1. Field of the Invention
The present invention relates to the identification of a power supply to a computing system.
2. Background of the Related Art
Computer power supplies are typically disposed in a chassis along with most of the computer components, such as the processors, memory and input/output devices, such as a graphics card. The power supply is typically responsible for converting an alternating current (AC) voltage into well-regulated direct current (DC) voltages and currents that are needed for the operation of a computer.
Power supplies also provide a signal called the Power Good signal, which is sometimes referred to as Power_OK or Power_Good. The purpose of the Power Good signal is to tell the computer that all is well with the power supply and that the computer can continue to operate normally. If the Power Good signal is not present, the computer shuts down. In this manner, the Power-Good signal prevents the computer from attempting to operate on improper voltages and damaging itself.
The Power Good signal is a +5 volt (V) signal generated in the power supply when it has passed its internal self-tests and the outputs have stabilized. This normally takes between 0.1 and 0.5 seconds (100-500 milliseconds) after you turn on the power supply switch. The Power Good signal is then sent to the computer's motherboard, where the signal is received by a control/decode module, which may be included in or part of a processor timer chip that controls the reset line to the processor. In the absence of the Power Good signal, the timer chip continuously resets the processor, which prevents the computer from running under bad or unstable power conditions. When the timer chip receives the Power Good signal, it stops resetting the processor. If the power supply cannot maintain proper outputs, such as when a brownout occurs, the Power Good signal is withdrawn, and the processor is automatically reset. When proper output is restored, the Power Good signal is regenerated, and the computer again begins operation. By withdrawing the Power Good signal, the computer never receives the bad power because it is stopped quickly (reset) rather than allowed to operate on unstable or improper power levels, which can cause parity errors and other problems.
Power supplies may be coupled to a computer in various ways, but power supplies typically have a connector with a well-defined pin out for coupling directly to the motherboard. The number of conductors in a power supply connector may vary from one power supply to another, although there are several connector pin outs that are widely used. These pin outs often include components that are color-coded to help assure that an appropriate power supply is being coupled to the computer and that the connector is oriented correctly. For example, the color black may indicate a conductor pin for electrical grounding, orange may indicate a +3.3 V DC pin, red may indicate a +5 V DC pin, yellow indicates a +12 V DC pin and so forth. In a common power supply connector, the color grey may indicate a conductor pin that is reserved for the Power Good signal.