DC/DC Converter Charge Pump Using Mixed Semiconductor Materials
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Solution Overview
Problem
The existing DC/DC converters in liquid crystal displays, particularly for small-sized devices, suffer from degraded voltage boost and drop characteristics due to irregular threshold voltages and gate oxide properties of thin film transistors made from low-temperature poly-silicon films, leading to insufficient driving current and reduced display performance.
Innovation Solution
A DC/DC converter design incorporating a charge pump with a thin film transistor, a capacitor, and a diode, where the thin film transistor is made from a non-monocrystal semiconductor and the diode from a mono-crystal semiconductor, improving voltage boost and drop characteristics by reducing threshold voltage irregularities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If low-temperature poly-silicon film is used to form thin film transistors on transparent glass substrate, then the transistor can be manufactured on vulnerable substrate at low temperature, but the threshold voltage becomes irregular and driving current capability is degraded
Solution Approach 1:
The patent applies local quality by using different semiconductor material types in different regions of the charge pump circuit. Specifically, p-channel transistors use one type of semiconductor layer while n-channel transistors use another type, allowing each region to have optimized properties for its specific function. This resolves the contradiction by enabling reliable voltage boosting despite the inherent irregularities of low-temperature poly-silicon fabrication.
Solution Approach 2:
The patent employs composite materials by combining multiple semiconductor layers with different characteristics. The charge pump uses a composite structure where p-channel and n-channel transistors are formed from different semiconductor materials, creating a system that compensates for the weaknesses of individual materials while maintaining compatibility with low-temperature glass substrate processing.
2Power
If charge pump uses p-channel and n-channel transistors with low-temperature poly-silicon channel areas, then voltage boosting can be achieved, but driving current capability is insufficient due to irregular threshold voltage
Solution Approach 1:
The patent implements local quality by assigning different semiconductor material properties to p-channel and n-channel transistors within the charge pump. This allows each transistor type to be optimized for its specific role, improving overall driving current capability while maintaining the voltage boosting function.
Solution Approach 2:
The patent applies parameter changes by modifying the semiconductor material parameters (type and properties) of the transistors in the charge pump. By changing from uniform low-temperature poly-silicon to differentiated semiconductor materials, the patent improves threshold voltage regularity and driving current capability while preserving voltage boosting functionality.
3Area of stationary object
If small-sized liquid crystal display is designed for portable devices, then area is reduced for portability, but space for peripheral circuits including DC/DC converter is restricted
Solution Approach 1:
The patent applies merging by integrating the DC/DC converter and charge pump circuits directly onto the glass substrate of the liquid crystal display, combining multiple functions into a single integrated structure. This reduces the overall device area while maintaining all necessary peripheral circuit functions.
Solution Approach 2:
The patent implements nesting by placing the charge pump and DC/DC converter circuits within the existing glass substrate structure, effectively nesting additional functionality within the available space without increasing the overall display area.
Data Source
AI summary
A DC/DC converter of a liquid crystal display includes a charge pump having a thin film transistor, a capacitor and a diode. The thin film transistor is formed on an insulating substrate. A first main electrode of the thin film transistor is connected to an output terminal and a control electrode of the thin film transistor receives a control signal. The thin film transistor includes a non-monocrystal semiconductor. The capacitor has a first electrode connected to a second main electrode of the thin film transistor and a second electrode receiving a variable voltage. The diode is electrically connected between the second main electrode of the thin film transistor, the first electrode of the capacitor, and a power terminal in series. The diode includes a mono-crystal semiconductor.