Patent Application
20070079153
The description herein relates to information handling systems having adapter-powered and battery-powered capabilities.
As the value and use of information continue to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system (“IHS”) generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
Some IHS form factors are designed to be portable (e.g., a “laptop” or notebook IHS, tablet computer, palm computer, wireless device, or media player). These form factors generally include a limited capability to operate exclusively from a battery, and a separate capability to operate from another power source (standard AC wall power, an automobile power outlet, etc.) through a power adapter. Typically, the power adapter can also recharge the battery, with some systems allowing the battery to be recharged while the IHS is drawing power from the power adapter.
A power adapter for an information handling system includes a voltage control section to set an output voltage of the power adapter in a nominal supply voltage range when an output current of the power adapter is below a first current level. A current control section controls the output current of the power adapter when the output current of the power adapter is above the first current level. The current control section allows the output voltage of the power adapter to fall below the nominal supply voltage range.
For purposes of this disclosure, an information handling system (“IHS”) includes any instrumentality or aggregate of instrumentalities operable to compute, classify, process, transmit, receive, retrieve, originate, switch, store, display, manifest, detect, record, reproduce, handle, or utilize any form of information, intelligence, or data for business, scientific, control, or other purposes. For example, an information handling system may be a personal computer, a network storage device, or any other suitable device and may vary in size, shape, performance, functionality, and price. The information handling system may include random access memory (RAM), one or more processing resources such as a central processing unit (CPU) or hardware or software control logic, ROM, and/or other types of nonvolatile memory. Additional components of the information handling system may include one or more disk drives, one or more network ports for communicating with external devices as well as various input and output (I/O) devices, such as a keyboard, a mouse, and a video display. The information handling system may also include one or more buses operable to transmit communications between the various hardware components.
A local area network (LAN) controller 150, alternatively called a network interface controller (NIC), is coupled to the chipset 110 to facilitate connection of the system 100 to other IHSs. Media drive controller 155 is coupled to the chipset 110 so that devices such as media drives 160 can be connected to the chipset 110 and the processor 105. Devices that can be coupled to the media drive controller 155 include CD-ROM drives, DVD drives, hard disk drives, and other fixed or removable media drives. An expansion bus 170, such as a peripheral component interconnect (PCI) bus, PCI express bus, serial advanced technology attachment (SATA) bus or other bus is coupled to the chipset 110 as shown. The expansion bus 170 includes one or more expansion slots (not shown) for receiving expansion cards which provide the IHS 100 with additional functionality.
Not all information handling systems include each of the components shown in
Power adapter 210 converts/conditions power to a range expected by power rail 220. In one embodiment, power adapter 210 receives power from a traditional AC power source 202, via, e.g., a wall outlet. Power adapter 210, when powered from an AC source, can contain common components (not shown) such as a transformer and rectification circuitry. These components supply power to the power adapter output circuitry shown in
The voltage control section 220 can be designed as a constant voltage source 222 with a grounded negative terminal and a positive terminal VP coupled to power cord 240 through a diode 224. The current control section 230 can be designed as a current source 232 coupled to power cord 240 through a current sense/limiter 234.
Operation of power adapter 210, for two different embodiments, is illustrated respectively in
In some embodiments, region I offers sufficient power to simultaneously operate a processor, solid state memory, main disk drive, display, cooling fan, and possibly several other components of the system, but does not offer sufficient power to operate all primary and auxiliary components of the system at once. Thus under periods of larger demand (power needs greater than IAMAX amperes at VT volts), the power adapter drops into operation in regions II and III. Referring to the circuit model in
In regions II and III, current source 232 attempts to deliver a constant current IA=IAMAX to power rail 220 without regard to the rail voltage. A current sense/limiter 234 includes the capability to disconnect current source 232 from power cord 240 (e.g., by tripping a mechanical or solid state circuit breaker), however, should the rail voltage decrease to a low threshold voltage VL. This low threshold voltage can be selected, for instance, based on the design limitations of the power adapter current source (it may not be able to deliver constant current below some voltage), the desire to safeguard against a ground fault, and the expected range of operation of the battery. For instance, in the stated example where the nominal power adapter voltage range (region I) is 19.5 to 20 V, the battery may be fully charged at 17 V and fully discharged at 6 Volts. Under these conditions, VL might be selected to have a value such as 12 volts, allowing the system to operate in regions II and III as long as the battery is charged to more than 12 volts. Although almost every system involves unique design considerations, many designers will find it desirable to use a minimum voltage in their embodiments, and to set this voltage at least 25% below the nominal supply voltage range to allow assistance from a battery at a range of battery charge levels.
Other embodiments need not select a constant current for current source 232 in regions II and III. For instance,
Those skilled in the art will recognize that other response curves are possible for power adapter 210, including without limitation stepped responses (the current is stair stepped in a desired response curve as rail voltage decreases) and smooth curves that lie somewhere between the examples shown in
Buck converter 430 comprises two power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) switches M1 and M2 and an inductor L, with an inductance in one embodiment of 15 μH. MOSFET switch M1 has a source-to-drain current path that couples a first end of inductor L to power rail 220 when the gate of M1 is energized. The body diode of M1 is connected as shown to resist current flow from the power rail to the inductor when the gate of M1 is de-energized. MOSFET switch M2 has a source-to-drain current path that couples the first end of inductor L to ground when the gate of M2 is energized. The body diode of M2 is connected as shown to resist current flow from the inductor to ground when the gate of M2 is de-energized. The second end of inductor L is connected to battery 420.
Buck converter 430 is operated in two modes, a charging mode and a supply mode. In the charging mode, M1 and M2 are operated alternately, such that the first end of inductor L is alternately connected to VR and to ground. Switching is performed at a relatively high rate compared to the effective time constant of inductor L. Since the inductor resists rapid changes in the current flowing through it, it responds to the switching of M1 and M2 by delivering a fairly level and controllable charging current ICH to battery 420. Charging current ICH depends on the battery voltage VB, the rail voltage VR, and the duty cycle of the buck converter, i.e., the percentage of the switching cycle during which M1, as opposed to M2, is operated. The charging current ICH can be decreased by decreasing the duty cycle, and can be increased by increasing the duty cycle.
In the supply mode, MOSFET switch M1 is continuously energized and MOSFET switch M2 is continuously de-energized. Thus in supply mode, the power rail voltage VR approaches the battery voltage VB, although some resistance to instantaneous power demand changes is observed due to the existence of inductor L.
Buck converter driver circuit 440 is responsible for driving buck converter 430 in both the charging mode and the supply mode. Buck converter driver circuit 440 comprises: a battery charge current sense circuit VCCS that produces a voltage signal representative of the measured charging current supplied to the battery; a charging reference circuit VREF that produces a second voltage signal representative of a desired charging current; a first amplifier comprising an operational amplifier 442, resistors R1 and R2, and a capacitor C; a sawtooth signal generator VST; a second amplifier 444; a buffer 446; an inverter 448; and two FET drivers 450, 452.
The first amplifier is connected to battery charge current sense circuit VCCS and charging reference circuit VREF as follows. Charging reference circuit VREF is connected between ground and the non-inverting input terminal of operational amplifier 442. Battery charge current sense circuit VCCS is connected between ground and one end of resistor R1. The opposite end of resistor R1 connects to the inverting input terminal of operational amplifier 442. Resistor R2 and capacitor C are connected in series between the inverting input terminal and output terminal of operational amplifier 442. In this configuration, the amplifier exhibits a frequency-dependent gain to differences between VREF and VCCS, with a high-frequency gain asymptotically approaching R2/R1, but allows the output voltage VA to contain a DC component based on an integrated response.
Second amplifier 444 receives, at its non-inverting input terminal, the output voltage VA of the first amplifier. The sawtooth signal generator VST is connected between ground and the inverting input terminal of second amplifier 444. No external feedback mechanism is provided for amplifier 444—thus the output voltage VC of amplifier 444 slews as fast as possible to the amplifier's positive rail voltage when VA>VST, and slews as fast as possible to the amplifier's negative rail voltage when VA<VST. The second amplifier output voltage VC ties to the inputs of buffer 446 and inverter 448, which respectively provide input signals to FET drivers 450 and 452. FET drivers 450 and 452 respectively provide gate drive signals to power MOSFET switches M1 and M2 of buck converter 430. Accordingly, when VA>VST, power MOSFET switch M1 is driven, and when VA<VST, power MOSFET switch M2 is driven.
In a battery charging circuit such as circuit 410, it is often desirable to allow several different levels of battery charging current. For instance, different charge profiles may be preferable depending on the degree of battery depletion, the battery type or capacity, the amount of overhead current available for charging, etc. The design shown in
In many embodiments, the power adapter will be housed in a separate unit that can be unplugged from the information handling system for portable usage of the IHS. In this situation the buck converter can be used to provide continued battery power to the system, or an alternate power path can be provided. The battery may be integrated into the IHS, removable, attached externally, or a combination of multiple batteries. It is left to the designer as to the power rating of the power adapter, although it is suggested that power adapter size, weight, and/or cost improvements can be realized in many embodiments by sizing the power adapter for less than the peak load that may be required by the information handling system. It is not necessary in all systems that the power adapter be capable of charging the battery, or that the batteries even be conventionally rechargeable. For instance, a fuel cell-type battery could provide the supplemental system current in voltage/current regions II and III, but would not be recharged in region I.
While the power adapter 205 charges the battery pack 215, the switch 410 is closed so that the batteries 405 are capable of receiving the charge currents. While charging the battery pack 215, the switch 415 is also closed so that the battery pack 215 is capable of supplying supplemental power to reduce voltage falls as discussed above (in connection with
Those skilled in the art will recognize that a variety of circuit designs are available to implement a power adapter that responds like a voltage source in one operating region and responds like a current source in another operating region. Such designs need not take the form shown in
Although illustrative embodiments have been shown and described, a wide range of other modification, change and substitution is contemplated in the foregoing disclosure. Also, in some instances, some features of the embodiments may be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be constructed broadly and in manner consistent with the scope of the embodiments disclosed herein.
