Drive methods and drive devices for active type light emitting display panel

• US 20040090186A1
• Filed: 11/04/2003
• Published: 05/13/2004
• Est. Priority Date: 11/08/2002
• Status: Active Grant

• Current Assignee: Tohoku Pioneer Company Limited (Pioneer Corporation)
• Original Assignee: Tohoku Pioneer Company Limited (Pioneer Corporation)
• Inventors: Kanauchi, Katsuhiro, Yoshida, Takayoshi
• Granted Patent: US 7,193,589 B2
• Time in Patent Office: Days
• US Class Current: 315/169.1
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0852 being a dynamic memory with more than one capacitor
• CPC Class Codes: G09G 2300/0866 by means of changes in the pixel supply voltage
• CPC Class Codes: G09G 2310/0254 Control of polarity reversal in general, other than for liquid crystal displays
• CPC Class Codes: G09G 2310/0256 with the purpose of reversing the voltage across a light emitting or modulating element within a pixel
• CPC Class Codes: G09G 2320/0252 Improving the response speed
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3241 the current through the light-emitting element being set using a data current provided by the data driver, e.g. by using a two-transistor current mirror
• CPC Class Codes: G09G 3/325 the data current flowing through the driving transistor during a setting phase, e.g. by using a switch for connecting the driving transistor to the data driver

Abstract

In a drive device for an active type light emitting display panel which can apply a reverse bias voltage to an EL element, in order to be able to compensate deterioration in light-emitting efficiency of the EL element accompanied by applying of the reverse bias voltage and the like, one pixel 10 is composed of a controlling TFT (Tr1), the driving TFT (Tr2), a capacitor C1, and the EL element E1. Switching switches SW1, SW2 mutually enables a supplying state of a forward current to the EL element E1 and an applying state of the reverse bias voltage to be selected. In one control form according to the present invention, when the applying state of the reverse bias voltage shifts to the supplying state of the forward current, by switching one switch first, the anode and cathode of the EL element E1 are made to the same electrical potential to allow electrical charges to be discharged. Thus, charge of the forward current for a parasitic capacitance of the EL element E1 can be performed rapidly, and rising of the lighting operation of the EL element can be advanced.

Claims

1. A drive method for an active type light emitting display panel provided with a light emitting element, a driving TFT which lighting drives the light emitting element, and a power supply circuit supplying a current of a forward direction to the light emitting element at a lighting operation time of the light emitting element, characterized in that

said drive method for an active type light emitting display panel executes, at a timing at which the light emitting element shifts to a lighting operation, a discharge operation in which electrical charges accumulated in a parasitic capacitance of the light emitting element are discharged by setting the electrical potentials of an anode and a cathode of the light emitting element to a same potential.

2. A drive device for an active type light emitting display panel provided with a light emitting element, a driving TFT which lighting drives the light emitting element, and a power supply circuit supplying a current of a forward direction to the light emitting element at a lighting operation time of the light emitting element, characterized in that

said drive device for an active type light emitting display panel comprises a discharge means operating at a timing at which the light emitting element shifts to a lighting operation and allowing electrical charges accumulated in a parasitic capacitance of the light emitting element to be discharged by setting the electrical potentials of an anode and a cathode of the light emitting element to a same potential.

3. A drive method for an active type light emitting display panel provided with a light emitting element, a driving TFT which lighting drives the light emitting element, and a power supply circuit supplying a current of a forward direction to the light emitting element at a lighting operation time of the light emitting element, characterized in that

said drive method for an active type light emitting display panel executes, at a timing at which the light emitting element shifts to a lighting operation, a switching operation of a select switch which gives the light emitting element a potential difference by which lighting is possible and a charge operation for a parasitic capacitance of the light emitting element via the select switch.

4. A drive device for an active type light emitting display panel provided with a light emitting element, a driving TFT which lighting drives the light emitting element, and a power supply circuit supplying a current of a forward direction to the light emitting element at a lighting operation time of the light emitting element, characterized in that

said drive device for an active type light emitting display panel comprises a charge means operating at a timing at which the light emitting element shifts to a lighting operation and performing charge for a parasitic capacitance of the light emitting element based on a switching function of a select switch which gives the light emitting element a potential difference by which lighting is possible.

5. A drive method for an active type light emitting display panel provided with a light emitting element, a driving TFT which lighting drives the light emitting element, and a power supply circuit supplying a current of a forward direction to the light emitting element at a lighting operation time of the light emitting element, characterized in that

said drive method for an active type light emitting display panel executes, at a timing at which the light emitting element shifts to a lighting operation, a charge operation in which a current from a power supply for charge is allowed to flow in the forward direction for a parasitic capacitance of the light emitting element from a connection point between the light emitting element and the driving TFT.

6. A drive device for an active type light emitting display panel provided with a light emitting element, a driving TFT which lighting drives the light emitting element, and a power supply circuit supplying a current of a forward direction to the light emitting element at a lighting operation time of the light emitting element, characterized in that

said drive device for an active type light emitting display panel comprises a power supply for charge which operates at a timing at which the light emitting element shifts to a lighting operation and which executes a charge operation in the forward direction for a parasitic capacitance of the light emitting element from a connection point between the light emitting element and the driving TFT.

7. A drive method for an active type light emitting display panel provided with a light emitting element, a driving TFT which lighting drives the light emitting element, and a power supply circuit supplying a current of a forward direction to the light emitting element at a lighting operation time of the light emitting element, characterized in that

said drive method for an active type light emitting display panel executes, at a timing at which the light emitting element shifts to a lighting operation, a charge operation in the forward direction for a parasitic capacitance of the light emitting element by a current which is greater than that of the lighting operation time of the light emitting element by controlling a gate voltage of the driving TFT.

8. A drive device for an active type light emitting display panel provided with a light emitting element, a driving TFT which lighting drives the light emitting element, and a power supply circuit supplying a current of a forward direction to the light emitting element at a lighting operation time of the light emitting element, characterized in that

said drive device for an active type light emitting display panel comprises a charge control means which operates at a timing at which the light emitting element shifts to a lighting operation and which performs a charge operation in the forward direction for a parasitic capacitance of the light emitting element by a current which is greater than that of the lighting operation time of the light emitting element by controlling a gate voltage of the driving TFT.

9. A drive method for an active type light emitting display panel provided with a light emitting element, a driving TFT which lighting drives the light emitting element, and a power supply circuit supplying a current of a forward direction to the light emitting element at a lighting operation time of the light emitting element, characterized in that

said drive method for an active type light emitting display panel executes, at a timing at which the light emitting element shifts to a lighting operation, a charge operation in the forward direction for a parasitic capacitance of the light emitting element by performing bypass control for the driving TFT which is connected in series to the light emitting element.

10. A drive device for an active-type light emitting display panel provided with a light emitting element, a driving TFT which lighting drives the light emitting element, and a power supply circuit supplying a current of a forward direction to the light emitting element at a lighting operation time of the light emitting element, characterized in that

said drive device for an active type light emitting display panel comprises a bypass control means which operates at a timing at which the light emitting element shifts to a lighting operation and which performs a charge operation in the forward direction for a parasitic capacitance of the light emitting element by bypassing the driving TFT which is connected in series to the light emitting element.

11. The drive device for an active type light emitting display panel according to any one of claims 2, 4, 6, 8, and 10, characterized in that

the power supply circuit is constructed so as to be able to apply a bias voltage opposite to the forward direction to the light emitting element.

12. The drive device for an active type light emitting display panel according to any one of claims 2, 4, 6, 8, and 10, characterized in that

the light emitting element is constituted by an organic EL element in which an organic compound is employed in a light emitting layer.