Abstract:
A multimedia/personal computer-based system for operating information, communication, and entertainment devices in a mobile vehicle uses a power management strategy which reduces power consumption and boot-up time in a manner which facilitates use of a complex instruction set computing (CISC) processor system. A loosely coupled power management strategy utilizes a low power microprocessor off board of the main motherboard for switching a plurality of regulated voltages to the main motherboard and other devices. The use of a separate board for input/output processing and power management provides for more robust power management and facilitates adaptation of the system for inclusion in different vehicles using different input/output devices and networks.

Description:
This application is related to co-pending application U.S. Ser. No. 09/353,684, entitled “Power Management Fault Strategy for Automotive Multimedia System,” filed concurrently herewith and incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates in general to a method and apparatus for supplying power to an automotive multimedia/personal computer system, and, more specifically, to a power management strategy which reduces vehicle battery consumption while reducing typical boot-up time of an automotive multimedia computer-based system. 
     Power management is an important issue in portable computing devices. This is especially true in mobile vehicles which have a limited battery capacity and which have stringent current limitations. As microprocessor-based systems become more powerful by using larger microprocessors and using a greater number of peripheral devices, power requirements increase. In vehicles containing an internal combustion engine and alternator, electric power generation may be sufficient to operate without much difficulty. In vehicles using other power plants or in an internal combustion engine vehicle with the engine shut off, significant limitations may be placed on current consumption (both normal operating current and quiescent current) of the multimedia/PC system. 
     Partly due to available power limitations, microprocessors having low power requirements are normally used in mobile vehicles. As mobile computing functions have been introduced into vehicles, reduced instruction set computing (RISC) microprocessors have been chosen since they are smaller and consume less power. Thus, complex instruction set computing (CISC) microprocessors such as Intel Pentium (×86) microprocessors and the Motorola 680×0 family of microprocessors have been avoided. However, RISC microprocessors often cannot run the same software as has been created for CISC microprocessors. Availability of operating system and applications software is much greater for CISC microprocessors because of the popularity of desktop and laptop personal computers. Therefore, it would be very beneficial to use a CISC microprocessor in a mobile vehicle. 
     An important performance issue for a multimedia/personal computer based system in a mobile vehicle is boot-up time. A multimedia system may be providing information, communication, entertainment, or other functions which the vehicle user may expect to be available as soon as the vehicle ignition switch is turned on. By example, the multimedia system may include a navigation function and the driver may want to initiate input of a desired destination as soon as possible after turning on the vehicle. By maintaining full or partial power to the multimedia system, boot-up time can be reduced or eliminated, but this conflicts with the need to minimize power consumption. CISC microprocessors such as the Pentium typically have reduced power states in which processing operations are suspended while the state of the memory and the internal microprocessor state are stored. Such a reduced power state may be entered in response to various conditions monitored by the microprocessor. However, the microprocessor can&#39;t go completely to sleep and still monitor the conditions which should wake it up. Furthermore, if the microprocessor has sole responsibility to conduct its own power management, then there is limited ability to recover from errors. 
     SUMMARY OF THE INVENTION 
     The present invention has the advantages of providing efficient and robust power management of an in-vehicle multimedia/personal computer-based system, allowing a CISC processor to operate in a mobile environment with low power consumption and fast boot-up time. 
     The present invention provides a loosely coupled power management strategy in which the majority of power management functions are performed by a low power microprocessor separate from the CISC computing device. 
     In one aspect of the invention, a vehicle information, communication and entertainment system provides mobile operation of information, communication and entertainment devices in a vehicle. The vehicle has a vehicle powered state and a vehicle unpowered state. A main motherboard contains a main application microprocessor, random access memory, and a power management chip set that controls power to the main application microprocessor and the memory. A power controller and regulator supplies a plurality of regulated voltages to the power management chip set and to at least one device remotely located from the main motherboard. A user control places the information, communication and entertainment system into an active user state or an inactive user state. A reduced power microprocessor controls the switching on and off of the regulated voltages in response to the user control and whether the vehicle is in the vehicle powered state or the vehicle unpowered state. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing a multimedia system employing the power management strategy of the present invention. 
     FIG. 2 is a state diagram showing state transitions of the system in FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to FIG. 1, a motherboard  10  is connected to a video processor card  11  and a vehicle input/output processor (VIOP) board  12 . Motherboard  10  includes a complex instruction set computing (CISC) processor  13  which may comprised of an Intel Celleron processor, for example. A support chip set  14  is connected to processor  13  and is adapted to function specifically with microprocessor  13 . Support chip set  14  may be one or more integrated circuits and may preferably be comprised of north and south portions of an Intel Banister Bridge. 
     Chip set  14  provides interfaces between processor  13  and various other devices and provides local power management for processor  13 . Support chip set  14  includes a DRAM memory controller for controlling a DRAM memory  15 . Chip set  14  also includes interface controllers for a mass storage devices such as a hard drive  16  and a CD-ROM drive  17 . Processor  13  is a main application processor and executes operating system software and application programs contained on hard drive  16  and/or CD-ROM drive  17 . 
     A time of day (TOD) unit  18  is connected to chip set  14  and keeps track of time of day in a conventional manner. A low quiescent current regulator that operates off of the vehicle battery (not shown) is preferably provided to maintain operation of TOD unit  18  even when power is off to motherboard  10 . 
     Chip set  14  receives several different regulated voltages from VIOP  12  as is described below. Chip set  14  helps control the regulated voltages to provide power to processor  13  and DRAM  15  according to its own, conventional power management strategy. Motherboard  10  may further include a core power supply  19  driven by chip set  14  to provide a regulated voltage at a value not being supplied by VIOP  12 . 
     A super-input/output (I/O) interface  20  is connected to chip set  14  and provides a serial communications port COM 1  which is connected to VIOP  12 . The serial communications link carries messages between processor  13  and VIOP  12  relating to power management and to input and output data and control signals. 
     Motherboard  10  includes other conventional components which are not shown such as a BIOS unit and standard bus interfaces such as ISA, PCI, and USB interfaces. Video card  11  may be connected to a PCI expansion slot, for example. Video card  11  includes a video output connected to a display  21  which is powered by an off-board regulator  22  under control of VIOP  12 . 
     VIOP  12  includes a reduced power microprocessor  25  which executes program instructions contained in a read-only memory (ROM)  26 , for example. Reduced power microprocessor  25  may be comprised of a Motorola  68  HC  912  processor, for example, or other low power processor of the type often used on automotive applications. A principle job of processor  25  is to control a power controller and regulator  27  which has a plurality of switched and unswitched regulated voltage outputs. For example, switched outputs of 3.3V, 5V, and 10V are provided along with an unswitched (i.e., continuous) supply of 3.3V. Each of these regulated voltages is provided to main motherboard  10  and then distributed to various components which use them, including chip set  14 . These voltages are used to operate microprocessor  13 , power memory  15  for refreshing and accessing memory contents, and for powering portions of chip set  14  itself. In addition, power may be directly supplied to hard drive  16 , CD-ROM  17  and TOD unit  18 . 
     Power controller and regulator  27  may also provide regulated voltages to devices located remotely from motherboard  10  and VIOP  12 . For example, a separate, remote module may include a GPS receiver and a wireless data transceiver receiving GPS power (GPS PWR) and transceiver power (XCVR PWR) from power controller and regulator  27 . 
     VIOP  12  includes a physical interface  28  for providing a serial port connection for microprocessor  25  to communicate with the COM 1  port of motherboard  10 . In addition, there are several direct communication lines connected between motherboard  10  and microprocessor  25 . Microprocessor  25  provides a power button signal in response to an on/off switch  30  controlled by the user to indicate when to place the multimedia system in an in-use condition, and a reset signal for causing the main application processor  13  to reboot. Chip set  14  provides three distinct signals SUS A, SUS B, and SUS C, which identify the suspended power state in which the power management strategy of chip set  14  is operating. 
     Microprocessor  25  also receives a signal from an ignition switch  31  to identify whether the vehicle is in a powered state or an unpowered state. Based upon the state of ignition switch  31  and on/off switch  30 , microprocessor  25  and microprocessor  13  each determine an appropriate power state for main application processor  13  and chip set  14 . Depending upon the current state and next desired state of microprocessor  13  and chip set  14 , microprocessor  25  may merely verify that the correct state has been implemented by chip set  14 , it may command a different state over the serial communication link, or it may switch the state of power controller and regulator  27  to provide different regulated voltages to main motherboard  10 . Also based upon the state of various switches or other inputs, microprocessor  25  may control the switching on and off of off-board regulator  22  for powering display  21  as appropriate. 
     A network interface  32  is contained in VIOP  12  and is connected to microprocessor  25 . Network interface  32  may be connected to a vehicle network for exchanging data and control signals between motherboard  13  and a vehicle communication or multiplex network (also using the serial communication link between motherboard  10  and VIOP  12 ). 
     Operation of the power management strategy for the multimedia system will be described in connection with the state diagram of FIG.  2 . Prior to application of any power, the multimedia system is in No Power state  40 . In No Power state  40 , main battery power is disconnected and all units are off. Once power is applied, the multimedia system transitions to a Sleep state  41 . Sleep state  41  is characterized by the following conditions: ignition is off, the VIOP unit is asleep, the main microprocessor and chip set are off, the display is off, remote wireless and GPS units are off, CD-ROM unit is off, and display backlighting is off (backlighting refers to background lighting of an LCD display and is desirable to provide general panel lighting of a vehicle dashboard during low light conditions even though the unit itself is off). During Sleep state  41 , if the vehicle external lights such as headlights are turned on, then it is desirable to supply backlighting power for the display. Thus, a lights-on condition triggers a transition to a Power Save state  42  in which the VIOP unit is awake and can control backlighting power to the display. When the lights then go off, a transition is made to return to Sleep state  41 . 
     Transition may be made to Sleep state  41  from any other state during a shutdown caused by an error or lock-up condition of the main microprocessor causing it to fail to respond to VIOP messages. In that case, the VIOP processor shuts down all switched power to main motherboard  10  thereby initiating Sleep state  41 . 
     Power Save state  42  is characterized by the following conditions: ignition is off, VIOP unit is awake, main application processor and chip set are asleep in a suspend-to-disk state (referred to as a D 3  state for an Intel Celleron chipset/ACPI spec), the display is off, wireless and GPS transceivers are off, CD-ROM unit is off, and display backlighting may or may not be on depending upon other vehicle settings (e.g., headlights). When the vehicle ignition turns on, a transition will be made out of Power Save state  42  depending upon the status of the on/off power button on the multimedia unit itself. If the power button is off, then a transition is made to Standby+ state  43 . If the power button is on, then a transition is made to Full Power state  44 . Standby+ state  43  is characterized by the following conditions: ignition is on, VIOP unit is awake, main processor and chip set are on, display is off, wireless data transceiver is off, GPS unit is on, CD-ROM unit is off, and backlighting of the display is dependent on other lamp states. While in Standby+ state  43 , a transition may be made to Full Power state  44  in response to the turning on of the power button, activity on any other button controls of the multimedia system as appropriate, or the insertion of a media such as a CD audio disc. If the ignition switch is turned off while in Standby+ state  43 , a transition is made to Standby state  45 . 
     Standby state  45  is characterized by the following conditions: ignition is off, VIOP unit is awake, the main processor and chip set are asleep in the suspend-to-RAM state (designated as state S 3  in the Intel Celleron power management strategy), display is off, wireless transceiver and GPS receiver are off, CD-ROM unit is off, and display backlighting depends upon vehicle lamps. When in Standby state  45 , a fairly low quiescent current consumption of about 100 mA may be obtained. Although this current draw is fairly low, it is higher than can be maintained for extremely long periods in a vehicle which must rely on its main battery for starting the vehicle internal combustion engine. Therefore, Standby state  45  includes operating of the time of day timer in order to detect a predetermined period of time, after which a transition is made to Power Save state  42 . In Power Save state  42 , the main processor and chip set switch to the suspend-to-disk condition and since the DRAM memory does not need to be continuously refreshed, the power consumption may drop to about 4 mA. 
     In a preferred embodiment, the predetermined period of time is about 24 hours. If the vehicle is restarted within 24 hours, the current state of memory will still be in DRAM and a much faster boot-up of the system can be achieved (a boot-up time of about one to two seconds as opposed to a boot-up time of from 6 to 10 seconds from the suspend-to-disk condition). If the ignition switch is turned on while in Standby state  45 , a transition is made to Standby+ state  43  or Full Power state  44  depending upon the position of the power button. 
     In the Full Power state  44 , all units are on and fully awake. If the power button is turned off while in Full Power state  44 , a transition is made to Standby+ state  43 . If the ignition switch is turned off while in Full Power state  44 , then a transition is made to Standby state  45 . 
     The main microprocessor and chip set may have many different suspend or low power states. In the preferred embodiment of the present invention, the suspend-to-RAM and suspend-to-disk power states are preferred to be used. In the suspend-to-RAM (S 3 ) power state, an instant on and boot-up time of between 1 and 2 seconds is achieved. During this power state, the DRAM is in a self refresh mode. In the preferred embodiment using an Intel Celleron processor and a Bannister Bridge chip set, the chip set is configured so that about 80% of the chip set is turned off. Specifically, the north bridge SUSPEND well is powered, the DRAM lines are set for self refresh mode, and the south bridge interrupt controller and power controller have power (i.e., RTC well and SUSPEND well) while the Pentium processor is off. The suspend-to-RAM state draws between 50 and 70 mA of current and the state may be exited by pressing the power button while the ignition is on, by a reset signal from the VIOP, or by other programmed resume events. 
     In the suspend-to-disk (D 3 ) power state, an image or snapshot of the DRAM memory contents is stored to disk (preferably a compact flash drive). The north bridge of the chip set is powered down and the south bridge is mostly powered down except for the south bridge section that has power control (i.e., south bridge SUSPEND well and RTC well). Current draw is between 1 and 2 mA in this power state. Current draw results in part from the need to drive the SUS A, B, and C lines for giving the power state status of the main controller and chip set.