JP2006066459A - Temperature detection circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a variation in the threshold voltage of a transistor from having an effect on a detected temperature. <P>SOLUTION: This temperature detection circuit comprises a temperature detection element D3 where a forward voltage varies as a temperature varies, a first FETM 3 connected in series with a temperature detection element D3 and lowering a voltage between gate-source electrodes, a second FETM 2 having a threshold voltage substantially identical to that of the first FETM 3 and current density per unit area higher than that of the first FETM 3 and performing temperature detection based on the fact whether the voltage between the gate-source electrodes is higher than the total voltage drop of the temperature detection element D3 and the first FETM 3 or not, and a circuit M1 for outputting a signal indicative of whether a threshold temperature is exceeded or not based on the operation of the second FETM 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to temperature detection and overheating prevention in a semiconductor device, and more particularly to a temperature detection circuit that detects an abnormal temperature and outputs a detection signal.

  In order to prevent overheating of semiconductor elements such as power transistors and power MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), a temperature detection circuit for detecting the temperature of these semiconductor elements is provided, and the power transistor according to the output of the temperature detection circuit Control such as turning off the power MOSFET is performed.

  FIG. 10 is a circuit diagram showing an example of an overheat detection circuit using a MOSFET. In FIG. 10, the power supply voltage Vdd is supplied to the power supply terminal VD. The power supply terminal VD is connected to one terminal of each of the constant current sources 1 and 2. The constant current sources 1 and 2 supply constant currents I1 and I2, respectively.

  The other terminal of the constant current source 2 is connected to the anode of the diode D2A. The cathode of the diode D2A is connected to the anode of the diode D2B. The cathode of the diode D2B is connected to the ground.

  The other terminal of the constant current source 1 is connected to the drain electrode of the N-type MOSFET M1. The gate electrode of the MOSFET M1 is connected to a connection point between the constant current source 2 and the diode D2A. The source electrode of the MOSFET M1 is connected to the ground.

  The output terminal OUT is connected to a connection point between the constant current source 1 and the drain electrode of the MOSFET M1. The output terminal OUT outputs an output signal Vout as a temperature detection result.

  In the overheat detection circuit shown in FIG. 10, overheat detection is performed by comparing the sum of the forward voltage of the diode D2A and the forward voltage of the diode D2B with the threshold voltage of the MOSFET M1.

  However, the variation in threshold voltage of MOSFET M1 is larger than the change in forward voltage of the diode due to temperature change. For this reason, the variation in overheat detection temperature is determined by the variation width of the threshold voltage. In the overheat detection circuit shown in FIG. 10, the forward voltage VF × 2 of the diode is compared with the threshold voltage Vth of the MOSFET M1. For example, when the variation range of the threshold voltage of the MOSFET M1 is 1 ± 0.2 V and the temperature characteristic of the diode is −2 mV / ° C., the overheat detection temperature varies by ± 50 ° C.

  In order to suppress the characteristic variation of the overheat detection, it is necessary to strictly manage the characteristic variation of the single element, which increases the manufacturing cost.

As a related technique of this type, an overheat detection circuit that uses a comparator to reduce variation in detection temperature is disclosed (see Patent Document 1).
Japanese Patent Laid-Open No. 11-17110

  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 preventing an influence on a detection temperature due to variations in threshold voltages of transistors.

  A temperature detection circuit according to a first aspect of the present invention includes a temperature detection element in which a forward voltage changes with a temperature change, and is connected in series to the temperature detection element and drops a voltage component between a gate and a source electrode. A first FET that has a threshold voltage substantially the same as that of the first FET, a current density per unit area greater than that of the first FET, and a voltage between a gate-source electrode and the first FET. A second FET that performs temperature detection based on whether or not the total voltage drop with respect to the 1 FET is equal to or greater, and an output that outputs whether or not the temperature is equal to or greater than a threshold temperature based on the operation of the second FET. Circuit.

  According to the present invention, it is possible to provide a temperature detection circuit that can prevent the detection temperature from being affected by variations in threshold voltages of transistors.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, elements having the same function and configuration are denoted by the same reference numerals, and redundant description will be given only when necessary.

(First embodiment)
FIG. 1 is a circuit diagram of an overheat detection circuit according to the first embodiment of the present invention. A power supply voltage Vdd is supplied to the power supply terminal VD. The power supply terminal VD is connected to one terminal of each of the constant current sources 1 to 3. The constant current sources 1, 2, and 3 supply constant currents I1, I2, and I3, respectively.

  The other terminal of the constant current source 3 is connected to one terminal of the temperature detection element D3. The temperature detection element D3 has a negative temperature characteristic. Specifically, the forward voltage (VF) of the temperature detection element D3 changes with a temperature change. Further, the forward voltage (VF) of the temperature detection element D3 decreases as the temperature increases.

  The other terminal of the temperature detection element D3 is connected to the drain electrode of the N-type MOSFET M3. The gate electrode and the source electrode of MOSFET M3 are connected. The source electrode of the MOSFET M3 is connected to the ground.

  The other terminal of the constant current source 2 is connected to the drain electrode of the N-type MOSFET M2. The gate electrode of the MOSFET M2 is connected to a connection point between the constant current source 3 and the temperature detection element D3. The source electrode of the MOSFET M2 is connected to the ground.

  The other terminal of the constant current source 1 is connected to the drain electrode of the N-type MOSFET M1. The gate electrode of the MOSFET M1 is connected to the connection point between the constant current source 2 and the drain electrode of the MOSFET M2. The source electrode of the MOSFET M1 is connected to the ground.

  The output terminal OUT is connected to a connection point between the constant current source 1 and the drain electrode of the MOSFET M1. The output terminal OUT outputs an output signal Vout as a temperature detection result. The constant current source 1 and the MOSFET M1 constitute an output circuit. The constant current sources 2 and 3, the MOSFETs M2 and M3, and the temperature detection element D3 constitute a temperature detection circuit.

  Incidentally, the current density (or current value) per unit area of the MOSFET M2 is set larger than the current density per unit area of the MOSFET M3. The unit area refers to the unit area of the MOSFET channel. Accordingly, the relationship between the gate-source voltage Vgs (M2) of the MOSFET M2 and the gate-source voltage Vgs (M3) of the MOSFET M3 is as follows.

Vgs (M2)> Vgs (M3)
As a method of setting the current density having the above relationship, when “I2 = I3”, the dimension W / L (M2) of the MOSFET M2 and the dimension W / L (M3) of the MOSFET M3 are set as follows. . W represents the channel width and L represents the channel length.

W / L (M2) <W / L (M3)
If the dimensions of MOSFET M2 and MOSFET M3 are equal, “I2> I3” is set. Alternatively, the current density may be set by changing both the constant currents I2 and I3 and the dimension of the MOSFET.

  Next, the operation of the overheat detection circuit configured as described above will be described. In the overheat detection circuit shown in FIG. 1, the temperature detection element D3 and the MOSFET M3 are connected in series between the gate and source electrodes of the MOSFET M2. That is, the voltage Vgs (M2) is determined by the voltage Vgs (M3) and the voltage drop VD3 generated by the temperature detection element D3. Therefore, overheat detection can be performed by comparing the voltage ΔVgs (= Vgs (M2) −Vgs (M3)) with the voltage VD3.

(1) When ΔVgs <VD3 A voltage sufficient to turn on the MOSFET M2 is supplied between the gate and source electrodes of the MOSFET M2. Therefore, the MOSFET M2 can sufficiently flow the constant current I2. As a result, the gate voltage of the MOSFET M1 becomes substantially zero, and the MOSFET M1 is turned off. Therefore, a high level (power supply voltage Vdd) output signal Vout is output from the terminal OUT.

(2) When ΔVgs ≧ VD3 A voltage sufficient to turn on the MOSFET M2 is not supplied between the gate and source electrodes of the MOSFET M2. Therefore, the MOSFET M2 cannot sufficiently flow the constant current I2. As a result, the gate voltage of the MOSFET M1 rises to the power supply voltage Vdd, and the MOSFET M1 is turned on. Therefore, the low level (0 V) output signal Vout is output from the terminal OUT.

  FIG. 2 is a diagram showing the relationship between temperature and voltage in the overheat detection circuit shown in FIG. The horizontal axis represents temperature (° C.) and the vertical axis represents voltage (V).

  The overheat detection temperature Ttsd (° C.) is calculated by the following equation.

Ttsd = (VD3 (@ 25 ° C.) − VD3 (@ ΔVgs = VD3)) / (dVD3 / dT) +25
“@” Represents a condition. “VD3 (@ 25 ° C.)” represents the voltage VD3 when the temperature is 25 ° C. “VD3 (@ ΔVgs = VD3)” represents the voltage VD3 when ΔVgs = VD3. In the following, “@” has the same meaning as described above. “DVD3 / dT” represents the amount of change in voltage VD3 per 1 ° C.

  In FIG. 2, the gate-source voltage Vgs (M2) of the MOSFET M2 decreases as the temperature increases. This is because the temperature detection element D3 has negative temperature characteristics. The overheat detection circuit outputs an overheat detection result when “ΔVgs = VD3”. That is, the overheat detection circuit outputs a low level output signal Vout.

  Next, variations in the threshold value of the overheat detection temperature will be described.

  The drain current Id of the MOSFET is expressed by the following equation.

κ = μ × Cox
Vth represents the threshold voltage of the MOSFET, μ represents the mobility, and Cox represents the gate oxide film capacitance.

  The gate-source voltage Vgs is expressed by the following equation.

  Therefore, the voltage ΔVgs (= Vgs (M2) −Vgs (M3)) is expressed by the following equation.

  As can be seen from this relational expression, the threshold voltage Vth of the MOSFET does not affect the calculation of the voltage ΔVgs. Therefore, compared with the conventional case where overheat detection is simply performed by the gate-source voltage Vgs of the MOSFET M1, the detection temperature variation width can be reduced by the amount corresponding to the variation factor of the threshold voltage Vth. .

  As described above in detail, the present embodiment includes the constant current sources 2 and 3, the MOSFETs M <b> 2 and M <b> 3, and the temperature detection element D <b> 3 having negative temperature characteristics as the temperature detection circuit. A temperature detection element D3 and a MOSFET M3 in which a drain electrode and a gate electrode are connected are connected in series between the gate and source electrodes of the MOSFET M2. The current density per unit area of MOSFET M2 is set larger than the current density per unit area of MOSFET M3.

  Therefore, according to the present embodiment, it is possible to prevent the influence of the threshold voltage of the MOSFET on the detected temperature. As a result, since it is not necessary to strictly manage the characteristic variation of the MOSFET, the manufacturing cost can be reduced.

(Second Embodiment)
The second embodiment is a more specific configuration example of the overheat detection circuit shown in the first embodiment. That is, a diode is used as a temperature detecting element having negative temperature characteristics, and a constant current source is formed by a P-type MOSFET and a resistor.

  FIG. 3 is a circuit diagram of an overheat detection circuit according to the second embodiment of the present invention. The constant current source includes P-type MOSFETs M1C, M2C, M3C, M4C, and a resistor R4. The power supply terminal VD is connected to the source electrodes of the P-type MOSFETs M1C, M2C, M3C, and M4C, respectively. The gate electrodes of the MOSFETs M1C, M2C, and M3C are connected to one terminal of the resistor R4.

  The gate electrode and the drain electrode of MOSFET M4C are connected. The drain electrode of the MOSFET M4C is connected to one terminal of the resistor R4. The other terminal of the resistor R4 is connected to the ground.

  The drain electrode of MOSFET M1C is connected to the drain electrode of MOSFET M1. MOSFET M1C supplies constant current I1 to MOSFET M1. The drain electrode of MOSFET M2C is connected to the drain electrode of MOSFET M2. MOSFET M2C supplies constant current I2 to MOSFET M2.

  In the present embodiment, the diode D3 is used as the temperature detection element having negative temperature characteristics. The drain electrode of MOSFET M3C is connected to the anode of diode D3. MOSFET M3C supplies a constant current I3 to diode D3. The cathode of the diode D3 is connected to the drain electrode of the MOSFET M3.

  Incidentally, the current density per unit area of the MOSFET M2 is set larger than the current density per unit area of the MOSFET M3. This can be done by setting the dimensions of the MOSFET M2C and MOSFET M3C constituting the constant current source. If the dimensions of MOSFET M2 and MOSFET M3 are equal, “I2> I3” is set.

  Even if the overheat detection circuit is configured in this manner, the same effect as in the first embodiment can be obtained. In addition, since the constant current source can be formed of a MOSFET, the circuit area can be reduced and the manufacturing cost can be reduced.

The constant current source is not limited to the above circuit, and may be any circuit that can supply a constant current.

(Third embodiment)
In the third embodiment, a diode D3 is used as a temperature detection element having negative temperature characteristics, and resistors R1 to R3 are used as constant current sources 1 to 3, and an overheat detection circuit is configured.

  FIG. 4 is a circuit diagram of an overheat detection circuit according to the third embodiment of the present invention. One terminal of each of the resistors R1, 2, and 3 is connected to the power supply terminal VD. The other terminal of the resistor R1 is connected to the drain electrode of the MOSFET M1. The resistor R1 is connected to the drain electrode of the MOSFET M1. The resistor R1 supplies a constant current I1 to the MOSFET M1.

  The other terminal of the resistor R2 is connected to the drain electrode of the MOSFET M2. The resistor R2 supplies a constant current I2 to the MOSFET M2. The other terminal of the resistor R3 is connected to the anode of the diode D3. The resistor R3 supplies a constant current I3 to the diode D3.

  The constant current I1 is expressed by the following formula.

I1 = (Vdd−Vout (@ ΔVgs = VD3)) / R1
The constant current I2 is expressed by the following formula.

I2 = (Vdd−Vgs (M1) (@ I1)) / R2
The constant current I3 is expressed by the following formula.

I3 = (Vdd−VD3−Vgs (M3) (@ I3)) / R3
When the constant currents I1 to I3 are set, the constant current source may be configured by combining a resistor and another constant current circuit.

  Even if the overheat detection circuit is configured in this manner, the same effect as in the first embodiment can be obtained. In addition, the manufacturing process can be simplified as compared with the second embodiment.

(Fourth embodiment)
In the fourth embodiment, an overheat detection circuit is configured such that the current settings of the constant currents I2 and I3 can be set by a similar method.

  FIG. 5 is a circuit diagram of an overheat detection circuit according to the fourth embodiment of the present invention. In FIG. 5, a diode D2 is connected in the forward direction between a resistor R2 and the drain electrode of the MOSFET M2. That is, the anode of the diode D2 is connected to the resistor R2, and the cathode of the diode D2 is connected to the drain electrode of the MOSFET M2. Other configurations are the same as those of the third embodiment.

  The constant current I1 is expressed by the following formula.

I1 = (Vdd−Vout (@ ΔVgs = VD3)) / R1
The constant current I2 is expressed by the following formula.

I2 = (Vdd−VD2−Vgs (M1) (@ I1)) / R2
The constant current I3 is expressed by the following formula.

I3 = (Vdd−VD3−Vgs (M3) (@ I3)) / R3
As can be seen from the above equations, the constant currents I2 and I3 are calculated from similar equations including the forward voltage of the diode. Thereby, the current value setting of the constant currents I2 and I3 can be facilitated. In addition, although this embodiment demonstrated by the example which added the diode D2 to the said 3rd Embodiment, of course, the same effect can be acquired even if it applies to the said 1st and 2nd embodiment.

(Fifth embodiment)
FIG. 6 is a circuit diagram of an overheat detection circuit according to the fifth embodiment of the present invention. In FIG. 6, resistors R2A and R2B are connected between the anode and cathode of the diode D2. Resistors R3A and R3B are connected between the anode and cathode of the diode D3. A gate electrode of MOSFET M2 is connected to a connection point between resistors R3A and R3B.

  In the overheat detection circuit configured as described above, the voltage VD3 is divided by the resistors R3A and R3B. That is, the voltage Vgs (M2) is set by the voltage of the resistor R3B and the voltage Vgs (M3).

  This facilitates temperature adjustment when setting the overheat detection temperature Ttsd. Further, since the voltage ΔVgs becomes small, the overheat detection temperature Ttsd can be set with a small voltage setting. Therefore, since the circuit element can be reduced, the chip size can be reduced.

  By the way, in order to realize the present embodiment, it is necessary to satisfy the following condition.

  If this condition is not satisfied, no current flows through the diode D3. Therefore, the temperature characteristic of the diode D3 is not reflected in the voltage Vgs (M2) of the MOSFET M2, and the temperature cannot be detected.

  The diode to which the dividing resistor is added may be only D3. Moreover, the same effect can be acquired even if division resistance is added to the said 1st-3rd embodiment.

(Sixth embodiment)
The sixth embodiment is a configuration example in which a hysteresis circuit is added to the overheat detection circuit shown in the fifth embodiment.

  FIG. 7 is a circuit diagram of an overheat detection circuit according to the sixth embodiment of the present invention. In FIG. 7, a hysteresis circuit is connected in parallel between the drain and source electrodes of the MOSFET M2. This hysteresis circuit is composed of N-type MOSFETs M2A and M2B.

  The drain electrode of MOSFET M2A is connected to the drain electrode of MOSFET M2. The gate electrode of MOSFET M2A is connected to the gate electrode of MOSFET M2. The back gate electrode (substrate gate electrode) of MOSFET M2A is connected to the ground. The source electrode of MOSFET M2A is connected to the drain electrode of MOSFET M2B. The gate electrode of the MOSFET M2B is connected to the output terminal OUT. The source electrode of MOSFET M2B is connected to the ground.

  The operation of the overheat detection circuit configured as described above will be described. When the temperature is lower than the overheat detection temperature Ttsd, the output signal Vout is at a high level, so that the MOSFET M2B is on. Therefore, the dimension of the MOSFET to which the constant current I2 is supplied is a dimension that combines the MOSFETs M2 and M2A. Thereby, the current density of the MOSFET to which the constant current I2 is supplied can be increased.

  On the other hand, when the temperature is higher than the overheat detection temperature Ttsd, the output signal Vout is at a low level, so the MOSFET M2B is off. Therefore, the dimension of the MOSFET to which the constant current I2 is supplied is the dimension of only the MOSFET M2. As a result, the current density of the MOSFET to which the constant current I2 is supplied becomes smaller than when the temperature is lower than the overheat detection temperature Ttsd.

  The gate-source voltage of the MOSFET M2 when the output signal Vout is low level is Vgs (M2) (@ Vout = L), and the gate-source voltage of the MOSFET M2 when the output signal Vout is high level is Vgs (M2) ( (@ Vout = H), these relationships are expressed by the following equation.

  By changing the dimension of the MOSFET to which the constant current I2 is supplied based on the voltage of the output signal Vout, the MOSFET M2 at the time of detection (when the temperature is rising) and at the time of recovery (when the temperature is falling) The gate-source voltage Vgs can be changed. That is, the MOSFET M2 can have hysteresis.

  By adding a hysteresis circuit in this manner, fluctuation or oscillation of the output signal Vout near the overheat detection temperature Ttsd can be prevented.

  Note that the configuration of the hysteresis circuit described above is merely an example, and the present invention is not limited to this. Further, by configuring the overheat detection circuit so that the constant current I2 has hysteresis, the same effect as described above can be obtained.

  Further, even if a hysteresis circuit is added to the first to fourth embodiments, the same effect as that of the present embodiment can be obtained.

(Seventh embodiment)
In the seventh embodiment, the overheat detection circuit is configured so as to set the voltage Vgs of the MOSFETs M2 and M3 using the back gate effect of the MOSFET.

  FIG. 8 is a circuit diagram of an overheat detection circuit according to the seventh embodiment of the present invention. In FIG. 8, a power source 5 is connected between the back gate and the source electrode of the MOSFET M2. The power source 5 supplies a voltage V2 between the back gate and the source electrode of the MOSFET M2. A power source 6 is connected between the back gate and the source electrode of the MOSFET M3. The power source 6 supplies a voltage V3 between the back gate and the source electrode of the MOSFET M2.

  The operation of the overheat detection circuit configured as described above will be described. By adding the power supply 5, the voltage Vgs (M2) of the MOSFET M2 can be arbitrarily set. Further, by adding the power source 6, it is possible to arbitrarily set the voltage Vgs (M3) of the MOSFET M3.

  Therefore, even when the MOSFETs M2 and M3 have the same dimensions, the current densities of the MOSFETs M2 and M3 can be changed by setting the voltages V2 and V3. Thereby, the same effect as the first embodiment can be obtained.

  Note that the back gate effect may be applied to the first to sixth embodiments.

(Eighth embodiment)
In the eighth embodiment, the output circuit and the temperature detection circuit are configured by P-type MOSFETs.

  FIG. 9 is a circuit diagram of an overheat detection circuit according to the eighth embodiment of the present invention. A power supply voltage Vdd is supplied to the power supply terminal VD. The power supply terminal VD is connected to the source electrodes of the P-type MOSFETs PM1, PM2, and PM3, respectively.

  The gate electrode and the drain electrode of MOSFET PM3 are connected. The drain electrode of the MOSFET PM3 is connected to one terminal of the temperature detection element D3. The other terminal of the temperature detection element D3 is connected to one terminal of the constant current source 3.

  The gate electrode of MOSFET PM2 is connected to the other terminal of temperature detection element D3. The drain electrode of the MOSFET PM2 is connected to one terminal of the constant current source 2.

  The gate electrode of MOSFET PM1 is connected to the drain electrode of MOSFET PM2. The drain electrode of the MOSFET PM1 is connected to one terminal of the constant current source 1. The other terminals of the constant current sources 1, 2, and 3 are connected to the ground.

  The output terminal OUT is connected to a connection point between the constant current source 1 and the drain electrode of the MOSFET PM1. The output terminal OUT outputs an output signal Vout as a temperature detection result. The constant current source 1 and the MOSFET PM1 constitute an output circuit. The constant current sources 2 and 3, the MOSFETs PM2 and 3, and the temperature detection element D3 constitute a temperature detection circuit.

  Similarly to the first embodiment, the current density per unit area of the MOSFET PM2 is set larger than the current density per unit area of the MOSFET PM3.

  Even if the overheat detection circuit is configured in this manner, the same effect as in the first embodiment can be obtained. In the overheat detection circuit shown in the first to seventh embodiments, the overheat detection circuit may be configured by changing the N-type MOSFET to the P-type MOSFET.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.

1 is a circuit diagram of an overheat detection circuit according to a first embodiment of the present invention. The figure which shows the relationship between the temperature and voltage in the overheat detection circuit shown in FIG. The circuit diagram of the overheat detection circuit which concerns on the 2nd Embodiment of this invention. The circuit diagram of the overheat detection circuit which concerns on the 3rd Embodiment of this invention. The circuit diagram of the overheat detection circuit which concerns on the 4th Embodiment of this invention. The circuit diagram of the overheat detection circuit which concerns on the 5th Embodiment of this invention. The circuit diagram of the overheat detection circuit which concerns on the 6th Embodiment of this invention. The circuit diagram of the overheat detection circuit which concerns on the 7th Embodiment of this invention. The circuit diagram of the overheat detection circuit which concerns on the 8th Embodiment of this invention. The circuit diagram which shows an example of the overheat detection circuit which uses MOSFET.

Explanation of symbols

  VD: power supply terminal, D2, D2A, D2B, D3 ... diode, M1, M2, M3, M2A, M2B ... N-type MOSFET, OUT ... output terminal, D3 ... temperature detection element, M1C, M2C, M3C, M4C, PM1, PM2, PM3... P-type MOSFET, R1, R2, R3, R4, R2A, R2B, R3A, R3B... Resistor, 1, 2, 3.

Claims (5)

A temperature detection element whose forward voltage changes with temperature change;
A first FET (Field Effect Transistor) that is connected in series to the temperature detection element and drops a voltage between the gate and the source electrode;
The first FET has substantially the same threshold voltage, the current density per unit area is larger than that of the first FET, and the voltage between the gate and source electrodes is a voltage drop between the temperature detection element and the first FET. A second FET that performs temperature detection based on whether or not the total of
An output circuit that outputs a signal indicating whether the temperature is equal to or higher than a threshold temperature based on the operation of the second FET;
A temperature detection circuit comprising:   The temperature detection circuit according to claim 1, wherein the temperature detection element has a negative temperature characteristic.   The temperature detection circuit according to claim 1, wherein a ratio of a channel width to a channel length of the second FET is smaller than that of the first FET. A first constant current circuit connected to a power supply voltage and supplying a first current to the temperature detection element;
A second constant current circuit connected to the power supply voltage and supplying a second current to the second FET;
The temperature detection circuit according to claim 1, wherein the second current is larger than the first current.   Hysteresis connected to the second FET so that the current density per unit area of the second FET changes between when the temperature rises to the threshold temperature and when the temperature falls to the threshold temperature. The temperature detection circuit according to claim 1, further comprising a circuit.

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