Electrical transmission or interconnection systems – Miscellaneous systems
Reexamination Certificate
1998-11-17
2002-10-01
Toatley, Gregory (Department: 2838)
Electrical transmission or interconnection systems
Miscellaneous systems
C340S315000, C307S13200T
Reexamination Certificate
active
06459175
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a universal, “plug and play” power supply. More particularly, the invention relates to a universal power supply that is able to deliver automatically the varied power requirements of multiple diverse devices attached to it and simultaneously and independently adjust the voltage or current or both supplied to each device.
BACKGROUND OF THE INVENTION
Power supplies are traditionally device-specific, in that the output voltage of the power converter, whether it be an AC/DC or DC/DC adapter, must be voltage-matched to the host device it was designed to power.
Devices which use an external (or internal) power converter are often designed to operate both with batteries and/or a power adapter. The adapter may be only a substitute for the internal batteries, for example, tape recorders, personal audio or video equipment, hand-held video game machines, etc. This is often the case when the batteries are non-rechargeable, so that the power supply is providing an alternate means of primary power. This enables the user to elect to operate the powered device some of the time with the power adapter, for example a PDA (Personal Digital Assistant) which normally operates on non-rechargeable pencells when being transported, but which also has an optional power adapter for use when the handheld computer is being used in the office or home.
In this case of a power supply which is acting as a battery surrogate, the power adapter is matched to the voltage of the removable batteries. Since there are so many combinations of cells which can be put together to create a battery pack, as well as slightly different voltages from the various types of battery cell chemistries, the operating voltage of any electronic device can vary significantly within the same type of electronic device, whether made by the same or a different manufacturer.
Consumers have some sense of the power supply incompatibility issues, and many know that you cannot plug a 16-volt power adapter from your laptop into a 7.2-volt cell phone. The manufacturers of such devices reinforce that thinking by intentionally installing a proprietary connector on the power supply, so that their power adapter will only mate with their electronic equipment. This provides some measure of safety, in that it helps prevent an incompatible, voltage-mismatched power supply from damaging electronic equipment.
This dedicated power supply model creates a series of problems. As the manufacturer builds more and more variants of its electronic products, each new voltage-specific power supply generates a new corresponding SKU (the Sales Kit Unit is an inventory number, typically a barcode). For example, Business Week (Nov. 4, 1996) reported that Toshiba, the world's leader in laptop computer sales, had released 15 new models of their mobile computers. Over time, the mere process of inventorying and warehousing a large number of power adapters becomes a labor and time-intensive activity. For a consumer electronics manufacturer who may release a dozen or more new products each year, the problem can become significant enough that a separate division, often known as “spares” or “accessories,” becomes necessary.
The federal government requires that manufacturers make replacement parts, such as power supplies, available for seven years. In other countries, the mandated time during which accessory items like power supplies must be kept in inventory is as long as 20 years. The logistical problems, as well as the huge cost to be compliant, has a significant effect on manufacturers' profitability.
Consumers, being dependent on the manufacturer to sell them a replacement or second power supply, are subject to product unavailability, power supplies which are back ordered, and the general inconvenience and loss of time to get an order processed and shipped.
All power supplies tend to look strikingly similar to each other. This is especially true in mobile computing, where a handful of power converter manufactures supply virtually all of the laptop manufacturers. To minimize costs, the same plastic housings are used for power supplies which have significantly different voltages, i.e., they all look alike, but are not interchangeable. This can be very frustrating to a corporate MIS (Management Information Systems) manager, who may be responsible for several thousand laptops throughout the company. It is not atypical that the MIS manager is responsible for purchasing, inventorying and distributing significant numbers of diverse-voltage power supplies. Keeping the proper number of the correct power supply, which corresponds to its matched laptop, requires time and effort. Maintaining a sufficient inventory of each brand and model of power adapter leads to high costs. Lost time, i.e., productivity, becomes an issue if the manufacturer does not have a particular power supply in stock.
While, as noted, manufacturers attempt to ensure that their device-specific power supply will only fit the equipment for which it was intended by using a slightly different connector, there are only so many connector designs available. For example, there are several dozen combinations of outer-barrel-diameter, and center-pin-diameter barrel connectors available. Generically known as a “5 mm” barrel connector, it is used extensively as a powerline interface throughout the consumer electronics and mobile computing industries. Once one manufacturer has used all the non-interchangeable combinations, it must find a new connector design, or start reusing the same connector family.
Some manufacturers, in an attempt to find more combinations, switch the polarity of the pin and barrel. The consumer, to whom all of these devices look amazingly alike, can easily find a power supply which looks like the one being replaced, has the correct voltage, and even has the same mechanical connector. Having verified all of the visual information, the consumer may not know that the pin and barrel were configured as reverse polarity for that equipment.
The impact of all of this consumer confusion, and product-mandated complexity by the manufacturers, is expressed in an article titled “Eureka! Laptops That Share Parts,” by Stephen H. Wildstrom. Mr. Wildstrom, in his article in
Business Week
(Jul. 14, 1997, page 14), states that
“Often, I'd like to use an accessory—a spare battery or an AC adapter left behind from a previous model. But these old parts never fit new notebooks because the design has changed.
“This is more than an annoyance for lots of laptop buyers. For companies that have invested many thousands of dollars in docking stations and spare disks—or even the individual buyer who popped for a spare battery and connection to a car's electrical system—the inability to reuse components involves real money. Corporations, which often buy top-of-the-line notebooks for senior executives and entry-level machines for sales or service people in the field, want to minimize the cost of stocking a common pool of spare parts.”
The author then points out why his ideal of totally interchangeable and reusable power-related accessories may be difficult to achieve:
“It can be hard for manufacturers to simplify their customers' lives. The switch from 486 to Pentium processors required major laptop redesigns to deal with increased power and cooling requirements.”
Power supplies, because of these complex issues, particularly that of multiple SKUs, are not products which lend themselves to the normal distribution and sales channels. Numerous SKUs lead to large inventory, warehousing and display requirements, so the power adapter is a poor candidate for ever being a locally available product sold in retail stores. Most retailers simply ignore power supplies as a marketable product class.
This is very unfortunate, because the power supply is definitely a “must have” accessory. A laptop computer is quickly rendered unusable if no power supply is available. Laptop computers do not operate with replaceable primary batteries. Unlike tape recorders, video game playe
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