I have read this document:
AN658 - LCD Fundamentals and the LCD Driver Module of 8-Bit PIC® Microcontrollers

I understand that the main concern is to maintain 0 Vdc bias on every pixel when driving LCD display.

But I do not understand why there are multiple bias voltages required to drive backplanes (= common nodes).

Why are required such crazy unintuitive waveforms? enter image description here

Why I can't use just static biasing?
For example when I want to make 1 pixel on:
1st frame would be BP0=1 (common), SEG0=0, the 2nd frame would be BP0=0 (common), SEG0=1. This would make 0 Vdc bias and the pixel would have the maximal contrast.

  • 1
    \$\begingroup\$ A specific difference charge voltage is necessary for a specific LCD video level. Erase charge sequence reduces memory effects. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 May 22 '17 at 8:15
  • \$\begingroup\$ @TonyStewart.EEsince'75 could you be more explanatory? I don't understand your comment. If specific voltage is required, then why not to use that specific single voltage level (static biasing), instead of 3, 4, or 5 different levels? \$\endgroup\$ – Chupacabras May 22 '17 at 20:13
  • 1
    \$\begingroup\$ charge storage in LCD is critically dependent on voltage levels for white and black levels as well as other effects such as polarized viewing angle. Until you understand this, I cannot explain. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 May 23 '17 at 17:54

Voltage at particular segment is a difference between voltage on two electrodes, lets call them row and column. There are 4 (four!!) cases:

  • Active segment in active row: |Vactivecol - Vactiverow| = Vmax.
  • Nonactive segment in active row |Vactiverow - Vnotcol| = 1/3 Vmax.
  • Nonactive segment in nonactive row while this segment column electrode is active |Vactivecol - Vnotrov| = 1/3 Vmax.
  • Nonactive segment in nonactive row |Vnotcol - Vnotrow| = 1/3 Vmax.
| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.