Driving circuit for organic thin film EL elements
AssigneeNEC Corporation
InventorsEitaro Nishigaki, Shingo Kawashima
Life of this patent
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Abstract
A pulse generator 1 creates a pulse in synchronization with a driving pulse 26. A charging circuit 2 charges EL elements 20 only for a period which is determined by an output from the pulse generator 1. The charging time is determined by resistance of a switching element 3 in its on condition and a junction capacity of the EL elements 20.
Claims10
A driving circuit for driving a matrix of a plurality of organic thin film electroluminescent elements comprising:
- light-emitting layers made of an organic substance;
- and
- signal electrodes and scanning electrodes at least either of which are transparent, said electrodes holding the light-emitting layers therebetween,
- wherein said driving circuit comprises:
- a current source circuit for supplying a direct current driving current to said organic thin film electroluminescent elements in response to a first pulse signal;
- a pulse generator responsive to receipt of said first pulse signal for outputting a second pulse signal in synchronization with said first pulse signal, a pulse width of said second pulse signal being narrower than a pulse width of said first pulse signal;
- and
- a charging circuit which charges a junction capacitance of said organic thin film electroluminescent elements to a predetermined potential responsive to said second pulse signal to shorten a period in which said junction capacitance is charged,
- wherein a current which is a sum of said driving current and said junction capacitance is supplied to said organic thin film electroluminescent elements to enhance luminance within a period of said first pulse signal.
A driving circuit for driving a matrix of a plurality of organic thin film electroluminescent elements comprising;
- light-emitting layers made of an organic substance;
- and
- signal electrodes and scanning electrodes at least either of which are transparent, said electrodes holding the light-emitting layers therebetween,
- wherein said driving circuit comprises:
- a current source circuit for supplying a direct current driving current to said organic thin film electroluminescent elements in response to a first pulse signal,
- a pulse generator responsive to receipt of said first pulse signal and for outputting a second pulse signal in synchronization with said first pulse signal, a pulse width of said second pulse signal being narrower than a pulse width of said first pulse signal;
- and
- a charging circuit which charges a junction capacitance of said organic thin film electroluminescent elements to a predetermined potential responsive to said second pulse signal to shorten a period in which said junction capacitance is charged,
- wherein a current which is a sum of said driving current and said junction capacity is supplied to said organic thin film electroluminescent elements to enhance luminance within a period of said first pulse signal, a period for supplying said current being shorter than said period of said first pulse signal.
A driving circuit for driving an organic electroluminescent element comprising a current driving circuit having an output node coupled to said organic electroluminescent element and generating a direct current driving current at said output node during a driving pulse, said driving pulse including a first period of time and a second period of time following said first period of time, said driving current having a first current value during said first period of time and a second current value which is smaller than said first current value during said second period of time, said electroluminescent element being driven by said driving current having said first and second current values to enhance luminance of said organic electroluminescent element within said driving pulse.
Dependencies are inferred from the claim text.