Power consumption reduction of a relay circuit for electric vehicles at high operating voltages
Patent Information
- Authority / Receiving Office
- DE · DE
- Patent Type
- Patents
- Current Assignee / Owner
- ELMOS SEMICON AG
- Filing Date
- 2020-04-27
- Publication Date
- 2026-07-30
Smart Images
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Abstract
Description
Field of invention The invention relates to a device for supplying the relay coil (L) of a relay (R1) with a relay voltage (VRel), wherein in a first embodiment the supply voltage (VBat) is divided into a first voltage range (VNoPWM) and a second voltage range (VPWM), and wherein the device does not modulate the relay voltage (VRel) in the first voltage range (VNoPWM), and wherein the device modulates the relay voltage (VRel) in the second voltage range (VPWM), in particular pulse-modulated and / or PWM-modulated and / or PDM-modulated, and wherein in a second embodiment the average relay voltage (VRel,av) is divided into a first voltage range (VRelNoPWM) and a second voltage range (VRelPWM), and wherein the device modulates the relay voltage (VRel) in the first voltage range (VRelNoPWM) of the average relay voltage (VRel,av) not modulated and wherein the device modulates the relay voltage (VRel) in the second voltage range (VRelPWM) of the middle relay voltage (VRel,av), in particular pulse-modulated and / or PWM-modulated and / or PDM-modulated. Corresponding methods and uses as well as a test use of the proposed device are also described. General Introduction As electric vehicles become more widespread, the need to connect or disconnect lines at high voltages using suitable switches is becoming increasingly important. This requires meeting galvanic isolation requirements, which even today make the use of relays seem advisable. This leads to a problem with power consumption, which is explained in Figures 1, 2, and 5. To meet the requirements, the control circuit and the relay coil must be designed for both low and high supply voltages. To ensure a minimum holding force even at low supply voltages, the relay coil must generate a minimum magnetic field. However, to avoid excessive losses at very high operating voltages, the relay coil must not have too many turns. Consequently, the relay coil becomes large and therefore expensive. The same applies to the switching element of the relay's control circuit. This is typically a MOS transistor whose current-carrying capacity must be designed for the high currents at maximum supply voltage. From EP 1 587 121 A1, a switching regulator is known which supplies a relay coil (reference numeral 7 of EP 1 587 121 A1) with a predetermined electrical current. By means of a shunt resistor (reference numeral 8 of EP 1 587 121 A1), the device of EP 1 587 121 A1 detects the value of the relay coil current and converts this value into a voltage signal, which a differential amplifier (reference numeral 4 of EP 1 587 121 A1) operating as a comparator converts into a control signal for a switching element (reference numeral 6 of EP 1 587 121 A1) by comparison with a reference voltage. The switching element (reference numeral 6 of EP 1 587 121 A1) switches the switching element (reference numeral 6 of EP 1 587 121 A1) to conducting when the relay current falls below the specified relay current value, so that essentially the supply voltage is then applied to the relay coil (reference numeral 7 of EP 1 587 121 A1).If the relay current exceeds the specified relay current value, the differential amplifier (reference numeral 4 of EP 1 587 121 A1) disconnects the relay coil (reference numeral 7 of EP 1 587 121 A1) from the supply voltage by opening the switching element (reference numeral 6 of EP 1 587 121 A1). The device of EP 1 587 121 A1 does not protect the relay coil (reference numeral 7 of EP 1 587 121 A1) from voltage fluctuations, since the relay coil (reference numeral 7 of EP 1 587 121 A1) only smooths the relay current. EP 2 688 209 A1 discloses a technical teaching for a driver circuit for controlling an inductor using an H-bridge. The circuit does not measure the current through the inductor, nor the value of the supply voltage. Therefore, the inductor is unprotected. Task The proposal is therefore based on the task of creating a solution that avoids the aforementioned disadvantages of the prior art and offers further advantages. The aim is to reduce power losses in the switching element and the relay coil, which allows for a miniaturization of these two components and thus a reduction in costs. This problem is solved by a device according to claim 1. Solution to the task The core idea of the proposal presented here is to use a relay coil (L) as the inductor of a switching regulator and to use the switching element (T1), which was previously only used to switch the relay (R1) on and off, as the switching element of this switching regulator. This allows the excessively high supply voltage on the supply voltage line (VDD) to be reduced to a tolerable level by this virtual new switching regulator. That is, if the supply voltage (Vbat) on the supply voltage line (VDD) exceeds a first threshold value (VNom), the switching control operation is initiated. By modulating the relay voltage (VRel) with PWM, and utilizing the smoothing effect of the relay current (IRel) through the relay coil (L), the effective average relay voltage (VRel,av) is reduced, and thus the relay current (IRel) through the relay coil (L) is also reduced.This also allows the switching element (T1), which is used to control the relay (r1), to have a higher on-resistance (Ron), since the lower relay current (IRel) results in lower power dissipation in the switching element (T1). If the switching element (T1) is, for example, a MOS transistor in a micro-integrated circuit, the chip area of such a transistor can be greatly reduced, which enables a significant, competitive advantage. Voltage control This virtual switching regulator typically has a control input (Sig) intended for controlling the relay's state. This control input (Sig) typically has at least one state, hereinafter referred to as the "on" state, and one state, hereinafter referred to as the "off" state. The information from the control input (Sig) is preferably binary or digitally encoded. Analog encoding is uncommon but conceivable. This virtual switching regulator has a supply voltage line (VDD) at a supply voltage (Vbat) relative to a reference potential in a ground (GND) line, which supplies the virtual switching regulator with electrical power. The virtual switching regulator also includes means (VM) for sensing the supply voltage (Vbat). In the off state, the switching regulator does not energize the relay coil (L) except for the current (Id) through any freewheeling diode (D1) that may be present, and in the on state applies a relay voltage (VRel) to the relay coil (L), which preferably deviates from the supply voltage (Vbat) by less than 25% and / or less than 10% and which is not modulated when the supply voltage (Vbat) is below a first threshold value (VNom). The proposed switching regulator with a relay coil (L) as a choke coil applies a relay voltage (VRel) to the relay coil (L) in the on state, which in its maximum magnitude deviates by less than 25% and / or preferably less than 10% from the magnitude of the supply voltage (Vbat) and which is modulated with a modulation signal, in particular a PWM and / or a PDM signal and / or another pulse-modulated signal, when the supply voltage (Vbat) is above the first threshold (VNom).This causes the switching regulator to lower or stabilize the effective mean relay voltage (VRel,av) across the relay coil (L). A PWM signal with a duty cycle is particularly preferred, where the duty cycle depends on the supply voltage (Vbat) when the supply voltage (Vbat) exceeds the first threshold (VNom), in order to regulate the effective mean relay voltage (VRel,av) as a function of the supply voltage (VBat). Alternatively, the modulation signal can also be, for example, a PDM signal with a pulse density, where the pulse density depends on the supply voltage (Vbat) when the supply voltage (Vbat) exceeds the first threshold (VNom), in order to regulate the effective mean relay voltage (VRel,av) as a function of the supply voltage (VBat). Preferably, the duty cycle of a PWM modulation depends on the supply voltage (Vbat) such that the average relay current (IRel) through the relay coil (L) is constant when the supply voltage (Vbat) is above the first threshold (VNom). In the case of a PDM modulation, the pulse density preferably depends on the supply voltage (Vbat) such that the average relay current (IRel) through the relay coil (L) is essentially constant when the supply voltage (Vbat) is above the first threshold (VNom). The modulation signal preferably has a PWM frequency (fPWM) and a corresponding PWM period (TPWM = 1 / fPWM). It should be explicitly noted here that in this document, the term PWM frequency refers to the instantaneous frequency of the modulation. The term PWM frequency was chosen because switching regulators in the prior art preferably use PWM modulation. Reference is also made to the glossary. The PWM frequency (fPWM), when the supply voltage (Vbat) is above the first threshold (VNom), is chosen so high that the fluctuation of the relay current (IRel) through the relay coil (L) and / or the fluctuation of a current (I) through a switching element (T1) of the switching regulator is less than 50% and / or better less than 25% and / or better less than 10% and / or better less than 5% and / or better less than 2% and / or better less than 1% and / or of the average relay current (IRel) respectively.of the current (I) through the switching element (T1) of the switching regulator in one PWM period (TPWM). The PWM frequency (fPWM) is typically chosen to be high enough in the on-state of the relay when the supply voltage (Vbat) is above the first threshold (VNom) so that the fluctuation of the relay current (IRel) through the relay coil (L) in one PWM period (TPWM) does not cause the relay to drop into the off state and / or so that the fluctuation of the relay current (IRel) through the relay coil (L) in one PWM period (TPWM) does not result in a noise level that can be perceived by a person at a distance of 10 cm between their ear and the relay switch (S) and / or relay coil (L). To achieve the latter, the magnitude of the PWM frequency (fPWM) should be higher than the magnitude of the upper hearing threshold frequency (femax) (see Fig. 3) and / or higher than 20kHz when the supply voltage (Vbat) is above the first threshold (VNom). S t r o m s t e u e r u n g When using a relay coil (L) as the inductor of a switching regulator, current control is also conceivable, but less recommended. The switching regulator then has a control input (Sig) that has at least one state, hereinafter referred to as the ON state, and a second state, hereinafter referred to as the OFF state. The switching regulator also includes a supply voltage line (VDD) at a supply voltage (Vbat) relative to a reference potential in a ground line (GND), which supplies the switching regulator with electrical energy. The switching regulator also has means (IM) for sensing the relay current (IRel) at the supply voltage (Vbat). In the OFF state, the switching regulator does not energize the relay coil (L), except for the current (Id) through any freewheeling diode (D1) that may be present.In its on-state, the switching regulator applies a relay voltage (VRel) to the relay coil (L) that deviates from the supply voltage (Vbat) by less than 25% and / or preferably less than 10%, and is unmodulated when the supply voltage (Vbat) is below a first threshold (VNom). In contrast, and this is the key feature, in its on-state, the switching regulator applies a relay voltage (VRel) to the relay coil (L) that deviates from the supply voltage (Vbat) by less than 25% and / or less than 10% in magnitude, and is modulated with a signal, specifically a PWM signal, a PDM signal, or a pulse-modulated signal, when the relay current (IRel) exceeds a current threshold (INom). Preferably, the modulation signal is a PWM signal with a duty cycle. The duty cycle preferably depends on the magnitude of the relay current (IRel) when the relay current (IRel) exceeds a current threshold (INom). Alternatively, the modulation signal can, for example, be a PDM signal with a pulse density, where preferably the pulse density depends on the magnitude of the relay current (IRel) when the magnitude of the relay current (IRel) exceeds a current threshold (INom). Typically, but not always, the duty cycle depends on the magnitude of the relay current (IRel) such that the average relay current (IRel) through the relay coil (L) is essentially constant when the magnitude of the relay current (IRel) exceeds a current threshold (INom). Alternatively, for example, the pulse density can depend on the magnitude of the relay current (IRel) such that the mean relay current (IRel) through the relay coil (L) is essentially constant when the magnitude of the relay current (IRel) is above a current threshold (INom). The modulation signal preferably has a PWM frequency (fPWM) and a corresponding PWM period (TPWM = 1 / fPWM). Reference is made to the above statements regarding the PWM frequency (fPWM). The PWM frequency (fPWM) is typically chosen to be high enough that the fluctuation of the relay current (IRel) through the relay coil (L) and / or the fluctuation of a current (I) through a switching element (T1) of the switching regulator is less than 50% and / or better than 25% and / or better than 10% and / or better than 5% and / or better than 2% and / or better than 1% and / or of the average relay current (IRel) or the current (I) through the switching element (T1) of the switching regulator in one PWM period (TPWM). Here too, as in the rest of the present document, the modulation signal preferably has a PWM frequency (fPWM) and an associated PWM period (TPWM=1 / fPWM), wherein the PWM frequency (fPWM) is chosen to be so high in the on state of the relay (R1) when the magnitude of the relay current (IRel) is above a current threshold (INom) that the fluctuation of the relay current (IRel) through the relay coil (L) in one PWM period (TPWM) does not cause the relay (R1) to fall into the off state. Here too, the PWM frequency (fPWM) is usually chosen so high that the fluctuation of the relay current (IRel) through the relay coil (L) in one PWM period (TPWM) does not lead to a sound development that can still be perceived by a person at a distance of 10cm between the person's ear and the relay switch (S) and / or relay coil (L). For this purpose, it is advantageous if the magnitude of the PWM frequency (fPWM) is higher than the magnitude of the upper hearing threshold frequency (femax) and / or higher than 20kHz in the event that the magnitude of the relay current (IRel) exceeds a current threshold (INom). Procedure In addition to the idea of using a relay coil as the choke coil of a switching regulator to prevent overcurrent when the relay (R1) is activated in the case of high supply voltages (VBat), a corresponding method for operating a relay (R1) can also be described, in which the relay (R1) again has a relay coil (L). The relay (R1) is supplied with electrical energy by means of a supply voltage (Vbat). The relay (R1) has an on state in which the relay coil (L) is energized with a relay current (IRel) and the relay switch (S) is closed, and an off state in which the relay coil (L) and the relay switch (S) are open. According to this method, the relay (R1) is supplied with an unmodulated relay voltage (VRel) in the on state when the magnitude of the supply voltage (VBat) is below a first threshold value (VNom).The relay (R1) is supplied with a relay voltage (VRel) modulated by a modulation signal when the magnitude of the supply voltage (Vbat) exceeds a first threshold value (VNom), according to the procedure. The modulation signal is preferably a pulse modulation. See the Glossary section for further details. The modulation signal can again be, for example, a PWM signal with a duty cycle, where the duty cycle depends on the supply voltage (Vbat) when the supply voltage (Vbat) is above the first threshold (VNom). Alternatively, the modulation signal can again be, for example, a PDM signal with a pulse density, where the pulse density depends on the supply voltage (Vbat) when the supply voltage (Vbat) is above the first threshold (VNom). The duty cycle of the PWM signal can depend on the supply voltage (Vbat) such that the average relay current (IRel) through the relay coil (L) is essentially constant when the supply voltage (Vbat) is above the first threshold (VNom). Similarly, the pulse density can depend on the supply voltage (Vbat) such that the average relay current (IRel) through the relay coil (L) is constant when the supply voltage (Vbat) is above the first threshold (VNom). The modulation signal has a PWM frequency (fPWM) and an associated PWM period (TPWM=1 / fPWM), wherein the PWM frequency (fPWM), when the magnitude of the supply voltage (VBat) is above a first threshold (VNom), should preferably be chosen to be so high that the fluctuation of the relay current (IRel) through the relay coil (L) and / or the fluctuation of a current (I) through a switching element (T1) that modulates the relay voltage (VRel) is less than 50% and / or less than 25% and / or less than 10% and / or less than 5% and / or less than 2% and / or less than 1% and / or of the mean relay current (IRel) or the current (I) through the switching element (T1) in one PWM period (TPWM). The PWM frequency (fPWM) should be chosen to be high enough that the fluctuation of the relay current (IRel) through the relay coil (L) in one PWM period (TPWM) does not lead to a change in the state of the relay (R1) to the off state when the magnitude of the supply voltage (VBat) is above a first threshold (VNom). Furthermore, the PWM frequency (fPWM) should be chosen high enough, when the magnitude of the supply voltage (VBat) exceeds a first threshold (VNom), in the switched-on state of the relay (R1) and when the magnitude of the supply voltage (Vbat) exceeds the first threshold (VNom), so that the fluctuation of the relay current (IRel) through the relay coil (L) in one PWM period (TPWM) does not lead to a sound development that can still be perceived by a person at a distance of 10cm between the person's ear and the relay switch (S) and / or relay coil (L). The magnitude of the PWM frequency (fPWM) should preferably be higher than the magnitude of the upper hearing threshold frequency (femax) and / or higher than 20kHz if the magnitude of the supply voltage (VBat) is above a first threshold (VNom). Device In addition to using a relay as an inductor and the associated method, a device for controlling a relay (R1) is also provided, which performs the above method. The device preferably comprises the relay (R1) with the relay coil (L) and the relay switch (S), a switching element (T1), and a control device (TR) having a control input (Sig). The device is supplied with electrical energy by a supply voltage (Vbat). The device further comprises a voltage measuring device (VM) for detecting the voltage value of the supply voltage (Vbat). The switching element (T1) can assume an on-switching state and an off-switching state. The control input (Sig) can have a first logic state and a second logic state. An electrical relay current (IRel) flows through the relay coil (L), which can also have a current value of 0 A.The electrical relay current (IRel) depends on the switching state of the switching element (T1). The relay switch (S) can be in an on relay switching state or in an off relay switching state. The relay coil (R1) controls the relay switching state of the relay switch (S) via its magnetic field and the resulting magnetic force on an armature (not shown in the figures), depending on the relay current (IRel). The control device (CTR) brings the switching element (T1) into the off switching element state when the control input (Sig) has the first logic state, and into the on switching element state when the control input (Sig) has the second logic state and the magnitude of the supply voltage (Vbat) is less than a first threshold value (VNom).The control device (CTR) toggles the switching element (T1) between the on and off states according to a modulation with the specified PWM frequency (fPWM), which need not be constant, when the control input (Sig) is in the second logic state and the magnitude of the supply voltage (Vbat) is greater than or equal to a first threshold (VNom). The modulation of the switching state is preferably pulse modulation. Preferably, the pulse modulation of the switching state has a duty cycle. The duty cycle preferably depends on the supply voltage (Vbat) when the supply voltage (Vbat) is above the first threshold (VNom).Instead of PWM modulation, PDM modulation with a pulse density can also be used, where the modulation is then a PDM modulation with a pulse density of switching the switching element state back and forth, and where the pulse density of switching the switching element state back and forth depends on the supply voltage (Vbat) when the supply voltage (Vbat) is above the first threshold (VNom). In the case of PWM modulation, the duty cycle of the switching back and forth of the switching element state preferably depends on the supply voltage (Vbat) such that the average relay current (IRel) through the relay coil (L) is essentially constant when the supply voltage (Vbat) is above the first threshold (VNom). In the case of an exemplary PDM modulation, the pulse density of the switching back and forth of the switching element state depends on the supply voltage (Vbat) such that the mean relay current (IRel) through the relay coil (L) is constant when the supply voltage (Vbat) is above the first threshold (VNom). The modulation of the switching back and forth of the switching element state also has a PWM frequency (fPWM) and an associated PWM period (TPWM=1 / fPWM), whereby the PWM frequency (fPWM) is chosen to be high enough when the supply voltage (Vbat) is above the first threshold (VNom) that the fluctuation of the relay current (IRel) through the relay coil (L) and / or the fluctuation of a current (I) through the switching element (T1) is less than 50% and / or better less than 25% and / or better less than 10% and / or better less than 5% and / or better less than 2% and / or better less than 1% of the average relay current (IRel) or the current (I) through the switching element (T1) in one PWM period (TPWM). Furthermore, the PWM frequency (fPWM) of switching the switching element state back and forth when the control input (Sig) has the second logic state and the magnitude of the supply voltage (Vbat) is greater than or equal to the first threshold (VNom) is preferably chosen to be so high that the fluctuation of the relay current (IRel) through the relay coil (L) in one PWM period (TPWM) does not lead to a change in the relay switching state of the relay (R1). The PWM frequency (fPWM) of switching the switching element state back and forth when the control input (Sig) has the second logic state and the magnitude of the supply voltage (Vbat) is greater than or equal to the first threshold (VNom) is preferably chosen to be high enough that the fluctuation of the relay current (IRel) through the relay coil (L) in one PWM period (TPWM) of switching the switching element state back and forth does not result in a sound development that can still be perceived by a person at a distance of 10 cm between the person's ear and the relay switch (S) and / or relay coil (L). The magnitude of the PWM frequency (fPWM) of switching the switching element state back and forth is, when the supply voltage (Vbat) is above the first threshold (VNom), preferably higher than the magnitude of the upper hearing threshold frequency (femax) and / or higher than 20kHz. A proposed vehicle, preferably an electric vehicle, preferably comprises at least one device as previously described. The relay switch (S) can typically disconnect or connect a supply line of an electric motor of the vehicle to a power supply of the vehicle, in particular to a battery and / or a generator and / or another electric motor. The relay switch (S) is preferably designed or used to electrically disconnect the power supply from a fault location or another faulty component of the vehicle in the event of a fault. Such a fault could be, for example, a short circuit detected somewhere in the wiring harness or in another component of the vehicle. Test procedure On this basis, a method for testing a relay (R1) can be specified, wherein the relay (R1) comprises a relay coil (L) for electromechanically actuating the relay switch (S) and wherein the relay switch (S) can be in an on relay state or an off relay state.The test procedure preferably comprises the following steps: • Controlling the relay coil (L) with a relay voltage (VRel) modulated by a modulation, wherein the modulation has a PWM frequency (fPWM) that is high enough to change the relay switch (S) from an off relay state to an on relay state; • Detecting the relay current (IRel), in particular the modulated component of the relay current (IRel), through the relay coil (L) or a dependent electrical current (I) in the form of a current value; • Inferring a state, in particular a fault state, of the relay (R1) if the magnitude of the current value at one or more time points does not correspond to an expected value or is not within an expected value range. The modulation is again preferably pulse modulation, in particular PWM modulation or PDM modulation. In an alternative test procedure, the relay (R1) again comprises the aforementioned relay coil (L) for electromechanically actuating the relay switch (S), wherein the relay switch (S) can be in an on relay state or an off relay state. The alternative procedure comprises the steps of: • activating the relay coil (L) with a relay voltage (VRel) modulated by a modulation, • wherein the amplitude of the modulation of the relay voltage (VRel) is so low that the relay switch (S) does not change its relay state during the test; • detecting the modulated component of the relay current (IRel) through the relay coil (L) or a dependent electrical current (I) in the form of a current value; • inferring a state, in particular a fault state, of the relay (R1) if the magnitude of the current value at one or more time points does not correspond to an expected value or is not within an expected value range. Here too, the modulation is preferably pulse modulation, in particular PWM modulation or PDM modulation. A corresponding vehicle, preferably an electric vehicle, then comprises at least one device with a relay (R1) that performs or is intended to perform a test procedure as described above. The relay (R1) can preferably use a relay switch (S) to disconnect or connect a supply line of an electric motor of the vehicle from a power supply, in particular from a battery and / or a generator and / or another electric motor. The relay switch (S) is preferably designed or used to electrically disconnect the vehicle's power supply from a fault location or other faulty device in the event of a fault. Relay voltage control This virtual switching regulator typically has a control input (Sig) intended for controlling the relay's state. This control input (Sig) typically has at least one state, hereinafter referred to as the "on" state, and one state, hereinafter referred to as the "off" state. The control input information is preferably binary or digitally encoded. Analog encoding is uncommon but conceivable. This virtual switching regulator has a supply voltage line (VDD) at a supply voltage (Vbat) relative to a reference potential in a ground (GND) line, which supplies the virtual switching regulator with electrical energy. The virtual switching regulator also includes means (VM) for sensing the supply voltage (Vbat). In the "off" state, the switching regulator does not energize the relay coil (L), except for the current (Id) through any freewheeling diode (D1) that may be present.The switching regulator, in its on-state, applies a relay voltage (VRel) to the relay coil (L) that deviates from the supply voltage (Vbat) by less than 25% and / or less than 10% and is unmodulated when the average relay voltage (VRel,av) is below a second threshold (VNom2). The proposed switching regulator, with a relay coil (L) acting as an inductor, applies a relay voltage (VRel) to the relay coil (L) in its on-state. The maximum magnitude of this relay voltage deviates from the magnitude of the supply voltage (Vbat) by less than 25% and / or preferably less than 10% and is modulated by a modulation signal, in particular a PWM and / or PDM signal and / or another pulse-modulated signal, when the average relay voltage (VRel,av) is above the second threshold (VNom2). This causes the switching regulator to lower or stabilize the effective mean relay voltage (VRel,av) across the relay coil (L). Preferably, the modulation signal is a PWM signal with a duty cycle, where the duty cycle depends on the average relay voltage (VRel,av) when the average relay voltage (VRel,av) is above the second threshold (VNom2), in order to regulate the effective average relay voltage (VRel,av) as a function of the average relay voltage (VRel,av). Alternatively, the modulation signal can also be, for example, a PDM signal with a pulse density, where the pulse density depends on the average relay voltage (VRel,av) when the average relay voltage (VRel,av) is above the second threshold (VNom2), in order to regulate and stabilize the effective average relay voltage (VRel,av) as a function of the average relay voltage (VRel). Preferably, the duty cycle of a PWM modulation depends on the mean relay voltage (VRel,av) such that the mean relay current (IRel) through the relay coil (L) is constant when the mean relay voltage (VRel,av) is above the second threshold (VNom2). In the case of a PDM modulation, the pulse density preferably depends on the mean relay voltage (VRel,av) such that the mean relay current (IRel) through the relay coil (L) is essentially constant when the mean relay voltage (VRel,av) is above the second threshold (VNom2). The modulation signal preferably has a PWM frequency (fPWM) and a corresponding PWM period (TPWM = 1 / fPWM). It should be explicitly noted here that in this document, the term PWM frequency refers to the instantaneous frequency of the modulation. The term PWM frequency was chosen because switching regulators in the prior art preferably use PWM modulation. Reference is also made to the glossary. The PWM frequency (fPWM) is chosen so high, when the average relay voltage (VRel,av) is above the second threshold (VNom2), that the fluctuation of the relay current (IRel) through the relay coil (L) and / or the fluctuation of a current (I) through a switching element (T1) of the switching regulator is less than 50% and / or better less than 25% and / or better less than 10% and / or better less than 5% and / or better less than 2% and / or better less than 1% and / or of the average relay current (IRel) respectively.of the current (I) through the switching element (T1) of the switching regulator in one PWM period (TPWM). The PWM frequency (fPWM) is typically chosen to be high enough in the relay's on state when the average relay voltage (VRel,av) is above the second threshold (VNom2) so that the fluctuation of the relay current (IRel) through the relay coil (L) in one PWM period (TPWM) does not cause the relay to switch off and / or so that the fluctuation of the relay current (IRel) through the relay coil (L) in one PWM period (TPWM) does not produce a noise that can be perceived by a person at a distance of 10 cm between their ear and the relay switch (S) and / or relay coil (L). To achieve the latter, the magnitude of the PWM frequency (fPWM) when the mean relay voltage (VRel,av) is above the second threshold (VNom2) should be higher than the magnitude of the upper hearing threshold frequency (femax) (see Fig. 3) and / or higher than 20kHz. V e r f a h r e n z u r R e l e g u n g m i t t e l s d e r R e l a i s s p a n n u n g In addition to the idea of using a relay coil as the choke coil of a switching regulator to prevent overcurrent when the relay (R1) is activated in the case of high supply voltages (VBat), a corresponding method for operating a relay (R1) can also be described, in which the relay (R1) again has a relay coil (L). The relay (R1) is supplied with electrical energy by means of a supply voltage (Vbat). The relay (R1) has an on state in which the relay coil (L) is energized with a relay current (IRel) and the relay switch (S) is closed, and an off state in which the relay coil (L) and the relay switch (S) are open. According to this method, the relay (R1) is supplied with an unmodulated relay voltage (VRel) in the on state when the magnitude of the average relay voltage (VRel,av) is below a second threshold value (VNom2).The relay (R1) is supplied with a relay voltage (VRel) modulated by a modulation signal when switched on, according to the procedure, if the magnitude of the average relay voltage (VRel,av) exceeds a second threshold (VNom2). The modulation signal is preferably a pulse modulation. Reference is made to the Glossary section. The modulation signal can again be, for example, a PWM signal with a duty cycle, where the duty cycle depends on the average relay voltage (VRel,av) when the average relay voltage (VRel,av) exceeds the second threshold (VNom2). Alternatively, the modulation signal can again be, for example, a PDM signal with a pulse density, where the pulse density depends on the average relay voltage (VRel,av) when the average relay voltage (VRel,av) exceeds the second threshold (VNom2). The duty cycle of the PWM signal can depend on the average relay voltage (VRel,av) such that the average relay current (IRel) through the relay coil (L) is essentially constant when the average relay voltage (VRel,av) is above the second threshold (VNom2). Similarly, the pulse density can depend on the average relay voltage (VRel,av) such that the average relay current (IRel) through the relay coil (L) is constant when the average relay voltage (VRel,av) is above the second threshold (VNom2). The modulation signal has a PWM frequency (fPWM) and an associated PWM period (TPWM=1 / fPWM), wherein the PWM frequency (fPWM), when the magnitude of the mean relay voltage (VRel,av) is above a second threshold (VNom2), should preferably be chosen to be so high that the fluctuation of the relay current (IRel) through the relay coil (L) and / or the fluctuation of a current (I) through a switching element (T1) that modulates the relay voltage (VRel) is less than 50% and / or less than 25% and / or less than 10% and / or less than 5% and / or less than 2% and / or less than 1% of the mean relay current (IRel) or the current (I) through the switching element (T1) in one PWM period (TPWM). The PWM frequency (fPWM) when the magnitude of the mean relay voltage (VRel,av) is above a second threshold (VNom2), in the switched-on state of the relay (R1) and when the magnitude of the mean relay voltage (VRel,av) is above the second threshold (VNom2), should preferably be chosen so high that the fluctuation of the relay current (IRel) through the relay coil (L) in one PWM period (TPWM) does not lead to a change of state of the relay (R1) to the switched-off state of the relay (R1). Furthermore, the PWM frequency (fPWM) should be chosen high enough that the fluctuation of the relay current (IRel) through the relay coil (L) in one PWM period (TPWM) does not result in a sound that can still be perceived by a person at a distance of 10 cm between the person's ear and the relay switch (S) and / or relay coil (L). The magnitude of the PWM frequency (fPWM) when the magnitude of the mean relay voltage (VRel,av) is above a second threshold (VNom2) should preferably be higher than the magnitude of the upper hearing threshold frequency (femax) and / or higher than 20kHz. Device with relay voltage control In addition to using a relay as an inductor and the associated method, a device for controlling a relay (R1) is also provided, which performs the above method. The device preferably comprises the relay (R1) with the relay coil (L) and the relay switch (S), a switching element (T1), and a control device (TR) having a control input (Sig). The device is supplied with electrical energy by a supply voltage (Vbat). The device further comprises a voltage measuring device (VM) for detecting the voltage value of the average relay voltage (VRel,av). The switching element (T1) can assume an on-switching state and an off-switching state. The control input (Sig) can have a first logic state and a second logic state. An electrical relay current (IRel) flows through the relay coil (L), which can also have a current value of 0 A.The electrical relay current (IRel) depends on the switching state of the switching element (T1). The relay switch (S) can be in an on relay switching state or in an off relay switching state. The relay coil (R1) controls the relay switching state of the relay switch (S) via its magnetic field and the resulting magnetic force on an armature (not shown in the figures), depending on the relay current (IRel). The control device (CTR) brings the switching element (T1) into the off switching element state when the control input (Sig) has the first logic state, and into the on switching element state when the control input (Sig) has the second logic state and the magnitude of the average relay voltage (VRel,av) is less than a second threshold value (VNom2).The control device (CTR) toggles the switching element (T1) between the on and off states according to a modulation with the specified PWM frequency (fPWM), which need not be constant, when the control input (Sig) is in the second logic state and the magnitude of the average relay voltage (VRel,av) is greater than or equal to a second threshold (VNom2). The modulation of the switching element state is preferably pulse modulation. Preferably, the pulse modulation of the switching element state has a duty cycle. The duty cycle preferably depends on the average relay voltage (VRel,av) when the average relay voltage (VRel,av) is above the second threshold (VNom2).Instead of PWM modulation, PDM modulation with a pulse density can also be used, where the modulation is then a PDM modulation with a pulse density of switching the switching element state back and forth, and where the pulse density of switching the switching element state depends on the mean relay voltage (VRel,av) if the mean relay voltage (VRel,av) is above the second threshold (VNom2). In the case of PWM modulation, the duty cycle of the switching back and forth of the switching element state preferably depends on the mean relay voltage (VRel,av) such that the mean relay current (IRel) through the relay coil (L) is essentially constant when the mean relay voltage (VRel,av) is above the second threshold (VNom2). In the case of an exemplary PDM modulation, the pulse density of the switching back and forth of the switching element state depends on the mean relay voltage (VRel,av) such that the mean relay current (IRel) through the relay coil (L) is constant when the mean relay voltage (VRel,av) is above the second threshold (VNom2). The modulation of the switching back and forth of the switching element state also has a PWM frequency (fPWM) and an associated PWM period (TPWM=1 / fPWM), whereby the PWM frequency (fPWM) is chosen to be high enough that the fluctuation of the relay current (IRel,av) through the relay coil (L) and / or the fluctuation of a current (I) through the switching element (T1) is less than 50% and / or better less than 25% and / or better less than 10% and / or better less than 5% and / or better less than 2% and / or better less than 1% of the average relay current (IRel) or the current (I) through the switching element (T1) in one PWM period (TPWM). Furthermore, the PWM frequency (fPWM) of switching the switching element state back and forth when the control input (Sig) has the second logic state and the magnitude of the mean relay voltage (VRel,av) is greater than or equal to the second threshold (VNom2) is preferably chosen so high that the fluctuation of the relay current (IRel) through the relay coil (L) in one PWM period (TPWM) does not lead to a change in the relay switching state of the relay (R1). The PWM frequency (fPWM) of switching the switching element state back and forth when the control input (Sig) has the second logic state and the magnitude of the mean relay voltage (VRel,av) is greater than or equal to the second threshold (VNom2) is preferably chosen to be high enough that the fluctuation of the relay current (IRel) through the relay coil (L) in one PWM period (TPWM) of switching the switching element state back and forth does not result in a sound that can still be perceived by a person at a distance of 10 cm between the person's ear and the relay switch (S) and / or relay coil (L). The magnitude of the PWM frequency (fPWM) of the switching back and forth of the switching element state when the mean relay voltage (VRel,av) is above the second threshold (VNom2) is preferably higher than the magnitude of the upper hearing threshold frequency (femax) and / or higher than 20kHz. A proposed vehicle, preferably an electric vehicle, preferably comprises at least one device as previously described. The relay switch (S) can typically disconnect or connect a supply line of an electric motor of the vehicle to a power supply of the vehicle, in particular to a battery and / or a generator and / or another electric motor. The relay switch (S) is preferably designed or used to electrically disconnect the power supply from a fault location or another faulty component of the vehicle in the event of a fault. Such a fault could be, for example, a short circuit detected somewhere in the wiring harness or in another component of the vehicle. Test procedure On this basis, a method for testing a relay (R1) can be specified, wherein the relay (R1) comprises a relay coil (L) for electromechanically actuating the relay switch (S) and wherein the relay switch (S) can be in an on relay state or an off relay state.The test procedure preferably comprises the following steps: • Controlling the relay coil (L) with a relay voltage (VRel) modulated by a modulation, wherein the modulation has a PWM frequency (fPWM) that is high enough to change the relay switch (S) from an off relay state to an on relay state; • Detecting the relay current (IRel), in particular the modulated component of the relay current (IRel), through the relay coil (L) or a dependent electrical current (I) in the form of a current value; • Inferring a state, in particular a fault state, of the relay (R1) if the magnitude of the current value at one or more time points does not correspond to an expected value or is not within an expected value range. The modulation is again preferably pulse modulation, in particular PWM modulation or PDM modulation. In an alternative test procedure, the relay (R1) again comprises the aforementioned relay coil (L) for electromechanically actuating the relay switch (S), wherein the relay switch (S) can be in an on relay state or an off relay state. The alternative procedure comprises the steps of: • activating the relay coil (L) with a relay voltage (VRel) modulated by a modulation, • wherein the amplitude of the modulation of the relay voltage (VRel) is so low that the relay switch (S) does not change its relay state during the test; • detecting the modulated component of the relay current (IRel) through the relay coil (L) or a dependent electrical current (I) in the form of a current value; • inferring a state, in particular a fault state, of the relay (R1) if the magnitude of the current value at one or more time points does not correspond to an expected value or is not within an expected value range. Here too, the modulation is preferably pulse modulation, in particular PWM modulation or PDM modulation. A corresponding vehicle, preferably an electric vehicle, then comprises at least one device with a relay (R1) that performs or is intended to perform a test procedure as described above. The relay (R1) can preferably use a relay switch (S) to disconnect or connect a supply line of an electric motor of the vehicle from a power supply, in particular from a battery and / or a generator and / or another electric motor. The relay switch (S) is preferably intended or preferably used to electrically disconnect the vehicle's power supply from a fault location or other faulty device of the vehicle in the event of a fault. Advantage With the aid of such a device, the current load on the relay coil (L) is significantly reduced and limited. Simultaneously, the required transistor area of the switching element (T1) can be reduced, since the maximum current load at maximum operating voltage (VBat) decreases. The regulation of the average relay voltage (VRel,av) can use either the supply voltage (VBat) or the average relay voltage (VRel,av) itself as the actual value. Furthermore, the device can also be used to test the relay (R1). If the relay is stuck, the resonant frequencies are detuned, and this can be detected. In the event of a fault, a signal is then generated or corresponding information is provided, for example, via a data interface of the control device (CTR). List of characters Fig. 1 shows a prior art relay control. Fig. 2 shows the current consumption and power consumption curve of a prior art device. Fig. 3 shows the human hearing threshold according to the prior art. Fig. 4 shows a proposed device. Fig. 5 shows, schematically simplified for clarity, the relay current (IRel) of a proposed device and the course of the average relay voltage (VRel,av) and the dependence of the power loss, primarily of the switching element (T1), on the supply voltage (VBat). Fig. 6 shows the course of the total power (Ptot) in the relay coil and in the switching element (T1) as a function of the supply voltage (VBat). Fig. 7 shows the total power consumption (Ptot) as a function of the supply voltage (VBat).Figure 8 shows a proposed device with a mechanism for detecting the average relay voltage (VRel,av) and for using this detected voltage value of the average relay voltage (VRel,av) as a reference variable for modulating the relay voltage (VRel). Figure 9 illustrates the second threshold (VNom2). Description of the characters Figure 1 Fig. 1 shows a prior art relay control. A driver (TR) generates the control signal (AS) depending on the control input (Sig), which controls the switching element (T1), preferably a MOS transistor or the like. Depending on the control signal (AS), the switching element (T1) either connects the supply voltage line (VDD) at the supply voltage potential (VBat) to a first terminal of the relay coil (L) of the relay (R1) or disconnects the supply voltage line (VDD) at the supply voltage potential (VBat) from the first terminal of the relay coil (L) of the relay (R1). Since the second terminal of the relay coil (L) is connected to the reference potential (GND), the relay coil (L) is thereby supplied with a relay voltage (VRel) which, when the switching element (T1) is closed, is essentially equal to the supply voltage (VBat).When the switching element (T1) is opened, the freewheeling diode (D1), which can also be a substrate diode of the switching element (T1), takes over the current with a diode current (ID). The switching element (T1) is then energized by the current (I). The relay coil (L) is energized by a relay current (IRel). If the relay current (IRel) is not 0 A and is greater in magnitude than a minimum switching current, the relay switch (S) is closed in the example shown in Fig. 1. Figure 2 Figure 1 shows the current draw and power consumption curve of a device according to the state of the art. The relay current increases linearly with the supply voltage (VBat). Accordingly, the total power loss (Ptot) in the switching element (T1) and the relay coil (L) increases quadratically. However, even at very low currents, the relay switch (S) is actuated. The corresponding operating voltage is therefore the minimum operating voltage, and the corresponding relay current is the minimum relay current. It has now been recognized that higher power levels and relay currents offer no benefit, and therefore, investments in increased robustness and current-carrying capacity of the switching element (T1) and the relay coil (L) are wasted and only incur additional costs. Figure 3 Fig. 3 shows the hearing threshold for humans according to the state of the art. Figure 4 Fig. 4 shows a proposed exemplary device in simplified schematic form. It largely corresponds to Fig. 1. However, a control device is now connected upstream of the driver (TR). A voltage measuring device (VM) detects the value of the supply voltage (VBat) on the supply voltage line (VDD) and generates a corresponding voltage measurement signal (VMS). For clarity, a current measuring device (IM) is shown here, although not actually necessary in parallel, which detects the value of the current I through the switching element (T1) and generates a corresponding current measurement signal (IMS). Alternatively, although also not actually necessary in parallel, a current measuring device (IM) could have been shown that detects the value of the relay current (IRel) through the relay inductance (L) and generates a corresponding second current measurement signal, which is not shown. The control device (CTR) and the subsequent driver (TR) now generate the control signal (AS) depending on the state of the control input (Sig) and the detected value of the supply voltage (VBat) and / or the detected value of the current (I) through the switching element (T1) and / or the detected value of the relay current (IRel) through the relay coil (L). If, for example, the supply voltage (VBat) is above a first voltage threshold (VNom), the control device (CTR) uses the control signal (AS) to generate, for example, a PWM modulation of the relay voltage (VRel). This reduces the average relay current (IRel) and the average relay voltage (VRel), and thus the electrical power dissipated in the relay coil (L). Furthermore, this process utilizes the fact that the relay coil (L) maintains and smooths the current to a first approximation.This means that a force continues to act on the relay switch (S), which in this example therefore remains closed if the PWM frequency (fPWM) of the PWM modulation of the relay voltage (VRel) used here is high enough. Figure 5 Fig. 5 shows the course of the mean relay voltage (VRel, av) and the relay current (IRel) as a function of the supply voltage (VBat). The power loss (PDis,drv) of the switching element (T1) increases quadratically. Figure 6 Figure 6 schematically illustrates, in a simplified manner, the relay current (IRel) of a proposed device, e.g., according to Figure 3, and the curve of the average relay voltage (VRel,av) and the dependence of the average power dissipation (Pdis,drv), primarily of the switching element (T1), on the supply voltage (VBat). If the magnitude of the supply voltage (VBat) exceeds a threshold value (VNom), the control device (CTR) begins pulse modulation of the relay voltage (VRel). In Figure 6, the maximum values of the relay voltage (VRel) are shown as increasing linearly with the supply voltage (VBat). The average relay voltage (VRel,av), which is not shown, remains constant in this example, which can be achieved, for example, by a corresponding change in the duty cycle as a function of the supply voltage (VBat). As a result, the magnitude of the relay current (IRel) above this threshold (VNom) for the supply voltage (VBat) also remains constant in this example and does not follow the curve (I'Rel) for the relay current without modulation. This results in a voltage range (VNoPWM) of the supply voltage (VBat) in which the relay voltage (VRel) is not modulated and a voltage range (VPWM) of the supply voltage (VBat) in which the relay voltage (VRel) is modulated. Figure 7 The graph shows the total power dissipation (Ptot) in the relay coil (L) and the switching element (T1) as a function of the supply voltage (VBat) when using a proposed device. The drop in total power dissipation is noteworthy. Figure 8 Fig. 8 largely corresponds to Fig. 4. Fig. 8 shows a proposed exemplary device in simplified schematic form. It also largely corresponds to Fig. 1. However, unlike Fig. 1 and as in Fig. 4, a control device (CTR) is connected upstream of the driver (TR). A second voltage measuring device (VM2) detects the value of the average relay voltage (VRel) at the first terminal of the relay coil (L) and generates a corresponding second voltage measurement signal (VMS2). The control device (CTR) and the subsequent driver (TR) now generate the control signal (AS) depending on the state of the control input (Sig) and the detected value of the average relay voltage (VRel). For example, if the value of the average relay voltage (VRel) exceeds a second voltage threshold (VNom2), the control device uses the control signal (AS) to generate a PWM modulation of the relay voltage (VRel). This reduces the value of the average relay voltage (VRel) and thus the average relay current (IRel), and consequently the electrical power dissipated in the relay coil (L). Furthermore, the fact that the relay coil (L) maintains and smooths the current to a first approximation is utilized. This also exerts a force on the relay switch (S), which in this example remains closed if the PWM frequency (fPWM) of the exemplary PWM modulation of the relay voltage (VRel) is high enough. Figure 9 Figure 6 schematically illustrates, in a simplified manner, the relay current (IRel) of a proposed device, e.g., according to Figure 3, and the curve of the average relay voltage (VRel,av) and the dependence of the average power dissipation (Pdis,drv), primarily of the switching element (T1), on the operating voltage (VBat). If the magnitude of the average relay voltage (VRel,av,av) exceeds a second threshold value (VNom2), the control device (CTR) begins pulse modulation of the relay voltage (VRel). In Figure 6, the maximum relay voltage values (VRel) are shown as increasing linearly with the supply voltage (VBat). However, the average relay voltage (VRel,av) remains constant in this example, which can be achieved, for example, by a corresponding change in the duty cycle as a function of the average relay voltage (VRel,av) as the actual value of the control system. This means that the magnitude of the relay current (IRel) above this second threshold (VNom2) for the mean relay voltage (VRel,av) also remains constant in this example and does not follow the curve (I'Rel) for the relay current without modulation. This results in a voltage range (VRelNoPWM) of the average relay voltage (VRel,av) in which the relay voltage (VRel) is not modulated and a voltage range (VRelPWM) of the average relay voltage (VRel,av) in which the relay voltage (VRel) is modulated. glossary Constant relay current (IRel) The relay current (IRel) is considered essentially constant within the meaning of this document if the magnitude of the relay current fluctuates by no more than 25% of its time-averaged value (IRel) due to modulation, and / or preferably by no more than 10% of its time-averaged value (IRel), and / or preferably by no more than 5% of its time-averaged value (IRel), and / or preferably by no more than 2% of its time-averaged value (IRel), and / or preferably by no more than 1% of its time-averaged value (IRel). A fluctuation of less than 1% of the time-averaged value (IRel) is particularly preferred in order to minimize EMC interference. Hearing threshold The hearing threshold of a healthy person is approximately at the reference value of the sound pressure level scale, p0 = 20 µPa. The hearing threshold varies from person to person and is frequency-dependent. Reference is made to Fig. 3. For the purposes of this document, a measurement distance of 10 cm to the relay coil L or the relay switch (S) is assumed, whereby the loudest part of the arrangement is to be used for the evaluation of the claims. Pulse modulation Pulse modulation, as used here, encompasses all modulation types in which the signal is switched between two values. These modulation types include, in particular, pulse amplitude modulation (PAM), a modulation type in which the amplitude of the signal is abruptly changed at specific time intervals; pulse code modulation (PCM), an extension of PAM in which, for the purposes of this document, the sequence of pulses reflects a binary code, preferably a pseudorandom number, in order to output a frequency band with a minimum and a maximum frequency instead of a single frequency, in order to optimize the EMC spectrum or audible perception; pulse frequency modulation (PFM), in which a square wave signal is modulated in its frequency, with the width of the pulses (their on-time or off-time) typically remaining constant; and pulse width modulation (PWM), which is a modulation of a square wave signal in its pulse width.where the frequency typically remains constant; pulse density modulation (PDM), where the pulse density of the pulses is modified within an equal time interval; pulse-pause modulation (PPM), where pauses of varying lengths occur between pulses of constant amplitude and length; pulse phase modulation (PPM), where pulses of equal amplitude and pulse length are transmitted, typically at the same frequency; and pulse position modulation (PPM), where the pulse positions are modulated to modify the spectrum. This document also covers combinations of these modulation types. When PWM frequency (fPWM) is mentioned herein, it always refers to the reciprocal of one period of such a pulse-modulated signal. The PWM frequency (fPWM) thus explicitly refers not only to PWM-modulated pulse-modulated signals, but to all pulse-modulated signals listed here. The PWM frequency (fPWM) need not be constant.but can be modified during operation according to requirements. For the control system to function fully, at least one modulation component must typically be a pulse modulation that leads to a change in the average value of the relay voltage (VRel) in order to regulate the relay current (IRel). Reference symbol list AS Driver signal (TR) for the switching element (T1); D1 Freewheeling diode; L Relay coil; femax Upper hearing threshold frequency; fPWM Frequency of the PWM signal used for modulation; fS Sound frequency; GND Reference potential line; I Current through the switching element (T1); Id Current through the freewheeling diode (D1); IMS Current measurement signal; INom Current threshold of the relay current (IRef); I'Nom Current through the switching element (T1), which is usually approximately equal to the current threshold (INom) of the relay current (IRef) and is assumed to be the same in this document for simplification; IRel Relay current; IM Current measuring device; Pdis,drv Power dissipation of the switching element (T1) and the control device (CTR); R1 Relay; Ron On-resistance of the switching element (T1); S Relay switch; SdT State of the art; Sig Control input; T1 Switching element. Typically, it is a transistor or thyristor.Preferably, this is a monolithically integrated MOS transistor; TPWMPWM period. The PWM period is the inverse of the PWM frequency (fPWM) of the PWM signal used to modulate the relay voltage (VRel). It is the period of fluctuation of the PWM signal between two consecutive falling or two consecutive rising edges of the relay voltage (VRel) when the latter is PWM-modulated, for example, because the supply voltage (Vbat) is above the first threshold (VNom); TR driver for controlling the switching element (TR) by means of the control signal (AS) depending on the control input (Sig).This is typically a simple power amplifier that amplifies the control signal (Sig) to compensate for the parasitic input capacitance of the switching element (T1); Vbat supply voltage; VDD supply voltage line; VM supply voltage measuring device (VBat); VM2 second intermediate relay voltage measuring device (VRel,av); VMS voltage measurement signal; VNo first threshold for supply voltage (VBat); VNom2 second threshold for intermediate relay voltage (VRel,av); VNoPWM-free range of supply voltage (VBat); VRel relay voltage; VREL,av intermediate relay voltage; VRelNoPWM-free range of relay voltage (VRel); VRelPWM-modulated range of relay voltage (VRel).
Claims
Device for controlling a relay (R1), wherein the relay (R1) has a relay coil (L), wherein the relay (R1) has a relay switch (S), wherein the device has a switching element (T1), wherein the device has a control device (CTR), wherein the device has a driver (TR), wherein the device has a voltage measuring device (VM2), wherein the device has a control input (Sig), wherein the device has a reference potential line (GND), wherein the device has a supply voltage line (VDD) at a supply voltage (Vbat) relative to the reference potential of the reference potential line (GND), wherein the device is supplied with electrical energy by the supply voltage (Vbat), wherein the control input (SIG) is different from the supply voltage line (VDD), and wherein the voltage measuring device (VM2) measures the value of the mean relay voltage (VRel) at the firstThe terminal of the relay coil (L) is detected and a corresponding voltage measurement signal (VMS2) is generated, wherein the voltage measurement signal (VMS2) is connected to the control device (CTR), wherein the relay coil (L) has a first terminal and a second terminal, wherein the relay voltage (VRel) drops from the first terminal of the relay coil (L) to the second terminal of the relay coil (L), wherein the second terminal of the relay coil (L) is connected to the reference potential line (GND), wherein the control device (CTR) and a subsequent driver (TR) generate the control signal (AS) depending on the state of the control input (Sig) and the detected value of the mean relay voltage (VRel), wherein the switching element (T1) has a first terminal, a second terminal, and a third terminal, wherein the first terminal of the switching element (T1) is connected to the supply voltage line (VDD), and wherein the third terminal of theThe switching element (T1) is connected to the control signal (AS), wherein the second terminal of the switching element (T1) is connected to the first terminal of the relay coil (L), wherein the switching element (T1) can assume an on switching element state and an off switching element state, wherein the control input (Sig) can have a first logical state and a second logical state, wherein an electrical relay current (IRel) flows through the relay coil (L), wherein the electrical relay current (IRel) depends on the switching state of the switching element (T1), wherein the relay switch (S) can be in an on relay switching state and in an off relay switching state, wherein the relay coil (L) controls the relay switching state of the relay switch (S) depending on the relay current (IRel), and wherein the control device (CTR) brings the switching element (T1) into the off switching element state when the control input (Sig)the first logical state and wherein the control device (CTR) brings the switching element (T1) into the switched-on switching element state when the control input (Sig) has the second logical state and the magnitude of the mean relay voltage (VRel,av) is less than a threshold value (VNom2) and wherein the control device (CTR) allows the switching element (T1) to switch back and forth between the switched-on switching element state and the switched-off switching element state according to a modulation when the control input (Sig) has the second logical state and the magnitude of the mean relay voltage (VRel,av) is greater than or equal to the threshold value (VNom2). Device according to claim 1, wherein the modulation of the switching back and forth of the switching element state is a pulse modulation. Device according to claim 2, wherein the pulse modulation of the switching back and forth of the switching element state has a duty cycle and wherein the duty cycle depends on the mean relay voltage (VRel,av) when the mean relay voltage (VRel,av) is above the threshold (VNom2). Device according to claim 2, wherein the modulation is a PDM modulation with a pulse density of switching the switching element state back and forth, and wherein the pulse density of switching the switching element state depends on the mean relay voltage (VRel,av) when the mean relay voltage (VRel,av) is above the threshold (VNom2). Device according to claim 3, wherein the duty cycle of the switching back and forth of the switching element state depends on the mean relay voltage (VRel,av) such that the mean relay current (IRel) through the relay coil (L) is substantially constant when the mean relay voltage (VRel,av) is above the threshold value (VNom2). Device according to claim 4, wherein the pulse density of the switching back and forth of the switching element state depends on the mean relay voltage (VRel,av) such that the mean relay current (IRel) through the relay coil (L) is constant when the mean relay voltage (VRel,av) is above the threshold (VNom2). Device according to one of claims 3 to 5, wherein the modulation of the switching back and forth of the switching element state has a PWM frequency (fPWM) and an associated PWM period (TPWM=1 / fPWM) and wherein the PWM frequency (fPWM), when the mean relay voltage (VRel,av) is above the threshold (VNom2), is selected to be so high that the fluctuation of the relay current (IRel) through the relay coil (L) and / or the fluctuation of a current (I) through the switching element (T1) is less than 50% and / or less than 25% and / or less than 10% and / or less than 5% and / or less than 2% and / or less than 1% and / or of the mean relay current (IRel) or of the current (I) through the switching element (T1) in one PWM period (TPWM). Device according to one of claims 3 to 7, wherein the modulation of the switching back and forth of the switching element state has a PWM frequency (fPWM) and an associated PWM period (TPWM=1 / fPWM) and wherein the PWM frequency (fPWM) of the switching back and forth of the switching element state, when the control input (Sig) has the second logic state and the magnitude of the mean relay voltage (VRel,av) is greater than or equal to the threshold (VNom2), is selected to be so high that the fluctuation of the relay current (IRel) through the relay coil (L) in one PWM period (TPWM) does not lead to a change in the relay switching state of the relay (R1). Device according to one of claims 3 to 8, wherein the modulation of the switching back and forth of the switching element state has a PWM frequency (fPWM) and an associated PWM period (TPWM=1 / fPWM) and wherein the PWM frequency (fPWM) of the switching back and forth of the switching element state, when the control input (Sig) has the second logical state and the magnitude of the mean relay voltage (VRel,av) is greater than or equal to the threshold (VNom2), is selected to be so high that the fluctuation of the relay current (IRel) through the relay coil (L) in one PWM period (TPWM) of the switching back and forth of the switching element state does not lead to a sound development that can still be perceived by a person at a distance of 10 cm between the ear of the person and the relay switch (S) and / or relay coil (L). Device according to one of claims 3 to 9, wherein the modulation of the switching back and forth of the switching element state comprises a PWM frequency (fPWM) of the switching back and forth of the switching element state and an associated PWM period (TPWM=1 / fPWM) of the switching back and forth of the switching element state, and wherein the magnitude of the PWM frequency (fPWM) of the switching back and forth of the switching element state, when the supply voltage (Vbat) is above the first threshold (VNom), is higher than the magnitude of the upper audible threshold frequency (femax) and / or higher than 20kHz. Vehicle, wherein the vehicle comprises at least one device according to one or more of claims 1 to 10. Vehicle according to claim 11, wherein the vehicle is an electric vehicle. Vehicle according to claim 12, wherein the relay switch (S) can disconnect or connect a supply line of an electric motor of the vehicle from a power supply of the vehicle, in particular from a battery and / or a generator and / or another electric motor. Vehicle according to one or more of claims 11 to 13, wherein the relay switch (S) is designed or used to electrically disconnect a power supply from a fault location or a faulty other device of the vehicle in the event of a fault.