US 4,707,692 A · Electroluminescent display drive system

Abstract

A resonant mode energy recovery circuit is disclosed for supplying drive pulses to an electroluminescent (EL) display arranged as a matrix of pixels addressed by a plurality of column and row electrodes. An external inductor is used to alternately store and supply energy from the column electrodes of the EL display which has an impedance equivalent to an array of capacitors and resistors. Switching transistors and diodes are used to start and stop the resonant current flow at 1/4 wavelength intervals of the resonant frequency of the resonant tank formed by the external inductor and the array capacitors coupled to the column electrodes in order to form the pulses required to address the columns of the matrix. Switched current sources are used to start and stop nonresonant current flow to form the refresh and write pulses used to form the pulses required to address the rows of the matrix. Together, the pulses applied to the columns and rows of the matrix provide the high voltage necessary to light the EL pixels while minimizing the address time and power required to operate the EL display.

Claims10

Dependent claims

A display drive system for driving a display having a matrix of pixels addressed by a plurality of column and row electrodes, said display drive system comprising:

a column multiplexer having a column drive input signal line and a plurality of column drive output signal lines, said plurality of column drive output signal lines coupled to the plurality of column electrodes;
and
column drive means coupled to the column drive input signal line for forming a resonant tank with the plurality of column electrodes and for driving the pluralilty of column electodes with pulses of current started and stopped at 1/4 wavelength intervals of the resonant period Lambda of the resonant tank, the column drive means having
a first switch and a first diode coupled in parallel with each other,
a second switch and a second diode coupled in parallel with each other, and directly connected in series at a first switch node with the parallel combination of the first switch and the first diode,
a third switch and a third diode coupled in parallel with each other,
a fourth switch and a fourth diode coupled in parallel with each other, and directly connected in series at a second switch node with the parallel combination of the third switch and the third diode, and
an inductor coupled between the first and second switch nodes.

5 more elements

Dependencies are inferred from the claim text.

Electroluminescent display drive system

Life of this patent

Electroluminescent display drive system

Life of this patent

Abstract

Claims10