JP2010091412A - Temperature detection circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature detection circuit capable of precisely detecting a wide range of temperature with an extremely small amount of correction. <P>SOLUTION: The collector current ratio of first and second transistors 7, 8 in a band gap circuit 22 is set to 1:A. Current that is B-times larger than a collector current Ic1 flowing to the first transistor 7 is allowed to flow to an output circuit 15, and at the same time a correction circuit 23 is provided. Further, current that is B/(1+A) times larger than base currents Ib1, Ib2 flowing to the transistors 7, 8 is allowed to flow to an output circuit 15, thus obtaining an output voltage Vout. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a temperature detection circuit using a band gap circuit.

  In recent years, semiconductor devices (ICs) have been highly integrated, and the amount of heat generated per unit area has increased. With the miniaturization of products and IC packages, the chip temperature tends to increase. For this reason, there is an increasing need for heat generation control and overheat detection for continuing the operation while limiting the heat generation amount in the chip to a predetermined value or less. For example, Patent Document 1 discloses an intelligent power that includes a temperature detection element that detects the temperature of a power amplification semiconductor element, and an additional circuit provided outside restricts the output of the power amplification semiconductor element based on the temperature detection signal. A module is disclosed. In order to perform such control, it is necessary to accurately detect the chip temperature.

  A conventional temperature detection circuit on a semiconductor chip uses a diode forward voltage Vf (see Patent Documents 2 and 3). For example, as shown in FIG. 5, this temperature detection circuit is configured by connecting a constant current circuit 1 and a diode 2 in series between power supply lines, and detects the temperature based on a forward voltage 4Vf of the diode 2. ing. Although this temperature detection circuit is small, since the forward voltage Vf varies due to manufacturing variations of diodes, it is difficult to detect the temperature with high accuracy in a wide temperature range.

  For this, as shown in FIG. 6, the forward voltage Vf of the diode 5 is measured by using two constant current circuits 3 and 4 that output different currents, and the difference between the forward voltages Vf becomes the absolute temperature. A method for detecting the temperature based on the proportionality has been proposed (see Patent Document 4). However, since it is necessary to switch the constant current circuits 3 and 4 or perform computation after measurement, there is a problem that the circuit scale becomes large and processing takes time.

In order to detect the temperature with higher accuracy, there is one using the temperature characteristics of a band gap circuit (see Patent Document 5). As shown in FIG. 7, the temperature detection circuit 6 includes a bandgap circuit 12 including transistors 7 to 10 and a resistor 11 and an output circuit 15 including a transistor 13 and a resistor 14. The voltage proportional to the absolute temperature is output.
JP 7-115354 A JP 2002-107232 A JP-A-6-242176 Japanese translation of PCT publication No. 2002-508062 JP-A-5-306958

  However, when the inventor of the present application analyzed the temperature detection circuit 6 shown in FIG. 7, it was found that a negative offset voltage was output according to the base current Ib1 flowing through the transistor 7. As a result, when adjusting the output characteristics of the temperature detection circuit 6 in the inspection process, it is necessary to adjust the offset voltage and the slope of the temperature characteristics at the same time. There was a problem that it was difficult to detect.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a temperature detection circuit capable of detecting a wide range of temperatures with high accuracy with as little correction as possible.

  According to the means described in claim 1, a current is passed through the first and second transistors whose bases are connected to each other (current ratio 1: A), and the collector current of the first transistor is changed to the fourth and sixth transistors. B times (B ≠ 0) is passed through the transistor to flow through the second resistor to obtain an output voltage. The size ratio of the first transistor and the second transistor is C: 1, the base current of the first transistor is Ib1, the collector current is Ic1, the thermal voltage is VT (= kT / q k: Boltzmann constant, T: If the resistance values of the first and second resistors are R1 and R2, Ib1 + Ic1 is VT / R1 · ln (A · C) and is proportional to the absolute temperature. Since only the collector current Ic1 flows through the fourth transistor, the current flowing through the second transistor through the sixth transistor becomes B · Ic1, and the voltage Vout at the output terminal is B · R2 / R1 · ln. (A.C) .VT-B.R2.Ib1. The voltage of the second term becomes the offset voltage.

  Therefore, the correction circuit generates a current B / (1 + A) times the base current passed through the first and second transistors via the third transistor, and this correction current is supplied to the second resistor via the output terminal. Shed. Since the base current ratio of the first and second transistors is 1: A like the collector current ratio, the correction current is B · Ib1, and the offset voltage of the second term of the voltage Vout is compensated to be zero. Become. As a result, in the output characteristic adjustment step, adjustment of the offset voltage is not necessary, and only the adjustment of the gradient of the temperature characteristic is required, so that a wide range of temperatures can be detected with high accuracy with as little adjustment as possible.

  According to the means described in claim 2, the correction circuit is connected between the seventh transistor, the second power supply line, and the output terminal connected between the second power supply line and the third transistor. And a mirror ratio of 1: B / (1 + A).

  According to the means described in claim 3, since the ninth transistor for supplying the base current to the seventh and eighth transistors is provided, the influence of the base current can be eliminated, and a more accurate mirror ratio can be obtained. .

  According to the means described in claim 4, the fourth, fifth and sixth transistors form a current mirror circuit, and the tenth transistor for supplying the base current to the fourth, fifth and sixth transistors is provided. As a result, the influence of the base current can be eliminated, and a more accurate mirror ratio can be obtained.

  According to the means described in claim 5, A, B and C are selected such that A and B are integers of 1 or more, B / (1 + A) is an integer, and A · C is other than 1. . In this case, for example, the mirror ratio of the current mirror circuit composed of the fourth, fifth, and sixth transistors and the mirror ratio of the current mirror circuit composed of the seventh and eighth transistors become an integer ratio. As a result, a current mirror circuit having a required mirror ratio can be easily configured by using transistors having the same structure in parallel.

  According to the means described in claim 6, since the start circuit of the band gap circuit is provided, it can be started immediately and reliably by supplying power.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 to 3.
FIG. 1 is a configuration diagram of a temperature detection circuit formed in an IC chip, and the same components as those in FIG. The temperature detection circuit 21 includes a band gap circuit 22, an output circuit 15, a correction circuit 23, and a starting circuit 24, and operates with a constant power supply voltage Vcc supplied through the first and second power supply lines 25 and 26. It is like that.

  The fourth, fifth, and sixth transistors 9, 10, and 13 whose bases are connected constitute a current mirror circuit. The tenth transistor 27 supplies a base current to these transistors 9, 10 and 13. The transistors 9, 10, and 13 are configured by connecting transistors having the same structure (hereinafter referred to as basic transistors) in parallel as necessary, and the mirror ratio is set to 1: A: B.

  In the band gap circuit 22, the first transistor 7 and the first resistor 11 are connected in series between the transistor 9 and the power supply line 25, and the second transistor is connected between the transistor 10 and the power supply line 25. Transistor 8 is connected. The bases of the transistors 7 and 8 are connected in common, and the size ratio of the transistors 7 and 8 is C: 1 (C = 1 in this embodiment as will be described later). The third transistor 28 supplies a base current to the transistors 7 and 8, and its collector is connected to the correction circuit 23 as will be described later.

  The output circuit 15 includes a sixth transistor 13 and a second resistor 14 connected in series with the output terminal 16 interposed between the power supply line 26 and the power supply line 25. As will be described later, the voltage Vout at the output terminal 16 is a voltage that is accurately proportional to the absolute temperature.

  The correction circuit 23 generates a current B / (1 + A) times the base current passed through the transistors 7 and 8 via the transistor 28 and outputs the current to the output terminal 16. The correction circuit 23 is provided between the power supply line 26 and the transistor 28. The current mirror circuit is composed of a connected seventh transistor 29 and an eighth transistor 30 connected between the power supply line 26 and the output terminal 16. The ninth transistor 31 supplies a base current to the transistors 29 and 30. The transistors 29 and 30 are configured by connecting the above-described basic transistors in parallel as necessary, and the mirror ratio is set to 1: B / (1 + A).

  For A, B, and C described above, in principle, A · C ≠ 1 and B ≠ 0 are indispensable conditions. In this embodiment, A is an integer of 2 or more, B is an integer of 1 or more, and C Is set to 1, and A and B are set so that B / (1 + A) is an integer. With this setting, the mirror ratio 1: A: B of the fourth, fifth and sixth transistors 9, 10 and 13 and the mirror ratio 1: B / (1 + A) of the seventh and eighth transistors 29 and 30 are set. Is an integer ratio, and there is an advantage that a desired mirror ratio can be obtained using only the basic transistor. Specifically, (A, B) = (2,3), (2,6), (3,4), (3,8), (4,5), (4,10), etc. are used.

  The starting circuit 24 includes a series circuit of a resistor 32 and a diode 33 connected between the power supply lines 26 and 25, and a backflow preventing diode 34 connected between the anode of the diode 33 and the collector of the transistor 8. ing. The diode 33 is a simple voltage source in which three or more diodes are connected in series. The diode 34 is biased in the forward direction when the power is turned on, so that the band gap circuit 22 is activated. After the activation, the diode 34 is reverse-biased to block the influence on the temperature detection operation.

  FIG. 2 shows an example of use of the temperature detection circuit 21. The A / D conversion circuit 35 A / D converts the voltage Vout output from the temperature detection circuit 21 into a digital value, and a microcomputer (not shown) executes heat generation amount control using the digital value. As described above, the heat generation amount control is a control for continuing the operation of the IC while limiting the heat generation amount in the IC chip to a predetermined value or less. The comparator 36 compares the voltage Vout output from the temperature detection circuit 21 with a reference voltage corresponding to the reference temperature, and outputs a temperature determination signal. This temperature determination signal can be used for determinations such as alarms and overheat protection.

Next, the output voltage Vout of the temperature detection circuit 21 is obtained analytically.
In the following description, the base current of the first transistor 7 is Ib1, the collector current is Ic1, the base current of the second transistor 8 is Ib2, the collector current is Ic2, the collector current of the third transistor 28 is Ic3, and the transistor 7 , 8 is assumed to be Is, the thermal voltage is assumed to be VT, and the resistance values of the first and second resistors 11 and 14 are assumed to be R1 and R2.

The base-emitter voltages VBE1 and VBE2 of the first and second transistors 7 and 8 are expressed by equations (1) and (2), respectively. Here, the thermal voltage VT is expressed by equation (3). k is the Boltzmann constant, T is the absolute temperature, and q is the charge of the electrons.

From the circuit configuration shown in FIG. 1, the relationship between the base-emitter voltages VBE1 and VBE2 of the transistors 7 and 8 is represented by the equation (4). By substituting the formulas (1) and (2) into the formula (4), the formula (5) is obtained.

  Since the base currents of the transistors 9, 10 and 13 flow through the transistor 27 and the base currents of the transistors 7 and 8 flow through the transistor 28, the collector currents Ic1 and Ic2 of the transistors 7 and 8 are in accordance with the mirror ratio. (6) Formula is materialized. Further, since the DC current amplification factors hfe of the transistors 7 and 8 are equal, the equation (7) is also established. Substituting Equations (6) and (7) into Equation (5) yields Equation (8). This equation (8) indicates that a thermal voltage VT is generated in the resistor 11 due to a voltage drop between the collector current Ic1 and the base current Ib1 of the first transistor 7.

Since only the collector current Ic1 of the transistor 7 is taken out to the output circuit 15 via the current mirror circuit, the current of B · Ib1 becomes insufficient. When the correction circuit 23 does not exist, the output voltage Vout is expressed by equation (9). It can be seen that the first term of the equation (9) is a term proportional to the absolute temperature, but the second term is a negative offset voltage. In particular, when the DC current amplification factor hfe of the transistors 7 and 8 is small, the ratio of the base current Ib1 to the collector current Ic1 is large, so that the generated offset voltage is also large. Further, when the base current Ib1 changes due to a temperature change, the offset voltage also changes. Therefore, in the case of the conventional temperature detection circuit 6, it is necessary to adjust the offset voltage and the temperature characteristic slope at the same time. Further, an offset voltage is generated due to the temperature change, and an error occurs in the temperature detection characteristics.

  Therefore, in the temperature detection circuit 21 of the present embodiment, a correction circuit 23 is added to compensate for the offset voltage. Since the transistor 28 supplies the base currents Ib1 and Ib2 of the transistors 7 and 8, the collector current Ic3 is given by equation (10). Since the mirror ratio of the correction circuit 23 is set to 1: B / (1 + A), the correction current Ix output from the correction circuit 23 to the output terminal 16 is expressed by equation (11). As a result, the output voltage Vout of the temperature detection circuit 21 is added with the correction voltage Ix · R2 corresponding to the correction current Ix shown in the equation (11) to the voltage before correction shown in the equation (9). (12) or (13).

  FIG. 3 shows the output voltage characteristic of the temperature detection circuit 21 with a solid line, and the output voltage characteristic of the conventional temperature detection circuit 6 with a broken line. The horizontal axis is the absolute temperature [K], and the vertical axis is the output voltage Vout [V]. As shown in the equation (12) or (13), by adding the correction circuit 23, the negative offset voltage which has existed conventionally is compensated to become zero (or a value very close to zero). I understand.

  According to the present embodiment described above, by adding the correction circuit 23, the offset voltage appearing in the output voltage Vout can be made almost zero. As a result, it is not necessary to adjust the offset voltage in the output characteristic adjustment process, and only the adjustment of the gradient of the temperature characteristic is required, so that a wide range of temperatures can be accurately detected with as little adjustment as possible. The inclination of the temperature characteristic can be easily adjusted by trimming the resistor 11 or 14. Further, since the transistors 27, 28, and 31 are provided, errors due to the flow of the base current can be reduced.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG.
FIG. 4 is a configuration diagram of a temperature detection circuit formed in the IC chip, and the same components as those in FIG. 1 are denoted by the same reference numerals. In this temperature detection circuit 41, A is 1 and C is an integer greater than or equal to 2 (that is, the first transistor 7 is composed of C basic transistors), and A · C ≠ 1 required in principle is satisfied. ing. Also, B is a multiple of 2 so that B / (1 + A) is an integer.

  In this case, the base-emitter voltage VBE1 of the first transistor 7 is expressed by equation (14). Substituting Equation (14) and Equation (2) into Equation (4) described above yields Equation (15). By substituting the above-described equations (6) and (7) into equation (15), equation (16) is obtained. In this embodiment, since C is not 1, there is a term of ln (A · C).

  In the case of the conventional configuration in which the correction circuit 23 does not exist (see FIG. 7), the output voltage Vout is expressed by equation (17) (A = B = 1, C ≠ 1 in the configuration shown in FIG. 7). It can be seen that the first term of the equation (17) is a term proportional to the absolute temperature, but the second term is a negative offset voltage. Therefore, the temperature detection circuit 41 of the present embodiment also compensates for the offset voltage by adding the correction circuit 23 as in the first embodiment. As a result, the output voltage Vout of the temperature detection circuit 41 is added with the correction voltage Ix · R2 corresponding to the correction current Ix shown in the equation (11) to the voltage before correction shown in the equation (17), and finally. It becomes (18) Formula or (19) Formula. As described above, the present embodiment can provide the same operations and effects as those of the first embodiment.

(Other embodiments)
The present invention is not limited to the embodiments described above and shown in the drawings, and can be modified or expanded as follows, for example.
In actual manufacture of the IC, it is preferable to set the mirror ratios 1: A: B and 1: B / (1 + A) to integer ratios, but from the operating principle of the temperature detection circuit 21, it is essential to have an integer ratio. It is not a condition.

  It is not essential that the transistor size ratio C: 1 be an integer ratio. In order to set the transistor size ratio to C: 1, the first transistor is composed of C basic transistors as shown in FIG. The area ratio of the emitter may be C: 1.

When the direct current amplification factor hfe of the transistors 9, 10, 13, 29, and 30 is sufficiently large, the transistors 27 and 31 may be omitted.
If the correction circuit generates a current B / (1 + A) times the base current passed through the first and second transistors 7 and 8 via the third transistor 28 and outputs it to the output terminal 16, Other circuit configurations may be used.
The transistors 9, 10, and 13 may be replaced with MOSFETs.

The block diagram of the temperature detection circuit which shows the 1st Embodiment of this invention Diagram showing usage example of temperature detection circuit Output voltage characteristics of temperature detection circuit FIG. 1 equivalent diagram showing a second embodiment of the present invention FIG. 1 equivalent view showing the first prior art FIG. 1 equivalent diagram showing the second prior art FIG. 1 equivalent view showing the third prior art

Explanation of symbols

  7, 8, 28, 9, 10, 13, 29, 30, 31, 27 are the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth Transistors 11 and 14 are first and second resistors, 15 is an output circuit, 16 is an output terminal, 21 and 41 are temperature detection circuits, 22 is a band gap circuit, 23 is a correction circuit, 24 is a start-up circuit, 25, Reference numeral 26 denotes first and second power supply lines.

Claims (6)

A first transistor having an emitter connected to a first power supply line via a first resistor; a first transistor having a base connected to the first transistor and an emitter directly connected to the first power supply line; Two transistors, a third transistor for supplying a base current to the first and second transistors, a fourth transistor connected between a second power supply line and the first and second transistors, respectively. A size ratio of the first transistor to the second transistor is set to C: 1, and a ratio of current flowing through the fourth and fifth transistors is set to 1: A. A band gap circuit;
A sixth transistor and a second resistor connected with an output terminal sandwiched between the second power line and the first power line, and a current ratio flowing through the fourth and sixth transistors is 1: an output circuit set to B (B ≠ 0);
And a correction circuit that generates a current B / (1 + A) times the base current passed through the first and second transistors via the third transistor and flows the current to the output terminal. Temperature detection circuit.   The correction circuit includes a seventh transistor connected between the second power supply line and the third transistor, and an eighth transistor connected between the second power supply line and the output terminal. 2. The temperature detection circuit according to claim 1, wherein the temperature detection circuit is constituted by a current mirror circuit comprising:   3. The temperature detection circuit according to claim 2, wherein the correction circuit includes a ninth transistor that supplies a base current to the seventh and eighth transistors.   A current mirror circuit is constituted by the fourth, fifth, and sixth transistors, and a tenth transistor that supplies a base current to the fourth, fifth, and sixth transistors is provided. Item 4. The temperature detection circuit according to any one of Items 1 to 3.   A, B and C are set such that A and B are integers of 1 or more, B / (1 + A) is an integer, and A · C is other than 1. 5. The temperature detection circuit according to any one of 4 above.   6. The temperature detection circuit according to claim 1, further comprising a start circuit for the band gap circuit.

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