1. Field of the Invention
The present invention is directed, in general, to power supplies and, more specifically, to a power supply embodying a volume-efficient construction allowing the power supply to fit within the chassis of a portable computer system.
2. Description of Related Art
Portable, battery-powered computers have become increasingly popular over the last several years due to their light weight and small size that permit them to be easily hand-carried in an ordinary briefcase and used by business travelers in cramped spaces, such as on airline seat back trays, lacking electrical plug-in facilities. In fact, a particularly small type of portable computer, the notebook computer, is very popular, generally having dimensions of 8.5".times.11" and a weight of less than 8 pounds. More recent developments in computer miniaturization have resulted in so-called "subnotebook" computers having still smaller dimensions.
The modern portable computer typically incorporates both hard and floppy disk drives, a display screen built into a pivoting display screen portion, and a keyboard built into a main chassis portion. It is thus a fully self-contained computer able to be conventionally used, for at least short periods of time, in situations and locations in which the use of a much larger desktop computer is simply not feasible.
As is well-known, however, even state-of-the-art portable computers have certain limitations and disadvantages, compared to their much larger desktop computer counterparts. One principal disadvantage is that portable computers are battery-powered and thus are subject to the limited life of the battery. Fortunately, however, almost all battery-powered portable computers are sold with an AC adapter. When plugged into a convenient source of AC power, the AC adapter converts the power into a form usable by the portable computer. The AC adapter comprises a line cord that plugs into the AC power source and an adapter cord that plugs into a designated power supply port usually on a backside of the portable computer main chassis. Power conversion is performed in a power supply that exists in the form of a power supply chassis separate from that of the portable computer and coupled between the line cord and adapter cord.
There are historical reasons for the power supply being housed in a separate power supply chassis. Because of notoriously tight volumetric constraints in portable computers main chassis, the components and subsystems therein have for years been the subject of constant, extensive design work directed toward making the components and subsystems as small as possible. Because the main chassis has always been fully occupied with necessary components and subsystems, there was no motivation to attempt to fit in less vital subsystems, such as the power supply. Thus, because prior art power supplies have been entirely external to the portable computer, they were never subjected to the intense miniaturization effort otherwise universally applied.
Accordingly, prior art separate supplies have been comparatively large and over-engineered. Heat-producing components in such supplies are most often cooled by mounting heat sinks to each component. The fins or projections of the heat sinks are bulky and heavy. The power supplies are surrounded by an electromagnetic interference ("EMI") shield to attenuate and guard against stray EMI. Thus, the prior art power supply chassis housing these power supplies and their associated shields have been correspondingly large, heavy and cumbersome, earning them the unflattering colloquial term "brick." The bulky and clumsy "brick" stood in stark contrast to the otherwise elegant and compact design of prior art portable computers.
Again, due to the tight volumetric requirements of components in the portable computer, it has not as yet been feasible to relocate the brick to within the portable computer main chassis. The power supply must undergo the same miniaturization effort through which the rest of the portable computer has already undergone. However, miniaturization of a power supply is not trivial. It not only entails an electrical redesign effort to minimize the size of the electronic components thereof, but also requires a fundamental rethinking of related mechanical, electromagnetic and thermal issues.
First, a volumetrically efficient means of mechanically attaching the power supply chassis within the portable computer chassis must be developed. Second, the power supply must be electromagnetically shielded from other components and subsystems in the portable computer, again, in a space-saving manner. Finally, and perhaps most critically, new techniques for removing heat from selected power supply components must be developed, as it is no longer acceptable to consume space with the individual finned heat sinks so often resorted to in the prior art.
Accordingly, what is needed in the art is a volume-efficient construction for a portable computer power supply that allows the power supply to fit within the confines of a portable computer system.