Patent ID: 6175350
Filing Date: 2001-01-16
Classification: G02F,G09G

Abstract:
A drive circuit for a ferroelectric shutter, in which a control voltage having a first value is input when said shutter is to be kept in a substantially transparent state, and a control voltage having a second different value is input when said shutter is to be kept in a substantially opaque state, said drive circuit being provided with a pulse generator providing shutter drive voltage pulses, said pulse generator being operable to maintain charge balance if said control voltage changes part-way through a shutter drive voltage pulse, wherein said pulse generator includes a counter adapted and arranged to provide a shutter drive voltage pulse having a first polarity during the time taken for said counter to count between two predetermined points in either an upwards or downwards direction when said control voltage changes from said first value to said second value, and to provide a shutter drive voltage pulse having the opposite polarity during the time taken for said counter to count in the opposite direction from the position in the count reached when said control voltage changes from said second value to said first value, thereby maintaining charge balance if said control voltage changes part-way through a shutter drive voltage pulse.