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Application Notes

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  Ultracompact LCD Backlight Inverters &mdash AN81
  PDF, 365 Kb, File published: Sep 1, 1999
  It has become desirable to fashion laptop computers with large area screens, leaving little room for the display's backlight inverter electronics. Miniaturization limitations of high voltage magnetic transformers impose limits on achievable space reduction. Another voltage step-up technology, piezoelectric transformers, permits the desired size reduction and provides additional benefits. This publication describes practical piezoceramic transformers and support circuitry. Ancillary benefits of the piezoelectric approach are also described. Appended sections detail transformer operation and feedback loop considerations.
  Extract from the document

  Application Note 81
  September 1999
  Ultracompact LCD Backlight Inverters
  A Svelte Beast Cuts High Voltage Down to Size
  Jim Williams, Linear Technology Corporation
  Jim Phillips, Gary Vaughn, CTS Wireless Components
  INTRODUCTION
  The liquid crystal display (LCD) has become ubiquitous. It
  is in use everywhere, from personal computers of all sizes
  to point-of-sale terminals as well as instruments, autos
  and medical apparatus. The LCD utilizes a cold cathode
  fluorescent lamp (CCFL) as a light source to back light the
  display. The CCFL requires a high voltage AC supply 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” has been designed around magnetic transformers. A great deal of effort has been directed
  towards these ends, accompanied by a large volume of
  descriptive material.1 Unfortunately, as available circuit
  board space continues to shrink, magnetic transformer
  based approaches begin to encounter difficulty. In particular, it is highly desirable to fashion laptop computers
  with large area screens, leaving little room for the backlight inverter board. In many cases there is so little space
  available that building the inverter function inside the LCD …

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Manufacturer's Classification

• Power Management > Switching Regulator > SEPIC Regulators
• Power Management > Switching Regulator > Step-Down (Buck) Regulators > Internal Power Switch Buck