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Switching frequency

  1. Mar 9, 2011 #1
    It is very basic and makes me angry because i did not understand exactly what does switching frequency means and why is the duty if this in SMPS?
    Cany one explaine me clearly?
  2. jcsd
  3. Mar 9, 2011 #2


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    I don't fully understand your question but I will reply. Generally the higher the frequency the physically smaller a transformer can be built. A tranformer operates most efficiently at 50% duty cycle. Of course the SMPS in question may not even use a transformer. Please elaborate.
  4. Mar 9, 2011 #3
    What does switching frequency means and I saw some products which display in their manual like switching frequency is 500kHZ etc..what exactly it specifies. Please I am new this topics.
  5. Mar 9, 2011 #4


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    A mains power supply works at 50Hz (or 60Hz). This involves a great big transformer and many sweaty components. ASMPS produces a high frequency and then can use a small transformer (that's the way it is with magnetic components). In addition, a SMPS can give you stabilisation, also without getting hot. The switching frequency is the frequency that the power supply uses to do its 'transforming' (which may not actually involve a transformer at all) - but that's for a future discussion.

    If you use 500kHz, you won't have problems like power supply hum!!!!
  6. Mar 9, 2011 #5
    Here is a very old unregulated (1960's) dc to dc converter (switching mode power supply) circuit using two 2N3055 transistors to generate about 300 volts from a 6 volt battery. This circuit uses a standard 60-Hz transformer, and the switching frequency (determined by the resistor and transformer inductance) is several hundred Hz.


    This evolved into the Delta Mark Ten kit about 1968. The Delta kit had a pot core transformer instead of a standard 60-Hz transformer.


    Bob S
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