OLED Source Driver Gamma Compensation for Power-Line IR Drop
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Solution Overview
Problem
The voltage drop (IR Drop) on power lines in OLED displays, caused by the distance between the power management integrated circuit (ELPMIC) and the display screen, results in lower screen brightness due to reduced voltage at the display screen, which affects the overall display quality.
Innovation Solution
A voltage compensation circuit integrated into the source driver circuit that adjusts the maximum and minimum Gamma voltages based on power supply voltage differences, using a sampling circuit and processing circuit to compensate for the IR Drop, thereby improving screen brightness by adjusting the data line voltage (Vdata) in real time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the power management integrated circuit (ELPMIC) is placed far from the OLED display screen, then the layout flexibility is improved, but the voltage drop (IR Drop) on power lines increases causing reduced screen brightness
Solution Approach 1:
The patent changes the voltage parameter by detecting the actual power supply voltage at the display screen and dynamically adjusting the Gamma voltage compensation values. When voltage drop is detected, the system increases the Gamma voltages to compensate, thereby maintaining screen brightness despite the physical distance between ELPMIC and display screen.
2Ease of manufacture
If the power lines are made longer to connect ELPMIC and OLED display screen, then the device integration is improved, but the voltage drop on power lines increases reducing display quality
Solution Approach 1:
The patent implements a feedback mechanism where the voltage compensation circuit continuously monitors the power supply voltage at the display screen and adjusts the Gamma voltages accordingly. This closed-loop feedback ensures that display quality is maintained despite long power lines by dynamically compensating for voltage drops during operation.
3Reliability
If voltage compensation is implemented by adding dedicated compensation circuits, then the IR Drop compensation effectiveness is improved, but the device complexity and area occupation increase
Solution Approach 1:
The patent merges the voltage compensation function with the existing source driver circuit by integrating the voltage compensation circuit into the Gamma voltage generation pathway. This approach achieves effective IR Drop compensation without adding standalone compensation circuits, thereby avoiding significant increases in device complexity and area occupation.
Solution Approach 2:
The voltage compensation circuit serves multiple functions: it detects power supply voltage, calculates compensation values, and adjusts Gamma voltages all within a single integrated module that works with the existing source driver circuit. This multi-functionality reduces the need for separate dedicated compensation components.
4Illumination intensity
If the Gamma voltages are increased to compensate for voltage drop, then the screen brightness is improved, but the power consumption increases
Solution Approach 1:
The patent employs dynamic voltage adjustment where the Gamma voltages are not fixed but are continuously adapted based on the detected power supply voltage. The compensation is applied only when and where needed, adjusting the voltage levels dynamically rather than maintaining constantly high voltages, thereby balancing brightness improvement with power consumption management.
Data Source
AI summary
Provided are a voltage compensation circuit (003), a source driver circuit (021), a display, and a voltage compensation method. The voltage compensation circuit (003) acquires a first power supply voltage on a power line (ELVDD) at an end of an OLED display screen (01) in a black frame insertion phase after the OLED display screen (01) is turned on, and obtains a reference voltage based on the first power supply voltage (S101); then acquires a second power supply voltage on the power line (ELVDD) when each frame of picture is displayed, and adjusts a pre-stored initial maximum Gamma voltage and a pre-stored initial minimum Gamma voltage based on a difference between the reference voltage and the currently obtained second power supply voltage, to obtain a target maximum Gamma voltage and a target minimum Gamma voltage (S102).