Circuit arrangement with a printed circuit board and temperature sensors arranged on the circuit board

Abstract

The invention relates to a circuit arrangement (M) with a printed circuit board and an arrangement arranged on the printed circuit board consisting of conductor tracks and electrical components which are connected to one another by the conductor tracks, wherein temperature sensors (S1, S2, S3, S4) are provided under the components, with which the temperature at various points on the printed circuit board can be detected, wherein the circuit arrangement (M) has an output and the output of the circuit arrangement (M) is connected to outputs of the temperature sensors (S1, S2, S3, S4), wherein the circuit arrangement has a means (MAX(T1, T2, T3, T4)) for determining a maximum temperature, wherein the outputs of the temperature sensors (S1, S2, S3, S4) are each connected to an input of the means (MAX(T1, T2, T3, T4)) for determining the maximum temperature and an output of the means (MAX(T1, T2, T3, T4)) for determining the maximum temperature is connected to the output of the circuit arrangement (M),the means (MAX(T1, T2, T3, T4)) for determining the maximum temperature is suitable and configured to determine the temperature signal indicating the highest temperature from temperature signals (T1, T2, T3, T4) present at the inputs and to apply this temperature signal or another signal (Tmax) indicating the maximum temperature to the output of the means for determining the maximum temperature and thus to the output of the circuit arrangement (M).

Description

The invention relates to a circuit arrangement having a printed circuit board and an arrangement, arranged on the printed circuit board, of conductor tracks and electrical components which are connected to one another by the conductor tracks, wherein the components include a plurality of temperature sensors, with which the temperature can be detected at different points on the printed circuit board, wherein the circuit arrangement has an output. The output of the circuit arrangement is connected to outputs of the temperature sensors. The measured temperatures can be output via the output of the circuit arrangement in order to be processed, for example, in a control device which controls the circuit arrangement.Circuit arrangements with such a structure are used, for example, in LED matrix headlights or large-area LED displays of vehicles. LED matrix headlights have circuit arrangements which have LEDs as electrical components, which are arranged on the circuit carrier. During operation of such circuit arrangements, a lot of heat is generated, which leads to heating of the components of the circuit arrangement. Too strong heating of the components can lead to damage to the components. In order to prevent a failure of the circuit arrangement, it is necessary to prevent the components from being damaged. A means for preventing excessive heating can be a dissipation of the heat after its generation with the aid of cooling bodies or with the aid of cooling by a coolant. Another means of preventing over-heating may be to prevent the generation of large amounts of heat. This can be achieved, for example, by temperature management.Temperature management can prevent the generation of so much heat, in particular by the components of the circuit arrangement, that the temperature of all or individual components rises so much that these are damaged. With such temperature management, the electrical power of the circuit arrangement can be reduced. The temperature is detected with a temperature sensor. An output of the temperature sensor is connected via an output of the circuit arrangement to a control device on which the temperature management is implemented. If there is the risk of damage to the circuit arrangement due to too high a temperature, the power of the components or some components or one of the components of the circuit arrangement is reduced by means of the control unit and thus the heat generated by the circuit arrangement.The temperature distribution of circuit arrangements is usually not homogeneous. In the case of large-area printed circuit boards, the temperature at different locations or regions can be very different. Especially in the case of circuit boards having many LEDs and drivers, it is not easy to find a suitable location for a temperature sensor. In which areas of a circuit arrangement the power must or should be reduced, in some known solutions temperature sensors distributed on the printed circuit board result. These detect the temperature at different points of the printed circuit board. Outputs of the temperature sensors are then connected to an output of the circuit arrangement. The output of the circuit arrangement can then in turn be connected to an input of a control device with which the circuit arrangement is controlled. This control device can then reduce the power on the basis of the measured temperatures in the regions of the circuit arrangement.This allows reaction to be carried out in a targeted manner to excessively high temperatures at the locations at which the high temperatures are produced. For each temperature sensor, at least one connection is necessary at the output of the circuit arrangement and at the corresponding input of the control device. This increases the number of connections required in the plug, the number of lines in the cable harness and the number of connections in the measurement input in the control unit. This results in increased system costs.The invention starts here.The invention is based on the object of configuring a circuit arrangement such that temperature management of a circuit arrangement with a heterogeneous temperature distribution during operation of the circuit arrangement is possible without each temperature sensor being connected to the control device for this purpose via the output of the circuit arrangement.This object is achieved according to the invention in that the circuit arrangement has a plurality of temperature sensors distributed on the printed circuit board and a means for determining a maximum temperature, wherein the outputs of the temperature sensors are each connected to an input of the means for determining the maximum temperature and an output of the means for determining the maximum temperature is connected to the output of the circuit arrangement, the means for determining the maximum temperature is suitable and configured to determine the temperature signal from temperature signals present at the inputs, which temperature signal indicates the highest temperature and to apply this temperature signal or another signal indicating the maximum temperature at the output of the means for determining the maximum temperature and thus at the output of the circuit arrangement. This signal present at the output of the circuit arrangement can be read into the control device and processed.The invention is based firstly on the finding that it is sufficient for functioning temperature management to know the maximum temperature on the printed circuit board of the circuit arrangement. For this purpose, the temperatures measured at different points on the printed circuit board could be transmitted to the control device and the maximum temperature could be determined in the control device in order then to set the circuit arrangement such that no overheating of the circuit arrangement or of parts of the circuit arrangement occurs. Although a functioning temperature managent would have been able to be achieved with such a solution, no reduction in the effort has yet been achieved with regard to the effort involved in transmitting information from the circuit arrangement to the control device.However, this outlay can be reduced in that the determination of the maximum temperature is provided not in the control unit but, according to the invention, in the means of the circuit arrangement provided for this purpose.The means for determining the maximum temperature of the circuit arrangement may comprise a diode network, a discrete transistor circuit, an operational amplifier circuit or an integrated circuit.Such a diode network may comprise a plurality of series connections of a resistance device and a resistance device with negative temperature coefficients (thermistors), the series connections being connected in parallel to an input of the network for a supply voltage.The resistance device may be connected to a high potential terminal of the supply voltage input, and the resistance device having the negative temperature coefficient may be connected to the low potential of the supply voltage. In each of these series connections, the node between the resistance device and the resistance device having the negative temperature coefficient may be connected via a diode to the output of the circuit arrangement. These diodes can be connected in the reverse direction from the nodes of the series connections to the output of the circuit arrangement. Furthermore, the connection for the high potential of the supply voltage of the diode network can be connected to the output of the circuit arrangement via a resistance component. This resistance component can alternatively also be arranged outside the circuit arrangement according to the invention, for example in a control device to which the circuit arrangement is connected. The resistance of this resistance device is much larger than any resistance of one of the resistance devices of one of the series connections. The resistances of the resistance components of the series connections are preferably the same. The resistances of the resistance components with negative temperature coefficients are likewise the same.In an alternative embodiment of the diode network, the resistance component with the negative temperature coefficient may be connected to a high potential terminal of the input for the supply voltage and the resistance component may be connected to the low potential of the supply voltage. In each of these series connections, the node between the resistance device and the resistance device having the negative temperature coefficient may be connected via a diode to the output of the circuit arrangement. These diodes may be connected in the forward direction from the nodes of the series connections to the output of the circuit arrangement. Furthermore, the terminal for the low potential of the supply voltage of the diode network can be connected to the output of the circuit arrangement via a resistance component. The resistance of this resistance device is much larger than any resistance of one of the resistance devices of one of the series connections. The resistances of the resistance components of the series connections are preferably the same. The resistances of the resistance components with negative temperature coefficients are likewise the same.An exemplary embodiment of a circuit arrangement according to the invention is illustrated in the figures. Furthermore, two alternatives for diode networks are shown in the figures, which can form means for determining a maximum temperature of the circuit arrangement according to the invention. It shows FIG. 1 shows an arrangement of a control device and a circuit arrangement as is known from the prior art, FIG. 2 shows an arrangement of a control device and the exemplary embodiment for the circuit arrangement according to the invention, FIG. 3 shows the exemplary embodiment with a first alternative for the diode network of the circuit arrangement according to the invention, and FIG. 4 shows the exemplary embodiment with a second alternative for the diode network of the circuit arrangement according to the invention.Both the arrangement shown in FIG. 1 and known from the prior art and the arrangement shown in FIG. 2 with the circuit arrangement M according to the invention have a control unit ECU and a circuit arrangement M', M, wherein the circuit arrangement M', M has a plurality of temperature sensors S 1, S 2, S 3, S 4.The circuit arrangements M', M have a printed circuit board and a conductor tracks and electrical components arranged on the printed circuit board, including the temperature sensors S 1, S 2, S 3, S 4, which are not shown in the figures, however, for the sake of better clarity with the exception of the temperature sensors S 1, S 2, S 3, S 4 and the conductor tracks provided for connecting the temperature sensors. The components are connected to one another by the conductor tracks. With the temperature sensors S 1, S 2, S 3, S 4, temperatures at different points of the printed circuit board can be detected. The circuit arrangement has an output.The output of the circuit arrangement M' (FIG. 1 ) known from the prior art has an output with a plurality of connections, of which within the circuit arrangement M' each connection is assigned to one of the temperature sensors S 1, S 2, S 3, S 4 and is connected to an output of this temperature sensor. Each terminal of the output of this circuit arrangement M' is connected to the control unit ECU. At each of these terminals, a temperature signal T1, T2, T3, T4 of the temperature sensor S1, S2, S3, S4 connected to it is displayed.The output of the circuit arrangement according to the invention (FIG. 2 ) has an output with a single connection. This is connected within the circuit arrangement M to the means MAX(T1,..., Tn) for determining a maximum temperature. This has a plurality of inputs, each of which is connected to an output of one of the temperature sensors S 1, S 2, S 3, S 4. During operation of the circuit arrangement, a signal T1, T2, T3, T4 is present at the inputs of the means MAX(T1,..., T4), which signal indicates the temperatures measured by the temperature sensors S1, S2, S3, S4.The means MAX(T1,..., Tn) for determining a maximum temperature determines from the temperature signals T1, T2, T3, T4 the signal indicating the maximum temperature and provides this signal or a signal Tmax on its output from which the maximum temperature measured by the temperature sensors S1, S2, S3, S4 can be determined. This signal Tmax is present at the output terminal and is transmitted to the control unit ECU.Temperature sensors S 1, S 2, S 3, S 4 can be used, for example, in the form of thermistors, i.e. resistance components having a negative temperature coefficient, as is the case in the variants of the circuit arrangements M illustrated in FIGS. 3 and 4.Both in the circuit arrangement M according to the invention according to FIG. 3 and in the circuit arrangement M according to the invention according to FIG. 4, diode networks are used. Each diode network has resistor components R 1, R 2, R 3, R 4, which together with the sensors S 1, S 2, S 3, S 4 form a series circuit S 1, R 1; S 2, R 2; S 3, R 3; S 4, R 4. A voltage is applied to nodes between the resistor devices R 1, R 2, R 3, R 4 and the sensors S 1, S 2, S 3, S 4, forming a signal indicative of the temperature sensed by the sensors S 1, S 2, S 3, S 4. The sensors S 1, S, S 3, S 4 are identical thermistors. The resistor components R1, R2, R3, R4 are also identical.In the circuit arrangement from FIG. 3, the resistor components R 1, R 2, R 3, R 4 of the diode network are connected to a positive potential Vb of the supply voltage and the sensors S 1, S 2, S 3, S 4 are connected to the negative potential of the supply voltage or to a reference potential Gnd. The nodes between the resistor devices R1, R2, R3, R4 and the sensors S1, S2, S3, S4 are connected via diodes D1, D2, D3, D4 of the diode network to the output of the circuit arrangement M, at which the signal indicating the maximum temperature is present. The diodes D1, D2, D3, D4 are reverse-biased from the node to the output. Furthermore, a resistor device Rm is arranged between the positive potential terminal of the supply voltage and the output of the circuit arrangement M. The electrical resistance of this resistor device Rm is much greater than the electrical resistance of the resistor devices R1, R2, R3, R4. This resistance component could alternatively also be arranged in the control unit ECU.The circuit arrangement M according to FIG. 3 can be explained most easily for a case in which the sensor S 1 measures the highest temperature and the temperatures at the other sensors S 2, S 3, S 4 are very low. Then, the resistance of the thermistor or sensor S1 is very small compared to the resistances of the thermistors or sensors S2, S3, S4. Due to the voltage dividers between the resistor devices R 2, R 3, R 4 and the sensors S 2, S 3, S 4, potentials are then established at the node between the resistor devices R 2, R 3, R 4 and the sensors S 2, S 3, S 4, which are close to the positive potential Vb of the supply voltage, while due to the voltage divider between the resistor device R 1 and the sensor S 1, a potential is then established at the node between the resistor device R 1 and the sensor S 1 which is close to the reference potential of the supply voltage. Due to the very high resistance of the component Rm, which is hardly conductive, a voltage Tmax is initially established at the output, which is close to the positive potential of the supply voltage. If, however, the voltage T1 is now very low on account of the temperature rise at the sensor S1, the diode D1 becomes conductive and the voltage T1 increases by the voltage drop across the diode D1 sets in at the output. The voltage Tmax at the output thus corresponds to the voltage T 1 increased by the diode voltage. In this idealised consideration, a current through Rm is not taken into consideration. The deviation of the voltage Tmax from the voltage T 1 is systematic and can be compensated in the control unit ECU during the evaluation of the temperature signal.In the circuit arrangement from FIG. 4, the sensors S 1, S 2, S 3, S 4 are connected to a positive potential Vb of the supply voltage, and resistor components R 1, R 2, R 3, R 4 of the diode network are connected to the negative potential of the supply voltage or to a reference potential Gnd. The nodes between the sensors S1, S2, S3, S4 and the resistance elements R1, R2, R3, R4 are connected via diodes D1, D2, D3, D4 of the diode network to the output of the circuit arrangement M, at which the signal indicating the maximum temperature is present. The diodes D1, D2, D3, D4 are connected in the forward direction from the nodes to the output. Furthermore, a resistor component Rm is arranged between the output of the circuit arrangement M and the connection for the reference potential Gnd of the supply voltage. The electrical resistance of this resistor device Rm is much greater than the electrical resistance of the resistor devices R1, R2, R3, R4.The circuit arrangement M according to FIG. 4 can also be explained most easily for a case in which the sensor S 1 measures the highest temperature and the temperatures at the other sensors S 2, S 3, S 4 are very low. Then, the resistance of the thermistor or sensor S1 is very small compared to the resistances of the thermistors or sensors S2, S3, S4. Due to the voltage dividers between the sensors S 2, S 3, S 4 and the resistor devices R 2, R 3, R 4, potentials are then established at the node between the resistor devices R 2, R 3, R 4 and the sensors S 2, S 3, S 4, which are close to the reference potential Gnd of the supply voltage, while due to the voltage divider between the sensor S 1 and the resistor device R 1, a potential is then established at the node between the sensor S 1 and the resistor device R 1, which is close to the positive potential of the supply voltage. Due to the very high resistance of the component Rm that is hardly conductive, a voltage Tmax is initially established at the output, which is close to the reference potential Gnd of the supply voltage. If, however, the voltage T1 is now very high on account of the temperature rise at the sensor S1, the diode D1 becomes conductive and the voltage T1 is reduced by the voltage drop across the diode D1 and is established at the output. The voltage Tmax at the output thus corresponds to the voltage T1 reduced by the diode voltage. In this idealised consideration, a current through Rm is not taken into consideration. The deviation of the voltage Tmax from the voltage T 1 is systematic and can be compensated in the control unit ECU during the evaluation of the temperature signal.Both with the circuit arrangement M according to FIG. 3 and with the circuit arrangement M according to FIG. 4, a voltage Tmax can be provided at its output, from which the control device can determine the maximum temperature of the circuit arrangement M.List of reference charactersM circuit arrangement according to the invention M' circuit arrangement according to the prior art MAX(T1, T2, T3, T4) means for determining a maximum temperature S1 sensor S2 sensor S3 sensor S4 sensor R1 resistance component R2 resistance component R3 resistance component R4 resistance component Rm resistance component D1 diode D2 diode D3 diode D4 diode Vb positive potential of the supply voltage Gnd reference potential of the supply voltage T1 voltage T2 voltage indicating temperature at the sensor S1 voltage T3 voltage indicating temperature at the sensor S3 voltage T4 voltage indicating temperature at the sensor S4 voltage Tmax temperature at the output

Claims

Circuit arrangement (M) having a printed circuit board and an arrangement, arranged on the printed circuit board, of conductor tracks and electrical components which are connected to one another by the conductor tracks, wherein these components include temperature sensors (S1, S2, S3, S4), with which the temperature can be detected at different points on the printed circuit board, wherein the circuit arrangement (M) has an output and the output of the circuit arrangement (M) is connected to outputs of the temperature sensors (S1, S2, S3, S4), characterized in that the circuit arrangement has a means (MAX(T1, T2, T3, T4)) for determining a maximum temperature, wherein the outputs of the temperature sensors (S1, S2, S3, S4), each of which is connected to an input of the means (MAX(T1, T2, T3, T4)) for determining the maximum temperature, and an output of the means (MAX(T1, T2, T3, T4)) for determining the maximum temperature is connected to the output of the circuit arrangement (M), the means (MAX(T1, T2, T3, T4)) for determining the maximum temperature being suitable and configured • to determine the temperature signal which indicates the highest temperature from temperature signals (T1, T2, T3, T4) present at the inputs, • applying this temperature signal or another signal (Tmax) indicating the maximum temperature at the output of the means for determining the maximum temperature and thus at the output of the circuit arrangement (M).Circuit arrangement (M) according to Claim 1, characterized in that the means (MAX(T1, T2, T3, T4)) for determining the maximum temperature has a diode network, a discrete transistor circuit, an operational amplifier circuit or an integrated circuit.Circuit arrangement (M) according to Claim 2, characterized in that the diode network has a plurality of resistance components (R1, R2, R3, R4), each of which is arranged in a series circuit with a resistance component having negative temperature coefficients as temperature sensors (S1, S2, S3, S4), the series circuit being connected in parallel to an input of the network for a supply voltage.Circuit arrangement (M) according to Claim 3, characterized in that the resistance component (R1, R2, R3, R4) is connected to a connection for the high potential (Vb) of the input for the supply voltage, and the resistance component having the negative temperature coefficient (S1, S2, S3, S4) is connected to the low potential (Gnd) of the supply voltage.Circuit arrangement (M) according to Claim 3, characterized in that the resistance component having the negative temperature coefficient (S1, S2, S3, S4) is connected to a connection for the high potential (Vb) of the input for the supply voltage, and the resistance component (R1, R2, R3, R4) is connected to the low potential (Gnd) of the supply voltage.Circuit arrangement (M) according to Claim 4 or 5, characterized in that each node between one of the resistor components (R1, R2, R3, R4) and one of the resistor components having the negative temperature coefficient (S1, S2, S3, S4) is connected to the output of the circuit arrangement (M) via a diode (D1, D2, D3, D4).Circuit arrangement (M) according to Claims 4 and 6, characterized in that the diodes (D1, D2, D3, D4) are connected in the reverse direction from the nodes of the series connections to the output of the circuit arrangement.Circuit arrangement (M) according to Claim 7, characterized in that the connection for the high potential (Vb) of the supply voltage of the diode network is connected via a resistance component (Rm) to the output of the circuit arrangement (M).Circuit arrangement (M) according to Claims 5 and 6, characterized in that the diodes (D1, D2, D3, D4) are connected in the direction of flow from the nodes of the series connections to the output of the circuit arrangement (M).Circuit arrangement (M) according to Claim 9, characterized in that the low-potential terminal (Gnd) of the supply voltage of the diode network is connected via a resistance component (Rm) to the output of the circuit arrangement (M).

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