CONTROL CIRCUIT FOR ELECTRIC MOTOR

Abstract

Control circuit (100) for an electric motor (112), comprising: a bridge circuit comprising at least two switches (102, 106) connected in series; a bridge node (104) arranged between the at least two switches (102, 106) and designed to provide a phase voltage and to be coupled to a phase winding of the electric motor (112); a decoupling switch (108) designed to be connected between the bridge nodes (104) and the electric motor (112); and a control unit (114) which is coupled to the decoupling switch (108) and to the at least two switches (102, 106), wherein the control unit (114) is designed in the event of a fault to: Switching off at least two switches (102, 106), determining whether a predefined condition is met, Switching off the decoupling switch (108), wherein the switching off of the decoupling switch (108) is delayed with respect to the switching off of the at least two switches (102, 106) if the predefined condition is not met, and simultaneous switching off of at least two switches (102, 106) and the decoupling switch (108) if the predefined condition is met, wherein the control (114) is designed to determine that the predefined condition is met when the decoupling switch (108) can be switched off without suffering permanent damage from the current applied to it at the time when the at least two switches (102, 106) are switched off, wherein the control (114) is further designed to detect a second fault case when the phase voltage exceeds or falls below a threshold value, wherein the decoupling switch (108) is designed as a field-effect transistor, and wherein the control (114) is further designed to switch the decoupling switch (108) back on after it has remained switched off as a result of the second fault and has operated in avalanche mode for a period of time during which a portion of energy was consumed in it which is equal to or less than its maximum rated energy loss portion.

Description

[0001] In various embodiments, a control circuit for an electric motor is provided.

[0002] Three-phase electric motors are widely used in automotive applications, among others. Some of the applications are safety applications, which require systems to enter a fail-safe mode even if the electronic unit controlling the system is no longer available, for example if it is damaged and therefore no longer able to control the system. In the case of a three-phase electric motor, which can be used for electrical steering in any type of vehicle, it should still allow the steering wheel to be turned in fail-safe mode. This is not a problem with an AC induction motor, i.e. an electric motor in which the magnetic field of the rotor is generated by an induced current. However, with an AC synchronous motor, such as a permanent magnet synchronous motor (PMSM), the motor must be in fail-safe mode.When using a PMSM (permanent magnet synchronous motor), which allows high torque to be generated from a compact and lightweight mechanical system, the problem is that after the motor is switched off, for example due to a system fault, the magnetic moment of the permanent magnet of the still-rotating rotor induces a current in the stator coils, effectively acting as a torque back on the rotor. This can lead to situations in which the motor stalls and can therefore no longer be rotated. To avoid such motor conditions when using a PMSM, it must be ensured that no current circulates in the windings of any phase in failsafe mode. To meet this requirement, suitable circuitry must be implemented to isolate the phases in failsafe mode. In early applications, isolation circuitry was based on mechanical relays.Today, mechanical relays are predominantly being replaced by solid-state relays in the form of transistors, which are placed between the inverter's half-bridges and the individual phases of the electric motor. However, when solid-state relays are used to separate the phases, a significant amount of energy must be expected to be consumed to shut down the system. This energy can prove problematic in that the solid-state relays can be damaged in failsafe mode, or expensive power components must be used to prevent this from happening.

[0003] The documents DE 10 2011 055626 A1, JP 2009 - 220705A and DE 102011 053 588 A1 each describe a device for controlling an electric drive motor with a circuit breaker for interrupting a phase line.

[0004] Likewise, the documents DE 10 2012 208 632A, US 2010 / 0017063 A1 and DE 10 2010 037 541 A1 describe a phase-controlled drive motor with a control for a fault situation.

[0005] According to various embodiments, a control circuit for an electric motor is provided, comprising: a bridge circuit having at least two switches connected in series; a bridge node arranged between the at least two switches and configured to provide a phase voltage and to be coupled to a phase winding of the electric motor; a decoupling switch configured to be connected between the bridge node and the electric motor;a controller coupled to the decoupling switch and to the at least two switches, wherein the controller can be configured, in the event of a fault, to switch off the at least two switches, determine whether a predefined condition is met, and to one of switch off the decoupling switch, wherein the switching off of the decoupling switch is delayed with respect to the switching off of the at least two switches if the predefined condition is not met; and to simultaneously switch off the at least two switches and the decoupling switch if the predefined condition is met;wherein the controller can be designed to determine that the predefined condition is met when the decoupling switch can be switched off without suffering permanent damage from the current applied to it at the time the at least two switches are switched off, wherein the controller is further designed to detect a second fault event when the phase voltage exceeds or falls below a threshold value, wherein the decoupling switch is designed as a field-effect transistor; and wherein the controller is further designed to switch the decoupling switch back on after it has remained switched off as a result of the second fault event and has operated in avalanche mode for a period of time during which a portion of energy equal to or less than its maximum rated dissipation energy portion has been consumed therein.

[0006] In one embodiment, the controller may be configured to determine that the predefined condition is met if the decoupling switch is robust enough to withstand an overvoltage condition caused by the potential difference between the bridge node and the phase winding. In another embodiment, the decoupling switch may be configured as a field-effect transistor. In another embodiment, the controller may be configured to determine that the predefined condition is met if the decoupling switch is capable of withstanding avalanche mode operation induced therein by the potential difference between the potential at the bridge node and the potential at the phase winding. In another embodiment, the controller may further be configured tothat it determines the potential at the phase winding from the position of a stator in relation to a rotor of the electric motor. In another embodiment, the controller can further be designed to delay the switching off of the decoupling switch with respect to the switching off of the at least two switches until a zero crossing of the phase voltage or the phase current. In another embodiment, the controller can further be designed to delay the switching off of the decoupling switch with respect to the switching off of the at least two switches until the value of a current driven by the electric motor to the bridge node has fallen below a first threshold. In another embodiment, the controller can further be designed to detect a first fault case,if the voltage at at least one of the at least two switches exceeds a second threshold value. In another embodiment, the controller can further be designed to control the decoupling switch in a clocked manner after it has been switched off as a result of the second fault event, such that it is switched on and off sequentially. In another embodiment, the controller can further be designed to control the decoupling switch in the clocked manner such that a portion of energy consumed therein during the time it remains switched off and operates in avalanche mode corresponds to or is less than its maximum rated energy loss portion. In another embodiment, the control circuit can further comprise: two further switches connected in series and provided in the bridge circuit; a further bridge node arranged between the further two switches,wherein the further bridge node is designed to provide a further phase voltage; a further decoupling switch coupled between the further bridge node and a further phase winding of the electric motor, wherein the controller is coupled to the further decoupling switch and the two further switches; wherein the controller is designed to switch off the at least two switches together with the further two switches in the event of a fault; and to switch off the further decoupling switch, wherein the switching off of the further decoupling switch is delayed with respect to the switching off of the switches if the predefined condition is not met, and / or to switch off the decoupling switch and the switches simultaneously if the predefined condition is met; wherein the controller is designed to determine that the predefined condition is met,if the further decoupling switch can be switched off without suffering permanent damage from the current applied to it at the time the at least two switches are switched off. In another embodiment, a first fault condition may correspond to a short circuit present at one of the switches. In another embodiment, the controller may further be designed to detect a first fault condition when the voltage at at least one of the switches exceeds a second threshold. In another embodiment, a second fault condition may correspond to an open circuit present at one of the switches. In another embodiment, the controller may be designed to detect the second fault condition when the further phase voltage exceeds or falls below a third threshold. In another embodiment, the controller may be designed to determine that the predefined condition is met,if the decoupling switches are robust enough to withstand an overvoltage condition caused by the corresponding potential difference between the bridge node and the phase winding. In another embodiment, the decoupling switches can be designed as field-effect transistors; and the controller can be designed to determine that the predefined condition is met if the decoupling switches are capable of withstanding operation in avalanche mode induced therein by the respective potential difference between the bridge node and the phase winding. In another embodiment, the controller can be further designed to delay the switching off of the further decoupling switch with respect to the switching off of the switches until a zero crossing of the further phase voltage or a further phase current. In another embodiment, the controller can be further designedthat it delays the switching off of the further decoupling switch with respect to the switching off of the switches until the value of a current that is fed back from the electric motor to the further bridge node has fallen below a first threshold. In another embodiment, the decoupling switches can be designed as field-effect transistors, and the controller can further be designed to switch on the decoupling switch that has operated in avalanche mode for the longest time after being switched off as a result of the second fault. In another embodiment, the controller can be designed to switch on the decoupling switch to which the highest phase voltage was applied after being switched off as a result of the second fault. In another embodiment, the decoupling switches can be designed as field-effect transistors; and the controller can be designedthat it controls at least one of the decoupling switches, after it has been switched off as a result of the second fault and operated in avalanche mode, in a clocked manner such that a portion of the energy consumed therein corresponds to or is less than its maximum rated energy loss portion. In another embodiment, the controller can further be designed to switch on and off at least two switches that have been operating in avalanche mode in an exclusive manner, with at least one of the switches being a decoupling switch.

[0007] In various embodiments, a method for operating a circuit arrangement is provided. The circuit arrangement comprises: an electric motor, a bridge circuit having at least two switches connected in series; a bridge node arranged between the at least two switches and configured to provide a phase voltage and to be coupled to a phase winding of the electric motor; a decoupling switch configured to be connected between the bridge node and the electric motor, wherein the decoupling switch is configured as a field-effect transistor; and a controller coupled to the decoupling switch and to the at least two switches. The method comprises: switching off the at least two switches in the event of a fault; determining whether a predefined condition is met;and switching off the decoupling switch, wherein the switching off of the decoupling switch is delayed with respect to the switching off of the at least two switches if the predefined condition is not met; and / or simultaneously switching off the at least two switches and the decoupling switch if the predefined condition is met; wherein the predefined condition is met if the decoupling switch can be switched off without suffering permanent damage from the current applied to it at the time the at least two switches are switched off, wherein the controller detects a second fault case if the phase voltage exceeds or falls below a threshold value, wherein the decoupling switch is designed as a field-effect transistor;and wherein the controller switches the decoupling switch back on after it has remained off as a result of the second fault event and has operated in avalanche mode for a period during which a portion of energy equal to or less than its maximum rated dissipated energy portion has been consumed therein;

[0008] In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the following description, various embodiments of the invention are described with reference to the following drawings, in which: Fig. 1 shows a circuit arrangement according to various embodiments with a half bridge; Fig. 2 shows a circuit arrangement according to various embodiments with three half bridges; Fig. 3 shows a further circuit arrangement according to various embodiments with three half bridges; Fig. 4 is a flowchart illustrating a process flow describing the configuration of the controller within the circuit arrangement according to various examples; and Fig. 5 is a flowchart illustrating a method for operating a circuit arrangement according to various examples.

[0009] The following detailed description refers to the accompanying drawings which illustrate specific details and embodiments in which the invention may be practiced.

[0010] The word "exemplary" is used herein to mean "serving as an example or illustration." Embodiments or interpretations described herein as "exemplary" are not necessarily to be interpreted as preferred or advantageous over other embodiments or interpretations.

[0011] The words "on, over," used with respect to an applied material that may be formed "on, over" a side or surface, may be used herein to mean that the applied material is formed "directly on," e.g., directly in contact with, the mentioned side or surface. The words "on, over," used with respect to an applied material that may be formed "on, over" a side or surface, may be used herein to mean that the applied material is formed "indirectly on" the mentioned side or surface, with one or more additional layers disposed between the mentioned side or surface and the applied material.

[0012] In Fig. 1 shows a circuit arrangement 100 according to various embodiments. The circuit arrangement 100 according to various embodiments can have an inverter circuit 110 (bridge circuit) which can have at least two switches connected in series, i.e. a first switch 102 and a second switch 106. The first switch 102 and a second switch 106 can form a half-bridge, such that the first switch 102 can be the high-side switch, and the second switch 106 can be the low-side switch. The at least two switches 102, 106 (which are also referred to below as bridge switches) can be designed as solid-state switches, for example as transistors, for example as field-effect transistors, such as metal-oxide-semiconductor field-effect transistors (MOSFETs).A terminal of the first switch 102 may be coupled to a first reference terminal 116, which may be at a first reference potential, for example, a battery potential or any other type of power supply potential, and a terminal of the second switch 106 may be coupled to a second reference terminal 118, which may be at a second reference potential, such as ground potential. The difference between the first reference potential and the second reference potential defines the bridge voltage. A bridge node 104 may be arranged between the at least two bridge switches 102, 106 and configured to provide a phase voltage, which may correspond to a sinusoidal phase voltage with an amplitude corresponding to the bridge voltage.The circuit arrangement 100 according to various embodiments may further comprise an electric motor 112 with at least one phase winding coupled to the bridge node 104 via a decoupling switch 108 connected between the bridge node 104 and the electric motor 112. Analogous to the at least two switches of the inverter circuit 110, the decoupling switch 108 may be designed as a solid-state switch, for example, a transistor, for example, a field-effect transistor such as a MOSFET.The circuit arrangement 100 according to various embodiments may further comprise a controller 114 which is coupled to the decoupling switch 108 and to the at least two bridge switches 102, 106, wherein the controller 104 may be designed such that, in the event of a fault, it switches off the at least two bridge switches 102, 106 to determine whether a predefined condition is met, and either switches off the decoupling switch 108, wherein the switching off of the decoupling switch 108 is delayed with respect to the switching off of the at least two bridge switches 102, 106 if the predefined condition is not met, or switches off the at least two bridge switches 102, 106 and the decoupling switch 108 simultaneously if the predefined condition is met.The controller 114 may be configured to determine that the predefined condition is met when the decoupling switch 108 can be turned off without suffering permanent damage from the current applied to it at the time the at least two switches 102, 106 are turned off. It should be noted that, in contrast to the depiction of the controller 114 as a single unit in FIG. Fig. 1 it may also comprise at least two separate modules which may be communicatively coupled to one another, wherein one module may be designed to control the at least two bridge switches 102, 106 and the other module may be designed to control the decoupling switch 108.

[0013] The underlying concept on which the various embodiments of the circuit arrangement and a corresponding method for controlling the circuit arrangement can be based is a mechanism and / or a method by which, for example, in the event of a fault, an optimal time for switching off the decoupling switch 108 can be selected. This optimal switching off can be achieved by delaying the switching off of the decoupling switch 108 with respect to the switching off of the at least two bridge switches 102, 106 of the inverter circuit 110 or by simultaneously switching off the decoupling switch 108 and the at least two bridge switches 102, 106. The decision as to whether the decoupling switch 108 should be switched off simultaneously or in a delayed manner with respect to the switching off of the at least two bridge switches 102, 106 is made by the controller 114.The controller 114 can be designed to evaluate at least one parameter, and it can be designed to switch off the at least two switches 102, 106 and simultaneously switch off the decoupling switch 108 in the event of a fault, based on the result of this evaluation, or to delay the switching off of the decoupling switch 108 by a specific time. The at least one parameter can include the rotational speed and / or the relative position between the rotor and the stator of the electric motor 112 at the time of switching off the inverter circuit 110, the value of the phase current, the value of the phase voltage, the value of the first reference potential (e.g., the battery voltage), the type of fault condition (short circuit or open circuit, position thereof within the circuit arrangement 100 according to various embodiments). The phase current can refer to a current that is supplied by the electric motor 112 at some point, i.e., during normal operation, i.e.,during operation of the circuit arrangement according to various embodiments in which no fault is present, or during operation thereof in a fault situation, ie after the at least two bridge switches 102, 106 have been switched off as a result of the detection of a fault situation.

[0014] In contrast to conventional safety applications, where one paradigm is that the system must be shut down as quickly as possible in a fault situation, the approach followed here may include cases, as already mentioned, in which the decoupling switch 108 is not switched off simultaneously with the at least two bridge switches 102, 106, i.e., not as quickly as possible. In the automotive field, safety applications typically have an application safety time. The application safety time, which may be approximately in the range of about 10 ms to about 30 ms, is the time allowed for an application to detect any deviations from the normal operating state and / or any anomalous conditions before entering fail-safe mode. During this time, the system dynamics may be uncontrolled and unpredictable.After the application safety time has elapsed, control of the system must be regained, and it can either return to normal operation or enter failsafe mode. The controller 114 can be configured to monitor error states of the circuit arrangement 100 according to various embodiments, for example, to monitor error state variables that may indicate whether or not a particular error has occurred. In the event of an error occurring, the controller 114 can use the application safety time to determine / estimate its potential impact on the system and subsequently determine whether the decoupling switch 108 should be turned off simultaneously with the at least two bridge switches 102, 106, or whether the turning off of the decoupling switch 108 should be delayed with respect to the turning off of the at least two switches 102, 106.In other words, the application safety time can be used to estimate the failure and therefore correspond to a failure estimation time.

[0015] The controller 114 may also be configured to respond to errors that occur outside the safety application, ie, to errors that occur outside the circuit arrangement 100 according to various embodiments. For this purpose, the controller 114 may have an external error terminal (in Fig. 1 not shown) in order to receive an external error signal from the outside. The controller 114 can be designed such that, when the external error signal is received, it enters the fail-safe mode, even if no error is detected within the circuit arrangement 100 according to various embodiments. However, the controller 114 can also be designed such that, in this case, it determines an optimal time for switching off the decoupling switch 108 by delaying the switching off of the decoupling switch 108 with respect to the switching off of the at least two bridge switches 102, 106 of the inverter circuit 110 or by simultaneously switching off the decoupling switch 108 and the at least two bridge switches 102, 106.In other words, the controller 114 can be configured to apply the same treatment scheme upon receiving the external fault signal according to which the circuit arrangement 100 is to be switched off according to various embodiments as if a fault were detected within the circuit arrangement 100 according to various embodiments. Alternatively, the controller 114 can be configured to simultaneously and immediately switch off the at least two bridge switches 102, 106 and the decoupling switch 108 of the inverter circuit 110 upon receiving the external fault signal according to which the circuit arrangement 100 is to be switched off according to various embodiments, provided that the decoupling switch can be switched off without being damaged by the phase current.

[0016] The circuit arrangement 100 according to various embodiments can be easily adapted to include more than one half-bridge. For example, the circuit arrangement according to various embodiments can have a further branch in the form of a half-bridge, which can provide another phase voltage if the load requires two different phase voltages. In the following, with reference to Fig. 2 describes a circuit arrangement 200 according to various embodiments, which has three half bridges.

[0017] The Fig. The circuit arrangement 200 shown in Figure 2 according to various embodiments can be considered as an extension of the circuit arrangement shown in Fig. 1, it can be seen that the inverter circuit 110 has three half-bridges instead of just one half-bridge. Therefore, three different phase voltages can be provided within the circuit arrangement 200 according to various embodiments and supplied to the three phase windings within the electric motor 112. In the circuit arrangement 100 shown in Fig. 1 according to various embodiments, a load was assumed that requires a single phase voltage, for example a single-phase electric motor 112, while in the circuit arrangement 100 shown in Fig. 2, according to various embodiments, a load can be assumed that requires three phase voltages, such as a three-phase electric motor 112. The circuit arrangement 200 shown in Fig. The circuit arrangement 200 shown in Figure 2 may therefore be designed to provide three phase voltages to the electric motor 112, wherein each phase voltage may have a phase shift of 120° with respect to the other.

[0018] In the following, the circuit arrangement 200 according to various embodiments is described starting from the Fig. 1 is described as a basis. In addition to the circuit arrangement 100 shown in Fig. 1, which will not be described again, the circuit arrangement 200 may, according to various embodiments, further comprise a second half-bridge having a third switch 122 and a fourth switch 126. A terminal of the third switch 122 may be coupled to the first reference terminal 116, which may be at the first reference potential, for example, a battery potential or any other type of power supply potential, and a terminal of the fourth switch 126 may be coupled to the second reference terminal 118, which may be at the second reference potential, such as the ground potential. A second bridge node 124 may be arranged between the at least two bridge switches 122, 126 of the second half-bridge and configured to supply a second phase voltage to a second phase winding of the electric motor 112.The second phase winding of the electric motor 112 can be coupled to the second bridge node 124 via a second decoupling switch 128. The circuit arrangement 200 according to various embodiments can further comprise a third half-bridge having a fifth switch 132 and a sixth switch 136. A terminal of the fifth switch 132 can be coupled to the first reference terminal 116, and a terminal of the sixth switch 136 can be coupled to the second reference terminal 118. A third bridge node 134 can be arranged between the two bridge switches 132, 136 of the third half-bridge and can be configured to supply a third phase voltage to a third phase winding of the electric motor 112. The third phase winding of the electric motor 112 can be coupled to the third bridge node 134 via a third decoupling switch 138. Analogous to the embodiments described with reference to FIG. Fig. 1, the bridge switches of the second half-bridge and the third half-bridge can be designed as solid-state switches, for example as transistors, for example as field-effect transistors, such as MOSFETs.

[0019] As in Fig. 2, the controller 114 is coupled to each bridge switch 102, 106, 122, 126, 132, 136 provided within the three half-bridges of the inverter circuit 110 and to each of the three decoupling switches 108, 128, 138. Regardless of the number of half-bridges within the inverter circuit 110, the controller 114 may be designed to switch off all of the bridge switches within the inverter circuit in the event of a fault, determine whether a predefined condition is met, and either delay the switching off of the decoupling switches 108, 128, 138 with respect to the switching off of the bridge switches 102, 106, 122, 126, 132, 136 if the predefined condition is not met, or switch off the bridge switches 102, 106, 122, 126, 132, 136 and the decoupling switches 108, 128, 138 simultaneously (in other words, simultaneously) if the predefined condition is met.Furthermore, regardless of the number of half-bridges present in the inverter circuit 110, the controller 114 may be configured to determine that the predefined condition is met when the decoupling switches can be turned off without suffering permanent damage from the phase current applied to them at the time the bridge switches 108, 128, 138 are turned off.

[0020] In the following, possible error scenarios are described with reference to Fig. 4 and its influence on the switch-off strategy of the circuit arrangement controlled by the controller 114 according to various embodiments. The description is based on a circuit arrangement according to various embodiments that has three half-bridges in the inverter circuit 110 (as shown in Fig. 2). However, it can be applied analogously to circuit arrangements with inverter circuits 110 with only one half-bridge or two half-bridges.

[0021] In Fig. 4 shows a flowchart 400 illustrating the process flow initiated by the controller 114 upon detecting the presence of a fault condition in step 402. The presence of the fault condition may be due to a fault detected by the controller 114 within the circuitry itself, according to various embodiments. Alternatively, the external fault signal that may be received by the controller 114 may prompt the circuitry to enter failsafe mode. The controller 114 is configured to shut down the system in either case in a manner that may minimize the risk of permanent damage to the bridge switches and / or the decoupling switches.

[0022] When the presence of a fault condition is detected in the circuit arrangement according to various embodiments, two scenarios may need to be handled. In one scenario, a short circuit occurs in one of the bridge switches. It is assumed that a short circuit in one bridge switch provides an electrical path with negligible ohmic resistance through this bridge switch. A short circuit in one of the bridge switches can be detected by monitoring the voltage at the other bridge switch and / or the phase current flowing through the other bridge switch in a respective half-bridge. If the other bridge switch is switched on, a short circuit between the first reference potential and the second reference potential exists and can be detected. In another scenario, an open circuit occurs in one of the bridge switches.It is assumed that an open circuit in any bridge switch corresponds to an infinite resistance such that no phase current is allowed to flow through it. An open circuit in one of the bridge switches can be detected by monitoring the phase voltage at the corresponding bridge node. When the bridge switches are turned off in the event of a fault and the rotor of the electric motor 112 continues to rotate, a phase current is still generated and driven to or drawn from the decoupling switch and / or the corresponding bridge node. In some cases, however, due to the inductances provided in the electric motor 112, a phase current may still be generated (induced) on timescales of up to several hundred microseconds, even after the electric motor 112 has stopped rotating. The phase voltage may then assume values ​​outside the voltage range of the bridge voltage.By monitoring the phase voltages, the controller 114 may therefore be able to determine whether an open circuit exists in a bridge switch in a respective half-bridge. In both cases, the presence of an open circuit or the presence of a short circuit in one of the bridge switches also includes cases in which an open circuit or short circuit exists at the periphery of the bridge circuit, affecting the electrical connections between the respective bridge circuit and other electrical components.

[0023] If a fault condition is detected by controller 114 or if a corresponding value of the external fault signal is received by controller 114, all bridge switches may be turned off in step 404 in flowchart 400. If there is an open circuit in one of the bridge switches, that bridge switch may remain turned on, as it may not be possible to turn off that bridge switch using appropriate switching signals applied to it by controller 114.

[0024] The controller 114 is designed such that, when the bridge switches are turned off, it decides whether the decoupling switches can be turned off immediately (i.e., at the same time as the bridge switches) or whether their turning off should be delayed to prevent the decoupling switches from being damaged. Since the controller 114 may have information about the position and speed of the rotor of the electric motor 112, it can calculate / predict whether the bridge switches and the decoupling switches can be turned off simultaneously. The value of each of the phase currents, which may generally be sinusoidal, may be known to the controller 114 at the time the short circuit at a bridge switch is detected. The controller 114 may therefore be designed such that, in step 406, it turns off all the decoupling switches immediately, i.e.,at the same time as the bridge switches are turned off if it determines that the decoupling switches are robust enough to withstand an overvoltage condition that may be caused by excessive phase current. That is, the controller 114 may turn off the decoupling switches along with the bridge switches if the phase current can be effectively blocked by the decoupling switches without causing permanent damage to them.

[0025] However, if the controller 114 determines that the decoupling switches are not robust enough to withstand an overvoltage condition, which may be caused by excessive phase current, it may delay the turning off of the decoupling switches in step 408, for example, until a zero crossing of the corresponding phase voltage. A zero voltage crossing may be detected by phase voltage feedback, which may be included in the controller 114 or provided as a separate unit in the circuitry according to various embodiments. The phase voltage feedback may be designed as a comparator circuit configured to compare one half of the inverter circuit voltage (i.e., one half of the bridge voltage), which may correspond to 12 V of a vehicle battery, with the actual phase voltage, i.e., the voltage at a respective bridge node.A positive value of this comparison may indicate that the upper electrical path is currently being used, i.e., that the corresponding phase winding is electrically coupled to the first reference terminal 116, wherein a freewheeling electrical path (e.g., a freewheeling diode) of the corresponding high-side switch may be used. A negative value of this comparison may indicate that the lower electrical path is currently being used, i.e., that the corresponding phase winding is electrically coupled to the second reference terminal 118, wherein a freewheeling electrical path (e.g., a freewheeling diode) of the corresponding low-side switch may be used. By triggering the turning off of a respective decoupling switch upon transition between these two states, the controller 114 may be able to switch the respective decoupling switch upon a zero crossing of the corresponding phase current.However, if the phase currents drop, all three decoupling switches may also be turned off upon a zero crossing of a phase current if the controller 114 is able to determine (for example, from a theoretical model or from a lookup table) that the drop in the phase currents is so rapid that there is no risk of permanent damage to the other decoupling switches if they are turned off at the zero crossing of the phase current of the other decoupling switch. In such a case, only one decoupling switch is turned off at the zero crossing of the corresponding phase current; the other two are turned off at non-zero values ​​of their phase currents. It should be noted that the freewheeling path through the body diode of a bridge switch may not be available after an open circuit occurs at the corresponding bridge switch.The phase voltage may no longer be determined to the value of a body diode threshold voltage above the bridge voltage or to the value of a body diode threshold voltage below the reference voltage. Therefore, an excessively large phase voltage, either positive, for example, a phase voltage above 20 V (instead of approximately a value corresponding to the bridge voltage plus the threshold voltage of a body diode of the corresponding high-side switch during normal operation of the circuit arrangement according to various embodiments), or negative, for example, a phase voltage below -20 V (instead of approximately a value corresponding to the reference voltage minus the threshold voltage of a body diode of the corresponding low-side switch during normal operation of the circuit arrangement according to various embodiments), may be an indicator of the presence of an open circuit at the corresponding bridge switch (i.e.a high-side switch or a low-side switch), for the detection of which the controller 114 may further be configured for diagnostic purposes.

[0026] In another scenario, represented by step 406, the controller 114 may delay turning off the decoupling switches until the phase current still generated by the electric motor 112 drops below a certain threshold. The threshold may be defined or based on the maximum rated operating parameters of the bridge switches. In general, delaying the turning off of the decoupling switches may allow the phase current to drop to levels low enough to be effectively blocked by low-power switches, which are typically cheaper, such as transistors designed for low-power switching, rather than expensive power transistors.

[0027] If the bridge switches and / or the decoupling switches are designed as semiconductor switches, for example, MOSFETs, the aforementioned overvoltage condition may be a condition in which a respective semiconductor switch is operating outside of its maximum rated operating values. For example, the aforementioned overvoltage condition may correspond to operation of a respective semiconductor switch in avalanche mode. Therefore, the decision made by the controller 114 as to whether a respective decoupling switch can be turned off for a given phase current applied to it may be based on the estimation of whether or not the respective decoupling switch enters avalanche mode and, if so, whether the respective decoupling switch is capable of maintaining operation in avalanche mode without being permanently damaged.The controller 114 can be designed to predict the further temporal development of the phase current, for example, based on theoretical models using available parameters, such as the speed of the rotor in the electric motor 112, the relative position between the rotor and the stator of the electric motor 112, the magnetic field of the rotor, and / or the internal resistance of the electric motor 112. However, actual measurements of the phase current can also be used to predict its further temporal development, since the necessary measuring circuits (e.g., Hall sensors, shunt resistors) are typically present in conventional motor control circuits.Alternatively, the controller 114 may use lookup tables that may contain information about whether a respective decoupling switch can be turned off at a given phase current or a given rotor speed and / or a given relative position between the rotor and the stator of the electric motor 112. In other words, the lookup tables may contain values ​​based on pre-calculated scenarios that take into account the specific design of the electric motor 112 as well as the nominal operating parameters of the semiconductor switches.

[0028] The controller 114 may be configured to further implement energy management after initiating any of the processes according to steps 406, 408, 410 in the flowchart 400. The goal of energy management may be to distribute the energy to be consumed in such a way that none of the bridge switches or decoupling switches are damaged. The energy to be consumed originates from the electric motor 112, in which the rotor does not immediately stop after the bridge switches are turned off, but continues to rotate and thereby induce a phase current in the stator. Turning off the decoupling switches is intended to block this phase current by disconnecting the inverter circuit 110 from the electric motor 112. It may also protect the bridge switches from damage caused by increased phase voltage and / or phase current.However, instead of using high-performance switches that can be turned off at any time, the approach in the circuit arrangement according to various embodiments is to use low-power switches to block currents that may be outside the rated operating range of the switches. Therefore, redistribution schemes for the energy to be consumed can be implemented to prevent damage to the decoupling switches.

[0029] Turning off the bridge switches can cause the phase voltage in at least one half-bridge within the inverter circuit 110 to rise above its nominal value. When the decoupling switches are turned off, this increased phase voltage can lead to overvoltage conditions, i.e., avalanche mode operation, in the case of decoupling switches designed as MOSFETs. The energy management employed by the controller 114 aims to distribute the energy to be consumed in order to alleviate the electrical (and thus thermal) stress on the switch(es) blocking the current path between the electric motor 112 and the inverter circuit 110. If the switches (be they bridge switches or decoupling switches) are designed as semiconductor switches, for example, as transistors such as MOSFETs, then the energy management can be said to aim to distribute avalanche energy among various transistors.For the purposes of this description, avalanche energy can refer to the energy dissipated by a transistor during its operation in avalanche mode, where the energy can be dissipated in the form of heat generated within the transistor. In other words, avalanche energy can refer to the amount of power over time that the transistor itself can absorb and dissipate during operation in avalanche mode.

[0030] One measure for implementing energy management may be the simultaneous switching off of several decoupling switches, as already described in step 410 of the Fig. 4. As a result, multiple decoupling switches actively block the circulating current in the circuit arrangement according to various embodiments, instead of just one decoupling switch, and therefore the energy to be consumed is distributed among them.

[0031] Another measure for implementing energy management can be turning off a switch (be it a bridge switch or a decoupling switch) operating in an overvoltage condition. This means that this switch no longer actively blocks the current path and can cease to function in an overvoltage condition. Its blocking property is then taken over by the other switch(es) in the respective half-bridge (including the corresponding decoupling switch). The switch that can be turned on can be the switch in which the highest avalanche energy was consumed compared to other switches that may also be operating in avalanche mode. The switch that can be turned on can be the switch in which a predefined avalanche energy was consumed, which can correspond toThis predefined avalanche energy can correspond to a maximum rated loss energy (taking into account a safety margin) that the switch can withstand without suffering permanent damage.

[0032] Yet another measure for implementing energy management may include a switching scheme in which the at least one switch most stressed by overvoltage is switched on and off at a specific frequency or at variable intervals to have alternating phases of thermal stress and thermal relaxation. For example, a PWM (pulse width modulation) scheme may be used. By switching on and off, for example, a semiconductor switch, the avalanche energy can be dosed according to the maximum rated operating parameters of the semiconductor switch. It is assumed that when a semiconductor switch operates in an avalanche mode, it is under high thermal stress and therefore in a phase of thermal stress. Consequently, it is assumed that when a semiconductor switch is not operating in avalanche mode, i.e.is not switched off and blocks the phase current, is under low thermal stress and therefore in a phase of thermal relaxation. The energy management employed by controller 114 is described below based on the principles described in . Fig. 2 according to various embodiments. For illustrative purposes only, it is assumed that the switches, i.e., the six bridge switches 102, 106, 122, 126, 132, 136 and the three decoupling switches 108, 128, 138, are designed as transistors, for example, MOSFETs. For illustrative purposes only, it is further assumed that the fault condition is due to an open circuit in the third switch 122, i.e., the high-side switch of the second half-bridge.

[0033] When the controller 114 detects the interruption in the third switch 122, all other bridge switches 102, 106, 126, 132, 136 are closed according to step 404 of the flowchart 400 of Fig. 4. Then, depending on the magnitude of the phase current, the decoupling switches 108, 128, 138 are turned off. In the meantime, the fourth bridge switch 126 may have operated in avalanche mode because the freewheeling path to the first reference terminal 116, e.g., through a freewheeling diode in the third bridge switch 122, is unavailable, and the phase current may therefore have generated a significant potential increase at the second bridge node 124, such that the fourth bridge switch 126 may not have been able to effectively block the voltage between the fourth bridge node 124 and the second reference terminal 118 and may have actually entered avalanche mode.Simultaneously turning off all three decoupling switches 108, 128, 138 results in a distribution of the voltage stress, for example, the avalanche energy, from the fourth bridge switch 126 to at least one and at most two of these three decoupling switches. It should be noted that, depending on the direction of the phase current, at least one and at most two of the three decoupling switches 108, 128, 138 can enter avalanche mode. The at least one other decoupling switch can conduct the phase current via its freewheeling path, e.g., a freewheeling diode (which can be provided in each of the decoupling switches in the form of a dedicated body diode of a MOSFET).In this example, the fourth bridge switch 126, the first decoupling switch 108, and / or the third decoupling switch 138 may be alternately turned on to apply a power management scheme intended to allow the switch that is turned on to recover from thermal stress during the period it remains on and therefore not be used to block phase current. In general, if the controller 114 determines that the phase current stress of at least one of the decoupling switches 108, 128, 138, or at least one of the bridge switches is too high, that decoupling switch or that bridge switch may be turned on for a period of time during which it can recover. For illustrative purposes only, it is assumed that the first decoupling switch 108 is at risk of being damaged by excessive avalanche energy dissipated thereon.If the first decoupling switch 108 is configured as a MOSFET having a gate voltage shown in . Fig. 3, this can only be the case if the current flows from the second reference terminal 118 through the first bridge node 104 to the electric motor 112, since then the electrical freewheeling path through the body diode of the first decoupling switch 108 is not available for this current flow direction. As a result, the potential between the first bridge node 104 and the first decoupling switch 108 can increase considerably, resulting in a large voltage being applied to the first decoupling switch 108. Consequently, the first decoupling switch 108 can enter avalanche mode operation. To prevent the first decoupling switch 108 from being damaged, it can be switched on for a certain period of time. In this example, current could also flow from the motor 112 to the second bridge node 124 and the third bridge node 134.The current flowing to the third bridge node 134 flows through the conducting body diodes of the third decoupling switch 138 and the fifth bridge switch 132 to the first reference terminal 116, e.g., the battery. The current flowing to the second bridge node 124 flows through the conducting body diode of the second bridge switch 128. Since, in this example scenario, the third bridge switch 122 is affected by an open circuit, this current is prevented from flowing to the first reference terminal 116. Instead, it can drive the fourth bridge switch 124 into avalanche mode. This means that, in this example, the first decoupling switch 108 and the fourth bridge switch 126 are affected by severe thermal stress.By only turning on the first decoupling switch 108 or the fourth bridge switch 126, energy management can be achieved between the two switches affected by the severe thermal load. During this process, the battery can be charged when current flows from the second reference terminal 118 through the electric motor 112 to the first reference terminal 116. During this process, the current is not increased; however, the phases during which the first decoupling switch 108 is turned on can increase the time it takes for the current to decay. After a certain period of time, e.g., after the first decoupling switch 108 has regenerated, i.e., cooled down, it can be turned off again, thereby blocking the electrical path for the phase current again.The first decoupling switch 108 may be turned on and off for different periods of time, for example, in a PWM scheme, since the amount of phase current generated by the electric motor 112 may require multiple stress and relaxation phases of the decoupling switch 108 until all of its rotational energy is consumed and it finally stops its rotational movement.

[0034] The operations just described can be applied to any other branch of the circuit arrangement 200 according to various embodiments, i.e., to the second branch comprising the second half-bridge (the third switch 122 and the fourth switch 126) and the second decoupling switch 128, and / or to the third branch comprising the third half-bridge (the fifth switch 132 and the sixth switch 136) and the third decoupling switch 138, independently of each other. For example, if the second decoupling switch 128 and the third decoupling switch 138 are to be repeatedly switched on and off, for example, using a PWM scheme, they can be switched on and off synchronously, or they can be switched on and off independently of each other.

[0035] In Fig. 3 shows a further implementation 300 of a circuit arrangement according to various embodiments. The implementation 300 is based on the Fig. 2. Each switch, i.e., the six bridge switches 102, 106, 122, 126, 132, 136 and the three decoupling switches 108, 128, 138, are designed as MOSFETs, each including its own body diode, which can be used as a freewheeling diode when the respective switch is turned off. It should be noted that the arrangement of the body diodes of the three decoupling switches 108, 128, 138 can be reversed, i.e., the direction of the freewheeling path can be reversed. In the implementation 300 of the circuit arrangement according to various embodiments, a resistor 310 is shown, which is coupled between the second reference terminal 118 and the low-side switches of the inverter circuit 110. The resistor 310 can be a shunt resistor, which can be used to determine the magnitude of the phase current. Its Fig. The arrangement shown in Figure 3 is exemplary; the shunt resistor or multiple shunt resistor may be provided in other positions within the circuit arrangement 300 according to various embodiments, e.g., in one of the electrical paths between one of the decoupling switches 108, 128, 138 and the electric motor 112. The detailed connections between the controller 114 and the switches have been omitted from the figure for clarity. In the Fig. 3, the controller 114 includes a dedicated circuit 306 designed to monitor the fault conditions and decide when the decoupling switches should be turned off in a fault condition. The small arrows 304 indicate the effect of the controller 114 on the bridge switches, which are turned off in the event of a detected or reported fault condition. The large arrow 308 indicates the effect of the dedicated circuit 306 on the decoupling switches, which are turned off either together with or delayed with respect to the turning off of the bridge switches, as based on the Fig. 4. The controller 114 further includes the external fault terminal 302, via which it receives the external fault signal indicating that the bridge circuit within the circuit arrangement 300 should be switched off according to various embodiments. In general, the controller 114 can receive signals indicating the phase voltages and / or the voltages applied to the bridge switches to determine short circuits at the bridge switches. The direction of the phase current determines whether the phase current flows through the high-side switch or through the low-side switch of the respective half-bridge of the circuit arrangement according to various embodiments.A transition from a current flow through the high-side switch to a current flow through the low-side switch and vice versa in a given half-bridge changes the phase voltage and thereby indicates a zero crossing of the phase current.

[0036] The Fig. 3, the freewheeling diodes are essentially unidirectional electrical paths that are always conductive when a voltage above the diode forward bias of the correct polarity is applied to them. This fact must be taken into account during the power management scheme, although it may not always be possible to open a decoupling switch thermally stressed by avalanche operation, as this may result in a slightly conductive electrical path between the electric motor 112 and the reference potentials.

[0037] In Fig.5 shows a flowchart 500 illustrating a method for operating a circuit arrangement according to various embodiments. In step 502, the method may include switching off the at least two switches (bridge switches) in the event of a fault. It should be noted that if a short circuit is present in a bridge circuit, it may not be possible to actively switch off this switch using a corresponding signal from the controller 114. In such a case, the affected bridge switch remains conductive.

[0038] In a next step 504, the method may comprise determining whether a predefined condition is met. As already mentioned, the predefined condition is met if the decoupling switch (or the decoupling switches) can be turned off without suffering permanent damage from the current applied to it (or them) at the time the at least two switches (bridge switches) are turned off. If this condition is not met, the method may comprise, in step 508, delaying the turning off of the decoupling switch (or the decoupling switches) with respect to the turning off of the at least two switches (bridge switches). In the case of a circuit arrangement according to various embodiments with more than one branch, i.e.with more than one half-bridge, the individual decoupling switches can be turned off simultaneously (but still some time after the bridge switches are turned off) or individually delayed by different times so that they are not turned off at the same time.

[0039] If this condition is met, the method may include simultaneously turning off the at least two switches (bridge switches) and the decoupling switch (or switches) in step 506.

[0040] The circuit arrangement according to various embodiments as described herein, as well as the method of operating the same, can be used, to give a feasible example, in power steering applications, for example in any type of vehicle.

[0041] The detection of fault conditions, for example, the first fault case and the second fault case, within the circuit arrangement according to various embodiments can be based on monitoring whether currents and / or voltages exceed or fall below certain thresholds, for example, the second threshold and the third threshold. The values ​​of the thresholds can be selected such that the presence of a fault condition can be practically guaranteed if a respective threshold is exceeded or fallen below by the monitored value.

[0042] However, instead of monitoring specific values, such as the phase current and / or phase voltage, to determine whether a fault condition exists, test patterns can be used instead or additionally. In other words, the response of the circuit arrangement to test patterns, for example, specific control pulses applied to the switches, can be analyzed according to various embodiments to detect faults. To give an example, a bridge switch or a decoupling switch can be switched on or off by an appropriately designed control signal. If no change in the phase current or phase voltage in the corresponding half-bridge is detected when an activating or deactivating control signal is applied to this switch, this switch can be classified as affected by an open circuit and therefore faulty.

[0043] According to various examples, a circuit arrangement is provided comprising: a bridge circuit having at least two switches connected in series; a bridge node arranged between the at least two switches, wherein the bridge node can be configured to provide a phase voltage; an electric motor having at least one phase winding coupled to the bridge node; a decoupling switch connected between the bridge node and the electric motor;a controller coupled to the decoupling switch and to the at least two switches, wherein the controller can be designed to switch off the at least two switches in the event of a fault, determine whether a predefined condition is met, and either switch off the decoupling switch, wherein the switching off of the decoupling switch can be delayed with respect to the switching off of the at least two switches if the predefined condition is not met; or switch off the at least two switches and the decoupling switch simultaneously if the predefined condition is met; wherein the controller can be designed to determine that the predefined condition is met if the decoupling switch can be switched off without suffering permanent damage from the current applied to it at the time the at least two switches are switched off.

[0044] According to further embodiments of the circuit arrangement, a first switch of the at least two switches can be coupled to a supply potential.

[0045] According to further embodiments of the circuit arrangement, a second switch of the at least two switches can be coupled to a reference potential.

[0046] According to further embodiments of the circuit arrangement, the controller may be designed to determine that the predefined condition is met when the decoupling switch is robust enough to withstand an overvoltage condition caused by the potential difference between the bridge node and the phase winding.

[0047] According to further embodiments of the circuit arrangement, the decoupling switch can be designed as a field-effect transistor.

[0048] According to further embodiments of the circuit arrangement, the controller may be designed to determine that the predefined condition is met when the decoupling switch is capable of withstanding operation in avalanche mode induced by the potential difference between the potential at the bridge node and the potential at the phase winding therein.

[0049] According to further embodiments of the circuit arrangement, the controller may further be designed to determine the potential at the phase winding from the position of a stator with respect to a rotor of the electric motor.

[0050] According to further embodiments of the circuit arrangement, the controller may further be designed to monitor the phase voltage.

[0051] According to further embodiments of the circuit arrangement, the controller can further be designed to delay the switching off of the decoupling switch with respect to the switching off of the at least two switches until a zero crossing of the phase voltage or the phase current.

[0052] According to further embodiments of the circuit arrangement, the controller can be further configured to delay the deactivation of the decoupling switch with respect to the deactivation of the at least two switches until the value of a current driven by the electric motor to the bridge node has fallen below a first threshold. The first threshold can be defined by or based on the nominal operating parameters of the switches and indicate a current at which a safe deactivation of the at least two switches is still possible, e.g., a deactivation by which the at least two switches are not damaged as a result of the current (phase current) still driven by the electric motor to and from the bridge node.

[0053] According to further embodiments of the circuit arrangement, the first threshold value of the current fed back from the electric motor to the bridge node may comprise an average current value or an instantaneous current value.

[0054] According to further embodiments of the circuit arrangement, the first threshold value of the current fed back from the electric motor to the bridge node may comprise an instantaneous value.

[0055] According to further embodiments of the circuit arrangement, a first fault case may correspond to a short circuit that occurs at one of the at least two switches.

[0056] According to further embodiments of the circuit arrangement, the controller may further be designed to monitor the voltage at at least one of the at least two switches.

[0057] According to further embodiments of the circuit arrangement, the controller may further be designed to detect the first fault case when the voltage at at least one of the at least two switches exceeds a second threshold while it is switched on. The second threshold may be determined by the resistance of the corresponding switch in the fully conductive state (R DS(on) in the case of a MOSFET transistor) multiplied by the maximum permissible phase current or equal to it (possibly taking into account a safety margin).

[0058] According to further embodiments of the circuit arrangement, a second fault case may correspond to an interruption that occurs at one of the at least two switches.

[0059] According to further embodiments of the circuit arrangement, the controller may be further configured to detect the second fault case when the phase voltage exceeds or falls below a third threshold. The third threshold may correspond to the bridge voltage (i.e., the voltage at the first reference potential 116) plus a diode forward voltage and plus a safety margin to reliably detect an open condition in a respective high-side bridge switch, or it may correspond to the second reference voltage (i.e., the voltage at the second reference terminal 118) minus a diode forward voltage and minus a safety margin to reliably detect an open condition in a low-side bridge switch.According to further embodiments of the circuit arrangement, the decoupling switch may be designed as a field-effect transistor, and the controller may further be designed to switch the decoupling switch back on after it has remained switched off as a result of the second fault and has operated in avalanche mode for a period of time during which a portion of energy equal to or less than its maximum rated dissipated energy portion has been consumed therein.

[0060] According to further embodiments of the circuit arrangement, the controller can further be designed such that, after the decoupling switch has been switched off as a result of the second fault, it controls it in a clocked manner such that it is switched on and off one after the other.

[0061] According to further embodiments of the circuit arrangement, the controller can be further configured to control the decoupling switch in a clocked manner such that the portion of energy consumed therein during the time it remains off and operates in avalanche mode is equal to or less than its maximum rated energy loss portion. The maximum rated energy loss portion can be the portion of energy that can be consumed in the switch without the switch suffering permanent damage, for example, due to melting due to overheating.

[0062] According to further embodiments, the circuit arrangement may further comprise: two further switches connected in series and provided in the bridge circuit; a further bridge node arranged between the further two switches, wherein the bridge node may be designed to provide a further phase voltage; a further decoupling switch coupled between the further bridge nodes and a further phase winding of the electric motor, wherein the controller may be coupled to the further decoupling switch and the two further switches; wherein the controller may be designed to switch off the at least two switches together with the two further switches in the event of a fault; and either switch off the further decoupling switch, wherein the switching off of the further decoupling switch may be delayed with respect to the switching off of the switches if the predefined condition is not met;or simultaneously deactivates the further decoupling switch and the switches if the predefined condition is met, wherein the controller may be configured to determine that the predefined condition is met if the further decoupling switch can be deactivated without suffering permanent damage from the current applied to it at the time the at least two switches are deactivated. According to further embodiments of the circuit arrangement, a first fault condition may correspond to a short circuit present at one of the switches.

[0063] According to further embodiments of the circuit arrangement, the controller may further be designed to monitor the voltage at at least one of the switches.

[0064] According to further embodiments of the circuit arrangement, the controller can further be designed to detect the first fault case when the voltage at at least one of the switches exceeds a second threshold value.

[0065] According to further embodiments of the circuit arrangement, a first switch of the further two switches can be coupled to a supply potential.

[0066] According to further embodiments of the circuit arrangement, a second switch of the further two switches can be coupled to a reference potential.

[0067] According to further embodiments of the circuit arrangement, a second fault case may correspond to an interruption that occurs at one of the switches.

[0068] According to further embodiments of the circuit arrangement, the controller can further be designed to monitor the further phase voltage.

[0069] According to further embodiments of the circuit arrangement, the controller can be configured to detect the second fault case when the phase voltage exceeds or falls below a third threshold. The third threshold can correspond to the bridge voltage (i.e., the voltage at the first reference potential 116) plus a diode forward voltage and plus a safety margin to reliably detect an open condition in a respective high-side bridge switch, or it can correspond to the second reference voltage (i.e., the voltage at the second reference terminal 118) minus a diode forward voltage and minus a safety margin to reliably detect an open condition in a low-side bridge switch.According to further embodiments of the circuit arrangement, the controller may be designed to determine that the predefined condition is met when the decoupling switches are robust enough to withstand an overvoltage condition caused by the corresponding potential difference between the bridge node and the phase winding.

[0070] According to further embodiments of the circuit arrangement, the decoupling switches may be designed as field-effect transistors, and the controller may be designed to determine that the predefined condition is met when the decoupling switches are capable of withstanding operation in avalanche mode induced therein by the respective potential difference between bridge node and phase winding.

[0071] According to further embodiments of the circuit arrangement, the controller may be designed to determine that the predefined condition is not met if the further decoupling switch is not robust enough to withstand an overvoltage condition caused by the potential difference between the potential at the further bridge node and the potential at the further phase winding.

[0072] According to further embodiments of the circuit arrangement, the decoupling switches may be designed as field-effect transistors; and the controller may be designed to determine that the predefined condition is not met if the further decoupling switch is unable to withstand avalanche mode operation induced therein by the potential difference between the potential at the further bridge node and the potential at the further phase winding.

[0073] According to further embodiments of the circuit arrangement, the controller can further be designed such that it delays the switching off of the further decoupling switch with respect to the switching off of the switches until a zero crossing of the further phase voltage or a further phase current.

[0074] According to further embodiments of the circuit arrangement, the controller can be further configured to delay the switching off of the further decoupling switch with respect to the switching off of the switches until the value of a current fed back from the electric motor to the further bridge node has fallen below a first threshold. According to further embodiments of the circuit arrangement, the first threshold of the current fed back from the electric motor to the further bridge node can have a medium current value.

[0075] According to further embodiments of the circuit arrangement, the first threshold value of the current fed back from the electric motor to the further bridge node can have an instantaneous value.

[0076] According to further embodiments of the circuit arrangement, the decoupling switches can be designed as field-effect transistors, and the controller can further be designed to switch on again the decoupling switch which has operated in avalanche mode for the longest time after being switched off as a result of the second fault.

[0077] According to further embodiments of the circuit arrangement, the controller can be designed to reactivate the decoupling switch to which the highest phase voltage was applied after it was deactivated as a result of the second fault. According to further embodiments of the circuit arrangement, the controller can further be designed to control at least one of the decoupling switches in a clocked manner after it was deactivated as a result of the second fault, such that it is switched on and off sequentially.

[0078] According to further embodiments of the circuit arrangement, the decoupling switches can be designed as field-effect transistors, and the controller can be designed to control the at least one of the decoupling switches, after it has been switched off as a result of the second fault and was in avalanche mode, in a clocked manner such that a portion of energy consumed therein corresponds to or is smaller than its maximum rated loss energy portion.

[0079] According to further embodiments of the circuit arrangement, the controller may further be configured to exclusively switch on and off at least two switches that have operated in avalanche mode, wherein at least one of the switches is a decoupling switch. In other words, the switches, ie, bridge switches or decoupling switches.

[0080] According to various examples, a method for operating the circuit arrangement is provided, wherein the circuit arrangement may comprise: a bridge circuit having at least two switches connected in series; a bridge node arranged between the at least two switches, wherein the bridge node may be designed to provide a phase voltage; an electric motor having at least one phase winding coupled to the bridge node; a decoupling switch connected between the bridge node and the electric motor; a controller coupled to the decoupling switch and to the at least two switches; and wherein the method may comprise: switching off the at least two switches in the event of a fault;Determining whether a predefined condition is met, and one of turning off the decoupling switch, wherein turning off the decoupling switch is delayed with respect to turning off the at least two switches if the predefined condition is not met; and simultaneously turning off the at least two switches and the decoupling switch if the predefined condition is met; wherein the predefined condition may be met if the decoupling switch can be turned off without suffering permanent damage from the current applied to it at the time the at least two switches are turned off.;

[0081] According to further embodiments of the method, the predefined condition may be met if the decoupling switch is robust enough to withstand an overvoltage condition caused by the potential difference between the bridge node and the phase winding.

[0082] According to further embodiments of the method, the decoupling switch can be designed as a field effect transistor.

[0083] According to further embodiments of the method, the predefined condition may be met if the decoupling switch is capable of withstanding operation in avalanche mode induced by the potential difference between the potential at the bridge node and the potential at the phase winding therein.

[0084] According to further embodiments, the method may further comprise determining the potential at the phase winding from the position of a stator with respect to a rotor of the electric motor.

[0085] According to further embodiments, the method may further comprise delaying the switching off of the decoupling switch with respect to the switching off of the at least two switches until a zero crossing of the phase voltage or the phase current.

[0086] According to further embodiments, the method may further comprise delaying the switching off of the decoupling switch with respect to the switching off of the at least two switches until the value of a current driven by the electric motor to the bridge node has fallen below a first threshold.

[0087] According to further embodiments, the method may further comprise detecting a first fault case when the voltage at at least one of the at least two switches exceeds a second threshold value.

[0088] According to further embodiments, the method may further comprise detecting a second fault event when the phase voltage exceeds the third threshold. According to further embodiments of the method, the decoupling switch may be configured as a field-effect transistor, and the method may further comprise re-energizing the decoupling switch after it has remained off as a result of the second fault event and has operated in avalanche mode for a period of time during which a portion of energy equal to or less than its maximum rated dissipation energy portion has been consumed.

[0089] According to further embodiments, the method may further comprise controlling the decoupling switch after it has been switched off as a result of the second fault in a clocked manner such that it is switched on and off one after the other.

[0090] According to further embodiments, the method may further comprise controlling the decoupling switch in a clocked manner such that a portion of energy consumed therein during the time it remains switched off and operates in avalanche mode corresponds to or is less than its maximum rated dissipated energy portion. According to further embodiments of the method, the circuit arrangement may further comprise: two further switches connected in series and provided in the bridge circuit; a further bridge node arranged between the further two switches, wherein the further bridge node is designed to provide a further phase voltage; a further decoupling switch coupled between the further bridge nodes and a further phase winding of the electric motor, wherein the controller may be coupled to the further decoupling switch and the two further switches;and the method may further comprise: switching off the at least two switches together with the two further switches in the event of a fault; and one of switching off the further decoupling switch, wherein the switching off of the further decoupling switch may be delayed with respect to the switching off of the switches if the predefined condition is not met; and simultaneously switching off the further decoupling switch and the switches if the predefined condition is met; wherein the predefined condition may be met if the further decoupling switch can be switched off without suffering permanent damage from the current applied to it at the time the at least two switches are switched off.;

[0091] According to further embodiments of the method, a first fault case may correspond to a short circuit that occurs at one of the switches.

[0092] According to further embodiments, the method may further comprise detecting the first fault case when the voltage at at least one of the switches exceeds a second threshold value.

[0093] According to further embodiments of the method, a second fault case may correspond to an interruption that occurs at one of the switches.

[0094] According to further embodiments, the method may further comprise detecting the second fault case when the further phase voltage exceeds the third threshold value.

[0095] According to further embodiments, the method may further comprise determining that the predefined condition is met when the decoupling switches are robust enough to withstand an overvoltage condition caused by the corresponding potential difference between the bridge node and the phase winding.

[0096] According to further embodiments of the method, the decoupling switches may be designed as field-effect transistors, and the method may further comprise determining that the predefined condition is met if the decoupling switches are capable of withstanding avalanche mode operation induced therein by the respective potential difference between bridge node and phase winding.

[0097] According to further embodiments, the method may further comprise determining that the predefined condition is not met if the further decoupling switch is not robust enough to withstand an overvoltage condition caused by the potential difference between the potential at the further bridge node and the potential at the further phase winding.

[0098] According to further embodiments of the method, the decoupling switches may be designed as field-effect transistors; and the controller may be designed to determine that the predefined condition is not met if the further decoupling switch is unable to withstand avalanche mode operation induced therein by the potential difference between the potential at the further bridge node and the potential at the further phase winding.

[0099] According to further embodiments, the method may further comprise delaying the switching off of the further decoupling switch with respect to the switching off of the switches until a zero crossing of the further phase voltage or a further phase current. According to further embodiments, the method may further comprise delaying the switching off of the further decoupling switch with respect to the switching off of the switches until the value of a current fed back from the electric motor to the further bridge node has fallen below a first threshold.

[0100] According to further embodiments of the method, the first threshold value of the current fed back from the electric motor to the further bridge node may have an average current value.

[0101] According to further embodiments of the method, the first threshold value of the current fed back from the electric motor to the further bridge node may have an instantaneous value.

[0102] According to further embodiments of the method, the decoupling switches may be designed as field-effect transistors, and the method may further comprise re-switching on the decoupling switch that has operated in avalanche mode for the longest time after being switched off as a result of the second fault.

[0103] According to further embodiments, the method may further comprise re-switching on the decoupling switch to which the highest phase voltage was applied after it was switched off as a result of the second fault.

[0104] According to further embodiments, the method may further comprise controlling at least one of the decoupling switches after it has been switched off as a result of the second fault in a clocked manner such that it is switched on and off one after the other.

[0105] According to further embodiments of the method, the decoupling switches may be designed as field-effect transistors, and the method may comprise driving the at least one of the decoupling switches, after it has been switched off as a result of the second fault and was in avalanche mode, in a clocked manner such that a portion of energy consumed therein corresponds to or is smaller than its maximum rated loss energy portion.

[0106] Although the invention has been shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made without departing from the spirit and scope of the invention as defined by the claims. The scope of the invention is accordingly indicated by the appended claims, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

[1] Control circuit (100) for an electric motor (112), comprising: a bridge circuit comprising at least two switches (102, 106) connected in series; a bridge node (104) arranged between the at least two switches (102, 106) and configured to provide a phase voltage and to be coupled to a phase winding of the electric motor (112); a decoupling switch (108) configured to be connected between the bridge node (104) and the electric motor (112); and a controller (114) coupled to the decoupling switch (108) and to the at least two switches (102, 106), wherein the controller (114) is configured in the event of a fault to: Switching off the at least two switches (102, 106), Determining whether a predefined condition is met, Switching off the decoupling switch (108), wherein the switching off of the decoupling switch (108) is delayed with respect to the switching off of the at least two switches (102, 106) if the predefined condition is not met, and simultaneously switching off the at least two switches (102, 106) and the decoupling switch (108) if the predefined condition is met, wherein the controller (114) is designed to determine that the predefined condition is met when the decoupling switch (108) can be turned off without suffering permanent damage from the current applied to it at the time the at least two switches (102, 106) are turned off, wherein the controller (114) is further designed to detect a second fault case when the phase voltage exceeds or falls below a threshold value, wherein the decoupling switch (108) is designed as a field effect transistor, and wherein the controller (114) is further configured to re-enable the decoupling switch (108) after it has remained off as a result of the second fault event and has operated in avalanche mode for a period of time during which a portion of energy equal to or less than its maximum rated dissipated energy portion has been consumed therein. [2] The drive circuit (100) of claim 1, wherein the controller (114) is configured to determine that the predefined condition is met when the decoupling switch (108) is robust enough to withstand an overvoltage condition caused by the potential difference between the bridge node (104) and the phase winding. [3] The drive circuit (100) of claim 1 or 2, wherein the controller (114) is configured to determine that the predefined condition is met when the decoupling switch (108) is capable of withstanding avalanche mode operation induced therein by the potential difference between the potential at the bridge node (104) and the potential at the phase winding. [4] The drive circuit (100) according to any one of claims 1 to 3, wherein the controller (114) is further configured to determine the potential at the phase winding from the position of a stator relative to a rotor of the electric motor (112). [5] The control circuit (100) according to any one of claims 1 to 4, wherein the controller (114) is further configured to delay the switching off of the decoupling switch (108) with respect to the switching off of the at least two switches (102, 106) until a zero crossing of the phase voltage or the phase current. [6] The drive circuit (100) of any one of claims 1 to 5, wherein the controller (114) is further configured to delay the turning off of the decoupling switch (108) with respect to the turning off of the at least two switches (102, 106) until the value of a current driven by the electric motor (112) to the bridge node (104) has fallen below a first threshold value. [7] The control circuit (100) according to any one of claims 1 to 6, wherein the controller (114) is further configured to detect a first fault condition when the voltage at at least one of the at least two switches (102, 106) exceeds a second threshold value. [8] The control circuit (100) according to any one of claims 1 to 7, wherein the controller (114) is further configured to control the decoupling switch (108) in a clocked manner after it has been switched off as a result of the second fault event, such that it is switched on and off sequentially; and wherein the controller (114) is further configured to control the decoupling switch (108) in the clocked manner such that a portion of energy consumed therein during the time it remains switched off and operates in avalanche mode is equal to or less than its maximum rated dissipated energy portion. [9] Control circuit (100) according to one of claims 1 to 8, further comprising: two additional switches connected in series and provided in the bridge circuit; a further bridge node arranged between the further two switches, the further bridge node being designed to provide a further phase voltage; and a further decoupling switch (108) coupled between the further bridge node and a further phase winding of the electric motor (112), wherein the controller (114) is coupled to the further decoupling switch and the two further switches, wherein the controller (114) is designed in the event of a fault to: Switching off the at least two switches (102, 106) together with the two other switches, Switching off the further decoupling switch, wherein the switching off of the further decoupling switch is delayed with respect to the switching off of the two further switches if the predefined condition is not met, and simultaneously switching off the decoupling switch (108) and the two further switches if the predefined condition is met, wherein the controller (114) is configured to determine that the predefined condition is met when the further decoupling switch can be turned off without suffering permanent damage from the current applied to it at the time the at least two switches (102, 106) are turned off. [10] Control circuit (100) according to claim 9, wherein a first fault case corresponds to a short circuit present at one of the switches. [11] The drive circuit (100) of claim 9, wherein the controller (114) is further configured to detect a first fault condition when the voltage at at least one of the switches exceeds a second threshold. [12] Control circuit (100) according to one of claims 9 to 11, wherein a second fault case corresponds to an open circuit present at one of the switches, wherein the controller (114) is designed to detect the second fault case when the further phase voltage exceeds or falls below the threshold value. [13] The drive circuit of any one of claims 9 to 12, wherein the controller (114) is configured to determine that the predefined condition is met when the decoupling switches are robust enough to withstand an overvoltage condition caused by the corresponding potential difference between the bridge node and the phase winding. [14] The drive circuit (100) of any one of claims 9 to 13, wherein the decoupling switches (108) are configured as field effect transistors, and wherein the controller (114) is configured to determine that the predefined condition is met when the decoupling switches are capable of withstanding avalanche mode operation induced therein by the respective potential difference between bridge node and phase winding. [15] The drive circuit (100) according to any one of claims 9 to 14, wherein the controller (114) is further configured to delay the switching off of the further decoupling switch with respect to the switching off of the switches until a zero crossing of the further phase voltage or a further phase current. [16] The drive circuit (100) according to any one of claims 9 to 15, wherein the controller (114) is further configured to delay the switching off of the further decoupling switch with respect to the switching off of the switches until the value of a current fed back from the electric motor (112) to the further bridge node has fallen below a first threshold value. [17] Control circuit (100) according to one of claims 12 to 16, wherein the decoupling switches are designed as field-effect transistors, and wherein the controller (114) is further designed to switch on again the decoupling switch which has operated in avalanche mode for the longest time after being switched off as a result of the second fault. [18] Control circuit (100) according to one of claims 12 to 17, wherein the controller (114) is designed to switch on again the decoupling switch to which the highest phase voltage was applied after it was switched off as a result of the second fault. [19] Control circuit (100) according to one of claims 9 to 18, wherein the decoupling switches are designed as field-effect transistors, and wherein the controller (114) is designed to control the at least one of the decoupling switches, after it has been switched off as a result of the second fault and operated in avalanche mode, in a clocked manner such that a portion of energy consumed therein corresponds to or is less than its maximum rated loss energy portion. [20] Control circuit (100) according to one of claims 9 to 19, wherein the controller (114) is further configured to turn on and off in an exclusive manner at least two switches that have operated in the avalanche mode, wherein at least one of the switches is a decoupling switch. [21] Method for operating a circuit arrangement (100), the circuit arrangement (100) comprising: an electric motor (112); a bridge circuit comprising at least two switches (102, 106) connected in series; a bridge node (104) arranged between the at least two switches (102, 106) and configured to provide a phase voltage and coupled to a phase winding of the electric motor (112); a decoupling switch (108) configured to be connected between the bridge node (104) and the electric motor (112), wherein the decoupling switch (108) is configured as a field-effect transistor; and a controller (114) coupled to the decoupling switch (108) and to the at least two switches (102, 106), the method comprising: Switching off the at least two switches (102, 106) in the event of a fault; Determining whether a predefined condition is met; Switching off the decoupling switch (108), wherein the switching off of the decoupling switch (108) is delayed with respect to the switching off of the at least two switches (102, 106) if the predefined condition is not met; and simultaneously switching off the at least two switches (102, 106) and the decoupling switch (108) if the predefined condition is met, wherein the predefined condition is met when the decoupling switch (108) can be turned off without suffering permanent damage from the current applied to it at the time the at least two switches (102, 106) are turned off, the method further comprising: Detecting a second fault when the phase voltage exceeds a threshold; and Re-activation of the decoupling switch after it remained off as a result of the second fault and operated in avalanche mode for a period during which a part of the energy consumed in it was equal to or less than its maximum rated dissipation energy part.

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