Nearly every electrical device in your house plugs into your outlets, receiving the same 120 volt current, and yet every device has different power needs. Your mp3 player and clock radio draw only a trickle of electricity, while your computer and refrigerator gobble it up. The DC converter is the device that allows all of these different circuits to be powered by the same source.
Function
Electricity comes in different configurations, and each configuration has different purposes. The electricity that comes in to your house is at 120 Volts AC, or alternating current. Alternating current switches from negative to positive about 60 times every second, whereas direct current always flows in the same direction. Because most converters need to use AC to work, and because AC travels better over long distances than DC or direct current, it makes sense for the energy coming into your house to be AC. Most appliances, however, require DC current to work properly. Each appliance that one has a DC converter built in to its power supply.
Types
There are two types of devices which can be called DC converters: AC-DC converters and DC-DC converters. An AC-DC converters takes the alternating current coming in to your house and converts it into DC current. There are many different ways in which this can be accomplished, but all of them involve only letting the electricity flow one way. When the electricity in the AC live wire is in the positive part of its cycle, it is shunted down the positive DC wire. When it is negative, it is sent down the negative DC wire. Therefore, the power is always flowing in the same direction.
There are several different types of DC converters. The simplest, called linear regulators, are used to flatten out and regulate the DC current. They turn any bumps in the electrical output into waste heat energy, which is released into the air. Other DC converters, called Switched mode converters, rapidly turn the DC voltage on and off to get a voltage which, on average, is the value desired.
Benefits
Electrical components waste some of the energy they use, turning it into heat. The more energy a component uses, the more it wastes. All this waste heat not only ups the energy bill, but also damages delicate electrical components such as transistors and capacitors. For this and other reasons, designers are always trying to come up with smaller and more efficient components for computers and other high-performance uses. DC-DC converters allow circuit designers to supply the circuit with just as much power as it needs. This allows designers to produce the most efficient circuit possible.
Size
The size of a converter whether AC or DC depends on how much electricity it has to handle and how much it has to do. The converters on power cables, for example, are several feet tall. They have to turn electric power at thousands of volts to 120 volts for household use, and so they need big, heavy-duty parts. Similarly, the AC-DC converter in a computer is about the size of a brick, while the AC-DC converter used for a guitar pedal is small enough to fit on a wall-plug. The computer power supply has to provide a lot more energy, and has to regulate that energy a lot more carefully, since computers are more sensitive than guitar pedals. A DC-DC converter which simply regulates and decreases the power can be small enough to fit on a circuit board in some circumstances.
Warning
Don't mess with power supplies if you don't know what you are doing. The power supply in your computer produces more than enough amperage to kill you several times over, so treat it with respect. Never work on an electronic circuit while it is plugged in, and never use two hands to work on it at the same time. If you use two hands, you can get a shock that goes from one hand to the other, shocking your heart in the process and potentially sending you into cardiac arrest. Also keep in mind that capacitors can store a charge for a week after a circuit has been turned off and unplugged. Just because a circuit is turned off and unplugged does not necessarily mean it is safe.
Tags: your house, power supply, AC-DC converter, AC-DC converters, alternating current