Patent Publication Number: US-2023139046-A1

Title: Monitoring circuit for monitoring of a protective earth connection in a vehicle charging interface of a vehicle

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to a monitoring circuit, a vehicle charging interface and an at least partly electrically powered vehicle. More particularly the present disclosure relates to monitoring of a Protective Earth (PE) connection in a vehicle charging interface of a vehicle. 
     The invention can be applied in at least partly electrical heavy-duty vehicles, such as trucks, buses and construction equipment etc. Although the invention will be described with respect to a fully electrified truck, the invention is not restricted to this particular vehicle, but may also be used in other vehicles such as buses, trailers, wheel loaders, articulated haulers, excavators, backhoe loaders, passenger cars, marine vessels etc. It may also be applied in electrical systems of e.g. electrically operated vessels and in various industrial construction machines or working machines. It is applicable in fully electrically operated vehicles as well as in hybrid vehicles, comprising also a combustion engine. 
     The terms vehicle and electric vehicle will be used interchangeably herein for the sake of simplicity when referring to a fully electrically powered vehicle and a hybrid vehicle. 
     BACKGROUND 
     The Combined Charging System (CCS) is a standard related to charging of electrical vehicles. The CCS standard describes a communication circuit, also referred to as a communication line or Control Pilot, located between the Electric Vehicle (EV) and the Supply Equipment Communication Controller (SECC) of the charging station. A charging inlet is located between the EV and the SECC at a suitable location on the communication circuit. The communication circuit may be described as a communication line for signalling charging level between the vehicle and the charging station, it may be used by the vehicle to initiate charging and for transmission of other information between the vehicle and the charging station. 
     The charging station may be referred to as Electric Vehicle Supply Equipment (EVSE). The EVSE may be described as a unit that provides electrical power for charging the electrical vehicle, and the SECC may be described as a control unit for the charging station. The SECC at the charging station communicates with the EV Communication Controller (EVCC) at the vehicle. Together, the SECC and the EVCC are responsible for control of the communication between the charging station and the vehicle 
     The Power Spectral Density (PSD) from the EVCC in the communication circuit, i.e, at the charging inlet of the charging station, must be kept within specified limits. PSD is a measure of a signal&#39;s power content versus frequency. In addition, the CCS standard states that the integrity of a PE connection between the vehicle and the EVSE must be monitored. To keep the PSD within the standardized limits it is necessary to do calibration of the EVCC for every variation of vehicle wire harness, e.g. length, routing layout, etc., and this will incur an increased development cost since the number of installations in various vehicle applications is large. 
       FIG.  1    illustrates a known solution for implementing the PE monitor function in an electric vehicle. The left part of  FIG.  1    represents the vehicle side and the right part represents the charging station side, and the sides are separated by the inlet  101 . The inlet  101 , also referred to as charging inlet, comprises an an inlet interface adapted to receive a connector, e.g. a charging cable.  FIG.  1    further illustrates the EVCC  105  at the vehicle and the SECC  108  at the charging station. There is a PE ground  110  at the charging station and a PE connection  113  at the vehicle. The PE connection  113  may be referred to as chassis ground or EV grounding point. The PE connection  113  is a PE connection to the chassis of the vehicle. The lines between the EVCC  105  and the SECC  108  represent a communication circuit, and the arrows following the lines represent communication signals going from the EVCC  105 , to the SECC  108  and back go the EVCC  105 . In the known solution illustrated in  FIG.  1   , the communication circuit return is routed through the PE connection point  113  on the vehicle chassis. This way, the communication will stop, and charging will not be possible if the PE connection  113  to the chassis is not good. The communication circuit return is illustrated in  FIG.  1    with the arrows going in the direction from the SECC  108 , via the inlet  101 , the PE connection  101  and to the EVCC  105 . 
     As seen from  FIG.  1   , the current communication circuit serves dual purposes: communication and PE monitoring. The communication path, illustrated with the arrows in  FIG.  1    depends on the PE connection  113 . Changes to the PE connection  113  or signal wires in the communication circuit necessitate calibration of the EVCC transmit power. 
     The downside of the known PE monitoring implementation illustrated in  FIG.  1    is that the choice of PE grounding point  110  will affect the PSD at the inlet  101  due to e.g. length of cables in the communication circuit. Any changes to the PE ground  110  or the communication circuit wiring in general might thus prompt a calibration of the EVCC  105  to keep the PSD within the bounds specified in the CCS standard. 
     Therefore, there is a need to at least mitigate or solve this issue. 
     SUMMARY 
     An objective of embodiments herein is therefore to obviate at least one of the above disadvantages and to provide improved monitoring of the PE connection. 
     According to a first aspect of the invention, the objective is achieved by a monitoring circuit for monitoring of a PE connection in a vehicle charging interface of a vehicle according to claim  1 . The vehicle is at least partly electrically powered. The monitoring circuit is connected to a first line of a communication circuit. The monitoring circuit and the communication circuit are separate circuits. The monitoring circuit comprises a current source, a current measuring unit and the PE connection. The current source is adapted to generate a current running through the monitoring circuit, and the current measuring unit is adapted to measure the current running through the monitoring circuit and thereby monitoring the PE connection. By the provision of a monitoring circuit which is separate and removed from the communication circuit, an advantage of that the same communication circuit can be used for all vehicle installations. Another advantage is that the separation of the monitoring circuit from the communication circuit makes the communication signals in the communication circuit independent of the PE connection such that a failure or error in the PE connection point will not affect the communication between the EVCC and the SECC. Consequently, it is possible to keep the PSD level at the inlet uniform for all vehicle installations. The monitoring of the PE connection is thereby improved. Note that even if it is possible to maintain the communication, the charging process must be stopped if the monitoring detects a problem with the PE connection. 
     According to one embodiment, the monitoring circuit may comprise a first branch, and the first branch comprises the current source connected in series with the current measuring unit. An advantage of this is that any suitable current source and current measuring unit may be utilized. Units that are easy to get hold of and to install may be used, and the only requirement is that they are adapted to provide current and to measure the current, respectively. Any suitable standard components with these characteristics may be used. This way, the selection of units that can be used is large, which provides flexibility. 
     According to a further embodiment, the monitoring circuit may comprise a second branch connected in parallel with the first branch, and the second branch may comprise a choke. An advantage of a choke in the second branch may be that it makes it difficult for communication signals traveling in the communication circuit to travel in the monitoring circuit. Thus, only the current from the current source travels through the monitoring circuit. The choke provides additional isolation between the monitoring circuit and the communication circuit. 
     According to another embodiment, the first branch and the second branch each have a first end and a second end. Both the first branch and the second branch are connected to the communication circuit at the first ends and to the PE connection at the second ends. This configuration of the monitoring circuit provides an advantage of being a simple and cost-effective configuration which. In addition, it enables the separation between the monitoring circuit and the communication circuit. 
     According to a second aspect of the invention, the objective is achieved by a vehicle charging interface according to claim  5 . The vehicle charging interface comprises:
         A charging inlet adapted to receive a charging cable.   A communication circuit located between the charging inlet and an EVCC. The communication circuit is adapted for communication between the EVCC and a SECC.   The monitoring circuit according to any of claims  1 - 4 .       

     The communication circuit may comprise the whole line from the EVCC via the inlet to the SECC. Advantages and effects of the vehicle charging interface are largely analogous to the advantages and effects of the first aspect. Further, all embodiments of the vehicle charging interface are applicable to and combinable with all embodiments of the monitoring circuit, and vice versa. 
     According to one embodiment, the communication circuit may be independent of the PE connection. An advantage of this may be that communication signals running can continue to run through the communication even in the event that there is a failure in the PE connection. Consequently, the PSD does not depend on the PE connection. The charging needs to be stopped if a problem with the PE connection is detected. However, it is possible to continue to send communication signals through the communication circuit even if the charging is stopped. Another advantage is that the same communication circuit can be used regardless of the vehicle installation, i.e. there is no need for any tailored communication circuit to each vehicle installation. 
     According to another embodiment, the charging inlet may comprise the EVCC, or the charging inlet and the EVCC may be separate units. An advantage of the charging inlet comprising the EVCC, i.e. that the EVCC may be integrated into the charging inlet, may be that the communication signal path is short and well-defined. This may reduce the cost and risk for communication link failure and communication signal failure. An advantage of that the charging inlet and the EVCC are separate units may be that they may be easily replaceable in case of any of them malfunctions and easy to install. 
     According to a third aspect of the invention, the objective is achieved by at least partly electrically powered vehicle according to claim  8 . The vehicle comprises the monitoring circuit according to any of claims  1 - 4 . Advantages and effects of the vehicle are largely analogous to the advantages and effects of the first aspect. Further, all embodiments of the vehicle are applicable to and combinable with all embodiments of the monitoring circuit, and vice versa. 
     Further advantages and advantageous features of the invention are disclosed in the following description and in the dependent claims. 
     The embodiments herein are not limited to the features and advantages mentioned above. A person skilled in the art will recognize additional features and advantages upon reading the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples. 
       In the drawings: 
         FIG.  1    is a schematic drawing illustrating a vehicle charging interface. 
         FIG.  2    is a schematic drawing illustrating an at least partly electrically powered vehicle. 
         FIG.  3    is a schematic drawing illustrating a vehicle charging interface. 
         FIG.  4    is a schematic drawing illustrating a monitoring circuit. 
     
    
    
     The drawings are not necessarily to scale, and the dimensions of certain features may have been exaggerated for the sake of clarity. Emphasis is instead placed upon illustrating the principle of the embodiments herein. 
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION 
       FIG.  2    is a schematic drawing illustrating a vehicle  200 . The vehicle  200  may be any arbitrary vehicle, for instance a car, truck, lorry, van, bus, motorcycle etc. The vehicle  200  may be at least partly autonomous or self-driven, it may be completely autonomous or self-driven, or it may be non-autonomous etc. The vehicle  200  is an at least partly electrically powered vehicle, i.e. it may be a fully electrically operated vehicle or a hybrid vehicle, comprising also a combustion engine. 
       FIG.  3    schematic drawing illustrating a vehicle charging interface  300 . As seen in  FIG.  3   , the vehicle charging interface  300  comprises a charging inlet  101 , an EVCC  105  and a SECC  108 . The charging inlet  101  and the EVCC  105  are comprised in the vehicle  200 . The SECC and the PE ground  110  are comprised in the charging station. The charging inlet  101  may be described as adapted to receive a charging cable (not illustrated in  FIG.  3   ) for charging the vehicle  200 . In other words, charging cable may comprise a plug adapted to be connected to a socket comprised in the charging inlet  101  of the vehicle  200 . 
     The vehicle charging interface  300  comprises a communication circuit  303  and a monitoring circuit  305 , both illustrated with dotted circles in  FIG.  3   . 
     The communication circuit  303  is adapted to enable communication between the EVCC  105  and the SECC  108 . When the charging cable is connected to the charging inlet  101 , communication signals travel through the communication circuit  303  between the EVCC  105  and the SECC  108 , One purpose of the communication signals may be to control the charging sequence, e.g. the current that the vehicle requests. The communication circuit  303 , also referred to as a control pilot circuit, may be, as seen from the vehicle perspective, located between the charging inlet  101  and the EVCC  105 , The communication circuit  303  may be located between the EVCC  105  and the SECC  108 . When the charging inlet  101  is located between the EVCC  105  and the SECC  108 , the communication circuit may be described as being located between the EVCC  105 , via the charging inlet  101 , to the SECC  108 . The communication circuit  303  may comprise communication lines, e.g. a first line  308  and a second line  310 . The first line  308  may be adapted to enable communication from the EVCC  105  to the SECC  108 , illustrated with the arrows pointing to the right in  FIG.  3   , or to enable communication from the SECC  108  to the EVCC  105 . The second line  310  may be adapted to enable communication from the SECC  108  to the EVCC  105 , illustrated with the arrows pointing to the left in  FIG.  3   , or to enable communication from the EVCC  105  to the SECC  108 . The communication signal travels on both the first line  308  and the second line  310 , and in opposite directions. The communication signal that travels through the communication circuit  303  may be referred to as a communication pilot or communication pilot signal. The first line  308  and the second line  310  may be separate and standalone communication lines, or they may be integrated into one communication line which is adapted to provide two-way communication. The charging inlet  101  may be located at any suitable point on the first line  308  and the second line  310 , for example in the middle between the EVCC  105  and the SECC  108 , closer to the EVCC  105  than to the SECC  108 , or closer to the SECC  108  than to the EVCC  105 . The total length of the cable between the SECC  108  and the EVCC  105  may be any suitable length, for example maximum 10 meters. The distance between the EVCC and the charging inlet  101  may be maximum 2 meters and the distance between the SECC  108  and the charging inlet  101  may be maximum 8 meters, i.e. maximum 10 meters in total. Note that this is only an example and that any other suitable length may be applicable. It may be preferred that the distance between the EVCC  105  and the charging inlet  101  is as short as possible. 
     The PE ground  110  may be connected to the first line  308  and between the charging inlet  101  and the SECC  108 . 
     The monitoring circuit  305  is illustrated in  FIG.  3    and in more detail in  FIG.  4   , and both these FIGS. will be used in the following when describing the monitoring circuit  305 . As seen in  FIG.  3   , the monitoring circuit  305  is separated from the communication circuit  310 . The PE monitoring function is removed from the communication circuit  303  (compared with  FIG.  1   ) and replaced by a separate monitoring circuit  305 , e.g. a small DC loop through the PE connection  113 . The communication signals will only travel through the communication circuit  303 , and not through the monitoring circuit  305 . It is only the monitoring signal that will travel through the monitoring circuit  305 , and not the communication signal. With the separation of the circuits, the communication between the EVCC  105  and the SECC  108  will continue, and charging will still be possible even if the PE connection  113  is malfunctioning or is experiencing problems. 
     As seen in  FIGS.  3  and  4   , the monitoring circuit  305  comprises a current source  313 , a current measuring unit  315  and the PE connection  113 . The current source  313  is adapted to generate a current running through the monitoring circuit  305 . The current source  313  may generate current and the current measuring unit  315  may measure the current when the vehicle  200  is connected to the charger, i.e. the monitoring may be active as long as the vehicle  200  is connected to the charger. The current measuring unit  315  is adapted to measure the current running through the monitoring circuit  305  and thereby monitoring the PE connection  113 . The current generated by the current source  31  may be of any suitable size sufficient to check the continuity of the PE connection  113 . A purpose of monitoring the PE connection  113  is to ensure that the connection between the charging station PE and the vehicle chassis is intact. A result of the monitoring will indicate that the PE connection  113  is correctly functioning or that the PE connection  113  is not functioning correctly, e.g. that it is malfunctioning, that it is an error associated with the PE connection  113 , that there is a discontinuity associated with the PE connection  113 . When the result of the monitoring of the PE connection  113  indicates that the PE connection  113  is function correctly, then this may be indicated by that the current measuring unit  315  measures a current that is substantially the same as the current generated by the current source  313 . When the result of the monitoring of the PE connection  113  indicates that the PE connection  113  is not function correctly, then this may be indicated by that the current measuring unit  315  measures a current that is different from the current generated by the current source  313 , possibly with some tolerance. 
     The current source  313  may be connected in series with the current measuring unit  315 , and possibly comprised in a first branch  401  of the monitoring circuit  305 . 
     The monitoring circuit  305  may comprise a second branch  403 , and the second branch  403  may be connected in parallel with the first branch  401 . The second branch  403  may comprise a choke  405 . The choke  405  may be for example a ferrite or any other suitable choke type. The purpose of the choke  405  may be to make it difficult for the communication signal to travel in the monitoring circuit  305 , further isolating the communication signal from the monitoring circuit  305 . The changes in the monitoring circuit  305  does not affect the characteristics of the communication circuit  303 , which avoids or reduces the need for calibration of the EVCC  105 . 
     The first branch  401  and the second branch  403  may each have a first end  406   a ,  406   b  and a second end  408   a ,  408   b . Both the first branch  401  and the second branch  403  may be connected to the communication circuit  303  at the first ends  406   a ,  406   b  and to the PE connection  113  at the second ends  408   a ,  408   b.    
     The present invention may be summarized as follows: 
     A monitoring circuit  305  for monitoring of a PE  113  connection in a vehicle charging interface  300  of a vehicle  200 . The vehicle  200  is at least partly electrically powered. The monitoring circuit  305  is connected to a first line  308  of a communication circuit  303 . The monitoring circuit  305  and the communication circuit  303  are separate circuits. The monitoring circuit  305  comprises a current source  313 , a current measuring unit  315  and the PE connection  113 . The current source  313  is adapted to generate a current running through the monitoring circuit  305 , and the current measuring unit  315  is adapted to measure the current running through the monitoring circuit  305  and thereby monitoring the PE connection  113 . 
     The monitoring circuit  305  may comprise a first branch  401 , and the first branch  401  may comprise the current source  313  connected in series with the current measuring unit  315 . 
     The monitoring circuit  305  may comprises a second branch  403  connected in parallel with the first branch  401 , and the second branch  403  may comprises a choke  405 . 
     The first branch  401  and the second branch  403  may each have a first end  406   a ,  406   b  and a second end  408   a ,  408   b . Both the first branch  401  and the second branch  403  may be connected to the communication circuit  303  at the first ends  406   a ,  406   b  and to the PE connection  113  at the second ends  408   a ,  408   b.    
     A vehicle charging interface  300  comprises a charging inlet  101  adapted to receive a charging cable. The vehicle charging interface  300  comprises a communication circuit  303  located between the charging inlet  101  and an EVCC  105 . The communication circuit  303  is adapted for communication between the EVCC  105  and a SECC  108 . The vehicle charging interface  300  comprises the monitoring circuit  305  as described herein. 
     The communication circuit  303  may be independent of the PE connection  113 . 
     The charging inlet  101  may comprises the EVCC  105 , or the charging inlet  101  and the EVCC  105  may be separate units. 
     An at least partly electrically powered vehicle  200  comprises the monitoring circuit  305  described herein. An at least partly electrically powered vehicle  200  comprises the vehicle charging interface  300  described herein. 
     According to the present invention, the monitoring of the PE connection  113  is separated from the communication circuit  303 . If this is combined with a standardized vehicle side harness, e.g. by integrating the EVCC  105  in the charging inlet  101 , the signal characteristics will be well defined, and changes in the PE cable routing does not affect the communication. Otherwise, changes to the PE cables might require recalibration of the EVCC  105  to ensure proper communication. 
     The PE integrity monitoring of the PE to chassis ground connection is made with a separate circuit, i.e. the monitoring circuit  305 . The communication signal path and thus the PSD does not depend on the PE connection  113 . To make the communication signal path as short and well-defined as possible, the EVCC  105  may be integrated into the charging inlet  101 . 
     The separate monitoring circuit  305  together with a specified communication circuit  310  harness between the EVCC  105  and the inlet  101 , the same PSD calibration can be used for all vehicles  200 . 
     Multiple solutions exist to keep the harness of the communication circuit  303  well defined, and one way may be to integrate the EVCC  105  into the charging inlet  101  itself, thus eliminating any external cables. 
     As mentioned earlier, the CCS standard states that integrity of the PE connection  113  should be monitored and that the PSD from the EVCC  105  in the communication circuit  301 , at the charging inlet  101 , must be kept within specified limits. The integrity of the PE connection  113  indicates that the PE wire from the charger is properly connected to the vehicle chassis. With the separation of the monitoring circuit  305  and the communication circuit  310 , the PSD level may be kept uniform, i.e. within the standardized limits, at the charging inlet  101  and even with variations in the routing and/or cable lengths of the PE wiring between the charging inlet  101  and the vehicle chassis. 
     With the present invention, the PSD level or PSD characteristics at the charging inlet  101  is kept uniform for all installations. This is made possible with two parts: 1) keeping the communication circuit  303  the same for all vehicle installations, and 2) removing any dependencies on the selection of the PE connection  113 , i.e. the chassi ground point. 
     Part one 1) is achieved by using a wiring of the communicatoin circuit  303  that is the same for all vehicle installations, or by removing the wires and integrating the EVCC  105  in the charging inlet  101 . 
     To resolve the part 2) a separate monitoring circuit  305  is used to monitor the PE connection  305 , i.e, the ground connection. To further minimize any impact on the PSD from the grounding structure, an optional choke  405  may be used to further prevent any communication signal from traveling in the ground wire or chassis structure. 
     It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims. 
     Directions as used herein, e.g. horizontal, vertical, lateral, relate to when the monitoring circuit  305  and/or the vehicle charging interface  300  is mounted in the vehicle  200 , with the vehicle  200  standing on flat ground. The monitoring circuit  305  and the vehicle charging interface  300  may be manufactured, stored, transported and sold as a separate unit. In that case, the directions may differ from when mounted in the vehicle  200 . 
     The embodiments herein are not limited to the above-described embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the embodiments, which is defined by the appended claims. A feature from one embodiment may be combined with one or more features of any other embodiment. 
     The term “at least one of A and B” should be understood to mean “only A, only B, or both A and B.”, where A and B are any parameter, number, indication used herein etc. 
     It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components, but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. It should also be noted that the words “a” or “an” preceding an element do not exclude the presence of a plurality of such elements. 
     The term “configured to” used herein may also be referred to as “arranged to”, “adapted to”, “capable of” or “operative to”. 
     It should also be emphasised that the steps of the methods defined in the appended claims may, without departing from the embodiments herein, be performed in another order than the order in which they appear in the claims.