CROSS REFERENCE TO RELATED APPLICATIONS 0001 This application claims priority to U.S. Provisional Application No. 60/274,269, which was filed on Mar. 8, 2001.

BACKGROUND OF THE INVENTION 0002 This invention generally relates to controls for electronic devices that need to be awakened out of a sleep mode where wake up time is limited. More particularly, this invention relates to a unique switching strategy within a wake up system for such electronic devices. 0003 Modern day vehicles include a variety of electronic components. The power consumption of all of these components can prove to be too much and designers are constantly facing the challenge of reducing power consumption while, at the same time, providing the same or enhanced options on a vehicle. One way of managing power consumption is to have various peripheral devices enter a sleep mode when the device is not in use. 0004 There are a variety of strategies for causing such devices to enter a sleep mode and for waking up the devices as needed. Typical arrangements include a linear voltage regulator, which introduces expense. Cost-savings are a critical concern in automotive applications. Another difficulty with conventional approaches is that they are not universally applicable and cannot meet some of the more stringent requirements regarding parasitic leakage current and limited wake up times. This difficulty is particularly present in devices where an energy reserve is part of a power supply to boost a battery voltage to a higher voltage level for powering the electronics of a particular device. 0005 In one example, the parasitic leakage current when a device is in sleep mode must be less than or equal to 500 micro amps. It is desirable to provide an arrangement that satisfies the low leakage current requirements, is versatile enough to be useful with a variety of devices, facilitates a fast wake up response and is cost effective to implement. This invention addresses those needs while avoiding the shortcomings of prior arrangements.

SUMMARY OF THE INVENTION 0006 In general terms, this invention is an assembly for controlling power consumption of at least one device supported on a vehicle that has a communication bus over which signals are transmitted to or from the device. 0007 The inventive assembly includes a controller that controls operation of the device. A power supply portion derives power from a vehicle power source, such as a battery, and provides power to the controller. A switch is placed between the power supply portion and the vehicle power source. The switch selectively opens the connection between the power supply portion and the vehicle power source when the device is in a sleep mode and closes the connection when the device is in an active mode. A transceiver receives a wake up signal provided on the communication bus. 0008 A switch locking portion responds to the wake up signal received by the transceiver to lock the switch into the closed position. The switch locking portion maintains the switch in the closed position until the controller provides an indication that the device is to enter the sleep mode. 0009 A significant advantage to the incentive approach is that it does not require a regulated voltage. 0010 In one example, the switch locking portion comprises a plurality of transistors, arranged to lock the switch into a conducting state while the device is in the active mode. The controller provides a signal that unlocks the switch when the controller determines that the device should enter into the sleep mode. 0011 In one example implementation of this invention, the switch locking device comprises a mono-flop that moves from a non-conducting state, which holds the switch open, to a conducting state, which closes the switch. Once in the conducting state, the mono-flop is unable to exit that state until it is reset by the controller determining that the device should enter the sleep mode. 0012 The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS 0013 FIG. 1 schematically illustrates an arrangement of a plurality of peripheral devices on a vehicle each being connected with a communication bus. 0014 FIG. 2 schematically illustrates a power supply control assembly designed according to this invention. 0015 FIG. 3 schematically illustrates in more detail, a selected portion of the embodiment of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 0016 As schematically shown in FIG. 1, a communication network 20 facilitates communications between a main control 22, for example over a communication bus 24 with a plurality of peripheral devices 26, 28 and 30. The illustrated arrangement can be particularly useful on a vehicle, for example, where the peripheral devices include items such as an airbag controller that enter a sleep mode to conserve energy. 0017 The main control 22 in one example provides a wake up signal on the bus 24 to wake up the devices 26, 28 and 30 as needed. 0018 The communication bus 24 in one example is a CAN communication bus as known. The plurality of peripheral devices receive and transmit signals that are propagated along the communication bus 24 in a known manner. The inventive arrangement is particularly well suited for controlling an amount of leakage current absorbed by the peripheral devices when they are in a sleep mode and for waking up the devices using a wake up signal promulgated along the communication bus 24. 0019 As can be appreciated from FIG. 2, an example one of the peripheral devices 30 is schematically illustrated with only selected portions of that device being shown in the drawing. The main control 22 provides signals along the communication bus 24 that are processed through a transceiver 32. In the illustrated example, the transceiver 32 comprises a conventional CAN transceiver as known in the art. 0020 A vehicle power source 34 such as a car battery provides a supply of energy to the device 30 through a rectifier 36. A switch 40 selectively separates the power source 34 from selected ones of the components within the device 30 when the device is in a sleep mode. 0021 A switch control 42 operates the switch 40 to electrically open or close the switch to provide a selective coupling between the power source 34 and other components within the device 30. The switch control 42 is powered based upon the operation of a switch locking portion 44 that is responsive to a signal on an input 45 from the transceiver 32 indicating that a wake up signal was received from the bus line 24. The switch locking portion 44 provides an output signal at 46 to the control 42. The power to the switch control 42 is derived from the vehicle power source 34. 0022 The same power source 34 powers the switch locking portion 44 along an input 48. 0023 The switch locking portion 44 receives an input signal at 45 from the transceiver 32. The transceiver 32 preferably responds to a wake up signal on the communication bus 24 by transmitting the signal at 45. In one example, the wake up signal comprises a 7 volt signal on the communication bus 24. The 7 volt signal, as known, is used for a wake up signal because it has a higher voltage than standard communication or control signals provided along the communication bus 24. The switch locking portion 44 enables the switch control 42 to change the switch 40 from a non-conductive state to a conducting state. Once activated, the control 42 closes the switch 40, which couples the power supply portion of the device 30 to the power source 34. The locking portion ensures that the control 42 keeps the switch 40 closed until the device 30 should enter the sleep mode once again. 0024 The illustrated example includes an energy reserve portion 50 and a power supply portion 52, each of which comprise components as known in the art. The energy reserve portion 50 facilitates boosting the battery voltage of the energy source 34 to a higher voltage. In some examples the boosted voltage may be 23 or 33 volts, for example whereas the battery voltage is typically between 8 and 16 volts. 0025 The power supply portion 52 provides the primary power to the device controller 54. When the controller 54 determines that the device 30 should enter the sleep mode, a reset signal is provided to the switch locking portion 44 along the output 56, which causes the switch locking portion 44 to effectively cut off the control 42 from the vehicle power source 34, which results in the switch 40 being opened. 0026 FIG. 3 schematically illustrates one example implementation of a switch locking portion 44 designed according to this invention. In the illustrated example, the switch locking portion 44 includes a plurality of transistors arranged so that a wake up signal received by the transceiver 32 causes the switch locking portion 44 to change to a conductive state allowing the control 42 to receive battery power to close the switch 40. In the illustrated example, the transistors 60, 62 and 64 are arranged, as can be appreciated from the illustration, in a manner so that the falling edge of a signal from the transceiver 32 at 45 results in the transistor 62 locking into a conductive state. Once the locking portion is locked, the power output at 46 is available to the control 42, which in turn closes the switch 40. The control 42 continues to maintain the switch 40 in a closed position as long as the transistor 62 is conducting between the input 48 (i.e., the power source 34) and the output 46. 0027 In the illustrated example, the base of the transistor 60 is held such that the transistor 60 is nonconducting when the device 30 is in the sleep mode. In the illustrated example, the transistor 60 and 64 are part of the same component and are interrelated such that when one is nonconducting, the other is nonconducting. When the transceiver 32 provides an output responsive to a wake up signal on the communication bus 24, the falling edge of that output enables the transistor 60 and the transistor 64 to be conducting. Once the transistors 60 and 64 are conducting, the base of the transistor 62 is effectively coupled through resistors to the vehicle power source 34. At this point, the transistor 62 is conducting and the voltage of the vehicle power source 34 is available at 46 to the switch control 42. 0028 In this condition, the transistor 64 is unable to stop conducting. Accordingly, it matters not whether the transistor 60 opens or closes once the transistor 62 is conducting. As such, the switch locking portion 44 is unable to independently switch itself out of a conductive state once the transistor 62 is conducting and effectively providing power to the switch control 42. 0029 Because the switch locking portion 44 changes from a non-conductive state to a conductive state and cannot change itself out of the conducting state, the illustrated example can be referred to as a mono-flop. The use of such a mono-flop locking portion ensures power supply to the switch control 42 maintains the switch 40 in a conductive state as long as the device 30 is to be active. 0030 Once the controller 54 determines that the device 30 should enter the sleep mode, it provides a reset signal at 56 to the base of a transistor 70. As the controller 54 in the illustrated example pulls down the base of the transistor 70, that pulls the base of transistor 64 to ground, which grounds the base of the transistor 62. This cuts off the power source 34 from the control 42, which in turn results in the control 42 opening the switch 40. An example situation where the controller 54 determines that the device should enter the sleep mode is when a specific function required of the device has been completed or when a wake up signal is received followed by no further signals within a specified period. 0031 The illustrations show one example implementation of this invention. Various modifications and other so-called mono-flop devices can be used to control the operation of a switch such as the switch 40 to provide power to the device 30 when it is in an active mode. The illustrated example is particularly advantageous because the leakage current is approximately 200 micro amps when the device is in the sleep mode and no regulated voltage is required. 0032 The illustrated example includes an ignition logic level portion 80 that is supplemental to the switch locking portion 44 so that the device 30 can be woken up by a signal as known other than a wake up signal received from the communication bus 24. 0033 The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.