Value inc carriage (exc tax):
DC Dimmer Switches: With so much information available on line, it is difficult to separate fact from fiction. With DC Dimmer Switches at least, we can dispell a few myths and confirm a few facts at the same time.
MYTH1: True DC dimmer switches regulate the output voltage regardless of input fluctuations.
FACT: Just like AC dimmers, DC dimmers reduce the input value by a particular value and input supply variations will result in similar changes to the output voltage A unit which regulates the output voltage is called a DC-DC Converter and is more complex and therefore expensive. DC-DC Converters can be used as dimmer switches but as the electronics involved are far more complex, it's like using a sledge hammer to crack a walnut.
MYTH2: Varying the operating frequency increases unit efficiency.
FACT: Switch-mode based dimmer efficiency is limited by the switching characteristics of the main mosfet. Switched on quickly and cleanly, a mosfet will dissapate heat based upon its RDS value (resistance between input and output of Mosfet) and altering the operating frequency won't alter the efficiency of a well designed dimmer utilising mosfet technology.
MYTH3: Switch mode dimmers are inherently noisy and may cause RFI.
FACT: This is some truth in the above however any noise is easily supressed and with an operating frequency of a few hundred hertz, DC dimmers are not generating significant levels of noise to begin with, unlike switch-mode power supplies which operate at much higher frequencies between 20KHZ and 200KHZ.
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