An intelligent power supply system for a portable computer

Abstract: A power supply control system for a portable computer comprising two rechargeable batteries and an AC adapter. When the computer is operated on batteries, the power supply controls which of the batteries is in a sufficient state of charge, and if one of the batteries is low, it is automatically recharged when the AC supply is selected.

Description: The present invention is directed to a portable computer, and, particularly, to a portable computer operable on an internal battery. More particularly, the present invention relates to a system and a method of providing concentrated management of the power supply of the portable computer. Various types of portable computers operable on an internal battery have recently been developed. This type of computer needs to always recognise the power status of a driving power and the statuses of individual units of the computer in both cases where an AC adapter is used and where an internal battery is used. It is also necessary to avoid various problems which may be caused by power failure or a low state of charge of the internal battery (hereinafter called low battery status) when power is supplied from the battery. The present applicant has proposed one example of such a portable computer which is disclosed in prior application no. 90306840.1, published under EP-A-0 404 588 at 27.12.1990. In brief, according to the prior proposal, the battery power supply is constituted of a single main battery detachable from the body of the portable computer and a dedicated power controller CPU (PC-CPU) is used to control the charging of the main battery with the power supplied from an AC adapter. According to the principles of the prior application, however, the PC-CPU controls a single battery power supply. When a liquid crystal display with a back light (EL-LCD), a plasma display (PDP) or the like is driven on power from the AC adapter, it is always necessary to supply power to the battery via the AC adapter as a consequence of the power dissipation of the display. In addition, a large-capacity battery needs to be installed in the body of the computer. This significantly increase the overall weight of the battery driving over a long period of time. EP-A-0273322 also discloses a power supply for a computer system including a rechargeable battery, an AC adapter and means for safely shutting down the computer to avoid data loss or damage caused by the battery running low during operation. However this system does not allow the operation of the computer to continue under battery power, in such a condition. The present invention therefore seeks to provide a computer having a battery power supply constituted of at least two main batteries detachable from the body of a computer, only one of which is used at a time, while the computer is driven on battery power. The present invention also seeks to provide a system in which the battery which is in use can be kept installed in the computer body while a spare battery is prepared for use, so as to ensure continuous battery driving for a long period of time. The present invention further seeks to provide a system which detects low battery status at the time an AC adaptor is used and inform a user that continuous operation on the battery power is not possible by means of an alarm. In accordance with the present invention, the foregoing objects among others, are achieved by providing a power supply system for a portable computer as claimed in claim 1 and a method for controlling the power supply for a portable computer as claimed in claim 13. Futher advantageous embodiments are detailed in the subclaims. Other objects, features and advantages of the present invention will become apparent from the following detailed description by way of example only with reference to the accompanying drawings, in which: Figure 1 is a schematic block diagram illustrating a power supply system with a power control CPU for use in a computer system, according to one embodiment of this invention; Figure 2 is a diagram illustrating the power control CPU shown in Figure 1; Figures 3a and 3b are flowcharts illustrating sequences concerning the battery check at the power-on time, which are performed by the power control CPU. Referring to Figure 1, a main CPU 11, which is realised by, for example, a 32-bit CPU chip, performs the general control of the system. In an Initial Reliability Test (IRT) process at power-on time, the main CPU 11 accesses a power control CPU (PC-CPU), which will be described later, to read out information of a power supply status and to determine whether or not the power level is normal. Internal buses 12 and 13 are connected to the CPU 11; the bus 12 is an internal data bus having a 16-bit width and the bus 13 is in an internal address bus having a 24-bit width. A maths compressor 14 is optionally provided which can be selectively connected via a connector to the internal data bus 12. A system bus 15 includes a 16-bit wide data bus 15D, a 20-bit wide lower address bus 15L and a 7-bit wide upper address bus 15U. A bus driver (BUS-DRV) 16 serves as an interface to connect the internal buses 12 and 13 to the system bus 15. A bus controller (BUS-CNT) 17 controls the system bus 15. A memory controller (MEM-CNT) 18 controls address transfer between the address bus 13 and the address buses 15U and 15L, and controls the read/write operation of a main memory (I-RAM) 19. That is, the main memory 19 is accessed by an address control executed by the memory controller 18. A ROM-BIOS 20 stores a basic input/output program (BIOS). When power for the system is switched on the IRT is executed. An I/O decoder (I/O-DEC) 21 decodes an I/O address on the system bus 15 and gives the decoded address to an associated I/O chip. An I/O controller (I/O-CNT) 22 performs the input/output control of I/O data. A super integration IC (SI) 23 includes various I/O controllers, such as a floppy disk interface, hard disk interface, a DMA controller and an interrupt controller. A frequency oscillator (VFO) 24 generates a sync clock for a floppy disk drive (FDD). A floppy disk drive interface (FDD-I/F) 25 is provided, and also a hard disk drive interface (HDD-I/F) 26 with an interface register for selectively setting an HDD motor OFF command (MSC) in the initialization routine shown in Fig. 3A. A keyboard controller (KBC) 27 processes key-in data entered from a keyboard 43 and/or a numeric pad or tenkey 44. A keyboard scan controller (SCC) 28 scans key-in data from the keyboard 43 and tenkey 44. A backup RAM (B-RAM) 29 is used as a memory at the time a resume function or the like is executed. An extended memory card (EXTM) 30 is arbitrarily connected to extended memory connectors C1, C2 and C3. A time module (RTC: Real-Time Clock) 31 has a built-in, exclusive drive battery and a built-in memory (CMOS-RAM) which is backed up by the battery. The CMOS-RAM stores set-up data set on a set-up screen or the like. An I/O port (PRT/FDD-IF) 32 is for connection of an I/O device, such as an external floppy disk drive (FDD) or a printer (PRT). A serial I/O interface (SIO) 33 is connected with an RS- 232C interface unit or the like. A power supply (IPS) 34 having a built-in power control CPU (PC-CPU) 306 constituted of a microprocessor, controls the supply of power to the computer. In this embodiment, two main batteries (BT-L341, BT-R342) are detachably coupled and are controlled by the PC-CPU 306. Information regarding the power status in the IPS 34 is sent via the I/O-CNT 22 to the CPU 11. Fig. 2 illustrates the internal structure of the IPS 34. Figs. 3A and 3B illustrate a sequence of battery checking processes conducted by the PC-CPU 306 provided in the IPS 34. A display controller (DISP-CNT) 35 control a so-called flat panel display, such as a plasma display (PDP), a liquid crystal display (LCD), or a color panel (color LCD), and a CRT display. An extension connector 36 is provided for connection of various extension modules, such as an extension display controller (display subsystem). A floppy disk drive 41 is incorporated in the computer and is connected to the FDD-I/F 25. An HDD 42, which is also incorporated in the computer, is connected to the HDD-I/F 26. The keyboard unit (KB) 43 and tenkey pad 44 are connected to the SCC 28. The display controller 35 is connected with an LCD 45 with a back light, a PDP 46 or a CRT 47. The internal structure of the IPS 34 will be described below referring to Fig. 2. A power switch 301, a reset switch 302, a display switch 303 and an extension unit switch 304 each have one end grounded and the other end connected to an parallel I/O 305. These switches are used to set the system ready for operation. The parallel I/O 305 holds the statuses of the individual switches 301 to 304 and set information of the PC-CPU 306, which will be described later. The PS-CPU 306 is a power control microprocessor, which receives information of individual sections of the power supply circuit and instruction information from the main CPU 11 through an internal bus 307. The PC-CPU 306 controls power supply to the individual sections of the computer based on the instruction from the CPU 11, the internal status, the external operation status, etc. In this embodiment, the PC-CPU 306 has a battery checking function as illustrated in Fig. 3. A buzzer (BZ) 308 is driven through the parallel I/O 305 and an I/O driver 309 under the control of the PC-CPU 306. In a case where the computer system is driven on battery power, when the battery serving as a driving power supply is in a low charge state and a standby battery which is not in use, is also in a low charge state or is disconnected the buzzer intermittently generates an alarm sound. The I/O driver 309 controls a power-ON status and operation speed indicating LED, a low battery status indicating LED, an AC adapter connection indicating LED and the buzzer 308 under the control of the PC-CPU 306. An I/O register 310 is used for data transfer between the PC-CPU 306 and a battery control circuit 311 to be described later. The battery control circuit 311, which is connected via the I/O register 301 and internal bus 307 to the PC-CPU 306, selectively controls the battery in use and charging battery. A current detector 312 detects the total current in the IPS 34 including charge currents of the BT-L341 and BT-R342. A current detector 314 detects a current flowing through the circuits in the IPS 34 (excluding the backup current). A DC-DC converter 315 generates power for driving the individual sections of the computer from the AC adapter power or main battery power coming through the current detector 314. An A/D converter 316 performs analog/digital conversion in order to supply the detected current values of the current detectors 312 and 314, the output voltages of the main batteries, the output voltage of the DC-DC converter 315, etc. as digital data to the PC-CPU 306. An I/O register 317, connected to the I/O-CNT 22, is used for information transfer between the PC-CPU 306 and the main CPU 11. Referring to the aforementioned diagrams, the battery checking operation executed by the PC-CPU 306 will be described below. The battery checking routine is illustrated in Figs. 3A and 3B. The PC-CPU 306 of the IPS 34 always monitors the operational status of the power switch 301. In other words, the PC-CPU 306 executes a power-OFF routine when the computer system is in a power-OFF status, and executes the battery checking routine as shown in Fig. 3A when the computer system is in a power-ON status. In the battery checking process, first it is determined whether or not the computer system is driven on the power from the AC adapter (step S1). When the computer system is driven on AC adapter power, the flow advances from step S1 to a charging process (steps S21-S29) shown in Fig. 3B. When the computer system is driven on the power from the battery, on the other hand, it is determined from which battery (BT-L341 or BT- R342) the power is supplied, from the content of the battery-backed-up internal memory 111 of PC- CPU 306 shown figs 1 and 2. If the battery BT-L341 is supplying the power, the status of the connection of this battery and its charge level are determined (steps S2-S5). If the battery BT-R342 is supplying the power, on the other hand, the status of the connection of this battery and its charge level are determined (steps S13-S15). In other words, it is determined whether or not the power-supplying battery is connected to the computer system from the latched status of the battery unit in the battery receiving section of the computer system. It is also determined whether or not the power-supplying battery is in a low charge condition. When the power-supplying battery is not judged to be in the low charge condition, the power from the power-supplying battery is supplied through the I/O register 310 and battery control circuit 311 (steps S9 and S19). When the PC-CPU 306 detects a low charge level, it switches the power-supply connection to the other battery and determines the charge level of the switched battery. It is determined that the new battery is not in a low charge state, the power of this battery is supplied (steps S6, S7 and S10; and S16, S17 and S20). When it is determined through the latch state discrimination process (steps S4 and S14) that the latch on the power supplying battery side is open, it is then determined whether the auxiliary battery is installed in the computer system and then whether it is in a low battery status. The steps of determining whether the auxiliary battery is installed in the computer are represented as steps S4a, S6a, S6a, S14a, and S16a of the battery checking process shown in Fig. 3a. If the auxiliary battery is usable, this battery is used as a power supplying battery and its power is output as driving power (Steps S8 and S10; and S18 and S20). When the latch of the power supplying battery is determined to be open in steps S4, and S14 and the auxiliary battery is not installed in the computer system or is in a low charge condition, it is then decided that continuous operation on battery power is not possible. When the PC-CPU 306 make this decision, it controls the buzzer 308 through the parallel I/O 305 and I/O driver 309 to generate an audible alarm signal to inform an operator that continuous operation on the battery power is not possible (steps S8, S18 and S11). If it is discriminated in the aforementioned step S1 that power is coming from the AC adapter, the PC-CPU 306 determines from the content of the internal memory which battery should be charged, and charges the battery until it is fully charged, as shown in Fig. 3(b). When the battery becomes fully charged, the other battery is charged to the full state. When the latter battery becomes fully charged, the charging process is terminated (steps S21-S29). If both batteries are fully charged, the charging operation will not be executed. With the arrangement of the present invention, the PC-CPU 306 performs battery control of two main batteries (BT-L and BT-R). That is, when the PC-CPU 306 recognizes the charge condition of each battery and detects that power is not supplied from the AC adapter and battery switching is not possible, the PC-CPU 306 informs the operator of this event by means of an alarm. Accordingly, the operator can positively determine whether continuous operation on the battery power is possible. The use of two main batteries (BT-L and BT-R) permits alternate use of sufficiently charged batteries. When the computer system is driven on power from the AC adapter, it is possible to succesively charge the batteries one at a time Further, providing a spare battery allows for continuous battery driving for a long period of time, and can divide the charge current, thus ensuring a compact and small-capacity AC adapter. The PC-CPU 306 can control the driving of that battery which is presently supplying power to the computer system, and at the same time, can control charging of the other, auxiliary battery when the auxiliary battery is not fully charged. Immediately upon detection of an abnormal status while monitoring the status of the battery connection and the charging status of the batteries, the PC-CPU 306 informs this abnormal status by an alarm.

Claims: A power supply system for a portable computer, the computer having a central processing unit (CPU) (11), and being operable in response to power supplied from either a rechargeable battery or an alternating current (AC) adapter, further comprising: a power control microprocessor (306) for controlling power supply independent of the CPU (11) and a battery control circuit means (311), connected to the AC adapter and the battery for supplying power from the AC adapter or the battery based on a control signal from the power control microprocessor (306); the system being characterized in that it comprises at least two rechargeable batteries (341, 342) and that the power control microprocessor (306) has means for generating the control signal based on battery select information for controlling the power supply; and the battery control circuit means (311), is connected to the AC adapter and each of the at least two batteries (341, 342) for supplying power from the AC adapter or one of the batteries (341, 342) based on the control signal from the power control microprocessor (306) and includes means for determining whether the AC adapter or one of the batteries (341, 342) is being used as the power-supply; means for detecting the charge levels of the batteries (341, 342); and means (306) for selecting that battery which is judged as sufficiently charged, as the battery for supplying power. A power supply system according to claim 1 in which the said batteries are detachable. A power supply system according to claim 1 or claim 2 characterised in that the portable computer comprises an internal bus (307) for connecting the CPU (11) to the power control microprocessor (306) to transfer the battery select information, and an I/O register (310) provided between the power control microprocessor (306) and the battery control circuit means (311) and used for data transfer therebetween. A power supply system according to any preceding claim characterised in that the power control microprocessor (306) has means for receiving the battery select information from the CPU (11) via the internal bus (307) and supplying the control signal to the battery control circuit means (311) via the I/O register (310). A power supply system according to any preceding claim, characterised in that the select means comprises: first means for directly selecting a first battery if it is not found to be in a low charge condition by the detecting means; and second means for alternatively selecting the second battery which is not found to be in a low charge condition by the detecting means when the detecting means determines that the first battery (341, 342) is in a low charge condition. A power supply system according to any preceding claim characterised in that the detecting means includes: at least one current detector (312, 314) for measuring values of currents from the batteries (341, 342); and A/D converter means (316) for performing analog-to-digital conversion of a current value detected by the current detector (312, 314) and supplying a digital output value to the judging means. A power supply system according to any preceding claim, characterised in that the portable computer further comprises means for charging the batteries while the computer is operated on power from the AC adapter when the AC adapter is selected as the power supply. A power supply system according to any preceding claim characterised in that the portable computer has means for charging the battery which is not sufficiently charged while the other battery serves as a power supply. A power supply system according to any preceding claim characterised in that the portable computer has an additional built in spare battery in addition to the batteries (341, 342), for supplying driving power to the computer for a specific period of time even when the batteries (341, 342) are detached from the computer. A power supply system for a portable computer according to any preceding claim, further characterised by: means for generating an alarm in response to the control signal output from the power control microprocessor (306). A power supply system according to any preceding claim, characterised in that the determining means includes first means for detecting whether the AC adapter is connected, second means for determining the charge condition of one of the batteries (341, 342), and third means for determining the charge condition of the other battery. A power supply system according to any preceding claim, further characterised by battery housing means including latch means, co-operating with each battery, and connected to the battery control circuit means (311) whereby the battery select information includes signals indicating the presence or absence of each battery. A method for controlling a power supply for a portable computer, the computer having a CPU (11), and being operable in response to power supplied from either a rechargeable battery or an alternating current (AC) adapter, the method comprising: a first step of determining whether or not the power is being supplied from the AC adapter when the computer is switched on; a second step of selecting a first one of at least two batteries (341, 342) as a power supply battery when it is judged in the first step that no power is supplied from the AC adapter; a third step of determining the state of charge of the first battery; a fourth step of switching to the second battery when it is determined in the third step that the first battery is insufficiently charged; and a fifth step of determining charge level of the second battery. A method according to claim 13, characterised in that the second step includes: a sixth step of selecting the first battery based on battery select information from the CPU (11); a seventh step of judging whether or not the first battery is connected to the computer; and an eighth step of generating an alarm when it is judged in the seventh step that the first battery is not connected to the computer. A method according to claim 13, characterised in that the third and fifth steps include: a ninth step of determining whether or not the battery is in a low battery status; and a tenth step of generating an alarm when it is determined in the ninth step that the battery is in a low battery status. A method according to claim 13, characterised by further comprising: an eleventh step of charging the battery which is insufficiently charged when it is judged in the first step that power is supplied from the AC adapter; and a twelfth step of determining whether or not the battery is charged up to a predetermined voltage.

Inventors: ISHIDA YASUHIRO, SHIMAMOTO HAJIME, ISHIDA, YASUHIRO, SHIMAMOTO, HAJIME, ISHIDA, YASUHIRO, C/O INTELL. PROPERTY DIV., SHIMAMOTO, HAJIME, C/O INTELL. PROPERTY DIV.
Applicants: TOSHIBA KK, KABUSHIKI KAISHA TOSHIBA
Application year: 1990
Main classification: G06F1
IPC codes: G06F1, H02J7, H02J9