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A regulated power supply is an embedded circuit; it converts unregulated AC (alternating current) into a constant DC. With the help of a rectifier it converts AC supply into DC. Its function is to supply a stable voltage (or less often current), to a circuit or device that must be operated within certain power supply limits.
For a 75% efficient power supply to produce 75 W of DC output it would require 100 W of AC input and dissipate the remaining 25 W in heat. Higher-quality power supplies can be over 80% efficient; as a result, energy-efficient PSUs waste less energy in heat and require less airflow to cool, resulting in quieter operation.
The 7805 is the most common, as its regulated 5-volt supply provides a convenient power source for most TTL components. Less common are lower-power versions such as the LM78Mxx series (500 mA) and LM78Lxx series (100 mA) from National Semiconductor.
The line regulation for an unregulated power supply is usually very high for a majority of operations, but this can be improved by using a voltage regulator. A low line regulation is always preferred. In practice, a well regulated power supply should have a line regulation of at most 0.1%. [1]
In a typical power supply/charger supplied with a laptop computer, average I CA is set at around 1.5 mA, including a 0.5 mA LED current and a 1 mA shunt current (2012 data). [ 7 ] Design of a robust, efficient and stable SMPS with TL431 is a common but complex task. [ 34 ]
An external power supply, AC adapter or power brick, is a power supply located in the load's AC power cord that plugs into a wall outlet; a wall wart is an external supply integrated with the outlet plug itself. These are popular in consumer electronics because of their safety; the hazardous 120 or 240 volt main current is transformed down to a ...
In contrast, a linear power supply regulates the output voltage by continually dissipating power in the pass transistor. The switched-mode power supply's higher electrical efficiency is an important advantage. Switched-mode power supplies can also be substantially smaller and lighter than a linear supply because the transformer can be much smaller.
The power supply is designed to only supply a maximum amount of current that is within the safe operating capability of the shunt regulating device. If the stabilizer must provide more power, the shunt output is only used to provide the standard voltage reference for the electronic device, known as the voltage stabilizer.