Source Driver Offset Cancellation via Periodic Signal Toggle
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Solution Overview
Problem
Conventional LCD devices face challenges in eliminating random offset components from output buffers, which are uncontrollable and affect image distortion, especially as LCD panel sizes increase and the number of data lines grows.
Innovation Solution
A source driver with a controller generating complementary signals that toggle at a predetermined frame period, an output buffer using differential input circuits, current mirrors, a floating current source, class-AB amplifier, and capacitive circuits to generate data-line drive signals with positive and negative offset values, alternately oscillating to cancel out random offsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the number of data lines increases to support larger LCD panels, then the display area increases, but the number of output buffers increases causing more random offset components and image distortion
Solution Approach 1:
The patent applies periodic action by toggling the offset values between positive and negative states at a predetermined frame period. The controller generates complementary signals that cause the output buffer to alternately apply positive and negative offset values to adjacent data lines, creating a periodic modulation that visually eliminates random offset components over time.
Solution Approach 2:
The patent changes the offset parameter dynamically by switching between positive and negative offset values. The controller modulates the offset value parameter based on complementary signals, transforming the static offset problem into a dynamic parameter variation that cancels out random offsets through temporal averaging.
2Device complexity
If conventional output buffers are used without offset modulation, then the circuit complexity is low, but random offset components cause image distortion that cannot be visually eliminated
Solution Approach 1:
The patent introduces periodic action by implementing a controller that generates complementary toggle signals at a predetermined frame period. These signals periodically modulate the offset values in the output buffer, causing random offset components to oscillate between positive and negative values, which visually cancels them out over time while maintaining relatively simple circuit architecture.
3Manufacturing precision
If systematic offsets are controlled by circuital modulation, then those offsets are reduced, but random offsets from transistor mismatch and processing variation remain uncontrollable
Solution Approach 1:
The patent addresses random offsets by applying periodic modulation to toggle offset values between positive and negative states. This temporal oscillation causes random offset components from transistor mismatch and processing variations to average out visually, complementing the existing circuital modulation that controls systematic offsets.
Solution Approach 2:
The patent changes the offset parameter dynamically by switching between positive and negative values based on complementary control signals. This parameter modulation affects random offset components differently than systematic offsets, enabling visual elimination of random offsets while maintaining the benefits of circuital modulation for systematic offset control.
Data Source
AI summary
A source driver for an LCD device. The source driver comprises a controller generating a pair of signals complimentary to each other, each of the signals toggling at a predetermined frame period, and an output buffer generating a data-line drive signal that is offset by positive and negative offset values in response to the pair of signals.