Power Supplies

Written by Kevin Tavolaro
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Power supplies are most broadly defined as items that provide electrical power to a device or a collection of devices. Individual power supplies are referred to as "units," and a single power supply unit is known as a PSU. The term "power supply unit" is largely used to describe units that are physically connected to the device that they provide power to. For instance, home computers, calculators, televisions, home appliances, and stereos are all fed by a power supply unit. Devices that provide power to or are powered by an electric utility grid, however, do not fit into the category of power supplies.

Power supplies can range from the lightweight and compact, such as disposable batteries, to the massive and sprawling, such as the electrical grid systems that provide electricity to households and neighborhoods.

The Importance of a Quality Power Supply

Efficiency and reliability are possibly the two largest concerns when it comes to evaluating a power supply. When electricity is transmitted from the power source to the destination, the ensuing process of reactions and regulation always results in the loss of some energy. This is known as "dissipation," and the value of a power supply is often directly related to how little dissipation of energy occurs with its usage.

When dealing with electrical power, heat must also be taken into consideration. The electricity transmitted through a device creates a byproduct of heat, which can have potentially detrimental effects if not properly regulated. Overheating occurs when excessive heat is generated by the power supply, causing the device's circuitry to malfunction or shut down. Most power supplies are equipped to manage the amount of heat produced by the degree of energy that they require. This heat can be dealt with in several ways, most notably through a heat sink. A heat sink is a small metal structure that is mounted directly to the circuitry that the device supplies energy to. The shape of a heat sink allows it to absorb heat through the metal of the circuit board, then disperse it to a cooler area that it is also touching. This helps to prevent heat from building up rapidly.

Prime Components of Power Supplies

There are numerous varieties of power supply units, but most are graded and categorized by similar criteria. The most common delineations among assorted power supplies include the amount of power that they can issue, the size of the device or devices that they can support, the length of time before the PSU can provide the power without being recharged, and the reliability of their output. More advanced concerns might include how they provide power (is the power supplied continuously, or in electric pulses), and the stability of their output (voltage or current) when saddled with different sized loads.

Power supplies must be chosen based on the environment they will be installed in, as well as the overall use of the applications they will power. For example, some power supplies provide consistent, stable power, but are extremely sensitive to heat, due to fragile components. Other power supplies may feature an easily accessible open-top interface, but cannot be installed in certain scenarios where the components might be damaged. Another may provide high voltages, but afford little control over the manual regulation of the flow. The key to choosing the correct power supply device is to fully understand the environment that it will be installed in, the volume of work done by the device that it will power, and the distance over which that power must travel to reach the device.

Learing about AC/DC Currents

The majority of power supplies run on either an alternating current (AC), or a direct current (DC). AC transmissions are capable of moving in any direction within a system, which makes them more adaptable to a variety of uses. However, the same properties that allow AC to adapt, also promote dissipation, which is detrimental to the overall integrity of the system. Dissipation occurs when a current loses energy as it travels through a system. The result is a decrease in the reliability and the strength of the power supply. Although there is no way to halt dissipation completely, there are steps that can be taken to insure a high level of energy efficiency.

DC power supplies are capable of providing stronger, more consistent power, but are hindered by the requirements of many modern devices. Because DC is unidirectional, it is limited in terms of compatibility with many power supplies. While AC is highly adaptable, but not always strong enough, DC has the strength without the adaptability.

As a result of this discrepancy, power supply components have been developed to maximize the advantages of both types of currents, while limiting their weaknesses. Power transformers, capacitors, and high voltage power supplies have been developed that regulate the use of AC and DC in tandem, playing to the strengths of each. These devices utilize one type of current for one purpose, then, using a system of electrical coils, transform the current into the other type in order to suit another purpose.

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