Abstract:
A body control module (BCM) of a vehicle has an output bus which provides addressed control signals to a plurality of electrical control units (ECUs) coupled to the bus. The ECUs include a power control relay and an addressable control circuit which responds to an address uniquely identifying a particular ECU for actuating the associated relay to provide power to an electrical device in the vehicle. The control signals from the BCM can be any one of several data processing protocols, including local interconnect network (LIN), and controller area network (CAN) to provide the address and data for controlling each of the relays.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a control circuit for controlling vehicle relays and, particularly, a control circuit which interfaces with the Body Control Module (BCM) of a vehicle to provide operating power to multiple relays utilizing a common bus communication link. 
       BACKGROUND OF THE INVENTION 
       [0002]    Many vehicle peripheral devices, such as headlamps, power seats, power windows, heated seats, and the like, require the use of a relay to provide sufficient current for powering the device. Such devices are typically controlled by operator input switch functions, which switch information is coupled to an Electronic Control Unit (ECU), such as a body control module, which typically contains a microprocessor, which, in turn, activates a solid state switch, such as a metal-oxide-semiconductor field-effect transistor (MOSFET), to provide sufficient current to a relay coil activating the power supplying relay. The relay contacts couple power from the vehicle&#39;s battery bus line to the accessory being activated. The utilization of discreet solid state switches, which are coupled by conductors from an ECU, requires numerous electrical connections in the vehicle requiring a bundle of wires between the ECU and relays, typically to the engine compartment where the relays are located. This adds additional cost and weight to the automotive electrical system and is difficult to modify during the design of a particular vehicle model, particularly, where additional accessories are added late in the development process. 
         [0003]    There exists a need, therefore, for an improved control system for devices requiring relatively high current loads that require relays to provide sufficient current to the device and which allows greater design flexibility while reducing the overall cost, weight, and complexity of the electrical control system for the vehicle. 
       SUMMARY OF THE INVENTION 
       [0004]    The system of the present invention provides such benefits by incorporating within, or in close association with each device relay, an addressable control circuit which receives an address and control command from a single bus coupled to an ECU, such as a Body Control Module and to each of the addressable circuits to be controlled. Any one of the popular automotive communication protocols can be used on a serial bus line, such as local interconnect network (LIN), controller area network (CAN) to provide the address and data for controlling each of the relays. Each relay includes its own control circuit which may include an application specific integrated circuit (ASIC) and a MOSFET driver coupled to the serial bus to receive a command control signal and provide current to the relay coil which responds to activate the relay contacts, providing power to a vehicle device or accessory. 
         [0005]    A relay control circuit can be any type of electronic control circuit which includes a microprocessor or other programmable control device for actuating a solid state switch in response to an identified address and data control signal. In some embodiments, the relay control circuit can be embedded within the body of the relay housing itself. In other embodiments, the relay may be mounted on a circuit board which includes the associated control circuit. In either approach, the number of conductors required for coupling power control relays to the ECU is reduced to a minimum, typically with a single bus line providing address and control signals for numerous circuit control power relays. 
         [0006]    These and other aspects, objects, and features of the present invention will be understood and appreciated by those skilled in the art upon studying the following specification, claims, and appended drawing. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0007]    In the drawing: 
           [0008]      FIG. 1  is a block and schematic circuit diagram of the system embodying the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0009]    Referring to  FIG. 1 , there is shown a block and schematic diagram of the system embodying the present invention. A vehicle, such as an automobile, SUV, truck, or the like will include an operator/passenger/software interface  10  comprising a plurality of switches S 1 -S n  coupled by conductors  1 -n to a body control module  20 . The switches are available to either the driver/operator or a passenger for controlling devices and accessories in the vehicle. Also, software for automatically controlling vehicle functions, such as an engine cooling fan, heater controls, and the like, can provide a control signal to the body control module  20 . Powered devices and accessories include, for example, headlamps, power seat position controls, heated seat controls, door locks, window controls and the like. Each of these switches, variously located in the vehicle, are coupled by conductors  1 -n to a body control module  20  to provide control signals thereto. Module  20  typically includes a microprocessor with suitable interface circuits which respond to signals on conductors  1 -n to execute an addressed command on output bus  22  uniquely identifying the device or accessory to be controlled using a conventional protocol, such as LIN, CAN, Flexray, Ethernet, a commercially available OEM protocol (such as GM protocol), or the like. The body control module in one embodiment included a microprocessor, such as an MPC 560xB manufactured by Freescale Semiconductor Inc. and known in connection with the Ford Motor Company vehicles as the Bolero system. 
         [0010]    Thus, for each switch activation in interface  10 , an output signal on bus  22  will be generated, as indicated by the pictorial representation  24  of the output control signal. Signal  24  includes an address section identified by arrow A and at least a data section indicated by arrow D in the pictorial representation  24 . Signal  24  includes the address A, which is typically referred to as a header including a synch break, synch field, and identification field. The data field includes the control signal and a check sum field for data checking accuracy. The LIN communication protocol is well known, as are the circuits employed using the protocol. 
         [0011]    The unique control signals on buss  22  will identify one of the numerous electrical control units (ECUs)  30 - 30   n  for accessories and devices. Currently, typically up to sixteen electronic control units  30 - 30   n  can be coupled to bus  22  and employ the LIN protocol. Each of the electronic control units, such as  30 , include a relay  40  having a movable contact  42  coupled to an input terminal  43 , in turn, coupled to the vehicle power supply conduit  60  from the battery through a suitable fuse  49 . Relay  40  also includes fixed contacts  41  and  44  and, when activated by control circuit  50 , provides current to energize the relay coil  46 , creating a magnetic field moving the movable metal contact  42  from an off position, as shown in  FIG. 1 , to contact  44 . This applies power from conduit  60  through fuse  49  and conductor  52  to the load  54  which can be any number of relatively high current devices or accessories, such as headlights, a window control motor, door lock solenoids, resistance seat heaters, or the like. 
         [0012]    Each control circuit  50 - 50   n  may include an application specific integrated circuit (ASIC, including a MOSFET) programmed to recognize the address on bus  22  identifying the specific associated load  54  which, when the identifying address is received together with a data command to activate the accessory, applies current to relay coil  46  to activate relay  40 , thereby powering the associated load  54 . 
         [0013]    The control circuits  50 - 50   n  can likewise include a microprocessor, such as a Star  12  available from Freescale Semiconductor Inc., together with an output solid state switch or driver for supplying power to the relay coil  46  and, in turn, the load. Circuits  50 - 50   n  may be built into the casing  45  of the relays, such that it is integrated and embedded into the relays  40 - 40   n,  as graphically illustrated in  FIG. 1 , as a high side drive shown or alternately as a low side drive. Alternatively, relays  40 - 40   n  can be mounted on an integrated circuit board including circuit  50  and the relatively small relay. Each of the electronic controlled relays  30 - 30   n  are substantially identical, except control circuits  50 - 50   n  are each programmed with a unique address which uniquely identifies the associated load  54 - 54   n.  Thus, when an operator or passenger or computer software actuates a particular device or accessory control switch, the electronic controlled relays  30  associated with the particular switch will be activated to provide operating power to the load. The electronic controlled relays  30  provide two-way communication between them and an ECU  20 , such that the status of the accessory being controlled is known by the ECU. Each of the control circuits  50  supply operating power through the normal solid state control power supply system (+V) for activation. Typically, the system shown in FIG. I also allows a sleep command to be sent along bus  22  when a vehicle is turned off to minimize current drain on the battery. 
         [0014]    In addition to the LIN protocol, other protocols, such as the CAN protocol or the like, can be employed with the system of the present invention, it being understood that the ECU  20  will include a communication circuit which provides two-way communications between the ECU  20  and each of the electronic controlled relays  30 - 30   n.  With such a system, therefore, the number of conductors necessary between the ECU and the electronic controlled relays  30 - 30   n  is limited to a single bus  22 , which provides greater flexibility for adding and removing ECUs depending on a particular vehicle and devices or accessories being employed, without the need for multiple wiring harnesses and other expensive electrical and related components. 
         [0015]    Thus, with the system of the present invention, an improved reduced cost and weight and yet reliable bus communication control system is provided for controlling vehicle devices and accessories that require significant current drain for their operation utilizing the necessary power control relays. 
         [0016]    It is to be understood that variations and modifications can be made on the aforementioned structure without departing from the concepts of the present invention, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise.