Demultiplexer Precharge Circuit for Display Data Sampling
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Solution Overview
Problem
In display devices using demultiplexers, voltage drops in power lines and vertical lines lead to increased power consumption and hinder appropriate sampling of data currents due to parasitic resistance, especially when sample/hold circuits are used for 1:N demultiplexing, which requires shortening the sampling time.
Innovation Solution
A display device with a demultiplexer that precharges signal lines with a precharge current before data sampling, using sample/hold circuits to hold and sample multiplexed currents, and a precharge unit that transmits a precharge current M times the multiplexed current to ensure appropriate sampling within a given time, reducing voltage drops and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If demultiplexers are used to reduce the number of data driver ICs, then device complexity is reduced, but voltage drop increases due to parasitic resistance in power lines
Solution Approach 1:
The patent applies preliminary action by precharging the signal lines before data sampling occurs. The precharge unit charges the signal lines to an appropriate voltage level in advance, which compensates for the voltage drop that would occur during normal operation due to parasitic resistance. This preliminary charging action ensures that when data currents are sampled, the voltage levels remain sufficient for proper operation.
2Productivity
If sample/hold circuits are used for 1:N demultiplexing, then productivity is improved by reducing IC count, but sampling time is shortened making appropriate sampling difficult
Solution Approach 1:
The precharge unit performs preliminary charging of signal lines before the sample/hold circuits attempt to sample the data currents. This advance preparation ensures that the signal lines are ready to receive and hold the data currents properly, even within the shortened sampling time window imposed by 1:N demultiplexing operations.
3Reliability
If power supply voltage is increased to compensate for voltage drop, then reliability is improved, but power consumption increases
Solution Approach 1:
Instead of increasing the power supply voltage to compensate for voltage drops, the patent uses preliminary action by precharging signal lines to appropriate voltage levels. This approach maintains the necessary voltage margins for reliable transistor saturation and proper operation without requiring higher power supply voltages, thus avoiding increased power consumption.
4Loss of energy
If precharge current is applied before data sampling, then voltage drop is reduced, but device complexity increases
Solution Approach 1:
The precharge unit acts as an intermediary component between the power supply and the signal lines. It provides the necessary voltage preparation function without requiring fundamental changes to the existing demultiplexer or data driver architecture. This intermediary approach reduces voltage drops through controlled precharging while maintaining compatibility with the overall system design.
Data Source
AI summary
Disclosed is a display device using a demultiplexer. The demultiplexer sequentially samples data currents that are multiplexed and applied by a data driver, and holds currents corresponding to the sampled data currents to a plurality of data lines. Since the demultiplexer is to sample the data currents corresponding to N data lines during a horizontal period when performing 1:N demultiplexing, the data current corresponding to one data line is to be sampled during a 1/N horizontal period. A signal line coupled between the demultiplexer and the data driver is precharged with a precharge current before sampling the data current. According to one embodiment, the precharge current is M times the data current, where M is a real number greater than 1.