Switch Frequency: Understand & Duty in SMPS

  • Thread starter Thread starter rama1001
  • Start date Start date
  • Tags Tags
    Frequency
Click For Summary

Discussion Overview

The discussion revolves around the concept of switching frequency and duty cycle in switch-mode power supplies (SMPS). Participants seek to clarify the definitions and implications of these terms, as well as their practical applications and historical context.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant expresses frustration over not understanding switching frequency and its relation to duty cycle in SMPS.
  • Another participant notes that higher switching frequencies allow for smaller transformers and mentions that transformers operate most efficiently at a 50% duty cycle, but acknowledges that not all SMPS use transformers.
  • A participant asks for clarification on what switching frequency means, referencing products that specify a frequency of 500 kHz and indicating their novice status in the topic.
  • Another participant explains that traditional mains power supplies operate at 50Hz or 60Hz, requiring larger transformers, while SMPS can operate at higher frequencies, allowing for smaller components and reduced heat generation.
  • A historical reference is made to an old unregulated DC to DC converter circuit from the 1960s, illustrating the evolution of switching technology and its relation to transformer design.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and knowledge about switching frequency and duty cycle, with no consensus reached on the definitions or implications of these concepts. Some participants provide insights while others seek clarification, indicating an ongoing exploration of the topic.

Contextual Notes

There are limitations in the discussion regarding the assumptions about the operation of SMPS and the specific conditions under which different frequencies and duty cycles apply. The historical context provided may not fully address modern applications.

Who May Find This Useful

This discussion may be useful for individuals new to switch-mode power supplies, those interested in the technical aspects of power supply design, and readers seeking historical perspectives on power conversion technology.

rama1001
Messages
130
Reaction score
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?
 
Engineering news on Phys.org
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.
 
Averagesupernova said:
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.
 
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!
 
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
 

Similar threads

Advice for a choke for blocking parasitic switching spikes
  • · Replies 58 ·
2
Replies
58
Views
9K
Getting a High Speed Synchronous N-Channel MOSFET Driver working right
  • · Replies 39 ·
2
Replies
39
Views
6K
Revolutionizing SMPS Efficiency with Innovative Pulsed Operation Technique
  • · Replies 19 ·
Replies
19
Views
2K
High-frequency transformers - how are they different?
  • · Replies 5 ·
Replies
5
Views
2K
Understanding SMPS Parameters: Burst Duty, Frequency & More
  • · Replies 3 ·
Replies
3
Views
3K
Few smps and/or amplifier questions
  • · Replies 2 ·
Replies
2
Views
2K
Generator size vs frequency question
  • · Replies 8 ·
Replies
8
Views
4K
What's the normal low-load working temperature for an SMPS transformer?
  • · Replies 27 ·
Replies
27
Views
6K
Simple class A amplifier for a different reason
  • · Replies 23 ·
Replies
23
Views
3K
Linear moving switch, decade counter, chaser
  • · Replies 49 ·
2
Replies
49
Views
5K