The present invention relates to battery backup systems and, more particularly, to battery backups for electrical appliances using wall transformers.
Many companies use keep track of employee time through the use of time clocks that punch time cards. Other time clocks read barcodes or magnetic strips and send the data read to a central computer. With either type of system, employees are unable to clock in or out when a power outage occurs. Although computer servers have battery backups, companies do not typically purchase AC inverters or expensive battery backup options for time clocks or other equipment powered from wall transformers.
A wall transformer is an enclosure that plugs directly into an AC power wall socket, and outputs either a low DC voltage or a low AC voltage, and outputs either a low DC voltage or a low AC voltage. The normal range of the voltages is 5 to 28 volts. The output voltage is communicated to the time clock or other electrical appliance through a wire cable.
Power outages occur for a number of reasons, including a failure at the power company or in the lines between the power company and the consumer. Power outages are a more-than-occasional inconvenience during periods of an energy crisis. A power failure at a business is a particular problem, resulting in substantial loss of operational efficiency, or even complete shutdowns. For many businesses, the expense of large traditional power backup systems is such that they are cost prohibitive. Rather than having to supply a custom backup system for every electrical appliance, a common, interchangeable backup system is preferably for many types of devices.
Uninterruptible power supply (xe2x80x9cUPSxe2x80x9d) systems are used to supply back-up power for computers and other electronic devices. Such systems supply a secondary source of high AC voltage. UPS""s have the disadvantage of being prohibitively expensive for many businesses. Other external backup systems use batteries that have DC-AC inverters to supply a secondary source of high AC voltage. Such systems plug directly into an AC outlet and have standard wall-type AC outlets of their own. In order to change which devices are using the backup, a series of disconnections and reconnections is necessary.
Accordingly, there exists a need to devise a common external backup system that mitigates the above mentioned drawbacks. Further, there exists a need to provide a system that could readily adopt to existing devices using a wall transformer, which could be moved from device to device as needed to properly shutdown or complete any necessary data transfer or operation.
A battery backup system is provided for power wall transformer when a power supply failure occurs. The system includes a detachable backup battery that may interface with the device to be powered without disconnecting the device from connection to an AC power supply. As such, the backup battery may be relocated as need to power different devices connected to an AC power supply.
In one embodiment the invention comprises an adaptor disposed intermediate the AC power supply and the device to be powered. The adaptor is plug connectable to an AC source, the device to be powered, and a backup battery. In normal operation the backup battery is charged by the AC source, which also operates the electrical device. During power interruption, the backup battery powers the device and is isolated from the power supply. In this embodiment the backup battery may be supported by the adaptor, and removed from the adaptor to the location of another adaptor, which does not have a backup battery connected thereto. By such means a limited number of backup batteries may be used to provide power to various electrical devices, on a priority basis.
In another embodiment the backup battery is plug connectable to a wall transformer that normally powers an electrical device by direct connection to an AC source. In this embodiment the backup battery is again relocatable to another source without a need to disconnect the wall transformer from its normal connection. Ths avoids interruptions in operation of a first electrical device, while the backup battery is relocated to power another device.
The invention is suitable for use to power AC or DC or DC devices, by means of conventional converter circuitry. Switching circuitry may also be provided to allow the system to adapt to either AC or DC operation.