Switching device and switching method

Abstract

The application relates to a switching device (10) for providing two supply voltages and for switching over between the supply voltages at a load, in particular at a vehicle sensor (12), in particular via the peripheral sensor interface 5, PSI5, and for switching between the two supply voltages, comprising: – a first supply voltage source (14) and a first transistor (18) connected to the first supply voltage source (14), the first transistor (18) being designed to provide a first supply voltage at a reference node (34); – a second supply voltage source (16) and a second transistor (26) connected to the second supply voltage source (16), the second transistor (26) being designed to provide a second supply voltage at the reference node (34); and – a precharge circuit (38) connected to a control terminal (20) of the first transistor (18) and designed to supply the control terminal (20) of the first transistor (18) with a precharge voltage.

Description

[0001] Switching device and switching method

[0002] The present invention relates to a switching device for providing two supply voltages to at least one vehicle sensor, in particular via the peripheral sensor interface (also referred to as Peripheral Sensor Interface 5 or PSI5) and for switching between the two supply voltages, as well as a corresponding method.

[0003] Communication with vehicle sensors can generally be achieved via one of several state-of-the-art interfaces. In particular, the use of PSI5 in vehicles has proven successful in recent years. PSI5 is based on a two-wire cable and enables reliable and cost-effective communication between a master unit and one or more sensors in a vehicle.

[0004] Some switching devices are known from the prior art. DE 10 2017 111 544 A1 describes a control unit designed to control a sensor selectively via a PSI3 data bus or a DSI3 data bus. Furthermore, US 2021 / 0132229 A1 describes a receiving circuit for a sensor.

[0005] In some applications, it is necessary to apply different voltage values ​​to a vehicle sensor. For example, it may be necessary to switch back and forth between a regular sensor supply and a voltage supply for generating the so-called SYNC pulse. For this purpose, two supply voltage sources can be provided, each with different output voltages that can be applied to a vehicle sensor. Furthermore, switches can be provided that are connected to the supply voltage sources and are used to provide the desired supply voltage for the vehicle sensor. Transistors are particularly suitable for this purpose, with field-effect transistors (FETs) being used preferably because they allow for particularly fast and low-loss switching.In practice, however, it turns out that the switching devices known from the prior art often have problems with electromagnetic compatibility (EMC). These EMC problems arise from undershoots that occur during the transition from a first voltage value to a second voltage value.

[0006] Based on the above-mentioned problem, the object of the present invention is to provide a switching device for providing two supply voltages to at least one vehicle sensor, in particular via PSI5, and for switching between the two supply voltages, wherein the switching device according to the invention comprises the following:

[0007] - a first supply voltage source and a first transistor connected to the first supply voltage source, wherein the first transistor is configured to provide a first supply voltage at a reference node;

[0008] - a second supply voltage source and a second transistor connected to the second supply voltage source, wherein the second transistor is configured to provide a second supply voltage at the reference node; and

[0009] - a precharge circuit connected to a control terminal of the first transistor and configured to supply the control terminal of the first transistor with a precharge voltage.

[0010] The switching device according to the invention makes it possible to reduce the above-mentioned undershoots and thereby improve the EMC of the switching device.

[0011] In the switching device according to the invention, the first transistor is supplied with a precharge voltage. This significantly accelerates the turn-on process of the first transistor, since the voltage difference required to turn on the first transistor is reduced. By providing the precharge voltage, the first transistor remains in a partially conductive state, thereby reducing the turn-on time of the first transistor. Preferably, the precharge voltage can be equal to the threshold voltage of the first transistor.

[0012] The first transistor and the second transistor each have a control terminal via which the respective transistors can be switched on and off. The transistors can preferably be configured as field-effect transistors (FETs), in particular metal-oxide-semiconductor field-effect transistors (MOSFETs), with the control terminal being referred to as the gate terminal in the aforementioned transistor types.

[0013] The first transistor can be selectively controlled by a first current source and a first resistor or by a voltage source arranged at the control terminal of the first transistor (also referred to as the first control terminal). Similarly, the second transistor can be controlled by a second current source and a second resistor or by a voltage source arranged at the control terminal of the second transistor (also referred to as the second control terminal).

[0014] The first supply voltage source is configured to provide a first supply voltage. The second supply voltage source is configured to provide a second supply voltage, wherein the second supply voltage is greater than the first supply voltage.

[0015] According to a preferred embodiment of the present invention, the precharge circuit can have a first transistor (also referred to as a first precharge circuit transistor), wherein the first precharge circuit transistor is connected to the first transistor in a current mirror circuit. The first precharge circuit transistor, which in the context of the present invention is also referred to as a copy transistor, acts like a current source and provides the desired current (also referred to as precharge current) in order to bias the first transistor. This current flows through the first resistor, which is arranged at the control terminal of the first transistor. A regulated current is provided in order to ensure the desired bias voltage at the control terminal of the first transistor, regardless of any temperature fluctuations.Various current mirror circuits known from the prior art can be used within the scope of the present invention. The use of the current mirror circuit advantageously ensures that the current generated in the precharge circuit can be applied to the first control node for setting the operating point of the first transistor with a high output impedance. The use of the current mirror circuit allows for potential conversion, which is why the current mirror circuit is also referred to as a level shifter or level converter.

[0016] According to a preferred embodiment of the switching device according to the invention, it can be provided that the pre-charging circuit further comprises a pre-charging circuit resistor, a second pre-charging circuit transistor, a pre-charging circuit current source and a current mirror circuit, wherein

[0017] - the first pre-charging circuit transistor is arranged between a potential terminal (in particular ground terminal) and the pre-charging circuit current source and is designed to discharge the current provided by the pre-charging circuit current source towards the potential terminal (in particular ground terminal);

[0018] - the pre-charging circuit resistor is arranged between the control terminal of the first pre-charging circuit transistor and a potential terminal (in particular ground terminal);

[0019] - the second precharge circuit transistor is arranged between the control terminal of the first precharge circuit transistor and the current mirror circuit; and

[0020] - the current mirror circuit is configured to mirror the current flowing through the precharge circuit resistor and to conduct it through a first resistor arranged at the control terminal of the first transistor, wherein the control terminal of the second precharge circuit transistor defines a reference node connecting the precharge circuit current source and the first precharge circuit transistor.

[0021] The above-described embodiment of the switching device offers the advantage that the precharge circuit can precharge the first transistor with the desired precharge voltage. At the same time, the current flowing through the first resistor (also referred to as the precharge current) is limited by the current mirror circuit. The precharge circuit allows the provision of a precharge current that ensures a constant bias voltage of the first transistor even when temperature changes occur, thus eliminating the need to readjust the operating point of the first transistor even when temperature fluctuations occur.

[0022] In the switching device according to the invention, it can be provided that the precharge circuit (38) has a first precharge circuit transistor (40), a second precharge circuit transistor (46), and a precharge circuit current source (42), wherein a first control terminal (20) of the first transistor (18) is connected to a first current source (22) and to a first terminal of a first resistor (24); the first current source (22) and the precharge circuit current source (42) are connected to the same potential; the first precharge circuit transistor (40) is arranged between a second terminal of the first resistor (24) and the precharge circuit current source (42) and is designed to discharge the current provided by the precharge circuit current source (42) in the direction of the second terminal of the first resistor (24);the second precharge circuit transistor (46) is arranged between the control terminal (48) of the first precharge circuit transistor (40) and a supply potential of the first current source (22) and the first precharge circuit current source (42); and the control terminal (50) of the second precharge circuit transistor defines a reference node connecting the precharge circuit current source (42) and the first precharge circuit transistor (40).

[0023] The above-described embodiment offers the advantage of not requiring a current mirror circuit. Furthermore, the above-described embodiment allows the first resistor to be used simultaneously by the precharging circuit, and no matching is required between a precharging circuit resistor and the first resistor. According to a further embodiment of the switching device according to the invention, the precharging circuit can be configured to feed the output current signal (= precharging current) directly into the first current source and thereby adjust the voltage at the control terminal of the first transistor.

[0024] Furthermore, a variably adjustable pre-charging circuit resistor or a variably adjustable first resistor can be provided in the switching device according to the invention.

[0025] Furthermore, it can preferably be provided that the first transistor and the first precharge circuit transistor are structurally identical. This results in the same voltage being applied to the first control terminal when the first transistor is off as to the control terminal of the first precharge circuit transistor.

[0026] Alternatively, it can be provided that the first transistor and the first precharge circuit transistor are not of identical construction and that the ratio between the voltages at the control terminal of the first precharge circuit transistor and at the first control terminal can be adjusted via the ratio of the transistor parameters (for example W / L in a MOSFET, where W denotes the channel width and L the channel length).

[0027] According to a preferred embodiment of the switching device according to the invention, the first transistor and the first precharge circuit transistor can be arranged on one (the same) substrate. By arranging the first transistor and the first precharge circuit transistor on the same substrate and in close proximity to one another, the temperature robustness of the switching device can be further improved.

[0028] Furthermore, according to one embodiment of the switching device according to the invention, it can be provided that 0.8 • Ri < Rv < 1.2 • Ri, preferably 0.9 • Ri < Rv < 1.1 • Ri and particularly preferably Rv = Ri applies for the pre-charging circuit resistance, where Rv denotes the pre-charging circuit resistance and Ri the first resistance. If Rv = Ri applies and, in addition, the first transistor and the first pre-charging circuit transistor are constructed identically, the potential set at the control terminal of the first pre-charging circuit transistor can be projected or copied onto the first control terminal. However, the first resistor and the pre-charging circuit resistor can also have different resistance values, for example if a different voltage than the control terminal of the first pre-charging circuit transistor is to be provided at the first control terminal.It can also be provided that Ri and Rv have different resistance values, for example, if the current mirror ratio is not 1:1 and the potential at the control terminal of the first precharge circuit transistor is nevertheless to be copied to the first control terminal. For example, it can be provided that the ratio of the currents flowing through the first resistor and through the precharge circuit resistor is defined as Ai = IRI / IRV and that Rv is preferably = Ri • Ai.

[0029] In addition, to achieve the object described above, a method is proposed for providing two supply voltages to at least one vehicle sensor, in particular via a peripheral sensor interface 5, PSI5, and for switching between a first supply voltage and a second supply voltage, the method comprising the following steps:

[0030] - Providing the first supply voltage via a first supply voltage source, wherein the first supply voltage can be switched via a first transistor having a first control terminal;

[0031] - providing the second supply voltage via a second supply voltage source, wherein the second supply voltage can be switched via a second transistor having a second control terminal;

[0032] - Providing a pre-charging voltage at the first control terminal via a pre-charging circuit;

[0033] - Turning off the second transistor; and

[0034] - Switching on the first transistor. The method according to the invention allows the switch-on time of the first transistor to be significantly reduced, thereby reducing the undershoots described above and improving the EMC of the switching process.

[0035] Preferably, it can be provided that the provision of the precharging voltage at the first control terminal takes place via a precharging circuit which has a first precharging circuit transistor, wherein the first precharging circuit transistor is connected to the first transistor in a current mirror circuit.

[0036] Furthermore, in the method according to the invention, it can be provided that the precharging circuit is designed to supply the control terminal of the first transistor with a precharging voltage 0.8 • VTHI < Vv < 1.2 • VTHI, preferably with a precharging voltage 0.9 • VTHI < Vv < 1.1 • VTHI and particularly preferably with a precharging voltage Vv = VTHI, where Vv denotes the precharging voltage and VTHI the threshold voltage of the first transistor (18).

[0037] Furthermore, the method according to the invention can provide that the precharging circuit is designed, in a switching phase in which the second transistor is switched on and the first transistor is switched off (i.e. before the first transistor is fully switched on), to supply the control terminal of the first transistor with a precharging voltage which is set to a first precharging voltage at a first point in time within said switching phase and which is set to a second precharging voltage at a second point in time within said switching phase, wherein the second precharging voltage is greater than the first precharging voltage. For example, the first precharging voltage can be 70 to 90%, preferably 75 to 85% and particularly preferably 80% of the threshold voltage of the first transistor VTHI. The second precharging voltage can in particular be 100 to 140%, preferably 110 to 130% and particularly preferably 120% of the threshold voltage VTH.For example, the potential at the control terminal of the first transistor can be raised from 0 to the first precharge voltage at the beginning of the third switching phase P3. Furthermore, the potential at the control terminal of the first transistor can be raised from the first precharge voltage to the second precharge voltage after 50%, 60%, 70%, 80%, 90%, or 95% of the aforementioned switching phase has elapsed. By gradually increasing the precharge voltage and precharging with an initially lower bias voltage (= first precharge voltage < second precharge voltage), the power consumed by the first transistor at the beginning of the aforementioned switching phase is reduced.In addition, by gradually increasing the pre-charging voltage, it is possible to increase the pre-charging voltage relatively shortly before the first transistor is turned on in order to enable a faster turn-on process, thereby achieving an increasing reduction in the undershoot amplitude.

[0038] It can also be provided in the method according to the invention that the provision of the precharging voltage at the first control terminal takes place via a precharging circuit, which also has a precharging circuit resistor, a second precharging circuit transistor, a precharging circuit current source and a current mirror circuit, wherein

[0039] - the first pre-charging circuit transistor is arranged between a potential terminal (in particular ground terminal) and the pre-charging circuit current source and is designed to discharge the current provided by the pre-charging circuit current source towards the potential terminal (in particular ground terminal);

[0040] - the pre-charging circuit resistor is arranged between the control terminal of the first pre-charging circuit transistor and a potential terminal (in particular ground terminal);

[0041] - the second precharge circuit transistor is arranged between the control terminal of the first precharge circuit transistor and the current mirror circuit; and

[0042] - the current mirror circuit is configured to mirror the current flowing through the precharge circuit resistor and to conduct it through a first resistor arranged at the control terminal of the first transistor, wherein the control terminal of the second precharge circuit transistor defines a reference node connecting the precharge circuit current source and the first precharge circuit transistor. Furthermore, it can preferably be provided that the precharge voltage is provided at the first control terminal via a precharge circuit in which the first precharge circuit transistor is structurally identical to the first transistor.

[0043] It can also be provided that the provision of the precharging voltage at the first control terminal takes place via a precharging circuit in which the first precharging circuit transistor is arranged together with the first transistor on a substrate.

[0044] Finally, the method according to the invention can provide the pre-charging voltage at the first control terminal via a pre-charging circuit in which the pre-charging circuit resistance is 0.8 • Ri < Rv < 1.2 • Ri, preferably 0.9 • Ri < Rv < 1.1 • Ri and particularly preferably Rv = Ri, where Rv denotes the pre-charging circuit resistance and Ri the first resistance. Furthermore, it can be provided that the ratio of the currents in the current mirror circuit (consisting of the first current mirror transistor and the second current mirror transistor) flowing through the first resistance and through the pre-charging circuit resistance is defined as Ai = IRI / IRV and that Rv = Ri • Ai is preferably.

[0045] The present invention will be explained in more detail below with reference to the figures.

[0046] Fig. 1 shows the voltage curve at a vehicle sensor when switching between two supply voltages using a switching device according to the prior art,

[0047] Fig. 2 shows a first embodiment of the switching device according to the invention, Fig. 3 shows an embodiment of the method according to the invention,

[0048] Fig. 4 Comparison of the voltage curves at the control terminal of the first transistor and at the vehicle sensor when switching between two supply voltages using the switching device according to the present invention and a switching device according to the prior art, and

[0049] Fig. 5 shows a second embodiment of the switching device according to the invention. Fig. 1 shows the voltage curve for a vehicle sensor which typically occurs when a switching device known from the prior art is used to switch between two supply voltages. In this case, a first supply voltage source, which provides a higher output voltage, is switched off, and then the second supply voltage source is switched on (break-before-make circuit). Switching on and off takes place via two transistors, each of which is connected to a supply voltage source. As can be seen in Fig. 1, when the first supply voltage source is switched off, the voltage provided to the vehicle sensor drops dynamically to a value which is below the target voltage (= output voltage of the first supply voltage source).This voltage drop is caused by the fact that current continues to flow through the vehicle sensor during the transition period between the first transistor turning off and the second transistor turning on. The resulting undershoot impairs the circuit's EMC performance, which is why it is desirable to avoid or at least reduce such undershoots.

[0050] Fig. 2 shows a first embodiment of the switching device 10 according to the invention for providing two supply voltages to a vehicle sensor 10 and for switching between the two supply voltages. The switching device 10 has a first supply voltage source 14 and a second supply voltage source 16. The output voltage of the second supply voltage source 16 is greater than the output voltage of the first supply voltage source 14. For example, the switching device shown in Fig. 2 can be used to provide the SYNC pulse for communication between a master unit and a sensor at PSI5. The first supply voltage source 14 can be used to provide the regular sensor supply, while the second supply voltage source 16 serves to generate the SYNC pulse via the second transistor 26 (also referred to as a sync pulse transistor).However, the present invention is not limited to the aforementioned application and can also be used in other applications in which a vehicle sensor is to be supplied with different supply voltages and switched between the two supply voltages. The first supply voltage source 14 is connected to a first transistor 18, which is designed to provide a first supply voltage at a reference node 34, which is connected to the vehicle sensor 12. The first transistor 18 can be controlled via a first control terminal 20. In the exemplary embodiment shown, the first transistor 18 is controlled via a first current source 22 and a first resistor 24, which are each assigned to the first transistor 18.The second supply voltage source 16 is connected to a second transistor 26, which is designed to provide a second supply voltage at the reference junction 28. The second transistor 26 can be controlled via a second control terminal 28. The second transistor 26 is controlled via a second current source 30 and a second resistor 32, which are each assigned to the second transistor 26. In practice, it can happen that a voltage provided by a supply voltage source is greater than the voltage desired at the reference junction 28. Therefore, an additional control unit can be used to accordingly regulate the voltage provided by one of the supply voltage sources. In the embodiment shown in Fig. 2, a control unit 36 ​​is provided, which serves to reduce the voltage output by the second supply voltage source 16.In the illustrated embodiment, the control unit 36 ​​is configured as a control transistor. However, the use of the control unit 36 ​​is considered optional for the switching device 10 according to the invention. According to one embodiment of the device according to the invention, the control unit 36 ​​can form a voltage source together with the second supply voltage source 16.

[0051] As already discussed in the introduction, in the switching devices known from the prior art, undershoots occur when switching between two supply voltages on a vehicle sensor, which cause EMC problems. Therefore, the switching device 10 according to the invention has a precharging circuit 38 that is connected to the first control terminal 20 and is designed to supply the first control terminal 20 with a precharging voltage. This allows the first transistor 18 to be kept in a partially conductive state. Consequently, the first transistor 18 can be switched on significantly faster because the voltage difference required to switch on the first transistor 18 is reduced and this voltage difference can be provided within a shorter time (compared to switching devices without a precharging mechanism).

[0052] In the embodiment shown in Fig. 2, the precharge circuit 38 has a first transistor 40 (also referred to as the first precharge circuit transistor), a current source 42 (also referred to as the precharge circuit current source), a resistor 44 (also referred to as the precharge circuit resistor), and a second transistor 46 (also referred to as the second precharge circuit transistor). The first precharge circuit transistor 40 and the second precharge circuit transistor 46 each have a control terminal 48, 50. The first precharge circuit transistor 40 is arranged between a ground terminal and the precharge circuit current source 42 and is designed to drain the current provided by the precharge circuit current source 42 toward ground. The precharge circuit resistor 44 is arranged between the control terminal 48 of the first precharge circuit transistor 40 and a ground terminal.The second precharge circuit transistor 46 is arranged between the control terminal 48 of the first precharge circuit transistor 40 and the current mirror circuit 52 and is configured to conduct the current flowing through the precharge circuit resistor 44 through the first resistor 24. The control terminal 50 of the second precharge circuit transistor 46 forms a node connecting the precharge circuit current source 42 to the first precharge circuit transistor 40.

[0053] In the precharge circuit 38, the potential at the reference point 50 is raised until the first precharge circuit transistor 40 becomes conductive. A voltage VTH then develops at the control terminal 48 of the first precharge circuit transistor 40, which voltage drops across the precharge circuit resistor 44. This results in a current Iv = VTH / Rv flowing through the precharge circuit resistor 44. This current causes the second precharge circuit transistor 46 to turn on. The current Iv flowing through the precharge circuit resistor 44 (also referred to as the precharge current) now flows through the precharge circuit transistor 46 into the current mirror circuit 52 (hereinafter also referred to as the current mirror 52). In the exemplary embodiment shown here, the current mirror 52 has two transistors, which are also referred to as the first current mirror transistor 54 and the second current mirror transistor 56. However, the present invention is not limited to the circuit shown in Fig.2. However, alternative embodiments of the current mirror 52 shown in Fig. 2 can also be used. In the illustrated embodiment, the current mirror 52 is used as a "level shifter" and ensures that the potential of the current source in the right-hand switching branch is raised. This ensures that a current flows from the precharging circuit 38 into the first resistor 24. The current flow into the first resistor 24 provides a precharging voltage at the control terminal 20 of the first transistor 18. As explained above, precharging the first transistor 18 allows it to be turned on more quickly. Consequently, the transition time between turning off the second transistor 26 and turning on the first transistor 18 is significantly reduced, thereby reducing the amplitude of the undershoot.Consequently, the switching device 10 exhibits improved EMC characteristics compared to the switching devices known from the prior art.

[0054] A further advantage of the switching device 10 according to the invention is that the desired precharge voltage at the first control terminal 20 is provided in a stable manner, regardless of any temperature fluctuations. In particular, if the precharge circuit transistor 40 is configured identically to the first transistor 18, the threshold voltage VTH,VI of the first precharge circuit transistor 40 changes with temperature fluctuations, so that the current Iv flowing through the precharge circuit resistor 44 is adjusted accordingly. If the precharge circuit resistor 44 and the first resistor 24 are also dimensioned the same, the mirrored current Iv, which also flows through the first resistor 24, causes a precharge voltage V = VTHI = VTH,VI, which is established at the first control terminal 20 regardless of temperature fluctuations.The switching device 10 thereby allows an operating point adjustment for the first transistor 18, which is carried out in an adaptive manner and the pre-charging voltage at the control terminal compensates for any temperature fluctuations.

[0055] 20 of the first transistor 18.

[0056] Although the present invention has been described using specific electronic components for the purpose of better understanding, it will be apparent to those skilled in the art that the invention is not limited to the specific selection of components shown in Fig. 2. In particular, the present invention is not limited to implementation using the transistors shown in Fig. 2.

[0057] Fig. 3 schematically illustrates an embodiment of the method 100 according to the invention. In a first method step 110, a first supply voltage is provided by a first supply voltage source. The first supply voltage source can be switched via a first transistor. In a second method step 120, a second supply voltage is provided via a second supply voltage source. The second supply voltage source can be switched via a second transistor. The first supply voltage and the second supply voltage can be provided by switching the transistors at a reference node that is connected to a vehicle sensor. The first transistor and the second transistor each have a control terminal (also referred to as first control terminal and second control terminal).In a third method step 130, a precharge voltage is provided at the control terminal of the first transistor using a precharge circuit. Preferably, a precharge voltage is provided that corresponds to the threshold voltage of the first transistor VTHI. In a fourth method step 140, the second transistor is turned off. In a fifth method step 150, the first transistor is turned on. By precharging the first transistor, the turn-on process of the first transistor is significantly accelerated, whereby the undershoot effects described above can be significantly reduced and the switching process is significantly improved with regard to EMC. The order of the method steps described above is to be regarded as purely exemplary. The method according to the invention is not limited to the order chosen in the above description.

[0058] Fig. 4 shows the voltage curves at the control terminal of the first transistor and at the vehicle sensor when switching between two supply voltages using the switching device shown in Fig. 2 and using a switching device known from the prior art. The solid line shows the voltage curves that occur when a switching device known from the prior art is used. The dotted lines show the voltage curves that occur when the switching device shown in Fig. 2 is used. In Fig. 4, the switching phases are divided into four areas P1 to P4. P1 describes the first switching phase in which the first transistor is switched on and the second transistor is switched off. P2 describes the second switching phase at the beginning of which the first transistor is switched off and the second transistor is switched on.At the beginning of the third switching phase P3, the first transistor is precharged with a precharge voltage. As can be seen in Fig. 4, in the exemplary embodiment shown here, the voltage at the control terminal of the first transistor is raised from 0 V to Vth. By raising the potential at the control terminal of the first transistor, the turn-on process for the first transistor is accelerated in the fourth switching phase P4. Accordingly, the voltage at the load (= vehicle sensor) does not drop as sharply as is the case with the prior art, since the dead time between the second transistor turning off and the first transistor turning on is reduced. Overall, the present invention thus allows a reduction in the amplitude of the undershoot and improved characteristics with regard to EMC. As already explained above, there are different ways of precharging the first transistor.While in the exemplary embodiment the potential at the control terminal of the first transistor was raised from 0 to VTH in a single step, in further embodiments it can be provided that the potential is raised gradually or stepwise. For this purpose it can be provided, for example, that the mentioned potential is raised within the third switching phase P3 first to a first precharge voltage and then to a second precharge voltage. For example, the first precharge voltage can be 70 to 90%, preferably 75 to 85% and particularly preferably 80% of the threshold voltage VTH. The second precharge voltage can also be 100 to 140%, preferably 110 to 130% and particularly preferably 120% of the threshold voltage VTH. For example, the raising of the potential at the control terminal of the first transistor from 0 to the first precharge voltage can be initiated at the beginning of the third switching phase P3.In addition, the potential at the control terminal of the first transistor can be increased from the first precharge voltage to the second precharge voltage after 50%, 60%, 70%, 80%, 90%, or 95% of the third switching phase P3 has elapsed. This makes it possible to reduce the power consumed by the first transistor at the beginning of the third switching phase (energy savings) and to increase the precharge voltage shortly before the first transistor is turned on to enable a faster turn-on process (further reducing the undershoot amplitude).

[0059] Fig. 5 shows a second embodiment of the switching device according to the invention. Similar to the embodiment shown in Fig. 2, the embodiment of the switching device 10 shown in Fig. 5 also has a precharge circuit comprising a precharge current source 42, a first precharge circuit transistor 40, and a second precharge circuit transistor 46. The precharge current source 42 and the first current source 22 are connected to the same potential terminal. This eliminates the need for a current mirror used as a "level shifter" (see Fig. 2). In the switching device 10 shown in Fig. 5, the precharge circuit is therefore integrated into the control of the first transistor. In addition to the advantage of eliminating the need for the current mirror discussed above, the embodiment shown in Fig.The embodiment shown in Fig. 5 has the advantage that the precharge circuit deactivates itself automatically when the first transistor 18 is fully switched on via the first current source 22. In this case, the control terminal 50 of the first precharge circuit transistor is discharged. Furthermore, in the embodiment shown in Fig. 5, it is no longer necessary to match the first resistor 24 and the precharge circuit resistor 44 to one another, since the precharge circuit uses the same resistor that is already used to drive the first transistor 18 as the first precharge circuit resistor.

[0060] List of reference symbols

[0061] switching device

[0062] Vehicle sensor first supply voltage source second supply voltage source first transistor first control terminal first current source first resistor second transistor second control terminal second current source second resistor

[0063] Reference node

[0064] control unit

[0065] Precharge circuit first precharge circuit transistor

[0066] Precharge circuit current source

[0067] Precharge circuit resistor second precharge circuit transistor

[0068] Control terminal of the first precharge circuit transistor

[0069] Control terminal of the second precharge circuit transistor

[0070] Current mirror circuit first current mirror transistor second current mirror transistor

[0071] Process first process step second process step third process step fourth process step fifth process step

Claims

Claims 1. Switching device (10) for providing two supply voltages to at least one vehicle sensor (12), in particular via the peripheral sensor interface 5, PSI5, and for switching between the two supply voltages, comprising: - a first supply voltage source (14) and a first transistor (18) connected to the first supply voltage source, wherein the first transistor (18) is designed to provide a first supply voltage at a reference node (34); - a second supply voltage source (16) and a second transistor (26) connected to the second supply voltage source, wherein the second transistor (26) is designed to provide a second supply voltage at the reference node (34); and - a precharging circuit (38) connected to a control terminal (20) of the first transistor (18) and configured to supply the control terminal (20) of the first transistor (18) with a precharging voltage.

2. Switching device (10) according to claim 1, characterized in that the pre-charging circuit (38) has a first pre-charging circuit transistor (40), wherein the pre-charging circuit transistor (40) is connected to the first transistor (18) in a current mirror circuit.

3. Switching device (10) according to claim 2, characterized in that the precharge circuit (38) further comprises a precharge circuit resistor (44), a second precharge circuit transistor (46), a precharge circuit current source (42) and a current mirror circuit (52), wherein - the first pre-charging circuit transistor (40) is arranged between a potential terminal, in particular a ground terminal, and the pre-charging circuit current source (42) and is designed to discharge the current provided by the pre-charging circuit current source (42) in the direction of the potential terminal, in particular a ground terminal; - the pre-charging circuit resistor (44) is arranged between the control terminal (48) of the first pre-charging circuit transistor and a potential terminal, in particular a ground terminal; - the second precharge circuit transistor (46) is arranged between the control terminal (48) of the first precharge circuit transistor (40) and the current mirror circuit (52); and - the current mirror circuit is designed to mirror the current flowing through the precharge circuit resistor (44) and to conduct it through a first resistor (24) arranged at the control terminal (20) of the first transistor (18), wherein the control terminal (50) of the second precharge circuit transistor defines a reference node connecting the precharge circuit current source (42) and the first precharge circuit transistor (40).

4. Switching device (10) according to claim 1, characterized in that the precharge circuit (38) comprises a first precharge circuit transistor (40), a second precharge circuit transistor (46), and a precharge circuit current source (42), wherein - a first control terminal (20) of the first transistor (18) is connected to a first current source (22) and to a first terminal of a first resistor (24); - the first precharge circuit transistor (40) is arranged between a second terminal of the first resistor (24) and the precharge circuit current source (42) and is designed to discharge the current provided by the precharge circuit current source (42) towards the second terminal of the first resistor (24); - the second precharge circuit transistor (46) is arranged between the control terminal (48) of the first precharge circuit transistor (40) and a supply potential of the first current source (22) and the first precharge circuit current source (42); and - the control terminal (50) of the second precharge circuit transistor defines a reference node connecting the precharge circuit current source (42) and the first precharge circuit transistor (40).

5. Switching device according to claim 4, characterized in that the first current source (22) and the precharge circuit current source (42) are connected to the same potential.

6. Switching device (10) according to one of claims 2 to 5, characterized in that the first transistor (18) and the first precharge circuit transistor (40) are of identical construction.

7. Switching device (10) according to one of the preceding claims, characterized in that the first transistor (18) and the first precharge circuit transistor (40) are arranged on a substrate.

8. Switching device (10) according to one of the preceding claims, characterized in that for the pre-charging circuit resistance (44) 0.8 • Ri < Rv < 1.2 • Ri, preferably 0.9 • Ri < Rv < 1.1 • Ri and particularly preferably Rv = Ri applies, where Rv denotes the pre-charging circuit resistance (44) and Ri denotes the first resistance (24).

9. Switching device (10) according to one of the preceding claims, characterized in that Rv = Ri • Ai, where Rv defines the pre-charge circuit resistance, Ri the first resistance and Ai defines a current mirror ratio Ai = IRI / IRV, where IRI denotes the current through the first resistance and IRV the current through the pre-charge circuit resistance.

10. Switching device (10) according to one of the preceding claims, characterized by a variably adjustable pre-charging circuit resistor (44) and / or by a variably adjustable first resistor (24).

11. Method (100) for providing two supply voltages to at least one vehicle sensor (12), in particular via the peripheral sensor interface 5, PSI5, and for switching between a first supply voltage and a second supply voltage, wherein the method (100) comprises the following steps: - providing (110) the first supply voltage via a first supply voltage source (14), wherein the first supply voltage can be switched via a first transistor (18) having a first control terminal (20); - providing (120) the second supply voltage via a second supply voltage source (16), wherein the second supply voltage can be switched via a second transistor (26) having a second control terminal (28); - providing (130) a pre-charging voltage at the first control terminal (20) via a pre-charging circuit (38); - switching off (140) the second transistor (26); and - Switching on (150) the first transistor (18).

12. The method (100) according to claim 11, characterized in that the provision of the precharging voltage at the first control terminal (20) is effected via a precharging circuit (38) which has a first precharging circuit transistor (40), wherein the precharging circuit transistor (40) is connected to the first transistor (18) in a current mirror circuit.

13. The method (100) according to claim 11 or 12, characterized in that the precharging circuit (38) is designed to supply the control terminal (20) of the first transistor (18) with a precharging voltage 0.8 • VTHI < Vv < 1.2 • VTH I ZU, preferably with a precharging voltage 0.9 • VTHI < Vv < 1.1 • VTHI and particularly preferably with a precharging voltage Vv = VTHI ZU, where Vv denotes the precharging voltage and VTHI the threshold voltage of the first transistor (18).

14. Method (100) according to one of claims 11 to 13, characterized in that the precharging circuit (38) is designed to, in a switching phase in which the second transistor (26) is switched on and the first transistor (18) is switched off, charge the control terminal (20) of the first transistor (18) with a Precharge voltage which is set to a first precharge voltage at a first time within said switching phase, and which is set to a second precharge voltage at a second time within said switching phase, wherein the second precharge voltage is greater than the first precharge voltage.

15. Method (100) according to one of claims 11 to 14, characterized in that the provision of the pre-charging voltage at the first control terminal (20) takes place via a pre-charging circuit (38) which also has a pre-charging circuit resistor (44), a second pre-charging circuit transistor (46) and a pre-charging circuit current source (42), wherein - the first pre-charging circuit transistor (40) is arranged between a potential terminal, in particular a ground terminal, and the pre-charging circuit current source (42) and is designed to discharge the current provided by the pre-charging circuit current source (42) in the direction of the potential terminal, in particular a ground terminal; - the pre-charging circuit resistor (44) is arranged between the control terminal (48) of the first pre-charging circuit transistor (40) and a potential terminal, in particular a ground terminal; and - the second precharge circuit transistor (46) is arranged between the control terminal (48) of the first precharge circuit transistor (40) and the control terminal (20) of the first transistor (18) and is designed to conduct the current flowing through the precharge circuit resistor (44) through a first resistor (24) arranged at the control terminal (20) of the first transistor (18), wherein the control terminal (50) of the second precharge circuit transistor defines a reference node connecting the precharge circuit current source (42) to the first precharge circuit transistor (40).

16. The method (100) according to any one of claims 11 to 15, characterized in that the provision of the precharging voltage at the first control terminal (20) is effected via a precharging circuit (38), in which the first precharging circuit transistor (40) is constructed identically to the first transistor (18).

17. The method (100) according to any one of claims 11 to 16, characterized in that the provision of the precharging voltage at the first control terminal (20) is effected via a precharging circuit (38), in which the first precharging circuit transistor (40) is arranged together with the first transistor (18) on a substrate.

18. Method (100) according to one of claims 11 to 17, characterized in that the provision of the pre-charging voltage at the first control terminal (20) takes place via a pre-charging circuit (38) in which the pre-charging circuit resistance (44) 0.8 • Ri < Rv < 1.2 • Ri, preferably 0.9 • Ri < Rv < 1.1 • Ri and particularly preferably Rv = Ri, where Rv denotes the pre-charging circuit resistance (44) and Ri the first resistance (24).

Images