JP2011064507A - Temperature detection circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature detection circuit wherein an output voltage of the temperature detection circuit is ratiometric operation in proportion to a supply voltage, and a differential signal output does not generate an error in a detection temperature even when a common mode potential is fluctuated, and the output voltage of the temperature detection circuit is changed linearly to the temperature. <P>SOLUTION: This temperature detection circuit is constituted by using a resistor wherein the reciprocal of a resistance value is changed linearly to the temperature, a resistor wherein the resistance value is changed linearly to the temperature, and an entire differential error amplifier. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a temperature detection circuit using a resistor as a temperature sensitive element.

  As a temperature detection circuit using a resistor as a temperature sensitive element, for example, a temperature detection circuit (temperature detector) as described in Patent Document 1 is known. The temperature detection circuit described in Patent Document 1 includes a first voltage dividing circuit in which a first resistor and a second resistor are connected in series for dividing a power supply voltage, and the power supply voltage. A second voltage dividing circuit in which a third resistor and a temperature-sensitive resistance element are connected in series, and a first connection point between the first resistor and the second resistor. Read the potential and the second potential at the connection point between the third resistor and the temperature-sensitive resistance element with an analog / digital converter, and calculate the potential ratio between the first potential and the second potential; Temperature detection is performed by acquiring a temperature corresponding to the calculated potential ratio as a detection temperature from a predetermined potential ratio-temperature characteristic prepared in advance.

  A conventional temperature detection technique for a temperature detection circuit divides a power supply voltage and uses it as a reference voltage, thereby reducing an error in detection temperature due to power supply voltage fluctuation. That is, the ratiometric of the temperature detection circuit is realized.

JP 2001-272282 A

  However, in the conventional temperature detection technology of the temperature detection circuit, since the signal is not a differential signal, if the common mode potential fluctuation of the ground potential occurs due to current consumption during operation, an error occurs in the detected temperature. There is. Furthermore, the voltage ratio of the temperature sensitive resistance element changes nonlinearly with respect to temperature. Therefore, there is a problem that a potential ratio-temperature conversion table is required.

  The present invention has been devised to solve the above-described problems, and is a ratiometric operation in which the output voltage of the temperature detection circuit is proportional to the power supply voltage. An object of the present invention is to provide a temperature detection circuit that is a differential signal output that does not cause an error, and that the output voltage of the temperature detection circuit changes linearly with respect to temperature.

  The temperature detection circuit of the present invention includes a first voltage dividing circuit composed of a first resistor and a second resistor, a second voltage dividing circuit composed of a third resistor and a fourth resistor, A fully differential error amplifier in which the negative voltage input is input to the output terminal of the first voltage dividing circuit, and the positive output terminal of the fully differential error amplifier is connected to the positive voltage input of the second voltage dividing circuit. And a fifth resistor connected between the output terminal of the first voltage dividing circuit and a sixth resistor connected between the negative output terminal of the fully differential error amplifier and the output terminal of the second voltage dividing circuit. The first resistor and the fourth resistor are constituted by a first resistance type, and the second resistor, the third resistor, the fifth resistor, and the sixth resistor are second resistors. The configuration is such that the potential difference between the negative output terminal and the positive output terminal of the fully differential error amplifier is output.

  According to the present invention, the output of the temperature detection circuit is formed by using the resistor whose reciprocal of the resistance value changes linearly with respect to the temperature, the resistor whose resistance value changes linearly with respect to the temperature, and the fully differential error amplifier. It is a ratiometric operation in which the voltage is proportional to the power supply voltage, is a differential signal output that does not cause an error in the detected temperature even if there is a common mode potential fluctuation, and the output voltage of the temperature detection circuit varies linearly with temperature Temperature detection circuit can be configured

It is a circuit diagram which shows the temperature detection circuit of this invention. It is a circuit diagram of a temperature detection circuit for digital output of the present invention.

  Hereinafter, a temperature detection circuit according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a circuit diagram of the temperature detection circuit of the present embodiment. A voltage dividing circuit 151 composed of a resistor 101 and a resistor 102 between the power supply voltage Vdd and the ground voltage, a voltage dividing circuit 150 composed of a resistor 103 and a resistor 104 between the power supply voltage Vdd and the ground voltage, and an output of the voltage dividing circuit 151 A fully differential error amplifier 107 in which a negative input is input to the terminal 110 and an output terminal 111 of the voltage dividing circuit 150 is connected to a positive input, and between the positive output 112 and the output terminal 110 of the fully differential error amplifier 107. And a resistor 106 connected between the negative output 113 of the fully differential error amplifier 107 and the output terminal 111.

  Here, the resistor 101 and the resistor 104 are temperature sensitive resistors and are made of high resistance polysilicon having a large temperature coefficient. For the sake of convenience, the resistance value is represented by R1. The resistors 102 and 103 are made of low-resistance polysilicon having a small temperature coefficient. For the sake of convenience, the resistance value is represented by R3. The resistors 105 and 106 are made of low-resistance polysilicon having a small temperature coefficient. For the sake of convenience, the resistance value is represented by R2.

  In the high resistance polysilicon that is a temperature sensitive resistor, the temperature characteristic of the reciprocal of the resistance value per unit area changes linearly with respect to the temperature. In the low resistance polysilicon, the temperature characteristic of the resistance value per unit area changes linearly with respect to the temperature.

  In the temperature detection circuit of FIG. 1, the output voltage is a potential difference from the negative output 113 based on the positive output 112 of the fully differential error amplifier 107. For convenience, the potential difference is referred to as VOUT.

  For convenience, if the potentials of the connection points 110, 111, 112, and 113 are expressed as V (110), V (111), V (112), and V (113), respectively, the Milman theorem is applied to the connection point 110. For example, equation (1) is obtained.

同様にして、接続点１１１についてミルマンの定理を適用すれば式（２）が得られる。

Similarly, if the Millman's theorem is applied to the connection point 111, Expression (2) is obtained.

全差動型誤差増幅器１０７の電圧利得は１よりも十分大きく、V(１１０)＝V(１１１)と近似できるとすると式（１）、式（２）より式（３）を得る。

Assuming that the voltage gain of the fully differential error amplifier 107 is sufficiently larger than 1, and can be approximated to V (110) = V (111), Expression (3) is obtained from Expression (1) and Expression (2).

式（３）より本発案の温度検出回路の出力電圧は電源電圧Vddに比例し、レシオメトリック出力となる。Ｒ１は感温抵抗体である高抵抗ポリシリコンで構成され、抵抗値の逆数は温度に対して線形に変化するのに対して、Ｒ２、Ｒ３は低抵抗ポリシリコンで構成され、抵抗値は温度に対して線形に変化する。

From equation (3), the output voltage of the temperature detection circuit of the present invention is proportional to the power supply voltage Vdd and becomes a ratiometric output. R1 is composed of high-resistance polysilicon that is a temperature-sensitive resistor, and the reciprocal of the resistance value changes linearly with respect to temperature, whereas R2 and R3 are composed of low-resistance polysilicon, and the resistance value is the temperature. Changes linearly with respect to.

  Therefore, R2 / R1, which is the first term of the formula (3), is a term that varies greatly linearly with respect to temperature, and R2 / R3, which is the second term, is composed of the same low-resistance polysilicon. Even if changes, it becomes a term whose value does not change.

  Therefore, the temperature sensitivity of the temperature detection circuit of the present invention is determined by appropriately selecting R2 / R1 as the first term, and the offset of the temperature detection circuit of the present invention by appropriately selecting R2 / R3 as the second term. The voltage can be determined.

  In this way, the output voltage of the temperature detection circuit is a ratiometric operation in which the output voltage is proportional to the power supply voltage, the differential signal output does not cause an error in the detection temperature even if there is a common mode potential fluctuation, and the output of the temperature detection circuit It is possible to configure a temperature detection circuit in which the voltage changes linearly with respect to the temperature.

  FIG. 2 is a circuit diagram of a temperature detection circuit for digital output according to the present invention.

  The digital output temperature detection circuit has the following configuration. The differential output of the temperature detection circuit 201 is connected to the VIN input of an analog / digital converter (ADC) 202. A connection point 114 and a connection point 115, which are outputs of the reference voltage circuit 203 composed of the resistor 120, the resistor 121, and the resistor 122, are connected to the VREF input of the analog / digital converter (ADC) 202.

  For convenience, the resistance values of the resistor 120, the resistor 121, and the resistor 122 are R4, R5, and R6, respectively, and the potentials of the connection point 114 and the connection point 115 are V (114) and V (115), respectively. The output voltage VREF is expressed by V (114) −V (115), and is expressed by Equation (4).

アナログ／デジタルコンバータ（ADC）２０２の出力コードはVOUT/VREFに比例するので式（５）に比例する。

Since the output code of the analog / digital converter (ADC) 202 is proportional to VOUT / VREF, it is proportional to the equation (5).

式（５）の値はVddの項が消去されるので電源電圧に影響されない。よって、電源電圧が変動しても検出温度が変化しないディジタル出力の温度検出回路を構成することができる。

The value of equation (5) is not affected by the power supply voltage because the Vdd term is eliminated. Therefore, it is possible to configure a digital output temperature detection circuit in which the detected temperature does not change even if the power supply voltage fluctuates.

101, 104 High resistance polysilicon resistors 102, 103, 105, 106 Low resistance polysilicon resistors 107 Fully differential error amplifier 201 Temperature detection circuit 202 Analog / digital converter (ADC)
203 Reference voltage circuit

Claims (3)

A first voltage dividing circuit composed of a first resistor and a second resistor;
A second voltage dividing circuit composed of a third resistor and a fourth resistor;
A fully differential error amplifier in which an output terminal of the first voltage dividing circuit is input with a negative input, and an output terminal of the second voltage dividing circuit is connected to a positive input;
A fifth resistor connected between the positive output terminal of the fully differential error amplifier and the output terminal of the first voltage dividing circuit;
A sixth resistor connected between the negative output terminal of the fully differential error amplifier and the output terminal of the second voltage dividing circuit;
The first resistor and the fourth resistor are configured by a first resistor type, and the second resistor, the third resistor, the fifth resistor, and the sixth resistor are second resistor types. Consists of
A temperature detection circuit characterized in that a potential difference between a negative output terminal and a positive output terminal of the fully differential error amplifier is used as an output. The first resistance type is high-resistance polysilicon in which the reciprocal of the resistance value changes linearly with respect to temperature,
2. The temperature detection circuit according to claim 1, wherein the second resistance type is low resistance polysilicon whose resistance value changes linearly with respect to temperature. An analog / digital converter in which an output terminal of the fully differential error amplifier is connected to an input terminal;
It is composed of a seventh resistor, an eighth resistor, and a ninth resistor connected in series, and the connection point of the seventh resistor and the eighth resistor, the eighth resistor, and the ninth resistor. The temperature detection circuit according to claim 2, further comprising: a power supply voltage dividing circuit having a connection point connected to a reference voltage input terminal of the analog / digital converter.

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