Source Driver Multi-Step Latch for EMI Peak Reduction
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Solution Overview
Problem
High-resolution liquid crystal panels face significant electromagnetic interference (EMI) peaks due to simultaneous changes in source output values from driver ICs, which violates strict international standards for EMI compliance, particularly in consumer, vehicle-mounted, and industrial equipment.
Innovation Solution
A source driver configuration that includes a first latch, a second latch, a digital-to-analog converter (DAC), and an amplifier, where the second latch latches the first data signal in multiple steps, either one bit at a time or in groups, to reduce the peak of EMI by controlling the gradation values of the source signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If source output values for multiple columns change simultaneously to drive high-resolution liquid crystal panels, then display resolution is improved, but electromagnetic interference (EMI) peaks increase
Solution Approach 1:
The patent divides the simultaneous change of source output values into multiple sequential steps using a multi-step latch circuit. Instead of all columns changing at once, the latch circuit updates column groups in sequence (e.g., first group of columns, then second group, etc.), segmenting the EMI-generating event into smaller temporal portions that reduce peak interference while maintaining the ability to drive high-resolution displays.
2Manufacturing precision
If the number of source output channels increases to support higher resolutions, then display capability is improved, but EMI compliance becomes more difficult to achieve
Solution Approach 1:
The patent implements periodic action by using clock signals to control the multi-step latch circuit. The source output values are updated in periodic cycles rather than all at once, with each cycle handling a portion of the columns. This periodic updating approach reduces EMI peaks while systematically supporting increased numbers of source output channels required for higher resolutions.
Data Source
AI summary
A source driver 130 includes a first latch 131 outputting a first data signal D1(1) having multiple bits (e.g., eight bits), a second latch 132 outputting a second data signal D2(1) by latching the first data signal D1(1) in a plurality of steps in units of one or more bits, a DAC 133 converting the second data signal D2(1) into an analog signal A(1), and an amplifier 134 receiving the analog signal A(1) to output a source signal S(1). The second latch 132 latches the first data signal D1(1), e.g., one bit at every clock, one bit at every plurality of clocks, a plurality of bits at every clock, or a plurality of bits at every plurality of clocks.