Liquid crystal display device
A LCD device, in which a multi-grayscale level state is produced in a liquid crystal layer by applying a different voltage thereto, includes a liquid crystal display panel having the liquid crystal layer between first and second electrodes, an electrode drive circuit applying drive voltage pulses generated from multi-voltage power sources to the first and the second electrodes, and a multi-voltage power generator circuit. The LCD device further includes a multi-voltage power switch circuit supplying the first or the second multi-voltage power sources from the first or the second multi-voltage power units to the electrode drive circuit, and a control circuit, in a first drive step, setting the first multi-voltage power unit to an active state, and, in a second drive step, setting the second multi-voltage power unit to the active state.
1. A liquid crystal display device, in which a multi-grayscale level state is produced in a liquid crystal layer by applying a different voltage thereto, comprising:
a liquid crystal display panel having the liquid crystal layer between first and second electrodes;
an electrode drive circuit, being supplied with multi-voltage power sources, and applying drive voltage pulses generated from the multi-voltage power sources to the first and the second electrodes; and
a multi-voltage power generator circuit supplying the multi-voltage power sources to the electrode drive circuit,
wherein the multi-voltage power generator circuit includes a first multi-voltage power unit generating first multi-voltage power sources with first stability and having a first consumption current, and a second multi-voltage power unit generating second multi-voltage power sources with second stability higher than the first stability, and having a second consumption current higher than the first consumption current, and
the liquid crystal display device further comprising:
a multi-voltage power switch circuit supplying the first or the second multi-voltage power sources from the first or the second multi-voltage power units to the electrode drive circuit; and
a control circuit, in a first drive step, setting the first multi-voltage power unit to an active state and switching the multi-voltage power switch circuit to a supplying state of the first multi-voltage power sources, and, in a second drive step, setting the second multi-voltage power unit to the active state and switching the multi-voltage power switch circuit to a supplying state of the second multi-voltage power sources, wherein
the first drive step includes a one-time binary drive phase for applying, to the first and the second electrodes, a first drive voltage pulse to set the liquid crystal layer to first and second grayscale levels,
the second drive step includes a plurality of times of multilevel drive phases for applying, to the first and the second electrodes, a second drive voltage pulse to set the liquid crystal layer, having been set to the first grayscale level, to a plurality of third grayscale levels.
2. The liquid crystal display device according to claim 1 ,
wherein the liquid crystal layer includes a cholesteric liquid crystal material,
in the first drive step, the control circuit sets the first multi-voltage power unit to the active state, and sets the second multi-voltage power unit to an inactive state.
3. The liquid crystal display device according to claim 1 ,
wherein, in the non-drive period other than the first and the second drive steps, the control circuit controls the second multi-voltage power unit to be in the inactive state.
4. The liquid crystal display device according to claim 1 ,
wherein the first multi-voltage power unit includes a plurality of Zener diodes connected in series between a first voltage and a second voltage lower than the first voltage, and a plurality of capacitors connected in parallel to the Zener diodes respectively.
5. The liquid crystal display device according to claim 4 ,
wherein the multi-voltage power unit includes a power switch inputting the first voltage, and
the control circuit sets the corresponding multi-voltage power unit to the active state by switching on the power switch, and sets the corresponding multi-voltage power unit to the inactive state by switching off the power switch.
6. The liquid crystal display device according to claim 1 ,
wherein the second multi-voltage power unit includes a plurality of resistors connected in series between a first voltage and a second voltage lower than the first voltage, and a plurality of voltage followers including operational amplifiers each having input of positive polarity connected to connection nodes of the plurality of resistors, and having input of negative polarity connected to output terminal outputting the second multi-voltage power source.
7. The liquid crystal display device according to claim 6 ,
wherein the multi-voltage power unit includes a power switch inputting the first voltage, and
the control circuit sets the corresponding multi-voltage power unit to the active state by switching on the power switch, and sets the corresponding multi-voltage power unit to the inactive state by switching off the power switch.