Measurements in switching devices

Abstract

Device comprising the following: a switch (11, 40, 51) with a control terminal (14), a first load connection (12) and a second load connection (13), a magnetoresistive sensor (15, 25, 26, 35, 41, 515, 516, 534, 67) configured to measure a current flowing between the first load terminal (12) and the second load terminal (13), and a current mirror-based sensor (16, 52, 53, 533) for measuring the current between the first load terminal (12) and the second load terminal (13).

Description

Technical field

[0001] The present application relates to devices and methods related to carrying out measurements in switching devices. background

[0002] Switching devices are used in many applications to selectively provide electrical connections. In many cases, transistors are used as switches in such switching devices.

[0003] In many applications, such as monitoring and / or diagnostics, it is desirable or even necessary to perform measurements on switching devices, for example, to monitor their operation. Typical measurements include current measurements, which measure the load current through the switching device; voltage measurements, which measure the voltage across the switching device; or temperature measurements, which measure the temperature of the switching device. This can be important, for example, in safety-critical applications to detect overcurrent, overvoltage, or overtemperature and to take countermeasures (such as opening the switch) to prevent damage to the switching device due to such conditions.

[0004] Various approaches to current measurement are conventionally used in switching devices. For example, a shunt resistor has been used for current measurement in some cases. However, current measurements using a shunt resistor are comparatively expensive because the resistor must be designed for high currents, requiring a correspondingly large area on a chip, and the resistor must also be very precise (low tolerance in its resistance value) to allow for accurate measurement. Especially for switching devices that handle a wide range of currents (for example, from a few milliamperes to several tens of amperes or more), designing and manufacturing a shunt resistor is a challenge for practical implementation. Furthermore, the voltage drop across typical shunt resistors is usually quite low, even for high currents (for example, a few microvolts), which makes measurement more difficult.

[0005] Other switching devices utilize a sensor transistor, which can be coupled to an actual switching transistor, for example, in a current mirror configuration. Such sensor transistors offer a relatively inexpensive solution for current measurements. However, measuring small currents with such sensing resistors can be challenging due to a low voltage drop.

[0006] Other approaches measure a voltage between the load terminals of the switching device as an indirect current measurement, for example, between the source and drain terminals of a switching transistor. However, this creates similar challenges to those mentioned above. Furthermore, comparators or operational amplifiers are required to evaluate a large voltage range.

[0007] Such comparators / operational amplifiers are also needed to measure the voltage drop across typical switching devices, especially when the switching devices are used for a wide range of common-mode voltages.

[0008] For temperature measurements, it is sometimes difficult to place a temperature sensor close enough to the switching device to provide accurate temperature measurements.

[0009] It is therefore a task to provide improved possibilities for carrying out measurements in switching devices.

[0010] US Patent 2005 / 0077890A1 discloses a current measurement in a transistor switch using a magnetoresistive sensor. Similar devices are also known from German Patent Application DE 102014111416B4, US Patent 7199435B2, US Patent 2013 / 0334531A1, and US Patent 2007 / 0064460A1. JP H07-209336A discloses a magnetoresistive current sensor with multiple measuring ranges. Summary

[0011] A device according to claim 1 or 3 and a method according to claim 16 or 18 are provided. The dependent claims define further embodiments. Brief description of the drawings Fig. Figure 1 is a block diagram of a switching device according to one embodiment. Fig. Figure 2 is a block diagram of a switching device according to a further embodiment. Fig. Figure 3 is a block diagram of a switching device according to a further embodiment. Fig. Figure 4A is a top view of an implementation example for a switching device according to one embodiment. Fig. 4B is a side view of the switching device made of Fig. 4A. Fig. 4C is a circuit diagram symbol for the switching device made of Fig. 4A and Fig. 4B. Fig. Figure 5 is a detailed diagram illustrating a switching device according to one embodiment. Fig. 6A and Fig. Figure 6B are representations illustrating a magnetoresistive sensor bridge according to some embodiments. Fig. Figure 7 is a diagram illustrating an open load. Fig. Figure 8 is a flowchart illustrating a procedure according to one embodiment. Fig. Figure 9 is a flowchart illustrating a procedure according to a further embodiment. Detailed description

[0012] The following describes various embodiments with reference to the accompanying drawings. These embodiments are provided merely as examples and are not to be considered limiting. While, for example, embodiments are described as including various features (e.g., components, elements, details, processes, etc.), some of these features may be omitted in other embodiments and / or replaced by alternative features. Furthermore, in addition to the features explicitly described here and shown in the drawings, other features may be provided, for example, features that are conventionally used for switching devices.

[0013] Unless otherwise noted, features of different embodiments may be combined to form further embodiments. Variations and modifications described for one embodiment may also be applicable to other embodiments.

[0014] Any direct connections or couplings between elements, i.e. connections or couplings without additional intervening elements (for example, simple metal connections), may be replaced by indirect connections or couplings, i.e., connections or couplings that include one or more intervening elements, and vice versa, as long as the general purpose of the connection or coupling, for example, to transmit a certain type of signal, to transmit a certain type of information, or to provide a certain type of control, is essentially maintained.

[0015] In some embodiments, switching devices are provided that include one or more switches. Switches and switching devices are generally described as comprising a control terminal and at least one first and one second load terminal. Depending on a signal supplied to the control terminal, the switch provides either a low-resistance connection between the first and second load terminals, allowing current to flow, or a high-resistance decoupling between the load terminals, so that substantially no current can flow (except for possible, usually undesirable, leakage currents). The low-resistance connection state described above is referred to here as a closed or on state of the switch or switching device, and the high-resistance state is referred to here as an open or off state of the switch or switching device.

[0016] In various embodiments, switches can be implemented as transistors. In the case of a field-effect transistor (FET), such as a metal-oxide-semiconductor field-effect transistor (MOSFET), the first and second load terminals correspond to the source and drain terminals, and the control terminal corresponds to the gate terminal. In the case of an insulated-gate bipolar transistor (IGBT), the first and second load terminals again correspond to the source and drain terminals, and the control terminal corresponds to a base terminal. In the case of a bipolar transistor, the first and second load terminals correspond to a collector and emitter terminal, and the control terminal corresponds to the base terminal. Unless otherwise noted, embodiments can be implemented using various types of transistors.

[0017] In some embodiments, magnetoresistive sensors are used to perform measurements in switching devices. Magnetoresistive sensors utilize magnetoresistive effects, which change resistance depending on a magnetic field. The magnetic field can be generated by a current flowing through the switch, particularly between the switch's load terminals.

[0018] Several magnetoresistive effects can be used to implement magnetoresistive resistors and sensors. Examples include anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), colossal magnetoresistance (CMR), and tunneling magnetoresistance (TMR), which are collectively referred to here as XMR. The implementation of magnetoresistive elements based on these effects is a conventional technique and will not be described in detail. To implement such magnetoresistive elements, several layers of ferromagnetic, antiferromagnetic, and / or dielectric materials are generally deposited on a substrate. One or more layers can be magnetized to serve as a reference layer(s).They serve, and contacts are provided to enable the measurement of the resistance of these elements in response to an applied magnetic field.

[0019] In some embodiments, magnetoresistive elements can be arranged in a bridge circuit configuration to provide a sensor, such as a current sensor. However, other arrangements of magnetoresistive elements are also within the scope of protection of the present application.

[0020] Now illustrated with attention to the figures Fig. 1 a block diagram of a switching device 10 according to an embodiment.

[0021] The switching device 10 from Fig. The circuit comprises a switch 11 with a control terminal 14, a first load terminal 12, and a second load terminal 13. In operation, for example, one of the load terminals 12, 13 can be connected to a supply voltage or a reference potential, while the other load terminal 12, 13 can be connected to a load to selectively couple the load to the supply voltage or the reference potential. In other applications, both load terminals 12, 13 can be connected to loads to selectively provide a connection between the loads. The operation of the switch is controlled by means of the control terminal 14. The switch 11 can be implemented using a transistor as described above.

[0022] The switching device 10 further comprises an XMR current sensor 15, which is arranged to detect a current flowing through the switch 11, for example, a current flowing between the load terminals 12 and 13. A flowing current generates a magnetic field, which in turn can be detected by the XMR sensor 15. In some embodiments, the XMR sensor 15 may include magnetoresistive elements arranged in a bridge configuration, as will be explained in more detail later. In other embodiments, the XMR sensor 15 may be used to measure a voltage across the switch 11 by applying a predefined current.

[0023] Furthermore, the switching device 10 includes an additional current measurement 16, which uses a different measurement technique than the XMR sensor 15 to measure the current flowing through the switch 11. For example, a conventional sensor transistor in a current mirror configuration or a measurement via a shunt resistor can be used. Providing the additional current measurement 16 offers redundancy in the current measurement; that is, if one current measurement 15, 16 fails, the other is still available. Furthermore, in the embodiment consisting of Fig. 1. A so-called diversity is provided, meaning that different techniques are used for current measurements. Both redundancy and diversity can help to meet functional safety requirements, for example, for ASIL requirements (ASIL: Automotive Safety Integrity Level). For example, functional safety requirements are defined in ISO 26262.

[0024] Similar to conventional approaches, in embodiments, if, for example, an overcurrent is detected using the XMR sensor 15 and / or the further current measurement 16, emergency measures such as opening the switch 11 can be taken.

[0025] Furthermore, in some embodiments, the XMR sensor 15 can also be used for temperature measurements by utilizing a temperature dependency of the magnetoresistive elements of the XMR sensor 15. Voltage measurements can also be provided.

[0026] In some embodiments, the XMR sensor 15 can be used to provide "lifetime" monitoring of the switch 11; for example, slow deterioration / degradation of the switch 11 can be detected so that the switch 11 or the switching device 10 can be replaced before failure becomes likely. This is described in more detail below. Before such details are explained, some further embodiments are described with reference to Fig. 2 and Fig. 3 described.

[0027] In some embodiments, the results of the current measurements by the XMR sensor 15 and / or the further current measurement 16 can be output via a diagnostic output 17 for use by other circuits or devices. In some embodiments, a measure of the measured current can be output. In other embodiments, a flag can be output if a fault condition, for example an overcurrent, is detected. In this case, an evaluation logic circuit or a microcontroller can be provided in the switching device 10 to perform such an evaluation.

[0028] To avoid repetition, elements that have already been referenced will be used. Fig. 1 were explained, in Fig. 2 and Fig. 3 the same reference figures as in Fig. 1 and will not be described in detail again. In particular, the embodiments from Fig. 2 and Fig. 3 a switch 11 with terminals 12, 13 and 14 and a diagnostic output 17.

[0029] Fig. Figure 2 illustrates a switching device 20 according to a further embodiment. The switching device 20 comprises a first XMR sensor for measuring a current flowing through the switch 11 and a second XMR sensor for measuring a current flowing through the switch 11. The first XMR sensor 25 and the second XMR sensor 26 can be configured for different measuring ranges. For example, the first XMR sensor 25 can be configured to measure currents below a first threshold, and the second XMR sensor 26 can be configured to measure currents above a second threshold, which may be the same as the first threshold or different from it. By using different thresholds, switching between measuring ranges can be avoided in a case where a current is close to a transition point between the two measuring ranges of the first and second XMR sensors 25, 26.

[0030] As in Fig. As shown in Figure 3, the first XMR sensor 25 and the second XMR sensor 26 can be implemented as separate sensors in some embodiments. To provide different measuring ranges, different magnetoresistive elements with different resistance values ​​can be used, for example. In other embodiments, a single XMR sensor can be provided, and switching between measuring ranges can be performed using different bias currents or bias voltages for the XMR sensor. This is similar to what is shown with regard to the switching device 10 in Figure 3. Fig. As explained in section 1, current measurements by the XMR sensors 25, 26 can be used to detect an undesired condition, such as overcurrent conditions or overtemperature conditions, in order to take appropriate countermeasures and / or to output appropriate signals via the diagnostic output 17.

[0031] Fig. Figure 3 illustrates a switching device 30 according to a further embodiment. The switching device 30 comprises a switch 11 as explained above and a multi-tap XMR sensor 35. A multi-tap XMR sensor is a sensor from which an output can be tapped at different locations, for example, to provide different offsets or to measure against different reference potentials. Accuracy can also be improved in some embodiments using such multi-tap XMR sensors.

[0032] It should be noted that the embodiments from Fig. 1-3 can be combined in numerous ways. For example, another current measurement can also be taken as the additional current measurement 16 from Fig. 1 in the switching devices Fig. 2 and Fig. 3 can be provided or the XMR sensors 15, 25 and / or 26 can be used as multi-tap XMR sensors than the multi-tap XMR sensor 35 Fig. 3 will be implemented. While the various techniques and features regarding Fig. Since the techniques presented in Figures 1-3 can be used independently, they can also be implemented in combination. Furthermore, the techniques described above can be applied not only to individual switches but also to circuits comprising multiple switches. For example, multiple switches can be provided in full-bridge or half-bridge configurations. Sensors, such as the XMR sensors mentioned above, for example, for current sensing, can be provided for one, some, or all of the sensors in such a multi-sensor circuit.

[0033] Therefore, the indefinite article “ein / eine” (e.g., ein Schalter, ein Sensor) in the context of this application is not to be understood as limiting to one, but rather as meaning “one or more”.

[0034] Examples of the various features that refer to Fig. Points 1-3, which were explained, will be described in more detail below.

[0035] The switching devices 10-30 can be implemented as integrated devices, with the switch and the XMR sensor(s) and / or possible additional current measurements implemented on the same chip. In other embodiments, they can be integrated in a single package but using separate chip dies. An example of an integration of an XMR sensor with a switch is shown in Fig. 4A and Fig. 4B illustrates this. In the example from Fig. 4A and Fig. 4B is an AMR sensor provided on a MOSFET. Fig. 4A illustrates a top view, whereas Fig. 4B illustrates a cross-sectional side view.

[0036] The in Fig. 4A and Fig. The device illustrated in Figure 4B includes, in particular, an AMR sensor 41 mounted on a MOSFET chip 40. As shown in the side view from Fig. As can be seen in Figure 4B, the MOSFET 40 is attached to a copper busbar 46 using adhesive 47. A copper clip 48 is provided, which carries the drain-source current of the MOSFET, i.e., the load current, by being coupled to the drain or source of the MOSFET. The AMR sensor 41 is mounted to the copper clip 48 using an insulating adhesive 49. Mounting the AMR sensor 41 on the copper clip 48 allows for accurate detection of the load current flowing through the copper clip 48. The load current is in Fig. 4B as I load designated.

[0037] In the embodiment from Fig. The AMR sensor 41 is a differential sensor. For example, the AMR sensor 41 can be coupled to connection pins 42-45 via bond wires.

[0038] The connection pins 44 and 45 can, for example, be used for a bias voltage (e.g., by supplying a positive supply voltage VDD to ground), and the connection pins 42 and 43 can be used as differential taps for the AMR sensor 41. In some embodiments, such a differential sensor can be implemented as a bridge configuration, as will be explained later. In some embodiments, differential detection can reduce the influence of external stray fields.

[0039] Other connection pins of the device can be used to contact the MOSFET 40, as shown in the circuit diagram symbol from Fig. 4 shown, where a first connection pin is coupled to the gate, a second connection pin is coupled to the drain, and a third connection pin is coupled to the source.

[0040] The components from Fig. 4A, Fig. 4B are provided in a package 410. In other embodiments, the AMR sensor 41 can be integrated with the MOSFET 40 in a single chip. The arrangement of Fig. 4 is merely an example.

[0041] The 410 housing is merely an example, and in general, XMR sensors like the ones shown here can be integrated using conventional integrated circuit technology, for example, integrated into a housing.

[0042] Next, possible implementations of the various features and techniques, referring to Fig. Figures 1-3 illustrate the concepts using more detailed circuit diagrams. These circuit diagrams are merely implementation examples, and other implementations are equally possible.

[0043] In Fig. Reference 57 generally refers to a circuit section comprising a switching transistor 51, together with a current measurement circuit that uses a current sensor transistor 52. Reference 59 generally refers to a circuit section comprising two XMR sensors 515, 516 and a temperature sensor 522. Reference 510 generally refers to a block diagram of a device 532 according to one embodiment. References 511, 512 and 513 generally refer to diagrams that include example signals for further illustration.

[0044] As already mentioned, the circuit section 57 includes the switching transistor 51. In the example from Fig. In the example from 5, the switching transistor 51 is controlled via a gate line 57 and is coupled with its load terminals (source and drain) between a supply voltage Vsupply and a load 56 in order to selectively couple the load 56 with the supply voltage Vsupply. Therefore, in the example from Fig. 5 as a high-side switch. In other embodiments, switching devices can be used as low-side switches (for example, between ground and a load) or as switches between circuit components.

[0045] Furthermore, the circuit section 57 includes a sensor transistor 52. The sensor transistor 52 is also controlled via the gate line 57 and can be designed similarly to the switching transistor 51, but with smaller dimensions, so that when the switching transistor 52 is switched on, it conducts a current that is proportional to the load current through the switching transistor 51 by a factor called the Kilis factor. For control purposes, the load terminals of transistors 52 and 51 are coupled, as shown, to the inputs of a differential amplifier 54, with one output of the differential amplifier 54 controlling a transistor 53 connected in series with transistor 52. A sensing resistor 55 is also connected in series with transistors 52 and 53. A voltage proportional to the load current of the switching transistor 51 can be tapped across the sensing resistor 55.

[0046] The number 511 generally refers to a graph showing an example measurement curve, where a resistance sensing current through the transistor 52, which leads to a corresponding voltage drop across the sensing resistor 55, is graphically represented against the load current of the switching transistor 51.

[0047] Current measurement via the transistors 52, 53, the differential amplifier 54 and the resistor 55 or other types of current mirror arrangements in some embodiments can be used for currents of different orders of magnitude, e.g. comparatively small currents (e.g. mA), but also large currents of e.g. several hundred amperes up to short-circuit detection including overload.

[0048] Furthermore, XMR sensors 515 and 516 are provided for current measurement. These sensors can be provided, for example, on a copper busbar or another conductor carrying the load current of the switching transistor 51, as described in reference to Fig. 5 discussed.

[0049] The XMR sensors 515 and 516 are each configured as a bridge circuit (Wheatstone bridge) comprising four magnetoresistive elements that change their resistance depending on a magnetic field generated by the load current. The XMR sensor 515 includes magnetoresistive elements 517 to 520, which are configured as shown in Fig. 5 are shown switched, and the XMR sensor 516 comprises magnetoresistive elements 523 to 526, which are as shown in Fig. The circuits are shown in Figure 5. Sensors 515 and 516 are biased by a supply voltage 514. Sensor 515 further includes a differential amplifier 521, which taps the nodes between resistors 517 and 519 and between resistors 518 and 520. Sensor 516 includes a differential amplifier 536, which taps the nodes between magnetoresistive elements 523 and 524 and between magnetoresistive elements 525 and 526. The magnetoresistive elements of sensors 515 and 516 can be any type of magnetoresistive element, for example, AMR, TMR, GMR, etc.

[0050] Outputs from the differential amplifiers 521 and 536 are supplied to an evaluation circuit 527, which receives the signals and outputs a signal in response to the signal. The output signal can, for example, include an alarm signal if the sensor 515 or 516 indicates an overcurrent or fault condition, or it can include a signal indicating the magnitude of the load current.

[0051] Furthermore, the circuit section 59 includes a temperature sensor 522 for measuring the temperature of the switch 51 and also for outputting a result to the evaluation circuit 527. The evaluation circuit 527 can use the measured temperature to determine, for example, an overtemperature condition. In other embodiments, the temperature sensor 522 can be omitted, and the temperature can be measured via the sensors 515, 516 using the temperature dependence of the magnetoresistive elements.

[0052] In the embodiment from Fig. 5. The magnetoresistive elements of sensor 515 can have different resistance values ​​than the magnetoresistive elements of sensor 516 to provide different measuring ranges. In other embodiments, different supplies can be used for sensors 515 and 516, for example, different bias voltages, to provide different measuring ranges. In still other embodiments, a single sensor 515 can be used, which can be selectively supplied with different bias voltages or currents. Measuring different ranges using sensors 515 and 516 is explained with reference to graphs 512 and 513.

[0053] Graph 512 shows example voltages Vout1 and Vout2 of sensors 515 and 516 across switching transistor 51 as a function of the load current. In this example, sensor 515 exhibits a linear response (curve 529) for low currents, while sensor 516 shows a linear response (curve 530) for high currents. Both sensors can be used in an area marked by dashed lines, and switching between them is performed by an evaluation circuit 527 within this area. Depending on the thresholds indicated by dashed lines in graph 512, a switching circuit 528 of the evaluation circuit 527 performs a switching operation and multiplies, for example, curve 529 and / or 530 by a scaling factor to combine the curves, so that an evaluation circuit 527 outputs a linear curve 531 over the entire measuring range, as shown in graph 513.In this way, a large measuring range can be covered.

[0054] Figure 510 is a block diagram of a device 532 according to an embodiment comprising the components discussed above. In particular, the device comprises a sensor, as illustrated in Figure 57, also referred to as a Kilis sensor, which operates based on a sensor transistor, such as the sensor transistor 52, and an XMR sensor 534, for example an AMR sensor or another XMR sensor, which is formed as a circuit part 59. Fig. 5 can be configured. An evaluation circuit 535 evaluates the outputs of the Kilis sensor 533 and the AMR sensor 534 and takes appropriate measures, for example, opening the switch 51 in the event of an overcurrent. Furthermore, the evaluation circuit 535 can also detect contradictions between the outputs of sensors 533 and 534; for example, if only one sensor measures a current, this can also lead to a kind of alarm signal or emergency opening of the switching transistor 51. In this way, redundancy and diversity are provided. As already mentioned with reference to Fig. As mentioned in 1-3, some of the elements can be derived from Fig. 5 may be omitted in other embodiments. For example, the Kilis sensor may be provided in some embodiments, while in others only an XMR sensor may be provided. Furthermore, a tappable XMR sensor is provided in some embodiments. This will be discussed next with reference to Fig. 6 explained.

[0055] As already mentioned with reference to Fig. As mentioned in section 3, XMR sensors can be implemented as multi-sampling XMR sensors in certain embodiments. For example, each of the sensors 515, 516 from Fig. 5 as such a multi-sampling sensor. An example of a multi-sampling sensor will now be given with reference to Fig. 6A and Fig. 6B discussed.

[0056] Fig. Figure 6B is a view of an XMR sensor that can be used in embodiments comprising a sensor bridge 67 with magnetoresistive elements 60, 61, 62 and 63. Fig. 6A is a more detailed view of bridge 67 to explain multiple taps.

[0057] Bridge 67 from Fig. 6A, Fig. 6B is supplied by a bias voltage 66. Nodes between magnetoresistive elements 60, 61 and between magnetoresistive elements 62, 63 are coupled to inputs of a differential amplifier 65, which outputs a sensor signal that is a measure of a current flowing through a conductor (for example, the one referred to in Fig. 4 copper clip mentioned), which is located near the sensor, flows.

[0058] In the more detailed view from Fig. Figure 6A shows that the magnetoresistive element 62 is divided into four magnetoresistive elements 62A to 62D. The number four is only an example here, and other numbers can be provided. Using switches 64A to 64D, nodes between the subcomponents 62A to 62D, or between subcomponent 62A and resistor 60, can be selectively tapped to be coupled to the amplifier 65. In this way, different offsets can be provided for the measurements. The different tapping can also be performed alternately, for example, and the results obtained can be combined to increase the accuracy of the measurement. Furthermore, by selecting a suitable tap, a desired offset can be provided, which can be helpful, for example, for measuring small currents. Variable tapping can also be used for calibration purposes.In some embodiments, switches 64A to 64D can be implemented as fuses and, for example, during a calibration process, one of the switches can be permanently closed while the others remain permanently open.

[0059] By providing an XMR sensor for current measurement, galvanic isolation is achieved. Furthermore, current measurement can be performed in both directions (for example, from the first terminal to the second load terminal of the switch, or from the second load terminal to the first terminal of the switch). In some embodiments, switches 64A to 64D can also be implemented as fuses and can be used to compensate for different currents in both bridge branches (60, 61 on one side and 62, 63 on the other) when the load current is zero, for example, during calibration.

[0060] By providing a multiple access point as in Fig. With a 6A rating, various voltages can be checked in the off state of the switch without a load current. For example, a positive supply voltage such as VCC or VDD can be checked above 64A, with half of this voltage connected to ground via other taps. Therefore, the supply voltage can be checked as an additional safety measure in a no-current state where the resistance values ​​of the resistors are known.

[0061] While a temperature sensor is provided in other embodiments, such a temperature sensor can, as mentioned, be omitted and a temperature can be measured using XMR sensors and their known temperature behavior, for example in a state with no load current in an open state.

[0062] It should be noted that the XMR sensor discussed above can not only be used to measure current, but can also be used to measure a voltage drop across the resistor.

[0063] For voltage measurement using an XMR sensor, a predetermined constant current can be applied to the switch (e.g., a switching transistor), for example, using a conventional constant current source such as a temperature-compensated constant current source. The resistance of magnetoresistive elements, such as those discussed above, then varies with the voltage across the switch, for example, in an inversely proportional manner, which can be detected at the sensor output.

[0064] Various cases can be distinguished by measuring the voltage, for example, a conventional voltage measurement or a voltage measurement using the XMR sensor. For example, no current flows in an off state, but the entire voltage drops across the switch. Other designs can provide detection of an open load. This is described with reference to Fig. 7 explained.

[0065] In Fig. A MOSFET switch 70, coupled to a load 73, is provided. In an open state of the switch 70, essentially the entire supply voltage drops across the switch 70, as long as the load 73 has a finite resistance. A case of a disconnected (open) load can be viewed as a high-resistance state of the resistor 73.

[0066] To detect / evaluate such a condition, embodiments provide a current source 72 that supplies a small current, e.g., in the range of 10–100 mA. A switch 71 is closed for detection. An open load then leads to a high voltage drop caused by this current, which can be detected, thus indicating the open load state. Furthermore, a drain-source voltage can be measured in embodiments. The on state of the switch can also be detected by detecting a current flow.

[0067] By monitoring the voltage and / or current, the threshold voltage of the switch can be monitored in certain embodiments. Monitoring the threshold voltage, or the source-gate voltage and source-drain voltage of a switching transistor over time, allows for the evaluation of aging or other temporal behavior (drift) of the switch, and enables, for example, the prediction of its lifespan and future drift behavior. For instance, if the threshold voltage increases, the voltage drop across the switch during normal operation also increases, which can be monitored. In some embodiments, this can allow for early detection that a switch needs to be replaced before it actually fails. In other embodiments, a different property of the switch, such as its on-resistance, can be monitored.

[0068] Such diagnostic functions can, for example, help to meet functional safety requirements.

[0069] Fig. Figure 8 is a flowchart showing a process according to one embodiment. The embodiment is from Fig. 7 can be used to connect any of the devices referred to in Fig. 1-7 were discussed, but it can also be used independently of these. Any modifications and variations made with reference to the switching devices from Fig. The procedures described in sections 1-7 can also be applied to the process described in section 1-7. Fig. 8 are applied. While the procedure from Fig. 8 is shown and described as a series of actions and events; the order in which these actions or events are shown and described is not to be interpreted as restrictive, and other orders are also possible.

[0070] At 80 in Fig. Section 8 comprises the method of providing a switch, for example a switching transistor such as a MOSFET, an IGBT, or a bipolar transistor. Section 81 comprises the method of providing at least one XMR sensor for the switch, which is arranged to measure a current flowing through the switch. The XMR sensor can, for example, have multiple taps, as in Fig. 6A, as illustrated, can be provided with a measuring range that switches through different current or voltage sources, and / or more than one XMR sensor can be provided to cover, for example, different measuring ranges. Optionally, at 82, another current sensor can be provided, for example, using a current mirror, as shown. Fig. 5, circuit section 57 is illustrated. In other embodiments, a supply with an additional current sensor may be omitted.

[0071] The procedure from Fig. Method 8 is merely an example, and other methods can also be provided. The switching device provided by method 8 can be operated as described above, for example, for overcurrent / undercurrent detection or for aging detection.

[0072] Fig. Figure 9 illustrates a flowchart of a method according to one embodiment for measuring a voltage, as explained above. At Figure 90, a predefined current is applied to a switch. At Figure 91, a voltage across the switch is measured using an XMR sensor, which provides galvanic isolation, based on the change in resistance of one or more magnetoresistive elements of the XMR sensor. At Figure 92, the voltage measurement can optionally be used to determine drift or aging, for example, by monitoring a threshold voltage, as explained above.

[0073] The embodiments described above serve only as illustrative examples and are not to be interpreted as limiting.

Claims

[1] Device comprising the following: a switch (11, 40, 51) with a control terminal (14), a first load connection (12) and a second load connection (13), a magnetoresistive sensor (15, 25, 26, 35, 41, 515, 516, 534, 67) configured to measure a current flowing between the first load terminal (12) and the second load terminal (13), and a current mirror-based sensor (16, 52, 53, 533) for measuring the current between the first load terminal (12) and the second load terminal (13). [2] Device according to claim 1, wherein the device is configured to measure a voltage across the switch (11, 40, 51) using the magnetoresistive sensor (15, 25, 26, 35, 41, 515, 516, 534, 67). [3] Device comprising the following: a switch (11, 40, 51) with a control terminal (14), a first load connection (12) and a second load connection (13), and a magnetoresistive sensor (15, 25, 26, 35, 41, 515, 516, 534, 67) configured to measure a current flowing between the first load terminal (12) and the second load terminal (13), wherein the device is set up to measure a voltage across the switch (11, 40, 51) using the magnetoresistive sensor (15, 25, 26, 35, 41, 515, 516, 534, 67). [4] Device according to one of claims 1-3, wherein the magnetoresistive sensor (15, 25, 26, 35, 41, 515, 516, 534, 67) comprises a magnetoresistive sensor bridge. [5] Device according to one of claims 1-4, wherein the magnetoresistive sensor (15, 25, 26, 35, 41, 515, 516, 534, 67) comprises a first magnetoresistive sensor (25, 515) and a second magnetoresistive sensor (26, 516), wherein the first and second magnetoresistive sensors are designed for different measuring ranges. [6] Device according to one of claims 1-5, wherein the magnetoresistive sensor (15, 25, 26, 35, 41, 515, 516, 534, 67) comprises several selectable taps. [7] Device according to claim 6, wherein the taps for controlling an offset of the magnetoresistive sensor (15, 25, 26, 35, 41, 515, 516, 534, 67) and / or for providing a calibration function and / or for providing a backup function are selectable. [8] Device according to one of claims 1-7, wherein the switch (11, 40, 51) comprises a switching transistor. [9] Device according to any one of claims 1-8, wherein the magnetoresistive sensor (15, 25, 26, 35, 41, 515, 516, 534, 67) is based on a giant magnetoresistive and / or a tunnel magnetoresistive and / or a colossal magnetoresistive and / or an anisotropic magnetoresistive. [10] Device according to one of claims 1-9, which further comprises an evaluation circuit (535) configured to monitor the switch (11, 40, 51) based on an output from the magnetoresistive sensor (15, 25, 26, 35, 41, 515, 516, 534, 67). [11] Device according to claim 10, wherein the evaluation circuit (535) is configured to detect an overcurrent based on the output of the magnetoresistive sensor (15, 25, 26, 35, 41, 515, 516, 534, 67). [12] Device according to claim 10 or 11, wherein the evaluation circuit (535) is configured to detect an overtemperature based on an output from the magnetoresistive sensor (15, 25, 26, 35, 41, 515, 516, 534, 67). [13] Device according to one of claims 10-12, wherein the evaluation circuit (535) is configured to detect aging based on an output from the magnetoresistive sensor (15, 25, 26, 35, 41, 515, 516, 534, 67). [14] Device according to one of claims 10-13, wherein the evaluation circuit (535) is configured to detect an on state and / or an open load. [15] Device according to one of claims 1-14, wherein the magnetoresistive sensor (15, 25, 26, 35, 41, 515, 516, 534, 67) is provided on a copper clip which conducts the current. [16] Method comprising the following: Providing a switch (11, 40, 51), Providing a magnetoresistive sensor (15, 25, 26, 35, 41, 515, 516, 534, 67) for measuring a load current through the switch (11, 40, 51), and The provision includes a sensor transistor-based additional current sensor (16, 52, 53, 533) for measuring the load current of the switch (11, 40, 51). [17] Method according to claim 16, wherein providing the magnetoresistive sensor (15, 25, 26, 35, 41, 515, 516, 534, 67) comprises providing the magnetoresistive sensor (15, 25, 26, 35, 41, 515, 516, 534, 67) with a switchable measuring range. [18] Method comprising the following: Applying a predetermined current to a switch (11, 40, 51), and Measuring a voltage across the switch (11, 40, 51) using a magnetoresistive sensor (15, 25, 26, 35, 41, 515, 516, 534, 67). [19] Method according to claim 18, further comprising determining a drift of a property of the switch (11, 40, 51) based on the voltage measurement. [20] Method according to claim 19, wherein the feature comprises a threshold voltage of the switch (11, 40, 51) and / or an on-resistance of the switch (11, 40, 51). [21] Method according to one of claims 18-20, further comprising monitoring an operation of the s (11, 40, 51) based on an output of the magnetoresistive sensor (15, 25, 26, 35, 41, 515, 516, 534, 67).

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