I've been interested in piezotransformers for some time now. Despite
the fact that they have been around for awhile, not many electronics
people seem to be familiar with them.

Currently, they are used to generate high voltage for ion air
purifiers (ozone), that are supposed to make the air safer to breathe.
Interestingly enough, these products aren't sold by reputable sellers
and they all come in plain boxes with no mention of the point of
origin. So, getting information about how they operate is easier said
than done::

They are also widely used as CCFL power sources, where the
requirements are ~600 VAC at 2 to 6 ma.

They excel at producing high voltage with resistive loads greater than
150 K ohms and up. In fact, they have so much voltage gain when the
load impedance is high, that they must be throttled back in order to
prevent the output voltage from arcing through the ceramic and
shattering them into pieces. Most will produce 2 kilovolts safely
however.

Anyway, I was curious whether anyone else knows about these units
and/or has designed drivers that work in constant voltage mode rather
than constant current (as the TI driver does). The specs for the TI
driver can be found at:

http://focus.ti.com/docs/prod/folder...t/ucc3977.html

The spec sheet has a very nice summary of the piezotransformer
operation in addition to chip specs.

The only US vendor that I know of (with standard products listed
online) is:

http://www.steminc.com/piezo/single_layer_transf.asp

They make multilayer and single layer piezotransformers.

CTS Ceramics claims to make them, but their website has no references
to actual part numbers of standard products.

Texas Instruments makes an evaluation kit, complete with
piezotransformers and driver chip, but it is not advertised on their
website. You have to ask specifically for it. The TI part number for
the evaluation kit (EVM) is UCC3976-77EVM. I have a pdf of the
technical info in the EVM and will send it to anyone who needs it.
I've also posted it in abse.

What say, anyone out there played with them?

Mebart

Currently, they are used to generate high voltage for ion air
purifiers (ozone), that are supposed to make the air safer to breathe.

Well, there's a distinction to be made between "negative ion
generators" and "ozonators". The former tend to operate at
significantly lower voltages, and aren't intended to create ozone (O3)
although they may produce a small amount as a side effect. Their
primary output is negative ions, which some people feel make the air
more pleasant to breathe, and which definitely have the effect of
causing pollutant particles in the air to precipitate out onto filters
and onto every nearby surface.

I used to run a negative-ion generator in a commercial office space
located right under the Los Angeles Airport approach pattern. Lots of
stinky jet-fuel fumes and soot in the air outside. It definitely made
the air in the office more breathable. It also made a horrendous mess
of the walls and ceiling... after a month of operation I could see a
"shadow" on the wall if I moved a calendar or poster, due to all of
the soot and gunk which had precipitated out of the air. I understand
that after I left the company, they had to repaint the office to get
rid of the stained appearance.

Ozone generators are another matter entirely... higher voltage, more
corona effect (or, they use a high-intensity shortwave UV lamp to
create a similar effect by different means). I hate these things...
can't stay in a room with one for more than a couple of minutes before
my eyes start to burn and my lungs to ache. Why anyone would wish to
generate a free-radical-producing government-listed airborne pollutant
in their living space is beyond me!

Those piezeotransformer gadgets sound pretty neat, although I haven't
played with one myself.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
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