Types of transformers used in LCD backlights

[KarlH]

How common are piezoelectric transformers in computer LCDs?

 

[davenn]

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

 

[meBigGuy]

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)

 

[davenn]

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)

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 surname

they 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

 

[KarlH]

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

Thanks much

they 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 !

So panels with LED backlights run at the same voltage/amperage as the output from the AC/DC converter?

mite do a couple of pix tomorrow if I get a chance to show the transformers in the CCFL type I work on

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

 

[davenn]

So panels with LED backlights run at the same voltage/amperage as the output from the AC/DC converter?

They have their own sub-PSU off the main PSU for the screen

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

 

[KarlH]

there's just too many variations to do that

Oh, I didn't mean that at all.

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.)

 

[davenn]

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.)

interesting, As far as I'm aware I have never seen a piezo type transformer

 

[KarlH]

Just knowing that there will be magnetic transformers in the enclosure is a good start. Thanks.

 

[thankz]

does anyone have a datasheet for one of these single layer piezo transformers? specifically the SMSTF150P1S7