OLED Driver Discharge Circuit Using Current Mirroring
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Solution Overview
Problem
Conventional organic light emitting device drivers rely on external zener diodes for discharge operations, which are prone to leakage currents and hinder integration due to their location outside the driver unit, requiring frequent replacement and affecting the stability of terminal voltage adjustments during discharge periods.
Innovation Solution
An organic light emitting device driver incorporating a discharge unit with a switching unit and a current mirroring unit, utilizing MOS transistors to generate and control discharge currents, eliminating the need for zener diodes and enabling stable voltage control during discharge periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external zener diodes are used for discharge operations, then discharge function is achieved, but leakage currents occur and integration is hindered
Solution Approach 1:
The patent merges the discharge unit with the driver unit by integrating MOS transistors (third transistor connected to segment line, fourth transistor connected to common line) directly into the driver circuitry. This eliminates the need for external zener diodes and enables full integration of the discharge function within the driver unit, resolving the contradiction between achieving discharge function and maintaining integration capability
Solution Approach 2:
The patent uses current mirroring technique where the third and fourth MOS transistors mirror reference currents to generate precise discharge currents. This copying approach replicates the voltage control function previously achieved by zener diodes using integrated MOS transistor pairs, maintaining reliability while enabling integration
2Reliability
If zener diodes are used for voltage control during discharge, then discharge function is achieved, but frequent replacement is required due to leakage
Solution Approach 1:
The integrated MOS transistor-based discharge unit operates without external components, using internally generated reference currents and current mirroring to maintain stable terminal voltages during discharge. This self-contained design eliminates leakage issues and reduces maintenance requirements, allowing the system to serve itself without external zener diodes that require replacement
3Device complexity
If MOS transistors are used to mirror reference currents, then integration is enabled, but precise voltage control during discharge must be achieved
Solution Approach 1:
The patent implements voltage control during discharge by using MOS transistors that respond to voltages supplied to unit pixels. The third transistor's gate is connected to the segment line and the fourth transistor's gate is connected to the common line, creating a feedback mechanism where the transistors automatically adjust their conduction based on the pixel voltage levels, ensuring precise voltage control during discharge operations
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows for precise control of voltage levels during discharge periods, preventing leakage currents and facilitating integration by mirroring reference currents to generate discharge currents, thus enhancing the stability and efficiency of the discharge operation.
Implementation Method 1
a current mirroring unit for outputting the discharge current generated by mirroring the reference current transferred by the switching unit
Data Source
AI summary
An organic light emitting device driver for driving an organic light emitting device including a plurality of unit pixels each of which includes an organic light emitting element, the organic light emitting device driver includes: a discharge unit for generating a discharge current during a discharge period to thereby discharge a charge charged in the unit pixel, wherein the discharge unit includes: a switching unit for transferring a reference current in response to a predetermined voltage supplied to the unit pixel; and a current mirroring unit for outputting the discharge current generated by mirroring the reference current transferred by the switching unit.