒｅｆを正電源Ｖ２、基準電圧端子ＡＶｓｓを負電源Ｇ２に接続する。
【００６０】
このような構成にすることで、センサー比較部を構成する電源と、ＡＤ変換器を含む制御部を構成する電源を分離することができる。
【００６１】
図９は、図８の構成において実装部分を分割し、センサー比較部Ａと制御部Ｂを信号ケーブルＣで接続した例である。
【００６２】
この実施例において、例えば
（１）電源１が故障した場合
（２）ケーブルＣが未接続の場合
は、比較部出力段のフォトカプラが非駆動状態になるか、あるいは、非駆動状態と同等の出力信号レベルになるため、故障判断ができるという利点もある。
【００６３】
比較部３によって、並列接続される抵抗回路部４を構成する抵抗値としては、最小の抵抗値をＲ（Ω）とすれば、それぞれＲ、２Ｒ、４Ｒ……という重み付けをすればよい。
【００６４】
図１０には抵抗回路部４を構成する抵抗本数が３本の場合の等価回路図を示し、図１１には抵抗値に重み付けをした場合の合成抵抗値、および電源電圧を１とした場合の出力電圧比を示す。（抵抗５として抵抗値を２Ｒ／３とした場合）
なお、図１１において、○は抵抗がスイツチ（比較部）によって基準電位に接続された場合、×は未接続の場合を示す。
【００６５】
このように抵抗値を設定することで、温度センサの複数の状態あるいは複数の温度センサの状態を検出して電圧情報に変換し、ひとつのＡＤ変換器に入力すれば、これら複数の状態を判別することができる。
【００６６】
第１〜第３の実施例のような構成をとることにより、温度センサの状態を判別するための閾値はそのままで、比較部内の基準電圧回路を構成する抵抗定数を変更することで、閾値を変更することなく制御用マイクロコンピュータのソフトウェアを使用することができる。
【００６７】
【発明の効果】
本発明によれば、温度センサの複数の状態あるいは複数の温度センサの状態をひとつのＡＤ変換器で検出することができる。
【００６８】
したがって、同時に多くのセンサ入力を必要とする加熱装置など、多数のＡＤ変換器が必要となる場合に、少ないＡＤ変換器数でまかなうことが可能となる。
【００６９】
また、温度センサの状態を検出し比較する部分と、比較結果から抵抗を合成する部分の間を絶縁回路で構成することにより、比較部の電源故障やケーブル断線などの不具合を、ＡＤ変換器を有する制御部側で検出が可能となる。
【００７０】
さらに、合成抵抗回路部の抵抗値を適切な重み付けすることによって、ひとつのＡＤ変換器で複数の温度センサの状態を検知することができる。
【００７１】
このような構成をとることにより、温度センサの状態を判別するための閾値はそのままで、比較部内の基準電圧回路を構成する抵抗定数を変更することで、閾値を変更することなく制御用マイクロコンピュータのソフトウェアを使用することができる。
【図面の簡単な説明】
【図１】本発明の第１の一実施例を示す温度検知回路の回路図である。
【図２】図１におけるセンサ温度と入出力電圧との関係図である。
【図３】図１における回路例出力部分の簡略図である。
【図４】図１における出力電圧と閾値の設定摸式図である。
【図５】本発明の第２の一実施例を示す温度検知回路の回路図である。
【図６】図５におけるセンサ温度と入出力電圧、および閾値との関係図である。
【図７】図５における回路例出力部分の簡略図である。
【図８】本発明の第３の一実施例を示す温度検知回路の回路図である。
【図９】図８における実装例を示す回路図である。
【図１０】比較部が３つある場合の出力部分の簡略図である。
【図１１】図１０の例における合成抵抗と出力電圧との関係図である。
【図１２】従来例を示す温度検知回路のブロック図である。（ＡＤ変換器を複数使用の場合）
【図１３】従来例を示す温度検知回路のブロック図である。（ＡＤ変換器の前に信号切替回路を接続の場合）
【符号の説明】
１ 温度センサ
２ 抵抗
３ 比較部
４ 抵抗回路部
５ 抵抗
６ ＡＤ変換器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a temperature detection circuit used in a heating device or the like that uses a temperature sensor and changes a control operation according to a result of a comparison means.
[0002]
[Prior art]
A heating device for cooking, for example, a rice cooker, a microwave oven, a cooking heater, etc., inputs the temperature state of the load, the temperature of the control circuit itself, etc., and controls the heating power so that appropriate heating can be performed.
[0003]
Usually, in order to input such temperature information, it is common to use a negative thermistor, convert a change in thermistor resistance value due to temperature into a change in voltage, and input it to the AD converter.
[0004]
Furthermore, it is necessary to simultaneously detect the voltage of the commercial power supply and the energization current during heating. These inputs are also input to the AD converter. A plurality of AD conversion results are comprehensively determined. For example, a control microcomputer performs heating power increase / decrease and temperature control.
[0005]
[Problems to be solved by the invention]
However, if the number of heating elements of the heating device increases or the control of the heating device itself becomes complicated, the information to be input increases and the number of necessary AD converter circuits also increases.
[0006]
In general, a multi-channel input AD converter built in a microcomputer is used or connected to an external AD converter.
[0007]
In particular, in an AD converter with a built-in microcomputer, which is frequently used in cooking heating devices, up to 8 channels are generally used. When an input exceeding that is required, as shown in the example of FIG. A plurality of AD converters (6-A, 6-B) are connected, or a signal switching circuit such as an analog switch circuit 8 or the like is required before the AD converter as in the example of FIG. (Sn indicates a sensor circuit)
Therefore, the cost increases such as an increase in AD converters or a plurality of AD converter peripheral circuits.
[0008]
Further, for example, when using a temperature sensor for protecting circuits and parts, there are many necessary control points, and information on the entire temperature detection range of the temperature sensor is not always necessary.
[0009]
Furthermore, depending on the location where the temperature sensor is attached, it may be necessary to have an insulation configuration with the control circuit section.
[0010]
Further, the threshold value for determining the state of the temperature sensor from the AD conversion result is usually fixed (masked) by the control software of the control microcomputer.
[0011]
The temperature sensor input related to the product safety is performed in parallel with the determination of the structure of the product housing and the test, and there is a possibility that the final threshold setting is shifted after the mask.
[0012]
[Means for Solving the Problems]
The present invention solves the above-described problem, and inputs a temperature sensor signal or a temperature sensor output, and a plurality of comparison circuits for discriminating a plurality of states, and outputs of the plurality of comparison circuits , respectively. A plurality of resistors connected in series to each other, the other ends of the plurality of resistors connected to each other, and a resistance circuit portion in which a combined resistance value changes according to outputs of the plurality of comparison circuits, and the resistance circuit portion serves as a reference A resistor is connected, the other end of the resistor is connected to a DC power source, and an AD converter that detects a voltage at a connection point between the resistor circuit unit and a resistor serving as a reference is used, and control is performed according to the conversion result. It was.
[0013]
Further, there is one temperature sensor, and the output of the one temperature sensor is input to the plurality of comparison circuits .
[0014]
In addition, there are a plurality of temperature sensors, and outputs of the plurality of temperature sensors are input to the plurality of comparison circuits .
[0015]
Furthermore, between the output and the resistor circuit of said plurality of comparator circuits it was assumed to be connected by a plurality of isolation circuit such as a photocoupler.
[0016]
In addition, the resistors used in the resistor circuit section are appropriately weighted.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a plurality of states of the temperature sensor or a plurality of temperature sensors can be detected by one AD converter.
[0018]
In addition, by configuring an insulation circuit between the part that detects and compares the state of the temperature sensor and the part that synthesizes the resistance from the comparison result, the AD converter can be used to prevent problems such as power failure and cable disconnection in the comparison part. Detection is possible on the control unit side.
[0019]
Furthermore, by appropriately weighting the resistance value of the combined resistance circuit unit, it is possible to detect the states of a plurality of temperature sensors with a single AD converter.
[0020]
【Example】
Hereinafter, the present invention will be described with reference to the drawings.
[0021]
FIG. 1 is an electric circuit diagram showing an embodiment of the present invention. A temperature sensor 1 is connected in series with a resistor 2 and is connected to positive and negative power supply terminals, respectively.
[0022]
The voltage at the connection point between the temperature sensor 1 and the resistor 2 is Vin.
[0023]
The comparison unit 3 includes a comparator and a reference voltage circuit, and the comparison circuit 30 connects the comparator 300 and resistors 301 and 302 in series, and connects the output of the reference voltage circuit connected to the positive and negative power sources to the non-inverting input terminal. .
[0024]
In addition, Vin is input to the inverting input terminal.
[0025]
Similarly, the comparison circuit 31 includes a comparator 310 and resistors 311 and 312.
[0026]
At this time, the reference voltage circuit outputs of the comparison circuit 30 and the comparison circuit 31 are set to different voltages (Vth30, Vth31).
[0027]
The resistors 40 and 41 of the resistor circuit section 4 are connected to the output terminals of the comparison circuits 30 and 31, respectively, and both are connected to one end of the resistor 5.
[0028]
The other end of the resistor 5 is connected to the positive power supply side.
[0029]
The voltage at the connection point of the resistors 40, 41, and 5 is Vout.
[0030]
The AD converter 6 connects the voltage reference AVref to a positive power supply, the reference voltage terminal AVss to a negative power supply, and inputs Vout to the AD conversion input terminal.
[0031]
With this configuration, the connection state of the resistance circuit unit 4 and the resistor 5 with respect to the positive and negative power sources varies depending on the state of the comparison unit 3.
[0032]
Therefore, Vin changed by the temperature sensor 1 is converted into Vout and output.
[0033]
FIG. 2 is an example showing changes in Vin and Vout with respect to the sensor temperature.
[0034]
Here, a negative characteristic thermistor is used as the temperature sensor 1.
[0035]
As the sensor temperature rises, the resistance value of the thermistor decreases and Vin rises.
[0036]
Assuming that the reference voltages of the comparison circuits 30 and 31 are Vth30 and Vth31, respectively, the output of the comparison circuit is inverted when Vin becomes that voltage.
[0037]
A region where Vin is Vth30 or less is A, a region from Vth30 to Vth31 is B, and a region where Vth31 or more is C is C.
[0038]
If the output terminal configuration of the comparators 300 and 310 is an oven collector, in the region A, the resistors 40 and 41 are not connected on the comparison unit 3 side, in the region B only the resistor 40 is connected to the negative power supply side, and in the region C, the resistor 40 is connected. , 41 are connected to the negative power supply side.
[0039]
FIG. 3 shows a simplified circuit state in each of the areas A, B, and C.
[0040]
The comparison circuits 30 and 31 can be replaced with switches.
[0041]
FIG. 4 is an example in which a threshold for determining the state of the temperature sensor 1 is set from the conversion result of the AD converter 6 in the circuit example of FIG.
[0042]
In region A,
Vout = V
In region B,

In region C,

It becomes.
[0043]
Since two threshold values are required for discriminating each region, if the discrimination between the region A and the region B is VthAB and the discrimination between the region B and the region C is VthBC,

Should be set.
[0044]
FIG. 5 shows a second embodiment in which a plurality of temperature sensors 11 and 12 are input.
[0045]
Here, two temperature sensors 11 and 12 are input, but the same circuit configuration is obtained even when three or more temperature sensors are used.
[0046]
In FIG. 5, temperature sensors 11 and 12 are connected in series with resistors 21 and 22, respectively, and are connected to positive and negative power supplies, respectively.
[0047]
Further, the respective connection point voltages are Vin1 and Vin2.
[0048]
The configuration from the comparison unit 3 to the AD converter 6 is the same as the configuration of FIG. 1, but the reference voltage circuit outputs Vth30 and 31 are set according to the detected temperature of each temperature sensor.
[0049]
FIG. 6 shows an example of the change in the detected temperature with respect to the sensor temperature and the output voltage Vout in the circuit of this configuration.
[0050]
FIG. 7 shows a simplified circuit state in each of the regions D, E, F, and G.
[0051]
As in the case of FIG. 3, the comparison circuits 30 and 31 can be replaced with switches.
[0052]
Since there are two states (D, E) of the sensor 11 and two states (F, G) of the sensor 12, Vout is an output of four levels.
[0053]
If the voltage when combining each is VoutDF, VoutDG, VoutEF, VoutEG,

It becomes.
[0054]
Since three threshold values are required for determining each state, the combination (D & F) and (D & G) are determined by VthDFDG, the combination (D & G) and (E & F) are determined by VthDGEF, and the combination (E & F) and (E & G). If VthEFEG is determined,

Should be set.
[0055]
FIG. 8 shows a third embodiment in which the output of the comparison unit 3 is configured by an insulating circuit, compared to the embodiment of FIG.
[0056]
5, the current limiting resistors 303 and 313 for photocoupler light emitting elements are connected to the output sides of the comparators 300 and 310, and further connected to the light emitting side terminals of the photocouplers 304 and 314. Here, the light emission side power supply terminals of the sensor circuit unit, the comparison unit, and the photocoupler are common power sources V1 and G1.
[0057]
The power source to which the resistor 5 is connected is connected to the power source V2-G2 side that is insulated from the common power sources V1 and G1.
[0058]
One of the output terminals of the photocouplers 304 and 314 is connected to the resistor circuit unit 4, and the other is connected to G2.
[0059]
Further, the AD converter 6 is connected with the voltage reference AVref to the positive power supply V2 and the reference voltage terminal AVss to the negative power supply G2.
[0060]
By adopting such a configuration, it is possible to separate the power source configuring the sensor comparison unit and the power source configuring the control unit including the AD converter.
[0061]
FIG. 9 shows an example in which the mounting portion is divided in the configuration of FIG. 8 and the sensor comparison unit A and the control unit B are connected by a signal cable C.
[0062]
In this embodiment, for example, (1) When the power supply 1 fails (2) When the cable C is not connected, the photocoupler at the output stage of the comparison unit is in the non-driven state or is equivalent to the non-driven state Since the output signal level is obtained, there is an advantage that a failure can be determined.
[0063]
As the resistance value constituting the resistance circuit unit 4 connected in parallel by the comparison unit 3, if the minimum resistance value is R (Ω), the weights may be weighted as R, 2R, 4R.
[0064]
FIG. 10 shows an equivalent circuit diagram when the number of resistors constituting the resistance circuit unit 4 is three, and FIG. 11 shows a case where the combined resistance value when the resistance value is weighted and the power supply voltage is 1. Indicates the output voltage ratio. (When resistance value is 2R / 3 for resistor 5)
In FIG. 11, ◯ indicates the case where the resistor is connected to the reference potential by the switch (comparison unit), and X indicates the case where it is not connected.
[0065]
By setting the resistance value in this way, a plurality of temperature sensor states or a plurality of temperature sensor states are detected, converted into voltage information, and input to a single AD converter. can do.
[0066]
By adopting the configuration as in the first to third embodiments, the threshold for determining the state of the temperature sensor remains unchanged, and the threshold is set by changing the resistance constant that constitutes the reference voltage circuit in the comparison unit. Control microcomputer software can be used without modification.
[0067]
【The invention's effect】
According to the present invention, it is possible to detect a plurality of temperature sensor states or a plurality of temperature sensor states with a single AD converter.
[0068]
Therefore, when a large number of AD converters are required, such as a heating device that requires many sensor inputs at the same time, it is possible to cover the number of AD converters.
[0069]
In addition, by configuring an insulation circuit between the part that detects and compares the state of the temperature sensor and the part that synthesizes the resistance from the comparison result, the AD converter can be used to prevent problems such as power failure and cable disconnection in the comparison part. Detection is possible on the control unit side.
[0070]
Furthermore, by appropriately weighting the resistance value of the combined resistance circuit unit, it is possible to detect the states of a plurality of temperature sensors with a single AD converter.
[0071]
By adopting such a configuration, the control microcomputer without changing the threshold value by changing the resistance constant constituting the reference voltage circuit in the comparison unit without changing the threshold value for determining the state of the temperature sensor. Software can be used.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a temperature detection circuit according to a first embodiment of the present invention.
FIG. 2 is a relationship diagram between sensor temperature and input / output voltage in FIG. 1;
3 is a simplified diagram of a circuit example output portion in FIG. 1; FIG.
4 is a schematic diagram for setting an output voltage and a threshold value in FIG. 1; FIG.
FIG. 5 is a circuit diagram of a temperature detection circuit showing a second embodiment of the present invention.
6 is a relationship diagram of sensor temperature, input / output voltage, and threshold value in FIG. 5;
7 is a simplified diagram of a circuit example output portion in FIG. 5. FIG.
FIG. 8 is a circuit diagram of a temperature detection circuit showing a third embodiment of the present invention.
FIG. 9 is a circuit diagram showing an example of mounting in FIG.
FIG. 10 is a simplified diagram of an output portion when there are three comparison units.
11 is a relationship diagram between the combined resistance and the output voltage in the example of FIG.
FIG. 12 is a block diagram of a temperature detection circuit showing a conventional example. (When using multiple AD converters)
FIG. 13 is a block diagram of a temperature detection circuit showing a conventional example. (When a signal switching circuit is connected in front of the AD converter)
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Temperature sensor 2 Resistance 3 Comparison part 4 Resistance circuit part 5 Resistance 6 AD converter

Claims (5)

A signal from the temperature sensor (1) or an output from the temperature sensor (1) is input, and a plurality of comparison circuits (30) for determining a plurality of states and a series of outputs from the plurality of comparison circuits (30) , respectively . A resistor circuit in which a plurality of connected resistors (40, 41) and the other ends of the plurality of resistors (40, 41) are connected to each other, and a combined resistance value is changed according to outputs of the plurality of comparison circuits (30). A resistor (5) serving as a reference, and the other end of the resistor (5) is connected to a DC power source (V), and the resistor circuit (4) A temperature detection circuit comprising an AD converter (6) for detecting a voltage at a connection point between the reference resistor (5) and a reference resistor (5), and performing control according to the conversion result. The temperature detection circuit according to claim 1, wherein there is one temperature sensor (1), and an output of the one temperature sensor (1) is input to the plurality of comparison circuits (30) . The temperature sensor (1) is a multiple, the temperature sensing circuit of claim 1, wherein the output of said plurality of temperature sensors (1) is input to each of the plurality of comparator circuits (30). The temperature detection circuit according to claim 1, wherein the outputs of the plurality of comparison circuits (3) and the resistance circuit section (4) are connected by a plurality of insulation circuits (304, 314) such as photocouplers. . The temperature detection circuit according to claim 1, wherein the resistors (40, 41) used in the resistor circuit section (4) are appropriately weighted.

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