Display device and its driving method

A method for driving a display device that displays image information, wherein the display device comprises a display panel comprising:

• a plurality of optical elements, each having a pair of electrodes including a first electrode, which is connected to a constant voltage source, and a second electrode, wherein each of the plurality of optical elements performs an optical operation according to current passing between the first and second electrodes thereof;
• a plurality of current lines;
• a plurality of power lines, each of which is adapted to be charged with a first voltage during a selection time such that the power line does not allow a current to flow therethrough to an optical element, and to be charged with a second voltage during a non-selection time such that the power line allows a current to flow therethrough to an optical element;
• a switch circuit that passes a write current with a predetermined current value through one of the current lines during the selection time and stops passing the write current during the non-selection time;
• a current storage circuit which:
• (i) is connected to one of the power lines and to the second electrode of the optical element, (ii) stores current data according to the current value of the write current passing through the current line during the selection time, and (iii) supplies the drive current having the current value, which is obtained by subtracting a predetermined offset current from the current value of the stored write current, to the optical element during the non-selection time;
• and
• a data driver that supplies a current having a current value obtained by adding a current value of the offset current to a current value of the drive current, wherein the current value of the drive current is set so as to accord to display data, and
• wherein each said current storage circuit comprises:
• a drive control transistor including a control terminal, and a current path having a first end connected to said one of the power lines and a second end connected to the second electrode of the optical element;
• a first capacitor device formed between the control terminal of the drive control transistor and one of the first and second ends of the current path of the drive control transistor;
• a write control transistor including a control terminal, and a current path having a first end connected to the control terminal of the drive control transistor and a second end connected to said one of the power lines;
• and
• a second capacitor device formed between the control terminal of the write control transistor and one of the first and second ends of the current path of the write control transistor;
• wherein the switch circuit for each of the optical elements comprises a current path control transistor including a current path having a first end connected to said one of the power lines and a second end connected to the current storage circuit for the display element, wherein the current path is made electrically conductive during the selection time, and the current path is made electrically non-conductive during the non-selection time;
• said method comprising:
• a current storing step for a display element executed in the selection time for the display element, the current storing step including:
• (i) setting the first voltage across the power line connected to the switch circuit and the current storage circuit for the display element, (ii) activating the write control transistor to supply the write current to the current line from the data driver and to supply the write current through the current line to the current storage circuit, and (iii) storing a charge of the write current to the first and second capacitance elements so that the stored charge serves as the current data, and
• a display step for the display element executed during the non-selection time for the display element, the display step including:
• (i) setting the second voltage across the power line connected to the switch circuit and the current storage circuit for the display element, (ii) deactivating the write control transistor to stop the supply of the write current to the current storage circuit, (iii) setting the offset current to a value determined by the change of electric potential of the control terminal of the drive control transistor caused in accordance with a difference between respective capacities of the first and second capacitance elements, and (iv) supplying the drive current with the current value, which is obtained by subtracting the value of the offset current from the stored current value of write current.