SE540704C2

SE540704C2 - Control unit for use in a vehicle and method for providing backup power to the control unit

Info

Publication number: SE540704C2
Application number: SE1750132A
Authority: SE
Inventors: Sommansson Joakim
Original assignee: Scania Cv Ab
Priority date: 2017-02-14
Filing date: 2017-02-14
Publication date: 2018-10-16
Also published as: DE102018000726B4; DE102018000726A1; SE1750132A1

Abstract

The present disclosure relates to techniques in the context of vehicles, and to a method for providing back-up power to a control unit 10a, 10b for use in a vehicle 1. The present disclosure also relates to a corresponding control unit 10a, 10b, and to a vehicle 1 comprising the control unit 10a, 10b. The control unit 10a, 10b comprises a first circuit part 11, a power input terminal 30, a wake-up input terminal 15. The first circuit part 11 is configured to perform a first set of functions. The power input terminal 30 is arranged to receive a main supply voltage S1. Furthermore, the driver circuitry 17a, 17b is arranged to power the first circuit part 11 using the wake-up signal as a back-up supply voltage, upon the main supply voltage S1 being absent at the power input terminal 30.

Description

Control unit for use in a vehicle and method for providing back-up power to the control unit Technical field The present disclosure relates to techniques in the context of vehicles, and in particular to a method for providing back-up power to a control unit for use in a vehicle. The present disclosure also relates to a corresponding control unit and to a vehicle comprising the control unit.

Background An Electrical Control Unit, ECU, is an embedded electronic device, basically a digital computer that controls one or more electrical systems (or electrical sub systems) of a vehicle based on e.g. information read from sensors placed at various parts and in different components of the vehicle. In more advanced vehicles such as buses, lorries, trucks, work vehicles and advanced cars; a network such as a CAN network (Controller Area Network) is used to handle the communication between various ECUs in the vehicle. The ECUs that are connected to the CAN may handle a large number of functions in the vehicle. These are, for example, functions related to change of gear, steering, engine control, braking, climate-control systems, lighting, driver comfort, alarms and safety.

Generally, each ECU comprises internal driver circuitry in order to provide power for itself, its communication interface and, where relevant, other components. Fuses are commonly arranged between the ECUs and a central power supply to protect the ECU and connecting cables during fault modes. This entails that when a fuse is blown at an ECU, the ECU is rendered useless until the fuse has been replaced. This might also cause other connected ECUs to lose communication with the ECU that has lost power due to the blown fuse. However, the fault indication will be lost communication and not loss of power.

Furthermore, some ECUs act as gateways for other ECUs in the vehicle. Hence, loss of power in one ECU may in some cases cause a chain reaction as it may render other ECUs dysfunctional. Hence, a blown fuse may become a safety critical issue.

Summary It is an object of the disclosure to alleviate at least some of the drawbacks with existing solutions. It is a still further object to provide a control unit by which problems related to loss of power due to e.g. a broken fuse are mitigated.

Furthermore, it is an object to facilitate quick replacements of components, such as fuses.

These object and others are at least partly achieved through a control unit and a method that enables life sustainable functionality in the ECU to function even when a main supply voltage from the central power supply is absent.

According to one aspect, the disclosure relates to a control unit for use in a vehicle. The control unit comprises a first circuit part, a power input terminal, a wake-up input terminal and driver circuitry. The first circuit part is configured to perform a first set of functions. The power input terminal is arranged to receive a main supply voltage. Furthermore, the first circuit part is arranged to be powered using the received main supply voltage. The wake-up input terminal is arranged to receive a wake-up signal and the control unit is arranged to deactivate a sleep mode in the control unit in response to receiving an active wake-up signal.

Furthermore, the driver circuitry is arranged to power the first circuit part using the wake-up signal as a back-up supply voltage, upon the main supply voltage being absent at the power input terminal.

By using the wake-up signal as back-up power supply, the control unit will still be able to perform basic operation even upon loss of the main supply voltage. Since the control unit utilizes the wake-up signal, which is a signal that is available in vehicles of today, the proposed technique may be implemented in existing vehicles without making any changes outside the control unit.

According to some embodiments, the driver circuitry comprises at least one controllable switch arranged to connect the wake-up signal to a power input of the first circuit part upon the main supply voltage being absent at the power input terminal.

According to some embodiments, the driver circuitry is arranged to detect whether the sleep mode is activated, and to power the first circuit part using the wake-up signal, upon detecting that the sleep mode is deactivated. By letting the driver circuitry activate the back-up power only after checking that the control unit is awake, the back-up power is only provided if power is required for performing functions in the vehicle.

According to some embodiments, the first circuit part comprises a communication interface configured to enable communication with one or more other devices within or outside the vehicle. Hence, the control unit may communicate on CAN even during loss of power.

According to some embodiments, the communication interface is configured to send a message indicating absence of the main supply voltage to at least one of the other devices, in response to the first circuit part being powered by the wakeup signal. This might e.g. imply setting a fault code for the issue, ex. loss of voltage or low voltage etc. The fault code shortens the time required to isolate the error. Consequently, the faulty component may be replaced without further investigation.

According to some embodiments, the communication interface is configured to receive messages from and/or forward messages to at least one of the other devices, while the first circuit part is being powered by the wake-up signal. Thus, the control unit will able to gate messages sent from other healthy control units, even when the main supply voltage is lost.

According to some embodiments, the control unit comprises a second circuit part configured to perform a second set of functions, wherein the second circuit part is arranged to be powered using the received main supply voltage. However, only the first part of the control unit is powered by the wake-up signal, when the main supply voltage is lost. Hence, power consumption may be kept low under this condition.

According to some embodiments, the first circuit part comprises life sustainable functionality of the control unit and the second circuit part comprises other functionality. Hence, the control unit may be kept alive, when the main supply voltage is lost.

According to some embodiments, the control unit comprises a processing unit configured to provide an inactive shut-down signal to the driver circuitry upon the deactivation of the sleep mode and wherein the driver circuitry is configured to power the first circuit part using the wake-up signal, upon the shut-down signal provided to the driver circuitry being inactive.

According to some embodiments, the processing unit is configured to determine whether at least one predetermined criterion is fulfilled, and upon determining that the predetermined criterion is fulfilled, activate the sleep mode and provide an active shut-down signal to the driver circuitry. Hence, the control unit may decide when to go back to the sleep mode on its own motion. According to some embodiments, the predetermined criterion comprises that the processing unit has no more instructions to execute.

According to some embodiments, the driver circuitry comprises a DC/DC converter, a first controllable switch and a second controllable switch. The DC/DC converter is arranged to convert an input voltage provided at an input end of the DC/DC converter to a predetermined output voltage and to power the first and second circuit parts using the output voltage. The power input terminal is connected to the input end of the DC/DC converter. The first controllable switch is arranged to connect the wake-up signal to the input end of the DC/DC converter upon the main supply voltage being absent at the power input terminal and the shut-down signal being inactive. Furthermore, the second controllable switch is arranged to disconnect the second circuit part from the output voltage of the DC/DC converter upon the main supply voltage being absent at the power input terminal and the output voltage supplied by the DC/DC converter being present.

According to some embodiments, the driver circuitry comprises a first DC/DC converter, a second DC/DC converter and a controllable switch. The first DC/DC converter is arranged to convert an input voltage provided by the power input terminal to a predetermined output voltage and to power the first and second circuit parts using the output voltage. The second DC/DC converter is arranged to convert an input voltage provided at an input end to the predetermined output voltage and to power the first circuit part using the output voltage upon the shutdown signal being inactive. The controllable switch is arranged to connect the wake-up signal to the input end of the second DC/DC converter upon the main supply voltage being absent at the power input terminal.

According to a second aspect, the disclosure relates to a vehicle comprising a main power supply configured to generate a main supply voltage, an ignition arrangement configured to provide a wake-up signal and the control unit according to any of the embodiments described above and below.

According to a third aspect, the disclosure relates to a method for providing backup power to a control unit for use in a vehicle, wherein the control unit comprises a first circuit part configured to perform a first set of functions, and wherein the control unit is arranged to deactivate a sleep mode in the control unit in response to receiving an active wake-up signal. The method comprises determining that a main supply voltage of the first circuit part is absent and powering the first circuit part using the wake-up signal as a back-up supply voltage in response to the determining. The same positive effects as obtained with the device may be achieved with the method.

According to some embodiments, the method further comprises determining that the sleep mode is deactivated, and then the powering comprises powering the first circuit part using the wake-up signal as a back-up supply voltage in response to determining that the main supply voltage of the first circuit part is absent and that the sleep mode is deactivated.

According to some embodiments the method further comprises indicating to at least one other device within or outside the vehicle that main supply voltage of the first circuit part is absent.

Brief description of the drawings Fig. 1 illustrates a vehicle in which the proposed control unit and method can be used.

Fig. 2 illustrates a control unit for use in a vehicle according to a first example embodiment.

Fig. 3 illustrates a control unit for use in a vehicle according to a second example embodiment.

Fig. 4 illustrates a flow chart of a method according to some embodiments.

Detailed description As mentioned above, the ECUs and their connecting cables in a vehicle are generally protected by fuses. When a fuse is blown at an ECU, the ECU will cease to function until it is replaced. Flowever, as a broken fuse at an ECU will render the ECU is completely out of power supply, there will be no visible indication about what has actually gone wrong. Instead communication with the ECU whose fuse is broken is simply lost. Flence, it might take some time to isolate and fix the problem. In the meantime, the consequences might be severe, due to the interaction between the different ECUs in the vehicle.

It is herein proposed to solve the above described deficiencies by letting a wakeup signal act a as a secondary power or back-up supply for an ECU’s life sustainable functionality, such as a microprocessor and a communication interface. The solution is based on the insight that the power required for those components is generally quite limited. Hence, if only one or a few ECUs in the vehicle have lost their main supply voltage, then a logical signal such as the wake-up signal (sometimes also referred to as the ignition signal) may be used to power at least the life sustainable functionality of this or those ECUs. The wakeup signal is a suitable signal for this purpose at is generally active high when the vehicle is operating. Furthermore, the wake-up signal is typically protected by one central fuse, and would therefore not be affected if a local fuse is blown.

Furthermore, the wake-up signal is used by many components in the vehicle, and may thus provide a current (e.g. of about 10A), which makes it suitable as a backup supply voltage, because 10A would typically be enough for powering the essential functions of one or a few ECUs. By using the wake-up signal as a backup power supply, communication with an ECU may be maintained even when the main power supply of the ECU is absent. In addition, an ECU that has lost power supply may send an error message to a control system of the vehicle, whereby the time required to isolate and fix the problem is decreased.

In the following a control unit and a method for providing back-up power supply to a control unit for use in a vehicle will be described.

Fig. 1 illustrates a vehicle 1 in which the proposed control unit and method can be used. The vehicle 1 of Fig. 1 comprises a main power supply 20, an ignition arrangement 21 and a control unit 10 i.e. an ECU. The vehicle 1 may e.g. be a work vehicle such as a truck, a bus or other heavy vehicle; or the vehicle 1 may be a regular car.

The main power supply 20 is a power source that is configured to generate a main supply voltage. The main power supply 20 is typically comprised in the main power system of the vehicle 1. The main power supply 20 is e.g. a battery system comprising a plurality of battery cell units together delivering a supply voltage of e.g. up to 48 volts.

The ignition arrangement 21 is an arrangement configured for controlling the ignition of the vehicle 1, or in other words the vehicle's engine starting function. The ignition arrangement 21 comprises a maneuverable ignition switch that is switchable between a switched-off position and switched-on position. Typically, an ignition key is needed to switch the ignition on. Historically, the ignition has been switched on by turning a mechanical ignition key. However, today the switching may alternatively be electronic and the ignition key may thus also be electronic.

The ignition arrangement 21 is further configured to provide a wake-up signal to the control unit 10. An active wake-up signal is generally provided when the maneuverable operating member is switched-on. The wake-up signal typically stays high until the maneuverable operating member is switched-off. The wake-up signal provided by the ignition arrangement 21 is often used by a plurality of electrical sub systems and components in the vehicle 1.

The control unit 10 is an embedded device that controls one or more electrical systems (or sub systems) in the vehicle 1. The control unit 10 comprises hardware and software. The hardware basically comprises various electronic components on a Printed Circuit Board, PCB. The most important of those components is typically a processing unit e.g. a microprocessor, along with a memory (Fig. 2 and Fig. 3) e.g. EPROM or a Flash memory chip. The software (also called firmware) is typically lower-level software code that runs in the microcontroller.

Typically, the vehicle 1 comprises multiple control units that are communicating over a Controller Area Network, CAN. The CAN network is used to handle the communication between various control units in the vehicle 1. Often, several CAN networks that are connected through a central control unit are arranged in the vehicle 1. Some modern motor vehicles have up to 80, or even more than 100, control units. However, for simplicity only one control unit 10 is illustrated in Fig. 1. Though, it must be understood that the proposed techniques may be implemented in any control unit 10 in the vehicle 1.

The control unit 10 is arranged to be driven by the main power supply 20. A fuse 8 (Fig. 2) arranged between the main power supply 20 and the control unit 10 protects the control unit 10 from excessive currents that may e.g. occur when the ignition is switched on.

The control unit 10 is typically permanently powered, also while the vehicle 1 is parked and locked. The power consumption during this time is taken out of the vehicle’s battery. Therefore, the control unit 10 may be put in a sleep mode, where current of the control unit 10 is extremely low (in the range of ??).

Hence, the control unit 10 may be in three different modes. More specifically it may be in a power-off mode, in a sleep mode or it may be in an active mode. The power-off mode corresponds to a completely switched off mode, i.e. no supply voltage is provided to the control unit 10.

In the power-off mode all power supplied to the control unit 10 is switched off. Consequently, all functions of the control unit 10 are switched off. In the active mode, the control unit 10 is powered by the main power supply 20 and a processing unit 19 (Fig. 2 and Fig. 3) of the control unit 10 is active, i.e. it is executing instructions in order to control one or more electrical systems in the vehicle 1. In the sleep mode, the control unit 10 is also powered by the main power supply 20. However, in contrast to in the active mode, the processing unit 19 is passive and the components of the control unit 10 are also switched off, at least to a large extent, in order to reduce power consumption.

The control unit 10 is arranged to receive the wake-up signal provided by the ignition arrangement 21. The purpose of the wake-up signal is to indicate to the control unit 10 that the vehicle 1 is in operation (e.g. the engine is running). Upon receiving an active wake-up signal the control unit 10 will deactivate or exit sleep mode and enter the active mode, as will be further described below.

Note that depending on the application, the control unit 10 may also be arranged to wake up from the sleep mode upon reception of other wake-up signals, herein referred to as secondary wake-up signals. These signals are e.g. received from other control units in the vehicle 1. The secondary wake-up signals may be messages received over the CAN or over separate signal lines. However, the secondary wake-up signals are physically separated from the wake-up signal received from the ignition arrangement 21 e.g. they are provided on separate terminals. In this disclosure, the wake-up signal received from the ignition arrangement 21 is used for providing back-up power. However, it is possible that other wake-up signals may as well be usable. Hence, the disclosure is not limited to the ignition signal.

While the control unit 10 is woken-up from the sleep mode by external signals such as the wake-up signal received from the ignition arrangement 21, the control unit 10 may go back to sleep, i.e. enter sleep mode, on own motion. Hence, the control unit 10 may continue to perform functions even after an inactive wake-up signal is provided, e.g. in order to shut down an electrical system after ignition is switched off. Alternatively, it may go back to sleep while the wake-up signal is still active. In other words, the control unit 10 may enter sleep mode while the ignition is still switched on. The sleep mode entry is typically handled by the processing unit 19 of the control unit 10 as will be further described below.

The control unit 10 will be further described with reference to a first example embodiment (control unit 10a) illustrated in Fig. 2 and a second example embodiment (control unit 10b) illustrated in Fig. 3.

Fig. 2 illustrates a control unit 10a for use in the vehicle 1 according to a first example embodiment. The control unit 10a of Fig. 2 comprises a first circuit part 11, a second circuit part 12, a wake-up input terminal 15, a common ground terminal 31, a power input terminal 30, a memory 13 and driver circuitry 17a. It must be noted that the illustration of Fig. 2 is just a schematic diagram. Hence, the control unit 10a may comprise other components and/or terminal that are not directly affected by the proposed technique.

As described above, the control unit 10a comprises hardware and software that controls, and where relevant drives, an electrical system or an electrical sub systems in the vehicle 1. Stated differently, the hardware and software of the control unit 10a is arranged to perform functions (i.e. vehicle functions) related to the electrical system or the electrical sub systems. This hardware and software is divided into the first circuit part 11 and the second circuit part 12. The parts may be physically separated. Alternatively, the separation may be functional, such that some hardware and software is de-activated under certain circumstances. In other words, the first circuit part 11 is configured to perform a first set of functions and the second circuit part 12 is configured to perform a second set of functions.

The motive to separate the functionality of the control unit 10a into two parts is to under certain circumstances being able to power only the first circuit part 11 . The first circuit part 11 comprises hardware and software for performing functions that are essential for basic operation of the vehicle 1 and that would cause severe damage if turned off. In this example the first circuit part 11 comprises a processing unit 19 configured to control perform basic control of the control unit 10a and a communication interface 101 configured to communicate with other control units within the vehicle 1 over the CAN. According to some embodiments, the communication interface 101 is also or alternatively configured to enable communication with devices outside the vehicle 1. The components of the first set of functions typically consumes a limited (and generally also pre-determined) amount of power. According to some embodiments the processing unit 19 is configured to execute instructions performed in a computer program P, stored in the memory 13. The memory 13 may be comprised in the first circuit part 11.

The second circuit part 12 comprises hardware and software for performing a second set of functions of an electrical system (or electrical sub system) of the vehicle 1. The second set of functions are e.g. functionality related to the vehicle’s heating system, navigation system, suspension system, braking system etc. The second set of functions may comprise driving one or more components of the electrical system or sub system. Hence, the second set of functions typically requires more power that the first set of functions. The second circuit part 12 is typically configured to perform functions that the vehicle 1 can do without, even when driven, or at least for a shorter time, e.g. while driving the vehicle 1 to a service station for fixing the problem. Furthermore, the second set of functions performed by the second circuit part 12 is typically controlled by the processing unit 19 of the first circuit part 11.

The power input terminal 30 is a physical terminal or port that is configured for connecting the control unit 10a to the main power supply 20 (Fig. 1). The common ground terminal 31 is a physical terminal or port that is configured for connecting the control unit 10a to a common ground S3. Hence, the main supply voltage S1 at the power input terminal 30 and is an electrical tension with regards to the common ground terminal 31. In other words, the power input terminal 30 is arranged to receive a main supply voltage S1.

The first and the second circuit parts 11, 12 need to be powered in order to perform their respective functions. The first and the second circuit parts 11, 12 are arranged to be powered using the main supply voltage S1 received at the power input terminal 30. The power is provided through the driver circuitry 17a. The driver circuitry 17a comprises a DC/DC converter 16 and two controllable switches 181, 182. The DC/DC converter 16 is electrically arranged between the power input terminal 30 and a respective power input port 111, 121 of the first and the second circuit parts 11, 12.

More specifically, the power input terminal 30 (where the main supply voltage S1 is received) is connected to an input end 16a of the DC/DC converter 16. The DC/DC converter 16 converts the main supply voltage S1 (e.g. a battery voltage) received at the input end 16a to a predetermined output voltage provided at an output end 16b. The DC/DC converter 16 is further configured to receive logical input signals (illustrated by arrows) and to perform the conversion and provide the output voltage based on the received logical signals, as will be further described below. The output end 16b of the DC/DC converter is connected to the respective power input port 111, 121 of the first and the second circuit parts 11, 12. The predetermined output voltage is a voltage suitable for driving the first and second circuit parts 11, 12 (e.g. 1,8-5 V). Stated differently, the DC/DC converter 16 is arranged to convert an input voltage provided at an input end 16a of the DC/DC converter 16 to a predetermined output voltage and to power the power the first and second circuit parts 11, 12 using the output voltage.

Hence, when the control unit 10a is functioning normally (i.e. when the main supply voltage S1 is present at the power input terminal 30), current flows in a forward direction from the main power supply 20 (Fig. 1) to the first and second circuit parts 11,12 via the power input terminal 30 and the DC/DC converter 16. Current will of course flow back from the processing unit 19 via the ground connection. A diode 14a is arranged between the power input terminal 30 and the DC/DC converter 16 in order to assure that no electric current passes in a reverse direction.

The wake-up input terminal 15 is arranged to receive a wake-up signal S2 e.g. provided by the ignition arrangement 21. The wake-up signal S2 is a logical signal and an active wake-up signal indicates an awake mode, e.g. that the ignition is switched on. The wake-up signal S2 is provided to the DC/DC converter 16 driving the first and second circuit parts 11, 12. Upon receiving an active wake-up signal S2, the DC/DC converter is switched on (and if a supply voltage is supplied on the input end 16a, then the predetermined output voltage is supplied on the output end 16b), whereby the processing unit 19 of the first circuit part is powered (or rather awakened). Upon being powered, the processing unit 19 starts to execute instructions in order to control the different functions of the control unit 10a. In other words, the processing unit 19 is arranged to deactivate a sleep mode in the control unit 10a, 10b in response to the control unit 10a, 10b receiving an active wake-up signal S2. Hence, deactivating the sleep mode corresponds to controlling the control unit 10 to perform functions.

While the control unit 10a typically exits sleep mode in response to reception of an external main supply voltage S1, sleep mode may be entered on the control units own motion. The sleep mode entry is initiated by the processing unit 19, when at least one predetermined criterion is fulfilled. For example, the sleep mode is initiated when the processing unit 19 has no more instructions to execute. Upon entering sleep mode, the processing unit 19 shuts down as much functionality within the processing unit 19 as possible. This involves e.g. deactivating driver circuits in order to minimize the power consumption of the processing unit 19. In this example, this is implemented by provision of a shut-down signal S4. The shutdown signal S4 is also a logical signal and an active shut-down signal S4 indicates that the control unit 10a has entered, or will soon enter, the sleep mode. On the other hand, an inactive shut-down signal indicates that the control unit 10a is active and that the processing unit 19 is running i.e. executing instructions.

The shut-down signal S4 is received by the DC/DC converter 16. Upon receiving an active shut-down signal S4 the DC/DC converter 16 deactivates the output power supplied on the power input ports 111, 121 of the first and second circuit parts 11, 12, whereby the first and second circuit parts 11, 12 are switched off. In other words, the processing unit 19 is configured to provide an inactive shut-down signal S4 upon the deactivation of the sleep mode. Furthermore, the processing unit 19 is configured to provide an active shut-down signal S4 to the driver circuitry upon the activation of the sleep mode.

In accordance with the proposed technique, the driver circuitry 17a is further arranged to power the first circuit part 11, when the main supply voltage S1 is absent i.e. missing or lost. By doing so, the fundamental or life sustainable functionality of the control unit 10a is kept alive, even when main power voltage is lost. Basically, the driver circuitry is arranged to power the first circuit part 11 using the wake-up signal S2 as a back-up supply voltage, upon the main supply voltage S1 being absent at the power input terminal 30. Thereby, the control unit 10a can still communicate and make decisions, for example enabling the control unit 10a to send information about the faulty mode, being able to gate signals etc. In addition to this the isolation of the possible failing parts is made easier by creation of a more specific fault code of the error, e.g. loss of power/low voltage instead of lost communication. For example, the communication interface 101 is configured to send a message indicating absence of the main supply voltage S1 to at least one of the other devices, in response to the first circuit part 11 being powered by the wake-up signal S2. The communication interface 101 is according to some embodiments configured to receive messages from and/or forward messages to at least one of the other devices, while the first circuit part 11 is being powered by the wake-up signal S2.

The driver circuitry is not arranged to power the second circuit part 12 using the wake-up signal S2 as a back-up supply voltage, upon the main supply voltage S1 being absent at the power input terminal 30. However, some control units 10a are only configured to perform coordination tasks or overall control, which are all life sustainable functions that typically do not require a significant amount of power. In such situations, there might not be any second set of functions. All functions of the control unit 10a would in such a situation be arranged to be powered using the wake-up signal S2 as a back-up supply voltage.

Furthermore, in some situations the control unit 10a may already have re-entered sleep mode when the main supply voltage S1 is lost. In such situations, there is no point in providing any back-up supply voltage to the control unit 10a. It might even be dis-advantageous as the driver circuitry 17a might increase power consumption in the sleep mode. Hence, according to some embodiments the driver circuitry 17a is further configured to detect whether the sleep mode is activated and the driver circuitry 17a is configured to only power the first circuit part 11 using the wake-up signal S2 as a back-up supply voltage upon detecting that the sleep mode is deactivated. In other words, the condition for driver circuitry 17a to activate the sleep mode is that the main supply voltage S1 is absent at the power input terminal 30 and that the control unit 10a is awake, i.e. the sleep mode of the control unit 10a is deactivated. The shut-down signal S4 may be used for this purpose, as an inactive shut-down signal S4 indicates that the control unit 10a is awake. Stated differently, the driver circuitry 17a is arranged to power the first circuit part 11 using the wake-up signal S2, upon the shut-down signal S4 provided to the driver circuitry 17a being inactive.

The driver circuitry 17a of the first example embodiment will now be described in further detail.

The first controllable switch 181 and the second controllable switch 182, also referred to as High Side Drivers, HSD, are controllable switches that may be implemented in hardware (e.g. comprising one or more transistors) or in software or in combination thereof. The switches open and close a connection between two points based on logical control signals (illustrated by arrows). “High side” refers to the high side of the main supply voltage S1, in contrast to the low side, i.e. ground.

The first controllable switch 181 is arranged to connect the output end 16b of the DC/DC converter to the power input port 111 of the first circuit part 11, under the condition that the main supply voltage S1 is absent while the control unit 10a is awake (i.e. the sleep mode is deactivated). Hence, when the first controllable switch 181 is closed, current flows in a forward direction from the main power supply 20 (Fig. 1) to the first circuit part 11 via the wake-up terminal 15 and the DC/DC converter 16. Current will of course flow back from the first circuit part 11 via the ground connection. A diode 14b is arranged between the wake-up terminal 15 and the first controllable switch 181 in order to assure that no electric current passes in a reverse direction. In other words, the first controllable switch 181 is arranged to connect the wake-up signal S2 to the input end of the DC/DC converter 16 upon the main supply voltage S1 being absent at the power input terminal 30 and the shut-down signal S4 being inactive.

However, in order to avoid that the wake-up power signal S2 is used for powering also the potentially more power consuming second circuit part 12, the second switch 182 is needed. Thus, when the conditions for closing the first controllable switch 181 are fulfilled, the second controllable switch 182 disconnects the second circuit part 12 from the output end 16b of the DC/DC converter 16, to avoid that the second circuit part 12 is powered by the wake-up signal S2. Hence, the second controllable switch 182 is arranged to disconnect the second circuit part 12 from the output voltage of the DC/DC converter 16 upon the main supply voltage S1 being absent at the power input terminal 30 and the output voltage supplied by the DC/DC converter being present.

Fig. 3 illustrates an alternative control unit 10b for use in the vehicle 1 (Fig. 1) according to a second example embodiment. As the control unit 10a of Fig. 2, the control unit 10b comprises a first circuit part 11, a second circuit part 12, a wakeup input terminal 15, a common ground terminal 31 and a power input terminal 30. Those components are equal or at least corresponding to the components of the control unit 17a of Fig. 2 and are therefore not described again. The control units 10b further comprises a driver circuitry 17b, which differs from the driver circuitry 17a of Fig. 2.

Common for both driver circuitries 17a, 17b is that both comprise at least one controllable switch 18 (Fig. 2), 181 arranged to connect the wake-up signal S2 to a power input 111 of the first circuit part 11 upon the main supply voltage S1 being absent at the power input terminal 30. However, in the driver circuit 17b of Fig. 3 only one controllable switch 18 is required. This is possible if separate DC/DC converters are used for the main power voltage S1 and the back-up power voltage (i.e. the wake-up signal S2).

Hence, the driver circuitry 17b comprises a first DC/DC converter 161 arranged to convert an input voltage provided by the power input terminal 30 (at an input end 161a) to a predetermined output voltage provided at an output end 161 b and to power the first and second circuit parts 11, 12 using the output voltage. Hence, when the control unit 10b is functioning normally, current flows in a forward direction from the main power supply 20 (Fig. 1) to the first and second circuit parts 11 via the power input terminal 30 and the first DC/DC converter 161.

Current will of course flow back from the first and second circuit parts 11, 12 via the ground terminal 31. A diode 14d is arranged between the first DC/DC converter 161 and the first and second circuit parts 11, 12, in order to assure that no electric current passes in a reverse direction.

The driver circuitry 17b further comprises a second DC/DC converter 162 arranged to convert an input voltage provided at an input end 162a to the predetermined output voltage provided at an output end 162b and to power the first circuit part 11 using the output voltage. As discussed above, it is generally not desirable to use the wake-up signal S2 as a back-up supply voltage if the control circuit is in the sleep mode. Hence, the second DC/DC converter 162 is only arranged to power the first circuit part 11 using the output voltage upon the shutdown signal S4 being inactive, i.e. upon the control unit 10b also being awake. Thus, the controllable switch 18 is simply arranged to connect the wake-up signal S2 to the input end 162a of the second DC/DC converter 162 upon the main supply voltage S1 being absent at the power input terminal 30. Hence, when the controllable switch 18 is closed, current flows in a forward direction from the main power supply 20 (Fig. 1) to the first circuit part 11 via the wake-up terminal 15 and the DC/DC converter 162. Current will of course flow back from the first circuit part 11 via the ground terminal 31. A diode 14c is arranged between the wake-up terminal 15 and the controllable switch 18 in order to assure that no electric current passes in a reverse direction.

It must also be appreciated that the back-up circuitry 17a, 17b of the respective embodiment may be implemented in different ways while still achieving the same effects. Hence, the disclosure is not limited to the example embodiments disclosed herein. For example, in the second embodiment of Fig. 3 the shut-down signal S4 might be arranged to control the controllable switch 18 instead of the second DC/DC converter 162. The driver circuitry 17a, 17b might possibly also be implemented as a logical circuit configured to perform a corresponding method, that will now be described.

Hence, the disclosure also relates to a corresponding method for providing backup power to a control unit 10 in the vehicle 1 (Fig. 1), for example in an electrical sub system. If the electrical sub system comprises multiple control units 10 the method may be implemented in any (or all) of the control units 10.

The method will now be explained with reference to the flow chart illustrated in Fig. 4, and to the illustrations in the other figures. The method may (at least partly) be implemented as program code, P, stored in a memory 13 in the control unit 10. The method may alternatively be hardware implemented (as above). The method may be performed at any time when the vehicle 1 is operated. In a typical scenario, the method steps are performed when a fuse protecting the power input terminal 30 is blown.

The method comprises determining A1 that a main supply voltage S1 of the first circuit part 11 is absent. This may e.g. correspond to determining that the main supply voltage S1 received by the control unit 10 is below a predetermined threshold value.

The method further comprises powering A3 the first circuit part 11 using the wakeup signal S2 as a back-up supply voltage in response to the determining A1. For example, the wake-up signal S2, which is a logical signal, is connected to a driver circuitry 17a, 17b of the control unit 10, such that power may be supplied from the main power supply 2 via the wake-up input port 15.

It may, as discussed above, only be desirable to utilize the wake-up signal S2 for power purposes when the control unit 10 has functions to perform. Hence, according to some embodiments the method comprises determining A2 that the sleep mode is deactivated and powering the first circuit part 11 using the wake-up signal S2 as a back-up supply voltage in response to determining A2, A3 that the main supply voltage S1 of the first circuit part 11 is absent and that the sleep mode is deactivated.

In further embodiments, the method comprises indicating A4 to at least one other device within or outside the vehicle 1 that main supply voltage S1 of the first circuit parts 11 is absent. For example, an error message is provided at the CAN. An error message provided at the CAN may be displayed on the dash board of the vehicle 1 or it may be transmitted to a service center by another electrical sub system in the vehicle 1.

The present disclosure is not limited to the above-described preferred embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the disclosure, which is defined by the appending claims.

Claims

1. A control unit (1 Oa, 10b) for use in a vehicle (1) characterized in that the control unit (10a, 10b) comprises: - a first circuit part (11) configured to perform a first set of functions, - a power input terminal (30) arranged to receive a main supply voltage (51), wherein the first circuit part (11) is arranged to be powered using the received main supply voltage (S1), - a wake-up input terminal (15) arranged to receive a wake-up signal (S2), wherein the control unit (10) is arranged to deactivate a sleep mode in the control unit (10a, 10b) in response to receiving an active wake-up signal (52), and - driver circuitry (17a, 17b) arranged to power the first circuit part (11) using the wake-up signal (S2) as a back-up supply voltage, upon the main supply voltage (S1) being absent at the power input terminal (30).

2. The control unit (10a, 10b) according to claim 1, wherein the driver circuitry (17a, 17b) comprises at least one controllable switch (18, 181) arranged to connect the wake-up signal (S2) to a power input (111) of the first circuit part (11) upon the main supply voltage (S1) being absent at the power input terminal (30).

3. The control unit (10a, 10b) according to claim 1 or 2, wherein the driver circuitry (17a, 17b) is arranged to detect whether the sleep mode is activated, and to power the first circuit part (11) using the wake-up signal (S2), upon detecting that the sleep mode is deactivated.

4. The control unit (10a, 10b) according to any of the preceding claims, comprising: - a second circuit part (12) configured to perform a second set of functions, wherein the second circuit part (12) is arranged to be powered using the received main supply voltage (S1).

5. The control unit (10a, 10b) according to claim 4, wherein the first circuit part (11) comprises life sustainable functionality of the control unit (10a, 10b) and wherein the second circuit part (12) comprises other functionality.

6. The control unit (10a, 10b) according to any of the preceding claims, wherein the processing unit (19) comprises a processing unit (19), wherein the processing unit (19) is configured to provide an inactive shut-down signal (S4) to the driver circuitry (17a, 17b) upon the deactivation of the sleep mode and wherein the driver circuitry (17a, 17b) is configured to power the first circuit part (11) using the wake-up signal (S2), upon the shut-down signal (S4) provided to the driver circuitry (17a, 17b) being inactive.

7. The control unit (10a, 10b) according to claim 6, wherein the processing unit (19) is configured to determine whether at least one predetermined criterion is fulfilled, and upon determining that the predetermined criterion is fulfilled, activate the sleep mode and provide an active shut-down signal (S4) to the driver circuitry (17a, 17b).

8. The control unit (10a, 10b) according to claim 7, wherein the predetermined criterion comprises that the processing unit (19) has no more instructions to execute.

9. The control unit (10a) according to 4 or 5 and any of claims 6 to 8, wherein the driver circuitry (17a) comprises: - a DC/DC converter (16) arranged to convert an input voltage provided at an input end (16a) of the DC/DC converter (16) to a predetermined output voltage and arranged to power the first and second circuit parts (11, 12) using the output voltage, wherein the power input terminal (30) is connected to the input end (16a) of the DC/DC converter (16), - a first controllable switch (181) arranged to connect the wake-up signal (S2) to the input end of the DC/DC converter (16) upon the main supply voltage (S1) being absent at the power input terminal (30) and the shutdown signal (S4) being inactive, and - a second controllable switch (182) arranged to disconnect the second circuit part (12) from the output voltage of the DC/DC converter (16) upon the main supply voltage (S1) being absent at the power input terminal (30) and the output voltage supplied by the DC/DC converter being present.

10. The control unit (10b) according to claim 4 or 5 and any of claims 6 to 8, wherein the driver circuitry (17b) comprises: - a first DC/DC converter (161) arranged to convert an input voltage provided by the power input terminal (30) to a predetermined output voltage and to power the first and second circuit parts (11, 12) using the output voltage, - a second DC/DC converter (162) arranged to convert an input voltage provided at an input end (162a) to the predetermined output voltage and to power the first circuit part (11) using the output voltage upon the shut-down signal (S4) being inactive, and - a controllable switch (18) arranged to connect the wake-up signal (S2) to the input end (162a) of the second DC/DC converter (162) upon the main supply voltage (S1) being absent at the power input terminal (30).

11. The control unit (10a, 10b) according to any of the preceding claims, wherein the first circuit part (11) comprises a communication interface (101) configured to enable communication with one or more other devices within or outside the vehicle (1).

12. The control unit (10a, 10b) according to claim 11, wherein the communication interface (101) is configured to send a message indicating absence of the main supply voltage (S1) to at least one of the other devices, in response to the first circuit part (11) being powered by the wake-up signal (S2).

13. The control unit (10a, 10b) according to claim 11 or 12, wherein the communication interface (101) is configured to receive messages from and/or forward messages to at least one of the other devices, while the first circuit part (11) is being powered by the wake-up signal (S2).

14. A vehicle (1) comprising: - a main power supply (20) configured to generate a main supply voltage (S1), - an ignition arrangement (21) configured to provide a wake-up signal (S2) and - a control unit (10a, 10b) according to any of claims 1-13.

15. A method for providing back-up power to a control unit (10a, 10b) for use in a vehicle (1), wherein the control unit (10a, 10b) comprises a first circuit part (11) configured to perform a first set of functions, wherein the control unit (10a, 10b) is arranged to deactivate a sleep mode in the control unit (10a, 10b) in response to receiving an active wake-up signal (S2), the method comprising: - determining (A1) that a main supply voltage (S1) of the first circuit part (11) is absent and - powering (A3) the first circuit part (11) using the wake-up signal (S2) as a back-up supply voltage in response to the determining (A1).

16. The method according to claim 15, comprising: - determining (A2) that the sleep mode is deactivated, and wherein the powering (A3) comprises powering the first circuit part (11) using the wake-up signal (S2) as a back-up supply voltage in response to determining (A2, A3) that the main supply voltage (S1) of the first circuit parts (11) is absent and that the sleep mode is deactivated.

17. The method according to claim 15 or 16, comprising: - indicating (A4) to at least one other device within or outside the vehicle (1) that main supply voltage (S1) of the first circuit part (11) is absent.