1. Field of the Invention
This invention relates to an electronic circuit and more particularly to a power interrupt circuit with remote activity detector for controlling power to a load device such as an electronic display.
2. Background of the Relevant Art
It is well known that an input/output device, such as an electronic display, is necessary for operation of programmable devices such as computers. An electronic display serves to depict information processed or stored within the computer. Each time the computer is turned on, the corresponding display must also be turned on in order to read or write information to the computer. The display is usually left on so long as the attached computer remains on. Even though the operator may not be presently using the computer, the display nonetheless remains on.
More recently, various screen saver programs have been devised for transmitting graphic information to the display from the computer. Screen saver programs often require a fully active central processing unit (CPU) in order to produce the graphically intense images presented across the screen. Screen saver programs function to turn off and on various pixels across the screen during times in which the computer is not being accessed. Toggling on and off various pixels thereby prevents one or more pixels from remaining constantly on. A pixel which remains on over a long period of time may cause permanent damage to the backing material (e.g., phosphor) associated with the screen. An image displayed over a long period of time may be permanently cast into the backing material causing what is often referred to as "screen memory."
Although screen saver programs help prevent damage to the screen by reducing screen memory, screen saver programs do nothing to alleviate unnecessary power consumption associated with the computer and attached display. In fact, screen saver programs purposefully maintain full performance of the CPU necessary to generate the graphical images. They also require a fully operational display necessary to present the image. The heat dissipation associated with active CPUs and associated displays can be fairly significant. Oftentimes, a business entity may employ numerous computers and associated displays within a work area. The computers and displays remain fully operational even though the employees are not presently using them. A large numbers of computers associated with many businesses remain on for extended periods of time contributing to a significant amount of heat dissipated into the working area.
The problems associated with heat dissipation normally present themselves in terms of the costs associated with cooling the work area. In work areas employing many computers and displays, it is necessary to maintain a fully operational air conditioning system. The system must cool the work area and expel the added heat being dissipated from the active displays even though the displays are not currently needed.
As used herein, "electronic display" represents any electronically controlled terminal or monitor for displaying graphic and/or alphanumeric symbols. Electronic display includes any active or passive display device. Active devices include displays utilizing the various light-emitting processes such as, for example, cathodoluminescence, photoluminescence, electroluminescence, plasma decay and blackbody radiation. Cathodoluminescence includes cathode ray tubes (CRTs), photoluminescence includes colored gas discharge devices and fluorescent lamps, and electroluminescent devices include light-emitting diodes (LEDs). Plasma decay and blackbody radiation techniques are typically used in gas discharge panels and tungsten filament projection devices, respectively. Passive displays include displays controlled by light-absorption or light-reflection processes. Passive displays include electromechanical, electrochromeric, electropolarization and electrophoretic display techniques. The most popular passive display, utilizing electropolarization, includes liquid crystal displays (LCDs).