The Fundamentals Of Personal Computer Power Systems


Direct current (DC) power is fundamental to the operation of any electronic device. Personal computers, which contain a host of different electronic components, require varying voltages of DC power in order to operate properly. CPU’s, CMOS chips, RAM, hard drives, and cooling fans are all jostling for a steady amount of carefully regulated voltage, all of which is provided by a computer’s power supply. The role that a computer’s power supply plays is critical – if the voltage isn’t precise and current isn’t clean, or if there’s just not enough juice to go around, problems can occur. A computer with a bad power supply can experience everything from random shutdowns and inconsistent performance to severe damage.

What’s more, many of the components in a computer have different voltage requirements. The main processor, for example, could require 3.3VDC while hard drives and cooling fans typically require 12VDC. In order to provide power at all of these different levels, a computer will have multiple DC-DC voltage converters.

How Power is Organized Inside A Personal Computer

Most computers have DC-DC converters at each circuit block on a motherboard. These DC-DC converters are responsible for delivering clean, precisely regulated power within manufacturer specs. Typically found in mono blocks of 2 to 10 watts, these converters feature output voltages ranging from 3.3V all the way up to 24V, depending on what each component requires. There are a number of different industry standards that are adhered to in the production of these converters, with most offering basic features such as ‘power OK’ and ‘power interrupt’ pins in order to protect computer parts from incorrect voltage.

A PC’s main power supply is tasked with providing clean DC power to each circuit block converter, and of course the main power supply obtains power from a standard 120VAC outlet. Typically, a PC power supply consists of a 120 VAC to 170 VDC converter. This high level of power is then itself managed by a central DC-DC converter that provides as many a six output voltages for the computer’s main DC voltage buses, which in turn distribute it throughout the machine primarily using ribbon cable networks.

As with any electrical system involving delicate equipment, localized DC-DC converters are employed as voltage regulators in order to fight the degradation of the electric current due to the resistance of the wires themselves, as well as the temporary drop in voltage associated with multiple components making simultaneous demands on a given electrical bus. These local DC-DC converters also help ensure that unusual voltage requirements from specific components can be more easily met.

Heat Management Is Critical

Computers generate significant heat during their operation, and this heat can have a negative effect on the reliable operation of the DC-DC converters that are used inside. Given that the electrical current used to power the machine is itself a major contributing factor to heat buildup within a computer case, it’s necessary to make use of a system of fans, cooling fins, and other measures designed to extract heat and improve circulation inside a PC.

Since the central DC-DC converter is the biggest heat source in the entire machine, it is outfitted with the largest integrated fan. Another heat management tactic that is becoming more commonplace – building more efficient circuitry that uses less power and radiates less heat. The reason? Many consumers are opting to purchase laptop or netbook PCs instead of traditional desktops, and because these laptop and netbook PCs operate on a battery pack, efficiency is hugely important. As a result in this shift in the market, more computer manufacturers and component suppliers are focusing their effort on energy-efficient circuitry.

As the computer industry moves forward and smaller, battery-powered computers become more common, it’s likely that the demand for efficient circuitry will only increase. This is good news all computer users, as that means lower electric bills and a smaller environmental footprint.

Author Ernest Herz works for SEC America, a manufacturer of precision DC to DC voltage converters for a variety of manufacturing and industrial needs.

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