Patent Application
20130179033
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.
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'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.
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.
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.
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.
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.
In the drawing:
Referring to
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.
The unique control signals on buss 22 will identify one of the numerous electrical control units (ECUs) 30-30n for accessories and devices. Currently, typically up to sixteen electronic control units 30-30n 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
Each control circuit 50-50n 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.
The control circuits 50-50n 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 50-50n may be built into the casing 45 of the relays, such that it is integrated and embedded into the relays 40-40n, as graphically illustrated in
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 30-30n. With such a system, therefore, the number of conductors necessary between the ECU and the electronic controlled relays 30-30n 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.
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.
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.
