Reference Voltage Circuit Power Management for AMLCDs
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Solution Overview
Problem
Existing reference voltage generating circuits in active matrix liquid crystal displays (AMLCDs) face issues with large circuit space occupation and unstable DAC operation due to high resistance in TFT switches and floating voltages during power-saving modes, leading to increased power consumption.
Innovation Solution
An integrated reference voltage generating circuit with a series resistor circuit and control switches that maintain connection to a power source during power-saving modes, using transistors of different doping types to manage voltage and reduce power consumption, and compensating for charge injection effects through carefully designed resistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If TFT switches are used to disconnect the R-string from power sources during power-saving modes, then power consumption is reduced, but the circuit occupies large space due to high resistance requiring large switch sizes
Solution Approach 1:
The patent extracts the disconnect function from the TFT switches and implements it through control switches (first and second switches) that selectively connect or disconnect the resistor circuit from power sources. This allows the resistor circuit to be completely disconnected during power-saving modes, achieving low power consumption without requiring large switch sizes to compensate for high resistance
Solution Approach 2:
The patent implements dynamic switching of the resistor circuit connection state based on display modes. Control switches dynamically connect the resistor circuit to power sources during full-gradation modes and disconnect during power-saving modes, enabling adaptive power management without fixed large switch sizes
2Loss of energy
If the R-string is disconnected from power sources during power-saving modes, then power consumption is reduced, but floating voltage levels are produced causing unstable DAC operation
Solution Approach 1:
The patent introduces control switches as intermediaries between the resistor circuit and power sources. These switches provide a controlled disconnection mechanism that maintains voltage stability at the resistor circuit terminals even when disconnected from power sources, preventing floating voltage effects while enabling power savings
Solution Approach 2:
The control switches are positioned and configured to preemptively prevent floating voltage conditions by maintaining proper voltage references at the resistor circuit terminals. This preliminary voltage stabilization occurs before any DAC operation, ensuring stable DAC performance during power-saving modes
3Speed
If large switches are used to achieve fast turn-on time and small voltage drop, then switching performance is improved, but the reference voltage generating circuit occupies large space
Solution Approach 1:
The patent extracts the high-performance switching function from the main circuit path by using control switches that operate in a different configuration. These control switches achieve fast turn-on and small voltage drop without requiring large sizes, as they control connection/disconnection rather than carrying full current continuously
Solution Approach 2:
The patent uses multiple control switches (first switch, second switch, third switch, fourth switch) that replicate the connection control function at different points in the circuit. This distributed switching approach achieves overall fast response and low voltage drop without requiring any single switch to be large
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution reduces power consumption and stabilizes DAC operation during power-saving modes without increasing circuit space, ensuring efficient voltage generation and data integrity.
Implementation Method 1
a conventional resistor string (R-string) approach is adopted for providing different voltages
Implementation Method 2
the resistance of a TFT is usually much larger than that of a MOSFET
Data Source
AI summary
Systems and methods for generating reference voltages are provided. A representative system comprises a resistor circuit; a first switch coupled between a first end of the resistor circuit and a first power source; a second switch coupled between the first end of the resistor circuit and a second power source; a third switch coupled to a second end of the resistor circuit; a fourth switch coupled to the second end of the resistor circuit; a first resistor coupled between the first end of the resistor circuit and the first switch; a second resistor coupled between the first end of the resistor circuit and the second switch; a third resistor coupled between the second end of the resistor circuit and the third switch; a fourth resistor coupled between the second end of the resistor circuit and the fourth switch; and a control circuit for controlling the switches.