* What is Piezoelectric
Transformer? (Or Piezoceramic Transformer)
A piezoelectric transformer is a small simple piece of piezoelectric ceramic
with several electrodes. A Couple (Electrically Excited) mechanical resonance
are exited through a low voltage electrode and high voltage is generated on
an output electrode.
*Introduction:
The liquid crystal display (LCD) has become ubiquitous. It is in use everywhere,
from personal computer of all sizes to point-of-sale terminals as well as instruments,
autos and medical apparatus. The LCD monitor utilizes a cold cathode fluorescent
lamp (CCFL) as light source to back light the display. The CCFL requires a high
voltage AC supplies for operation. Typically, over 1000 volts RMS is required
to initiate lamp operation, with sustaining voltages ranging from 200VAC to
800VAC. To Date, the high voltage section of backlight " Inverters"
had been designed around magnetic transformers.
*Limitations and Problem
of Magnetic CCFL Transformers:
Construction and high voltage breakdown characteristics of magnetic transformer
present barriers to implementing them in these forthcoming space intensive designs.
Additionally, as refined as magnetic technology is, other inverter problems
associated with it also exist. Such problems include the necessity to optimize
and calibrate the inverter for best performance with given display type. Practically,
this means that the manufacturer must, via either hardware or software, adjust
inverter parameters to achieve optimum performance with a given display type.
Changes in display choice must be accompanied by commensurate adjustments in
inverter characteristics. An other problem area is fail-safe protection due
to self-destructive transformer malfunctions. Finally, the magnetic filed provided
by conventional transformers can interfere with operation of adjacent circuitry.
With the exception of size, all of these problems are addressable, although
incurring economic and circuit/system penalties. What is really needed is high
voltage generating capability that is inherently better suited to coming generation
of backlight inverters. Piezoceramic transformers, arcane and little known technology,
has been tamed and made available for CCFL Inverter use.