DC to DC converter
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In electrical engineering, a DC to DC converter is a circuit which converts DC power from one voltage to a another. It is a special class of power converter.
DC to DC converters are important in mobile devices such as cellular phones and laptop computers, which are supplied with power from batteries. Often space limitations in a device do not allow multiple batteries to supply different parts of the device.
One simple method of DC to DC conversion is a circuit known as a voltage divider. This technique involves inserting a resistor in series with the voltage supply to lower the voltage. However, this method suffers serious drawbacks:
- Provides poor voltage regulation
- Requires knowledge of the resistance of the load
- Extremely poor efficiency, which also leads to excess heat
- Impossible to generate voltages higher than the supply voltage
- Impossible to generate negative voltages
Any kind of voltage regulator solves the first two problems. However, linear regulators still have the remaining three problems.
Recently, specialized devices have become available which convert from one DC voltage to another. These devices, a kind of switched-mode converter, generally perform the conversion by the following steps:
- Convert DC to AC, for example an oscillator or chopper.
- Change voltage at AC, using a transformer or inductor or diode voltage multiplier.
- Convert back to DC, using a rectifier (and usually provide voltage regulation).
In general, the term "DC to DC converter" almost always refers to one of these switching converters.
Switching DC to DC converters are available in a wide variety of input and output voltages. Commonly used converters include 3 V to 5 V, 12 V to 5 V, and +10 V to −10 V. As of 2004, efficiency upwards of 85% is not uncommon.
DC to DC converters used to be somewhat large for use in devices such as cell phones; however, with the advent of hybrid circuits, they are now available as single package, even surface mount, devices.