Why do laptop transformer sizes vary so much?

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    Laptop Transformer
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Discussion Overview

The discussion revolves around the varying sizes of laptop transformers, exploring factors that contribute to these differences, including power output and design considerations. Participants also touch on the function of a specific component in the power supply cable related to electromagnetic interference.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants suggest that the size variation in laptop power supplies is primarily due to differences in current capabilities, with larger transformers needed for higher amperage outputs.
  • Others note that while most laptop power supplies are switchmode types, there can still be significant size differences due to design and manufacturing choices.
  • A participant mentions a specific example of a Toshiba transformer being much larger and heavier than an ASUS transformer, raising questions about the consistency of size relative to age and model.
  • There is a discussion about the importance of voltage and current ratings in determining transformer size, with some participants emphasizing that current demand is a key factor.
  • One participant explains the function of the ferrite core in the power supply cable, stating it filters high-frequency noise and prevents the cable from acting as an antenna.
  • Another participant highlights the ongoing efforts in electronic design to create more compact power supplies, indicating that design skill and heat management are critical factors in transformer size.

Areas of Agreement / Disagreement

Participants express differing views on the extent of size variation among laptop transformers, with some agreeing that current capacity is a primary factor, while others point to design and manufacturing differences as significant contributors. The discussion remains unresolved regarding the reasons for specific size discrepancies among different models.

Contextual Notes

Participants reference the importance of specific voltage and current ratings, but these details are not fully explored in the discussion. There is also mention of potential overheating issues related to design choices, indicating limitations in the reliability of smaller transformers.

Charles123
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Why laptops transformer size varies so much?
Also, the little cylinder right next to the cable connector to the laptop is there to avoid that the laptop works as an antenna? How does that work?
Thank you
Regards
 
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Hi Charles

Most laptop PSU's these days are switchmode type. There isn't too much variation in physical size. any variation in size is mainly related to the variation in current capabilities of the supply. a 5A or so supply is going to need a physically larger transformer than one that only requires 3 or 4 Amps.

That little cylinder is an encapsulated ferrite core that the DC supply cable passes through before getting to the laptop.
It has 2 purposes ...
1) to filter any hi frequency generated by the SMPS from getting into the electronics of the laptop and causing instability problems
2) it also has the reverse filtering effect. the microprocessor circuitry etc of the laptop produces lots of RF at many frequencies. That ferrite core filters much of that out so that the DC power cable doesn't act like an antenna and radiate those signals

Dave
 
Thank you for your answer. But actually, and just as an example my Toshiba Qosmio x770, has a transformer twice as big and tree times heavier that my ASUS… none of them is more than 2 years old.
 
What wattage does each output? How big are the laptops?
 
russ_watters said:
What wattage does each output? How big are the laptops?

yeah that was going to be my next question

what is the voltage and current ratings of the large one compared to the small one ?

I still stand by what I stated its all to do with the current the unit needs to supply that determines its overall size


D
 
I understood your explanation, I was just comenting the diference in sized because you wrote - "There isn't too much variation in physical size.".
Thank you again
Regards
 
@ OP:

each is labelled with its output volts and amps. Look carefully at the small print on nametag.

If you read electronic design magazines there is a continual push to pack more power into smaller volume
so your observation is right - there is a LOT of variation even among swichers.it comes down to the skill of the design and manufacturing teams, can they find small parts and can they arrange to get rid of the waste heat
there have been plenty of overheating failures from "design oops'es", believe me.
 

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