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Regulated vs Unregulated Power Supply


An "unregulated" power supply is typically a simple DC power supply, which typically contains a step down (or Up) transformer, some rectifier diodes and possibly a filter capacitor. An unregulated DC power supply provides only approximate output, and the output is "unregulated" and the input voltage and the load will typically cause the output to change, so the output does not remain constant. Unregulated power supply output is specified by their output voltage at the rated load, but the output can be almost twice as much when there is no load. For example, a 12VDC /1A DC power supply will give you 12V when connected to a load drawing 1A, but may give you 17V when loaded at 0.5A, or 9V when overloaded at 1.5A. Wall Plug-in (plug directly into the wall) power adapters are typical examples of the unregulated DC power supplies. 

There are two basic types of regulated DC power supplies based upon how the regulation is accomplished: linear regulated DC power supplies and switching regulated DC power supplies (also known as switch mode power supplies or SMPS). A linear power supply uses a big transformer to drop voltage from AC line to much lower AC voltage, and then uses a series of rectifier circuitry and filtering process to produce a very clean DC voltage.  That low DC voltage is then regulated into the desired voltage level by dropping the difference in voltage across transistor or IC (the shunt regulator). Linear supplies tend to have little noise and ripple.

A Switching DC power supply (also known as switch mode power supply) regulates the output voltage through a process called pulse width modulation (PWM). The PWM process generates some high frequency noise, but enables the switching power supplies to be built with very high power efficiency and small form factor. With a good design, a switching power supply can have excellent load and line regulation. 


Both designs provide an output that remains very close to its specification; usually within 1% or better over a wide range of load changes and line changes (here the line refers to the input AC line).


All of the DC power supplies under Mastech or Volteq brand are regulated DC power supplies. We do not make any unregulated power supplies.





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