Drive method of EL display panel
View Patent ↗A switching transistor is controlled to turn on or off depending on a turn-on voltage or a turn-off voltage applied to a gate signal line. A driver transistor is supplied with an image signal applied to a source signal line through a switching transistor. A voltage based on the supplied image signal is retained by a capacitor. The driver transistor supplies a light-emitting current to an EL element based on the voltage retained in the capacitor. A capacitor is formed between one terminal of the capacitor (that is, a gate terminal of the driver transistor) and a gate signal line. The capacitor causes the gate terminal voltage of the driver transistor to be varied depending on variation of the potential on the gate signal line.
1. An EL display apparatus comprising:
a display area in which pixels are arranged in a matrix, each of the pixels having an EL element;
source signal lines which transfer an image signal to the pixels;
gate signal lines;
a source driver circuit; and
a selection circuit;
wherein each of the pixels has:
a driver transistor which supplies an electric current to the EL element;
a first switching transistor which supplies the image signal applied to the source signal lines to the driver transistor;
a first capacitor connected to a gate terminal of the driver transistor, the first capacitor retaining a voltage which defines the electric current passing through the driver transistor; and
a second capacitor having a first terminal and a second terminal, said first terminal being connected to said gate signal line and said second terminal being connected to said gate terminal of the driver transistor,
wherein a gate terminal of the first switching transistor is connected to one of the gate signal lines, and
capacity of the second capacitor changes a potential on the gate terminal of the driver transistor depending on variation of a voltage applied to the one of the gate signal lines,
a change of said potential on the gate terminal of the driver transistor acts such that said driver transistor reduces said electric current supplied to said EL element,
said source driver outputs a signal from a signal output terminal,
said selection circuit has a plurality of groups, each one of said groups including one input terminal and a plurality of selection output terminals that can be connected with said one input terminal,
each one of said input terminals is connected with said signal output terminal of said source driver circuit, and each one of said selection output terminals is connected with each one of said source signal lines, and
said selection circuit selects one or more selection output terminals from said a plurality of selection output terminals and impresses said signal of said source driver circuit impressed to said input terminal of said selection circuit to said source signal line connected with said selected selection output terminal.
2. The EL display apparatus according to claim 1 , further comprising a gate driver circuit which drives the gate signal lines,
wherein the gate driver circuit applies a voltage which causes the first switching transistor to turn on or off to the gate signal lines,
a first terminal of the second capacitor is connected to one of the gate signal lines connected to the gate terminal of the first switching transistor, and
a second terminal of the second capacitor is connected to the gate terminal of the driver transistor or one terminal of the first capacitor.
3. The EL display apparatus according to claim 1 , further comprising a second switching transistor which causes a short-circuit between the gate terminal of the driver transistor and another terminal of the driver transistor,
wherein the second switching transistor has a multi-gate structure including dual gates or more.
4. The EL display apparatus according to claim 1 , wherein a capacity of the second capacitor is smaller than a capacity of the first capacitor.
5. The EL display apparatus according to claim 1 , wherein channel polarity of the driver transistor is the same as that of the first switching transistor.
6. The EL display apparatus according to claim 1 , further comprising a third switching transistor in the pixel between the driver transistor and the EL element.
7. The EL display apparatus according to claim 1 , further comprising a fourth switching transistor in the pixel,
wherein a first terminal of the fourth switching transistor is connected to the gate terminal of the driver transistor,
a second terminal of the fourth switching transistor is connected to an electrode or wire to which a predetermined voltage is applied, and
by operating the fourth switching transistor, the predetermined voltage is applied to the gate terminal of the driver transistor.
8. The EL display apparatus according to claim 1 , wherein an encapsulation film is formed on an upper layer of an EL film constituting the EL element.
9. The EL display apparatus according to claim 1 , further comprising a gate driver circuit which selects the gate signal lines,
wherein a control signal to the gate driver circuit is supplied from a source driver circuit.
10. The EL display apparatus according to claim 1 , wherein at least a pixel having a first color and a pixel having a second color are arranged in a matrix in a display screen, and
a capacity of the second capacitor for the pixel having the first color is different from a capacity of the second capacitor for the pixel having the second color.
11. The EL display apparatus according to claim 1 , wherein a film constituting the semiconductor for the transistors is formed in a laser anneal process in which striped laser shots are sequentially moved in parallel to a direction in which the source signal lines are formed.