Backlight Current Control IC Offset Correction
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Solution Overview
Problem
Conventional backlight devices for LCD panels face challenges in maintaining uniform light emission and preventing flicker due to current deviations in light emitting diode channels, particularly at low current levels, caused by offset voltage and gain deviations in the dependent current source, which affect gray and dark uniformity.
Innovation Solution
A current control integrated circuit that divides light emitting diode channels into control units, using a buffer with an offset controller and memory for offset correction data, and dependent current sources with gain correction data to generate sampling voltages and control driving currents, thereby compensating for current deviations and maintaining consistent light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional backlight devices use standard current control without offset correction, then the device complexity is low, but current deviation occurs at low current levels causing poor gray and dark uniformity
Solution Approach 1:
The patent applies preliminary action by measuring and storing offset voltage values for each light emitting diode channel before normal operation. The offset correction data is pre-calculated and stored in memory, then applied during current control to compensate for deviations. This preliminary measurement and storage approach enables precise current uniformity without adding complex real-time correction circuits.
2Use of energy by moving object
If the light emitting diode channels operate at low current levels (20 uA to 200 uA), then energy consumption is reduced, but current deviation due to offset voltage becomes significantly larger
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the offset correction data based on the driving current level. Different offset correction values are stored and applied for different current ranges (e.g., low current mode vs. high current mode). This allows the system to maintain current uniformity across the entire operating range while enabling energy-efficient low current operation when needed.
3Illumination intensity
If the backlight device uses a large number of light emitting diode channels to achieve high resolution backlight, then the illumination intensity and coverage are improved, but current deviations across channels cause non-uniform light emission
Solution Approach 1:
The patent applies feedback by measuring the actual offset voltage of each light emitting diode channel and using this information to correct the driving current. The system continuously monitors and compensates for channel-to-channel variations, ensuring that all channels emit uniform light intensity even when operating at different current levels. This feedback mechanism maintains backlight uniformity across high-resolution displays with numerous channels.
Data Source
AI summary
A current control integrated circuit of a backlight device for display includes a buffer configured to receive a column signal; a plurality of driving current controllers configured to receive the column signal outputted from the buffer and row signals corresponding to a plurality of light emitting blocks of a control unit, and control driving currents for light emission of the light emitting blocks, in response to the column signal and the row signals; and a memory unit, wherein an offset voltage of the buffer is controlled by offset correction data stored in the memory unit.