Active Matrix Substrate Demultiplexer with Boost Circuits
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Solution Overview
Problem
The challenge in active matrix substrates is to reduce drive power consumption while using oxide semiconductor TFTs for demultiplexer circuits, as oxide semiconductor TFTs have lower mobility than polycrystalline silicon TFTs, requiring larger channel widths or higher drive voltages, which increase power consumption and gate capacitance.
Innovation Solution
The implementation of a demultiplexer circuit with oxide semiconductor TFTs, including boost circuits that pre-charge, boost, and reset the gate electrode voltage, allowing for efficient voltage distribution to multiple source bus lines, reducing the need for larger TFTs or higher voltages and thus minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If oxide semiconductor TFTs are used for DEMUX circuit, then fabrication process compatibility is improved, but drive power consumption increases due to lower mobility requiring larger channel widths or higher drive voltages
Solution Approach 1:
The boost circuit pre-charges the gate electrode of the switching TFT before the TFT needs to operate. By preliminarily charging the gate electrode to a higher voltage level, the TFT achieves sufficient drive current with its naturally lower mobility, avoiding the need for even larger channel widths or continuously higher voltages during operation.
Solution Approach 2:
The invention changes the voltage parameter dynamically by using a boost circuit to temporarily increase the gate electrode voltage above the normal drive voltage. This parameter change allows the oxide semiconductor TFT to achieve polycrystalline silicon-level drive current during critical switching periods without permanently requiring higher voltage operation that would increase overall power consumption.
2Power
If larger channel widths are used to compensate for lower mobility, then drive current is improved, but gate capacitance load and drive power increase
Solution Approach 1:
Instead of permanently increasing channel width to boost drive current, the invention temporarily increases the gate voltage using a boost circuit. This parameter change achieves high drive current during switching operations without the permanent structural change that would increase gate capacitance and continuous power consumption.
3Speed
If higher drive voltages are applied to compensate for lower mobility, then switching speed is improved, but drive power consumption increases
Solution Approach 1:
The boost circuit applies higher voltage preliminarily to the gate electrode before the switching operation occurs. This preliminary high voltage ensures fast switching speed when needed, while the TFT operates at normal voltage levels during non-switching periods, thereby reducing overall power consumption compared to continuously applying high drive voltages.
Data Source
AI summary
An active matrix substrate according to an embodiment of the present invention includes: a plurality of source bus lines provided on a substrate; a source driver disposed in a peripheral region; signal output lines each connected to a corresponding one of output terminals of the source driver; and a demultiplexer circuit disposed in a peripheral region. The demultiplexer circuit includes unit circuits each configured to distribute a display signal from one signal output line to n source bus lines (n is an integer larger than or equal to 2). Each unit circuit includes n switching TFTs configured to perform individual on/off control of electrical connections of the n branch lines to the n source bus lines. The n branch lines being connected to one signal output lines. The demultiplexer circuit further includes a plurality of boost circuits each configured to boost a voltage applied to a gate electrode of a corresponding one of the n switching TFTs.