JP7056595B2 - Temperature detector - Google Patents

Description

The present invention relates to a temperature detection device that detects a temperature.

Conventionally, a temperature detecting device for detecting the temperature of a switching element such as an IGBT provided in a power supply circuit or the like of a vehicle is known (Patent Document 1). In the temperature detection device of Patent Document 1, resistors are connected to both ends of the temperature sensitive diode (detection element) in order to suppress common mode noise.

Japanese Unexamined Patent Publication No. 2010-249687

By the way, in the system of Patent Document 1, the ground to which the low voltage system circuit such as the comparison circuit is connected and the ground to which the high voltage system circuit such as the power supply unit is connected are insulated. However, some vehicles do not have a circuit that distinguishes between a low-voltage system and a high-voltage system, and have a system connected to the same ground. In this case, there is a problem that the influence of the normal mode noise (differential mode noise) becomes large and the temperature detection accuracy is lowered.

The present invention has been made in view of the above circumstances, and a main object thereof is to provide a rotary electric machine capable of suppressing the influence of noise and improving the temperature detection accuracy.

The first means for solving the above-mentioned problems are a temperature-sensitive diode whose forward voltage changes according to the temperature of the detection target, a reference power supply that outputs a reference voltage, a forward voltage of the temperature-sensitive diode, and the above. In a temperature detection device including a comparison circuit that compares the reference voltage of the reference power supply and outputs a detection result, the first input terminal of the comparison circuit is the reference power supply and the anode side terminal of the temperature sensitive diode. The second input terminal is connected to the second electric path provided between the cathode side terminal and the ground terminal of the temperature sensitive diode, and is connected to the first electric path provided between the two. The comparison circuit compares the forward voltage of the temperature sensitive diode with the reference voltage of the reference power supply based on the voltage input from the first input terminal and the voltage input from the second input terminal. A passive element is provided at least on the first electric path so that a current is less likely to flow in the first electric path as compared with the second electric path.

The normal mode noise may flow from the circuit to which the detection target is connected to the first electric path or the second electric path of the temperature detection device via the stray capacitance or the like. Then, due to the diode characteristics of the temperature-sensitive diode, the forward voltage (that is, the detection result) is larger when the current flows in the opposite direction than when the current flows in the forward direction with respect to the temperature-sensitive diode. It is known to have an impact.

Therefore, a passive element is provided at least on the first electric path so that the current is less likely to flow in the first electric path as compared with the second electric path. As a result, it is possible to suppress the flow of noise current in the opposite direction to the temperature-sensitive diode and facilitate the flow in the forward direction. Therefore, the influence of normal mode noise can be suppressed.

The second means for solving the above-mentioned problems are a temperature-sensitive diode whose forward voltage changes according to the temperature of the detection target, a reference power supply that outputs a reference voltage, a forward voltage of the temperature-sensitive diode, and the above. In a temperature detection device including a comparison circuit that compares the reference voltage of the reference power supply and outputs a detection result, the first input terminal of the comparison circuit is the reference power supply and the anode side terminal of the temperature sensitive diode. The second input terminal is connected to the second electric path provided between the cathode side terminal and the ground terminal of the temperature sensitive diode, and is connected to the first electric path provided between the two. The comparison circuit compares the forward voltage of the temperature sensitive diode with the reference voltage of the reference power supply based on the voltage input from the first input terminal and the voltage input from the second input terminal. The wiring resistance of the first electric path and the second electric path is set so that the current does not easily flow in the first electric path as compared with the second electric path.

As a result, it is possible to suppress the flow of noise current in the opposite direction to the temperature-sensitive diode and facilitate the flow in the forward direction. Therefore, the influence of normal mode noise can be suppressed.

Circuit configuration diagram of the in-vehicle power supply system. Circuit configuration diagram of the temperature detector. The figure which shows the inflow path of a noise current. The figure which shows the diode characteristic. The circuit block diagram of the temperature detection device in another example. The circuit block diagram of the temperature detection device in another example.

Hereinafter, embodiments embodying the present invention will be described with reference to the drawings. In the present embodiment, in a vehicle (hybrid vehicle) traveling by using an engine (internal combustion engine) and a motor as a drive source, a temperature detection device 20 used in an in-vehicle power supply system 10 that supplies electric power to various devices of the vehicle is embodied. It is supposed to be done.

As shown in FIG. 1, the in-vehicle power supply system 10 is a dual power supply system including a lead storage battery 11 and a lithium ion storage battery 12, and the storage batteries 11 and 12 are connected to the starter 16 and the electric loads 13 and 15. Power can be supplied. Further, each of the storage batteries 11 and 12 can be charged by the rotary electric machine 14. In this system, the lead storage battery 11 and the lithium ion storage battery 12 are connected in parallel to the rotary electric machine 14, and the lead storage battery 11 and the lithium ion storage battery 12 are connected in parallel to the electric load 15.

The lead storage battery 11 is a well-known general-purpose storage battery. On the other hand, the lithium ion storage battery 12 is a high-density storage battery having a smaller power loss in charging / discharging, a higher output density, and a higher energy density than the lead storage battery 11. The rated voltage of each of these storage batteries 11 and 12 is the same, for example, 12V.

Although a specific description by illustration is omitted, the lithium ion storage battery 12 is housed in a storage case and is configured as a battery unit U integrated with a substrate. In FIG. 1, the battery unit U is shown surrounded by a broken line. The battery unit U has external terminals P0, P1 and P2, of which a lead storage battery 11, a starter 16 and an electric load 13 are connected to the external terminal P0, and a rotary electric machine 14 is connected to the external terminal P1 to be external. The electric load 15 is connected to the terminal P2. The starter 16 is used when starting the engine.

The rotary electric machine 14 is a generator with a motor function having a three-phase AC motor and an inverter as a power conversion device, and is configured as an ISG (Integrated Starter Generator) integrated with mechanical and electrical power. The rotary electric machine 14 has a power generation function of generating power (regenerative power generation) by rotating an engine output shaft or an axle, and a power running function of applying a rotational force to the engine output shaft. The rotary electric machine 14 supplies the generated power to the storage batteries 11 and 12 and the electric load 15.

The electric load 15 includes a constant voltage load in which the voltage of the supplied power is required to be constant or fluctuate within a predetermined range. The electric load 15 can be said to be a protected load. Further, it can be said that the electric load 15 is a load to which a power failure is not allowed. Specific examples of the electric load 15 which is a constant voltage required load include various ECUs such as a navigation device, an audio device, a meter device, and an engine ECU. The electric load 15 may include a traveling system actuator such as an electric steering device or a braking device.

The electric load 13 is a general electric load other than the constant voltage required load. Specific examples of the electric load 13 include a seat heater, a heater for a defroster of a rear window, a headlight, a wiper of a front window, a blower fan of an air conditioner, and the like.

Next, the battery unit U will be described. The battery unit U is provided with an electric path L1 connecting the external terminals P0 and P1 and an electric path L2 connecting the connection point N1 on the electric path L1 and the lithium ion storage battery 12 as an electric path in the unit. .. Of these, the switch module SW1 is provided in the electric path L1, and the switch module SW2 is provided in the electric path L2. The generated power of the rotary electric machine 14 is supplied to the lead storage battery 11 and the lithium ion storage battery 12 via the electric paths L1 and L2.

Further, in the battery unit U of the present embodiment, in addition to the electric paths L1 and L2, the connection point N2 (the point between the external terminal P0 and the switch module SW1) on the electric path L1 and the external terminal P2 are connected. It has an electrical path L4. The electric path L4 forms a path that enables power to be supplied from the lead storage battery 11 to the electric load 15. A switch module SW4 is provided in the electric path L4 (specifically, between the connection point N2- and the connection point N4).

Further, in the battery unit U, the connection point N3 of the electric path L2 (the point between the switch module SW2 and the lithium ion storage battery 12) and the connection point N4 on the electric path L4 (the point between the switch module SW4 and the external terminal P2). ) And an electric path L3 connecting the two. The electric path L3 forms a path that enables power to be supplied from the lithium ion storage battery 12 to the electric load 15. A switch module SW3 is provided in the electric path L3 (specifically, between the connection points N3- and the connection points N4).

Further, as shown in FIG. 2, each switch module SW1 to SW4 includes semiconductor switches S1 and S2 as a set of two switching elements, respectively. FIG. 2 illustrates the switch module SW1. The semiconductor switches S1 and S2 are MOSFETs, and the parasitic diodes of the two sets of MOSFETs are connected in series so as to be opposite to each other.

The battery unit U includes a control circuit 51 that controls each switch module SW1 to SW4. The control circuit 51 is composed of a microcomputer including a CPU, ROM, RAM, an input / output interface, and the like. As a specific example of the control circuit 51, a BMU (battery management device, battery management unit) or the like can be considered.

The control circuit 51 controls the switch modules SW1 to SW4 and the like based on the storage state and the like of the storage batteries 11 and 12. For example, the control circuit 51 calculates the SOC (residual capacity: State Of Charge) of the lithium ion storage battery 12. Then, the control circuit 51 controls the switch modules SW1 to SW4 so that the SOC is maintained within a predetermined range of use, and controls the charging and discharging of the lead storage battery 11 and the lithium ion storage battery 12. That is, the control circuit 51 selectively uses the lead storage battery 11 and the lithium ion storage battery 12 to charge and discharge. As a result, the control circuit 51 functions as a switch control unit that controls the open / closed state of each switch module SW1 to SW4.

Further, each switch module SW1 to SW4 is provided with a temperature detecting device 20 for detecting the temperature. More specifically, a temperature detection device 20 is provided for each of the semiconductor switches S1 and S2 constituting the switch modules SW1 to SW4. Here, the temperature detection device 20 will be described.

The temperature detection device 20 outputs a signal corresponding to the temperature of the semiconductor switches S1 and S2 to be detected. The temperature detection device 20 includes a temperature-sensitive diode 21 whose forward voltage changes according to the temperature to be detected, a reference power supply 22 that outputs a reference voltage, a forward voltage of the temperature-sensitive diode 21, and a reference voltage of the reference power supply 22. A comparison circuit 23, which compares with and outputs a detection result, is provided.

The temperature sensitive diode 21 is an element whose forward voltage changes depending on the temperature of the detection target. A plurality of temperature sensitive diodes 21 are provided and are connected in series. These temperature-sensitive diodes 21 are arranged in the vicinity of the semiconductor switches S1 and S2 to be detected, and are integrally resin-molded together with the semiconductor switches S1 and S2 to form the switch modules SW1 to SW4.

The anode terminal of the temperature sensitive diode 21 arranged at one end of the plurality of temperature sensitive diodes 21 is connected to the reference power supply 22 via the first electric path L21. The first input terminal 23a of the comparison circuit 23 is connected to the connection point N21 in the first electric path L21. That is, the first input terminal 23a of the comparison circuit 23 is connected to the first electric path L21 provided between the reference power supply 22 and the anode-side terminal of the temperature-sensitive diode 21.

Further, the cathode terminal of the temperature sensitive diode 21 arranged at the other end of the plurality of temperature sensitive diodes 21 is connected to the ground terminal GND via the second electric path L22. This ground terminal GND is common to the ground terminal GND of the battery unit U, the rotary electric machine 14, and the like. For example, the temperature detecting device 20 and other devices such as the battery unit U are grounded to the vehicle body or the like. That is, the ground is not separated between the temperature detecting device 20 and another device such as the battery unit U, and the voltage level of the ground is the same.

The second input terminal 23b of the comparison circuit 23 is connected to the connection point N22 in the second electric path L22. That is, the second input terminal 23b of the comparison circuit 23 is connected to the second electric path L22 provided between the cathode side terminal of the temperature sensitive diode 21 and the ground terminal GND.

The reference power supply 22 is a DC power supply device (DC power supply device), and is a device that allows a constant current to flow. The comparison circuit 23 is a circuit that compares the forward voltage of the temperature sensitive diode 21 with the reference voltage of the reference power supply 22 and outputs a signal as a detection result to the control circuit 51 via the output terminal 23c. The comparison circuit 23 compares the forward voltage of the temperature sensitive diode 21 with the reference voltage of the reference power supply 22 based on the voltage input from the first input terminal 23a and the voltage input from the second input terminal 23b. It is configured as follows.

Explaining the configuration in detail, two resistors R21 and R22 are connected in series to the third electric path L23 between the first input terminal 23a and the ground terminal GND. The non-inverting input terminal 24a of the comparator 24 is connected to the connection point N23 between the resistors R21 and R22.

Two resistors R23 and R24 are connected in series to the fourth electric path L24 provided between the second input terminal 23b and the output terminal 23c of the comparison circuit 23. Then, the inverting input terminal 24b of the comparator 24 is connected to the connection point N24 between the resistor R23 and the resistor R24.

Next, the outline of the operation of the temperature detection device 20 will be described. The semiconductor switches S1 and S2 are switched on and off by control by the control circuit 51. When a current flows along with the switching, the temperature of the semiconductor switches S1 and S2 rises. As the temperature of the semiconductor switches S1 and S2 to be detected rises, the forward voltage of the temperature-sensitive diodes 21 connected in series changes. The forward voltage of the temperature sensitive diode 21 is input to the second input terminal 23b. On the other hand, the reference voltage of the reference power supply 22 is input to the first input terminal 23a. Then, the comparison circuit 23 compares the forward voltage of the temperature sensitive diode 21 with the reference voltage based on the comparison between the voltage input to the first input terminal 23a and the voltage input to the second input terminal 23b. Then, a signal corresponding to the magnitude of the forward voltage is output. The control circuit 51 executes various processes including switching control based on the signal input from the comparison circuit 23.

By the way, if the ground terminal GND is shared between the temperature detection device 20 and the battery unit U, the influence of normal mode noise may increase. Normal mode noise is noise current in which a noise source enters in series with a power supply line and flows in the same direction as the power supply current. For example, the rotary electric machine 14 may be a noise source N.

As shown in FIG. 3, when a noise current flows from the noise source N to the semiconductor switch S1, it flows from the semiconductor switch S1 to the temperature sensitive diode 21 via the stray capacitance SC. This noise current further flows from the temperature sensitive diode 21 to the first electric path L21 or the second electric path L22. Although the case where the noise current flows from the side of the semiconductor switches S1 and S2 to the side of the temperature sensitive diode 21 has been described, the noise current may also flow from the side of the temperature sensitive diode 21 to the side of the semiconductor switches S1 and S2. possible.

When such a noise current passes through the temperature sensitive diode 21, it affects the forward voltage of the temperature sensitive diode 21 and makes it difficult to accurately detect the temperature. Therefore, the configuration as shown in FIG. 1 is added to the first electric path L21 and the second electric path L22. Hereinafter, it will be described in detail.

Before explaining the configuration for suppressing the noise current, first, the diode characteristic of the temperature sensitive diode 21 will be described. As shown in FIG. 4, the temperature-sensitive diode 21 has a property that the forward voltage increases according to the energizing current. Further, as shown in FIG. 4, when the energizing current is equal to or higher than a certain threshold value Vh, it can be seen that the amount of increase in the forward voltage is gradual as compared with the amount of increase in the energizing current. That is, it is known that the forward voltage hardly changes. On the other hand, when it is less than the threshold value, it can be seen that the amount of decrease in the forward voltage is sharper than the amount of decrease in the energizing current.

Therefore, even if a noise current flows, it can be seen that the error in the forward voltage is small if the threshold value is Vh or more. Therefore, it can be understood that the error can be suppressed by increasing the energizing current, that is, by facilitating the flow of the noise current in the forward direction.

This will be described in more detail in FIG. In FIG. 4, a case where the noise current can flow in both the forward direction and the reverse direction in the same manner and a case where the noise current flows in the forward direction more than in the reverse direction will be described in comparison. In FIG. 4, the error e1 in the case where the noise current can flow in both the forward direction and the reverse direction is illustrated by a broken line. Further, the error e2 in the case where the flow in the forward direction is larger than that in the reverse direction is illustrated by the alternate long and short dash line. Further, the energization current when there is no noise current is shown as a reference value Vs.

As shown by the broken line, when the energization current becomes smaller than the threshold value Vh due to the influence of the noise current in the reverse direction, the error e1 (voltage difference) of the forward voltage becomes large. On the other hand, as shown by the alternate long and short dash line, when the current flows in the forward direction more than in the reverse direction and the energizing current becomes larger than the threshold value Vh regardless of which current flows, the error in the forward voltage e2. Is smaller than the error e1.

Therefore, no matter which of the electric paths L21 and L22 the noise current flows, the reference value Vs is set so that the energizing current is equal to or higher than the threshold value Vh (that is, the forward voltage is equal to or higher than the predetermined voltage value Vf). And the impedance in the electric paths L21 and L22 was set. Specifically, the temperature detection device 20 is configured so that the current is less likely to flow in the first electric path L21 as compared with the second electric path L22. That is, the temperature detection device 20 is configured so that the impedance of the first electric path L21 is larger than that of the second electric path L22.

As shown in FIG. 2, in this embodiment, it is realized by providing an inductor 30 (coil) as a passive element on the first electric path L21. The inductor 30 is provided on the side of the temperature sensitive diode 21 with respect to the connection point N23 between the first input terminal 23a and the first electric path L21. The impedance of the inductor 30 makes it difficult for noise current to flow in the first electric path L21, and makes it easy for noise current to flow on the side of the second electric path L22.

It is desirable that the impedance of the inductor 30 be set so as to be large in the frequency band where the noise current can be taken. Specifically, the range of the energization current to which the error is allowed is specified from the target accuracy and the diode characteristics, and the impedance of the inductor 30 is determined so that the energization current is within the range even if a noise current is generated. ..

Further, a constant current circuit 25 is provided on the second electric path L22. More specifically, the constant current circuit 25 is provided on the side of the ground terminal GND with respect to the connection point N22 between the second input terminal 23b and the second electric path L22. The constant current circuit 25 controls the current so as to approach the reference value Vs when the energization current becomes larger (or less) than the reference value Vs. That is, the constant current circuit 25 controls the current so that it becomes the reference value Vs when the energization current becomes larger than the reference value Vs due to the noise current flowing in the second electric path L22. This makes it possible to suppress the influence of noise current. The constant current circuit 25 also controls the current even when the energizing current is small due to the noise current.

By the way, the responsiveness of the constant current circuit 25 is limited, and if the noise current is in the low frequency region, the influence of the noise current can be suitably suppressed, but if the noise current is in the high frequency region, the noise current is preferably suppressed. It is hard to say that the effect can be eliminated.

Therefore, in the second electric path L22, a noise reducing capacitor C1 is provided in which one end is connected to the temperature sensitive diode 21 side of the constant current circuit 25 and the other end is connected to the ground terminal GND. The capacitor C1 suppresses the influence of noise current in the high frequency region.

The effect in this embodiment will be described.

The normal mode noise can flow from the battery unit U to which the semiconductor switches S1 and S2 to be detected are connected to the first electric path L21 or the second electric path L22 of the temperature detection device 20 via the stray capacitance SC or the like. There is sex. Then, due to the diode characteristics of the temperature-sensitive diode 21, a noise current flows in the forward direction with respect to the temperature-sensitive diode 21, and a noise current flows in the reverse direction as compared with the case where the energizing current increases, and the energizing current becomes It was found that the decrease had a greater effect on the forward voltage (that is, the detection result).

Therefore, an inductor 30 as a passive element is provided on the first electric path L21 so that the current is less likely to flow in the first electric path L21 as compared with the second electric path L22. This suppresses the flow of noise current in the opposite direction to the temperature-sensitive diode 21 and makes it easier to flow in the forward direction. Therefore, the influence of normal mode noise can be suppressed.

The inductor 30 is provided on the side of the temperature sensitive diode 21 with respect to the connection point N21 between the first input terminal 23a and the first electric path L21. As a result, it is possible to effectively suppress the flow of noise current from the temperature sensitive diode 21 toward the reference power supply 22 or the first input terminal 23a of the comparison circuit 23. Therefore, it is possible to suppress an error due to noise current.

As a passive element that makes it difficult for current to flow, a resistor, an inductor (coil), or the like can be considered. The inductor has a high impedance at a predetermined frequency. Therefore, if the inductor is set in consideration of the frequency of the noise current, the voltage is less likely to drop as compared with the resistor, and the input voltage to the temperature sensitive diode 21 is less likely to be affected. Therefore, an inductor 30 is adopted as a passive element that makes it difficult for current to flow in the first electric path L21. As a result, when the noise current does not exist, the input voltage to the temperature sensitive diode 21 is not affected as compared with the case where the resistor is adopted, and the detection accuracy can be improved.

In the inductor 30, a range in which noise current can be made difficult to flow is defined. Therefore, it is desirable to predict the frequency of the noise current and use an appropriate inductor 30 according to the frequency of the noise current.

A constant current circuit 25 is provided on the side of the ground terminal GND with respect to the connection point N22 between the second input terminal 23b and the second electric path L22. By providing this constant current circuit 25, when a noise current flows from the temperature sensitive diode 21 to the second electric path L22, the influence of the noise current can be suppressed by the current control (feedback control) of the constant current circuit 25. can. That is, the energization current of the temperature sensitive diode 21 can be adjusted to be close to the reference value Vs, and the influence on the forward voltage can be suppressed.

Further, by providing the constant current circuit 25, even when a noise current flows from the temperature sensitive diode 21 to the first electric path L21 and the energization current decreases, the current control of the constant current circuit 25 causes the noise current. The effect can be suppressed.

By the way, the responsiveness of the constant current circuit 25 is limited, and if the noise current is in the low frequency region, the influence of the noise current can be suitably suppressed, but if the noise current is in the high frequency region, the noise current is preferably suppressed. It is hard to say that the effect can be eliminated.

Therefore, in the second electric path L22, a noise reducing capacitor C1 is provided in which one end is connected to the temperature sensitive diode 21 side of the constant current circuit 25 and the other end is connected to the ground terminal GND. With this capacitor C1, the influence of noise current in the high frequency region can be suppressed and the detection accuracy can be improved. Further, by providing the capacitor C1 on the side of the temperature sensitive diode 21 with respect to the constant current circuit 25, it is possible to suppress the input of noise current in the high frequency region to the constant current circuit 25.

The ground terminal GND of the temperature detection device 20 is shared with the ground terminal of the noise source, that is, the ground terminal used for the battery unit and the rotary electric machine 14. As a result, common node noise can be suppressed.

No matter which of the electric paths L21 and L22 the noise current flows, the reference value Vs and electricity so that the energization current is equal to or higher than the threshold value Vh (that is, the forward voltage is equal to or higher than the predetermined voltage value Vf). The impedance in the paths L21 and L22 was set. As a result, the influence of the noise current can be reduced and the detection accuracy can be improved.

(Other embodiments)
The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the gist of the present invention. In the following, the parts that are the same or equal to each other in each embodiment are designated by the same reference numerals, and the description thereof will be referred to for the portions having the same reference numerals.

In the above embodiment, as shown in FIG. 5, the inductor 30 may be provided on the side of the reference power supply 22 with respect to the connection point N21 between the first input terminal 23a and the first electric path L21. If there is a passive element such as an inductor 30 on the side of the temperature sensitive diode 21 from the connection point N21 between the first input terminal 23a and the first electric path L21, the input voltage of the temperature sensitive diode 21 is higher than the voltage of the reference power supply 22. descend. In this case, it may cause a detection error when there is no noise current. Therefore, the inductor 30 is provided on the side of the reference power supply 22 with respect to the connection point N21 between the first input terminal 23a and the first electric path L21. As a result, in the electric path between the temperature sensitive diode 21 and the first input terminal 23a, there is nothing that obstructs the current, and the detection accuracy can be improved when there is no noise current.

Generally, the resistor R21 is connected in series to the non-inverting input terminal 24a of the comparator 24. Therefore, even with the above configuration, it is difficult for noise current to flow through the non-inverting input terminal 24a of the comparator 24.

-In the above embodiment, the wiring resistance of the first electric path L21 and the second electric path L22 may be set so that the current is less likely to flow in the first electric path L21 as compared with the second electric path L22. .. In this case, it is not necessary to provide a passive element such as an inductor 30 in the first electric path L21.

-In the above embodiment, a resistor (register) may be adopted instead of the inductor 30 as the passive element provided in the first electric path L21. Further, a passive element such as an inductor may be provided in the second electric path L22 as well.

In the above embodiment, as shown in FIG. 6, the constant current circuit 25 may be provided on the side of the reference power supply 22 with respect to the connection point N21 between the first input terminal 23a and the first electric path L21. In this case, it is not necessary to provide the capacitor C1 in the second electric path L22.

20 ... temperature detector, 21 ... temperature sensitive diode, 22 ... reference power supply, 23 ... comparison circuit, 23a ... first input terminal, 23b ... second input terminal, 30 ... inductor, L21 ... first electric path, L22 ... first 2 electrical paths.

Claims (9)

A temperature-sensitive diode (21) whose forward voltage changes according to the temperature of the detection target,
The reference power supply (22) that outputs the reference voltage and
A comparison circuit (23) that compares the forward voltage of the temperature-sensitive diode with the reference voltage of the reference power supply and outputs a detection result.
In the temperature detection device (20) provided with
The first input terminal (23a) of the comparison circuit is connected to the first electric path (L21) provided between the reference power supply and the anode side terminal of the temperature sensitive diode, and is connected to the second input terminal (23b). Is connected to a second electric path (L22) provided between the cathode side terminal and the ground terminal of the temperature sensitive diode.
The comparison circuit compares the forward voltage of the temperature sensitive diode with the reference voltage of the reference power supply based on the voltage input from the first input terminal and the voltage input from the second input terminal. It is configured as
A passive element (30) is provided at least on the first electric path so that a current is less likely to flow in the first electric path as compared with the second electric path .
The passive element is a temperature detector which is an inductor . The temperature detecting device according to claim 1, wherein the passive element is provided on the side of the reference power source with respect to the connection point (N21) between the first input terminal and the first electric path. The temperature detecting device according to claim 1, wherein the passive element is provided on the side of the temperature sensitive diode from the connection point (N21) between the first input terminal and the first electric path. According to any one of claims 1 to 3 , a constant current circuit (25) is provided on the side of the ground terminal from the connection point (N22) between the second input terminal and the second electric path. The temperature detector of the description. A claim in which a noise reduction capacitor (C1) is provided in the second electric path, one end connected to the temperature sensitive diode side of the constant current circuit and the other end connected to the ground terminal. Item 4. The temperature detection device according to item 4. According to any one of claims 1 to 3 , a constant current circuit (25) is provided on the side of the reference power source from the connection point (N21) between the first input terminal and the first electric path. The temperature detector of the description. A temperature-sensitive diode (21) whose forward voltage changes according to the temperature of the detection target,
The reference power supply (22) that outputs the reference voltage and
A comparison circuit (23) that compares the forward voltage of the temperature-sensitive diode with the reference voltage of the reference power supply and outputs a detection result.
In the temperature detection device (20) provided with
The first input terminal (23a) of the comparison circuit is connected to the first electric path (L21) provided between the reference power supply and the anode side terminal of the temperature sensitive diode, and is connected to the second input terminal (23b). Is connected to a second electric path (L22) provided between the cathode side terminal and the ground terminal of the temperature sensitive diode.
The comparison circuit compares the forward voltage of the temperature sensitive diode with the reference voltage of the reference power supply based on the voltage input from the first input terminal and the voltage input from the second input terminal. It is configured as
The wiring resistance of the first electric path and the second electric path is set so that the current does not easily flow in the first electric path as compared with the second electric path .
A constant current circuit (25) is provided on the side of the ground terminal from the connection point (N22) between the second input terminal and the second electric path.
In the second electric path, a temperature at which one end is connected to the temperature sensitive diode side of the constant current circuit and the other end is connected to the ground terminal to provide a noise reduction capacitor (C1). Detection device. The temperature detection device according to any one of claims 1 to 7 , wherein the ground terminal of the temperature detection device is common to the ground terminal of the noise source. The detection target is a switching element (S1, S2) used in the power supply system (10) of the vehicle.
The temperature detection device according to any one of claims 1 to 8 , wherein the ground terminal of the temperature detection device is common to the ground terminal used in the power supply system.

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