Abstract: A structure and method for controlling a liquid crystal display takes advantage of the sharp reflectance change over a small voltage change for new liquid crystal display materials, applying ON and OFF pixel voltages very close to the transition voltage of the liquid crystal material and regulating the applied voltage to remain reliably near and on the desired side of this transition voltage. Also, a net zero DC voltage across pixels of the crystal is maintained using a switching mode close to half the frequency of prior art modes. Driving voltages are provided by a switching regulator rather than the prior art voltage divider, resulting in a significant reduction in operating power. The preferred switching regulator generates only three additional voltages for driving rows and columns of the display, in contrast to the five generated voltages of the prior art voltage divider.

Abstract: A back light for a liquid crystal display has a self-contained power source and can be attached to the unit having the liquid crystal display when needed in a dark ambient, and removed from the display or not carried by the user of the display when not needed. This portable back light allows the unit with the liquid crystal display to be smaller and lighter in weight than a unit having a built-in back light, and to require a smaller power supply than a unit with a built-in back light. Additinally batteries supplying power to a liquid crystal display unit will last longer. Yet with this portable back light, the user has the convenience of sufficient brightness for viewing the liquid crystal display unit when needed.