DE102021203009A1 - Electronic circuit for temperature measurement - Google Patents

Abstract

The invention relates to an electronic circuit (20) for measuring the temperature of a component (30) on a circuit board (10). The electronic circuit (20) includes a temperature-dependent resistor (200), a first resistor (201) and a measuring device (201a), which is set up to measure a voltage drop across the first resistor (201). A first connection of the temperature-dependent resistor (200) is electrically connected to a first connection of the first resistor (201) via a first line (211). The electronic circuit (20) further comprises a second resistor (202), wherein a second terminal of the temperature-dependent resistor (200) is electrically connected to a first terminal of the second resistor (202) via a second line (212), the first resistor ( 201), the temperature-dependent resistor (200) and the second resistor (202) are connected in series and form a voltage divider.

Description

The invention relates to an electronic circuit for measuring the temperature of a component on a circuit board. The electronic circuit includes a temperature-dependent resistor, a first resistor and a measuring device that is set up to measure a voltage drop across the first resistor. A first connection of the temperature-dependent resistor is electrically connected to a first connection of the first resistor via a first line.

The invention also relates to an electronic device that has at least one electronic circuit according to the invention, at least one component whose temperature is to be measured, and a circuit board, the at least one electronic circuit according to the invention and the at least one component being arranged on the circuit board.

State of the art

NTC resistors (Negative Temperature Coefficient, NTC), also known as thermistors, or PTC resistors (Positive Temperature Coefficient, PTC), also known as PTC thermistors, are temperature-dependent resistors and are used in conjunction with a voltage divider and downstream analog -Digital converter (ADC) or comparator used for monitoring the temperature of components. In particular, SMD-NTC/PTC resistors (Surface Mounted Device, SMD) are brought here on circuit boards as close as possible to the corresponding components.

The problem here, particularly in the case of components at a higher voltage potential, is that a certain distance between components and conductor tracks must be maintained. On the one hand, this leads to a more sluggish and inaccurate temperature measurement due to the distance to the component and, on the other hand, to a reduction in the copper surfaces of conductor tracks on the circuit boards to dissipate the heat generated. This is a problem in particular in high-current paths on power semiconductors. The temperature usually has to be monitored with an NTC or PTC resistor, at the same time the ohmic and thermal resistance increases due to the space required for the NTC or PTC resistor and the large distance, which in turn leads to a higher temperature at the component leads. Expensive solutions, such as using optocouplers and DC/DC converters to match the voltage level to that of the components to be measured, are currently a costly alternative.

The document CN 210442486 U describes a thermal runaway detection circuit. The circuit relates to the field of battery technology and is used to increase the safety of a battery pack.

From the document US 2004/0059538 A1 a device for measuring the temperature in an oven is known.

Disclosure of Invention

An electronic circuit for measuring the temperature of a component on a circuit board is proposed. In this case, the electronic circuit comprises a temperature-dependent resistor, a first resistor and a measuring device which is set up to measure a voltage drop across the first resistor. The temperature-dependent resistor can be designed as an NTC or a PTC resistor. The measuring means preferably includes an additional resistor and/or an analog/digital converter. A first connection of the temperature-dependent resistor is electrically connected to a first connection of the first resistor via a first line.

According to the invention, the electronic circuit also has a second resistor. In this case, a second connection of the temperature-dependent resistor is electrically connected to a first connection of the second resistor via a second line. The first resistor, the temperature-dependent resistor and the second resistor are thus connected in series and form a voltage divider.

A second connection of the second resistor and a second connection of the first resistor can be connected to a voltage supply. In this case, the second connection of the first resistor can be connected to ground. If the measuring device for measuring the voltage drop across the first resistor includes an additional resistor and an analog/digital converter, a first connection of the additional resistor can be electrically connected to the first connection of the first resistor via an additional line. In this case, the second connection of the additional resistor and the second connection of the first resistor are connected to the analog/digital converter.

Are the second terminal of the second resistor and the second terminal of the first resistor connected to the voltage supply, such as 5V, and the second terminal of the first resistor is connected to the Connected to ground, there is a supply voltage between the second terminal of the second resistor and the second terminal of the first resistor, and a measurement voltage, which depends on the resistance value of the temperature-dependent resistor, is present between a second terminal of the additional resistor and the second terminal of the first resistor on.

The resistance value of the first, the second and the additional resistor is to be selected in such a way that each of the resistors can withstand the power loss that could occur in it, for example in the event of an electrical connection between the components to be measured and the electronic circuit according to the invention, due to the smaller distance between them, without being destroyed can. In addition, the selection of the resistance value of the first, the second and the additional resistor depends on the desired measuring accuracy and also on the resistance value of the temperature-dependent resistor. The resistance of the additional resistor can be selected to be greater than the resistance of the first and second resistors. It also depends on the connected analog-to-digital converter or the corresponding evaluation circuit. With a geometrically larger resistor, a larger power loss can usually be dissipated, so a smaller resistance value can be selected.

The first and second resistors preferably have the same resistance value. The term "same resistance value" preferably means that deviations in the range of normal component tolerances are considered to be the same. However, a different resistance ratio between the first and the second resistor is also conceivable.

The electronic circuit proposed according to the invention can advantageously be used when measuring the temperature of an individual component which represents a heat source. However, it is also conceivable that the electronic circuit proposed according to the invention is used for measuring the temperature of a group of components.

An electronic device is also proposed. In this case, the electronic device comprises at least one electronic circuit proposed according to the invention, at least one component whose temperature is to be measured, and a printed circuit board. The at least one electronic circuit proposed according to the invention and the at least one component to be measured are arranged on the circuit board.

The at least one component to be measured is preferably an electronic component for a high voltage level, such as 60 V, or for a high current intensity.

The circuit board preferably has a high-voltage area and a low-voltage area. For example, the at least one component to be measured is arranged on the high-voltage area of the circuit board, while the low-voltage area of the circuit board is used for measurement. The first and second resistors are preferably arranged outside the high-voltage area.

For example, the first, the second and the additional resistance can be located exactly on the boundary between the high-voltage range and the low-voltage range. A distance between the high-voltage area and the low-voltage area should be able to be bridged by the geometric size of the first, the second and the additional resistor. If this is not possible due to a smaller geometric size, a resistor can also be replaced by two or any number of resistors connected in series to achieve the distance between the high-voltage area and the low-voltage area.

The at least one component can be any heat-generating component. For example, the at least one component can be designed as a semiconductor switch. The at least one component is preferably designed as a field effect transistor (FET) or IGBT (insulated gate bipolar transistor). However, the at least one component can also be in the form of a diode.

A battery system is also proposed which comprises at least one electronic circuit proposed according to the invention and/or at least one electronic device proposed according to the invention.

Furthermore, a vehicle is proposed which comprises at least one electronic circuit proposed according to the invention and/or at least one electronic device proposed according to the invention and/or at least one battery system proposed according to the invention.

Advantages of the Invention

With the solution proposed according to the invention, the distances between the temperature-dependent resistors and the components to be measured or between the electronic circuit according to the invention and the high-voltage area can be reduced. Thus, the temperature-dependent resistances or the electronic circuit according to the invention can be attached closer to the components to be measured with a higher potential or the high-voltage range and thus more copper surface of conductor tracks on the circuit board is available for dissipating the heat generated, which means that more heat is dissipated with the same installation space can be. As a result, an electronic device that includes at least one electronic circuit proposed according to the invention can also be made smaller.

The electronic circuit proposed according to the invention also enables a faster reaction to temperature changes and thus faster temperature detection.

Compared to a galvanic isolation for temperature measurement, such as by means of an optocoupler and DC/DC converter, the electronic circuit proposed according to the invention also offers a more cost-effective solution for temperature measurement.

character list

Embodiments of the invention are explained in more detail with reference to the drawings and the following description.

• 1 eine schematische Darstellung einer Platine mit einer elektronischen Schaltung zur Temperaturmessung gemäß dem Stand der Technik,
• 2 eine schematische Darstellung einer Platine mit einer erfindungsgemäßen elektronischen Schaltung zur Temperaturmessung und
• 3 eine Tabelle, die ein Beispiel des Verhältnisses zwischen Temperatur, Widerstandswert und Spannung des als NTC-Widerstand ausgebildeten temperaturabhängigen Widerstands darstellt.

Show it:

• 1 a schematic representation of a circuit board with an electronic circuit for temperature measurement according to the prior art,
• 2 a schematic representation of a circuit board with an electronic circuit according to the invention for temperature measurement and
• 3 a table showing an example of the relationship between temperature, resistance value and voltage of the temperature-dependent resistor designed as an NTC resistor.

In the following description of the embodiments of the invention, the same or similar elements are denoted by the same reference symbols, with a repeated description of these elements being dispensed with in individual cases. The figures represent the subject matter of the invention only schematically.

1 shows a schematic representation of a circuit board 10 of an electronic device. The electronic device includes a component 30 whose temperature is to be measured, and an electronic circuit 20 for measuring the temperature of component 30 . Electronic circuit 20 and component 30 to be measured are arranged on circuit board 10 .

The component 30 to be measured is an electronic component 30 which is at a high voltage level, such as 60 V, for example. The component 30 can be formed, for example, as a MOSFET, diode or other electronic component and represents a heat source.

The circuit board 10 is divided into a high-voltage area 101 and a low-voltage area 102 . The component 30 to be measured is arranged on the high-voltage area 101 of the circuit board 10, while the low-voltage area 102 of the circuit board 10 is used for the measurement. A first spacing 103 is designed between the high-voltage area 101 and the low-voltage area 102 in order to insulate the low-voltage area 102 from the high-voltage area 101 .

The electronic circuit 20 includes a temperature-dependent resistor 200, a first resistor 201, which can be in the form of an NTC or PTC resistor, and a measuring device 201a, which is set up to measure a voltage drop across the first resistor 201. The measuring means 201a includes an additional resistor 203 and an analog/digital converter (not shown). A first connection of the temperature-dependent resistor 200 is electrically connected to a first connection of the first resistor 201 via a first line 211 . A second terminal of the first resistor 201 is connected to ground.

A first connection of the additional resistor 203 is electrically connected to the first connection of the first resistor 201 via an additional line 213 . A second connection of the additional resistor 203 and the second connection of the first resistor 201 are connected to the analog/digital converter. A second terminal of the temperature-dependent resistor 200 and the second terminal of the first resistor 201 are connected to a voltage supply of 3.3 V, for example. In this case, the second connection of the temperature-dependent resistor 200 is connected to a connection of the voltage supply via a second line 212 .

In this case, a supply voltage U1 is present between the second connection of the temperature-dependent resistor 200 and the second connection of the first resistor 201 , and a measurement voltage U2 which is dependent on the resistance value of the temperature-dependent resistor 200 is present between the second terminal of the additional resistor 203 and the second terminal of the first resistor 201 . The measurement voltage U2 is read from the analog-to-digital converter.

The temperature-dependent resistor 200 and the component 30 are arranged opposite one another at the first distance 103 . In this case, the temperature-dependent resistor 200 with the first resistor 201 represents a voltage divider, which results in the measurement voltage U2. The additional resistor 203 is used to protect electronic devices connected to it, such as an analog-to-digital converter, a voltage follower and a comparator, which have a high-impedance input resistance. Between the additional resistor 203 and ground, ie the second connection of the first resistor 201, an appropriate protection against excessive voltages at the analog-to-digital converter input by z. B. can be provided to ground a diode. The first line 211 and the additional line 213 need only have a second distance 104, which is smaller than the first distance 103, to the high-voltage area 101, since here in the case of an electrical connection between the first line 211 and a high voltage potential, the current flow through the first resistor 201 is severely limited. The second line 212 must maintain the higher, first distance 103, since an electrical connection between the second line 212 and the higher voltage potential results in a direct short circuit to the supply voltage U1. In the first line 211 and the additional line 213, when there is contact with the high-voltage area 101, the current can also flow indefinitely after the voltage supply if the resistance value of the temperature-dependent resistor 200 approaches zero at high temperatures. In this case, therefore, the second distance 104 would have to be selected in the same way as the first distance 103 .

Embodiments of the invention

2 shows a schematic representation of a circuit board 10 with an electronic circuit 20 according to the invention for temperature measurement. In this case, the electronic device includes the electronic device according to 1 a component 30 whose temperature is to be measured, and an electronic circuit 20 proposed according to the invention for measuring the temperature of the component 30. The electronic circuit 20 proposed according to the invention and the component 30 to be measured are arranged on the printed circuit board 10.

The component 30 to be measured is also an electronic component 30 which is at a high voltage level, such as 60 V, for example. The component 30 can be formed, for example, as a MOSFET, diode or other electronic component and represents a heat source.

The circuit board 10 is divided into a high-voltage area 101 and a low-voltage area 102 . The component 30 to be measured is arranged on the high-voltage area 101 of the circuit board 10, while the low-voltage area 102 of the circuit board 10 is used for the measurement. A first spacing 103 is designed between the high-voltage area 101 and the low-voltage area 102 in order to insulate the low-voltage area 102 from the high-voltage area 101 .

The electronic circuit 20 proposed according to the invention comprises a temperature-dependent resistor 200, which can be in the form of an NTC or PTC resistor, and a first resistor 201 and a measuring device 201a, which is set up to measure a voltage drop across the first resistor 201. The measuring means 201a includes an additional resistor 203 and an analog/digital converter (not shown). A first connection of the temperature-dependent resistor 200 is electrically connected to a first connection of the first resistor 201 via a first line 211 . A second connection of the first resistor 201 is connected to ground. A first connection of the additional resistor 203 is electrically connected to the first connection of the first resistor 201 via an additional line 213 . A second connection of the additional resistor 203 and the second connection of the first resistor 201 are connected to the analog/digital converter.

In order to reduce the distance between the temperature-dependent resistor 200 and the component 30 from the first distance 103 to the second distance 104, the electronic circuit 20 proposed according to the invention also comprises a second resistor 202.

In this case, a second connection of the temperature-dependent resistor 200 is electrically connected to a first connection of the second resistor 202 via a second line 212 . The first resistor 201, the temperature-dependent resistor 200 and the second resistor 202 are thus connected in series and form a voltage divider.

A second connection of the second resistor 202 and the second connection of the first resistor 201 are connected to a voltage supply of 5 V, for example. In this case, a supply voltage U1 is present between the second terminal of the second resistor 202 and the second terminal of the first resistor 201, and a measurement voltage U2, which is dependent on the resistance value of the temperature-dependent resistor 200, is between a second terminal of the additional resistor 203 and the second Connection of the first resistor 201 to. It is also possible for the second connection of the second resistor 202 to be connected to ground, while the second connection of the first resistor 201 is connected to the other connection of the voltage supply.

The resistance value of the first, the second and the additional resistor 201, 202, 203 is to be selected so that each of the resistors 201, 202, 203 the power loss that occurs at it, for example in the case of an electrical connection of the components to be measured 30 or the conductor tracks of the high-voltage area 101 and the electronic circuit 20 according to the invention due to the smaller distance between them, can survive without being destroyed. In addition, the selection of the resistance value of the first, the second and the additional resistor 201, 202, 203 depends on the desired measuring accuracy and also on the resistance value of the temperature-dependent resistor 200.

dabei ist R₁ der Widerstandswert des ersten Widerstands 201 und P₁ die Verlustleistung des ersten Widerstands 201, die im Datenblatt des ersten Widerstands 201 zu finden ist.For example, the voltage level of the high-voltage area 101 is 60 V. The resistance value of the first resistor 201 should be selected as follows: $$R_1=\frac{{\left(60V\right)}^2}{P_1}$$

where R ₁ is the resistance of the first resistor 201 and P ₁ is the power dissipation of the first resistor 201, which can be found in the data sheet of the first resistor 201.

dabei ist R₂ der Widerstandswert des zweiten Widerstands 202 und P₂ die Verlustleistung des zweiten Widerstands 202, die im Datenblatt des zweiten Widerstands 202 zu finden ist.The resistance value of the second resistor 202 should be chosen as follows: $$R_2=\frac{{\left(60V-5V\right)}^2}{P_2}$$

where R ₂ is the resistance of the second resistor 202 and P ₂ is the power dissipation of the second resistor 202, which can be found in the data sheet of the second resistor 202.

The calculation of the resistance value of the additional resistor 203 can be the same as that of the first resistor 201 . The resistance value of the additional resistor 203 can also be selected to be greater than the resistance value of the first and second resistors 201, 202. It also depends on the connected analog-to-digital converter or the corresponding evaluation circuit.

In this case, the first and second resistors 201, 202 can have the same resistance value. However, a different resistance ratio between the first and second resistors 201, 202 is also conceivable.

Because of the first and second resistors 201, 202, the same conditions apply to the first and second lines 211 and 212, provided that the first and second resistors 201, 202 have the same resistance value. The distance between the second line 212 and the high-voltage region 101 can thus also be reduced from the first distance 103 to the second distance 104 . A direct short circuit can no longer occur. In this case, however, the first, the second and the additional resistor 201, 202, 203 should also maintain a PAD distance of at least the first distance 103. Depending on the system, 1.8 V, 3.3 V or 5 V can be used as supply voltage U1, for example.

For example, the supply voltage U1 for the temperature-dependent resistor 200 can be 5 V, while a reference voltage of the analog/digital converter is 3.3 V. Here, if the first and second resistors 201, 202 also have the same resistance value, for an infinitely high temperature, i. H. the temperature-dependent resistor 200 has a resistance value of 0 Ω, yielding 2.5 V at the analog/digital converter. Thus, the 3.3 V reference voltage is almost completely used. This can be adjusted even further by adjusting the first and the additional resistors 201, 203.

The first and the second line 211, 212 are respectively limited by the first or the second resistor 201, 202 when they come into contact with the high-voltage region 101.

3 FIG. 12 shows a table showing an example of the relationship between temperature, resistance value and voltage of the temperature-dependent resistor 200, which is formed as an NTC resistor. The table includes, from left to right, a first column, a second column, and a third column. In the first column, temperatures of the temperature-dependent resistor 200 in °C specified. In the second column, resistance values of the temperature-dependent resistor 200 are given in kΩ. Voltages of the temperature-dependent resistor 200 in V are specified in the third column.

In this case, the supply voltage U1 is 5 V. The first and the second resistor 201, 202 each have a resistance value of 10 kΩ. The temperature dependent resistor 200 has a resistance value of 47 kΩ at a temperature of 25°C. The voltage level of the high-voltage area 101 is 60 V.

an Verlustleistung abführen können. Der zweite Widerstand 202 sollte dabei $$\frac{{\left(60V-5V\right)}^2}{10k\Omega }=303mW$$

an Verlustleistung abführen können.The temperature is measured between -50 °C and 300 °C. More precisely, the temperature is measured between 0 °C and 100 °C. The first resistor 201 should be in contact with the high voltage area 101 $$\frac{{\left(60V\right)}^2}{10k\Omega }=360mW$$

can dissipate power loss. The second resistor 202 should be there $$\frac{{\left(60V-5V\right)}^2}{10k\Omega }=303mW$$

can dissipate power loss.

If the reference voltage of the analog-digital converter is chosen to be 2.5 V, the measurement accuracy increases. The temperature window to be precisely resolved can be set here by a different choice of the temperature-dependent resistor 200 and/or the limitation options.

The invention is not limited to the exemplary embodiments described here and the aspects highlighted therein. Rather, within the range specified by the claims, a large number of modifications are possible, which are within the scope of expert action.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• CN 210442486 U [0005]
• US 2004/0059538 A1 [0006]

Claims (8)

Electronic circuit (20) for measuring the temperature of a component (30) on a circuit board (10), comprising a temperature-dependent resistor (200), a first resistor (201) and a measuring device (201a) which is used to measure a value connected to the first resistor (201 ) falling voltage is set up, wherein a first terminal of the temperature-dependent resistor (200) is electrically connected via a first line (211) to a first terminal of the first resistor (201), characterized in that the electronic circuit (20) also has a second Resistor (202), wherein a second terminal of the temperature-dependent resistor (200) is electrically connected via a second line (212) to a first terminal of the second resistor (202), and wherein the first resistor (201), the temperature-dependent resistor ( 200) and the second resistor (202) are connected in series and form a voltage divider. Electronic circuit (20) after claim 1 , characterized in that the first and the second resistor (201, 202) have an equal resistance value. Electronic device, comprising at least one electronic circuit (20). claim 1 or 2 At least one component (30) whose temperature is to be measured, and a circuit board (10), wherein the at least one electronic circuit (20) and the at least one component (30) are arranged on the circuit board (10). Electronic device after claim 3 , characterized in that the at least one component (30) is designed as a semiconductor switch. Electronic device after claim 4 , characterized in that the at least one component (30) is designed as an FET or IGBT. Electronic device after claim 3 , characterized in that the at least one component (30) is designed as a diode. Battery system, comprising at least one electronic circuit (20). claim 1 or 2 and/or at least one electronic device according to any one of claims 3 until 6 . Vehicle, comprising at least one electronic circuit (20). claim 1 or 2 and/or at least one electronic device according to any one of claims 3 until 6 and/or at least one battery system claim 7 .

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