Data Driver Polarity Inversion Circuit Reduces Charge Discharge Current
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Solution Overview
Problem
During the driving of display panels, large charge/discharge currents are generated when the polarities of output nodes of a data driver are exchanged, leading to instability in voltage due to higher impedances in glass substrate traces, affecting the operation of the data driver.
Innovation Solution
A data driver and driving method that includes a control unit, polarity inversion circuit, and multiple driving channels with latch, level shift, and digital-to-analog conversion circuits, which generate and output data voltage signals of opposite polarities during specific line periods, and a polarity control signal to manage polarity inversion between consecutive frame periods, reducing charge/discharge currents by outputting a middle voltage during polarity changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polarity exchange is performed between output nodes of the data driver, then the display panel can operate with proper polarity inversion, but large charge/discharge current is generated causing voltage instability
Solution Approach 1:
The patent applies preliminary action by pre-charging the output node to a middle voltage level (e.g., 0V) before polarity exchange occurs. This preparatory step reduces the voltage differential that must be bridged during polarity switching, thereby minimizing the charge/discharge current spike. The control unit detects the upcoming polarity exchange and activates the pre-charge circuit in advance, ensuring smooth transition without current surges.
Solution Approach 2:
The patent introduces an intermediary voltage level (middle voltage) as a buffer between positive and negative polarity states. Instead of directly switching from positive to negative voltage, the system transitions through this intermediate state, which acts as a mediator to reduce the abrupt current change. This intermediary approach is implemented through additional switching circuits that can connect the output node to the middle voltage reference during polarity transitions.
2Ease of manufacture
If COG package type is used with traces on glass substrate, then the data driver can be mounted on the panel, but the high impedance of traces causes voltage instability during load charging
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the voltage level at the output node during specific operation phases. By changing the voltage parameter to a middle level before polarity exchange, the system reduces the current demand on the high-impedance traces, thereby maintaining voltage stability despite the inherent limitations of the COG packaging approach.
Data Source
AI summary
A data driver for driving a display panel includes a first driving channel coupled to a polarity inversion circuit and configured to generate a first data voltage signal having a positive polarity output to the display panel according to a plurality of first pixel data; a second driving channel coupled to the polarity inversion circuit and configured to generate a second data voltage signal having a negative polarity output to the display panel according to a plurality of second pixel data; wherein the first data voltage signal is output to first output node through the polarity inversion circuit during a first line period and the second data voltage signal is output to the first output node through the polarity inversion circuit during a second line period after the first line period, and the first line period and the second line period respectively belong to two consecutive frame periods.