Switch Frequency: Understand & Duty in SMPS

[rama1001]

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?

 

[Averagesupernova]

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.

 

[rama1001]

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.

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.

 

[sophiecentaur]

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!

 

[Bob S]

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.

http://www.wbnoble.com/WN_articles/CD-ignition-SK.pdf

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.

http://www.selectric.org/delta/index.html

Bob S