- #1
KarlH
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How common are piezoelectric transformers in computer LCDs?
Types of transformers used in LCD backlights
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Discussion Overview
The discussion revolves around the types of transformers used in LCD backlights, specifically focusing on the prevalence and application of piezoelectric transformers compared to traditional magnetic transformers in various LCD models, including CCFL and LED backlit displays.
Discussion Character
- Debate/contested
- Technical explanation
- Exploratory
Main Points Raised
- Some participants question the commonality of piezoelectric transformers in computer LCDs, noting that their experiences with dismantled monitors have predominantly involved ferrite cored transformers.
- One participant suggests that piezoelectric transformers may primarily be used in CCFL backlit monitors, although they express uncertainty about their frequency of use in such displays.
- Another participant mentions that LED backlit monitors do not require high voltage power supplies, implying a different transformer requirement.
- There is a discussion about the voltage and amperage requirements for LED backlit panels, with a suggestion that they have their own sub-power supply off the main PSU.
- A participant reflects on past laboratory experiences with electromagnetic interference and raises concerns about potential sources of interference from transformers in LCDs, particularly in relation to testing precision.
- One participant expresses interest in obtaining part numbers or datasheets for specific piezo transformers, indicating a desire for more technical specifications.
Areas of Agreement / Disagreement
Participants do not reach a consensus on the prevalence of piezoelectric transformers in LCDs, with some asserting they have not encountered them, while others suggest they may be relevant in specific contexts like CCFL backlighting. The discussion remains unresolved regarding the frequency and application of different transformer types.
Contextual Notes
Participants note the variability in transformer types across different LCD models, indicating that there may be many variations that complicate generalizations about their use.
Who May Find This Useful
Individuals interested in the technical aspects of LCD design, particularly those focused on transformer applications in display technologies, may find this discussion relevant.
- #2
davenn
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I don't know
None of the dozens of different types of LCD monitors I have dismantled have had piezoelectric transformers
they have all been the typical low profile high voltage low current ferrite cored transformers
None of the dozens of different types of LCD monitors I have dismantled have had piezoelectric transformers
they have all been the typical low profile high voltage low current ferrite cored transformers
- #3
meBigGuy
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davenn -- how many of those were CCFL backlit? I think that's the only type that would use piezo to create the high voltage. (I don't know the answer as to how often they are used in CCFL monitors)
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davenn
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meBigGuy said:
just call me Dave
... I have used davenn as a user name all over the net since the early to mid 1990's the 2 x n's are the first and last letters of my surnamethey were all CCFL, the LED backlit ones ( of which I have stripped dozens) of course don't need HV PSU's ... but what a wonderful source of strips of LEDs !
mite do a couple of pix tomorrow if I get a chance to show the transformers in the CCFL type I work on
Dave
- #5
KarlH
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davenn said:
Thanks much
davenn said:
So panels with LED backlights run at the same voltage/amperage as the output from the AC/DC converter?
davenn said:
I was going to ask if anyone had a part number or two so that I could look up dimensions, but a picture would be even cooler
- #6
davenn
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KarlH said:
They have their own sub-PSU off the main PSU for the screen
KarlH said:I was going to ask if anyone had a part number or two so that I could look up dimensions, but a picture would be even cooler
there's just too many variations to do that
- #7
KarlH
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Oh, I didn't mean that at all.davenn said:
I used to work in a laboratory that did a lot of spindle error motion testing using capacitance gauges. We were worried about errors in the low single digit nanometers (and sometimes low double-digit picometers), so EMI was a concern. Even when the target was buried in a probe nest made of 1-2" thick 414 stainless, we would often see a blip at 60Hz on the FFT.
A while ago I read an article comparing piezo and magnetic transformers in CCFL LCDs, and that made me wonder whether we were missing a source of interference in all of those tests (since it could be at a different frequency). The FFT cutoff was often set to 100Hz, since there hadn't been much beyond that in earlier tests, but if the internal PSU in the display that sat right next to the probe nest ran at a higher frequency, we would have been blind to it. (I'd be pretty embarrassed if that were the case.)
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- #8
davenn
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KarlH said:
interesting, As far as I'm aware I have never seen a piezo type transformer
- #9
KarlH
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Just knowing that there will be magnetic transformers in the enclosure is a good start. Thanks.
- #10
thankz
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does anyone have a datasheet for one of these single layer piezo transformers? specifically the SMSTF150P1S7
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