Dual-Mode Output Amplifier Circuit for Low-Voltage Display Drivers
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Solution Overview
Problem
Display panel drivers face increased power consumption due to larger display panel sizes and the need for lower operating voltages, while existing solutions require intermediate power supply voltages, which can be costly and complex to manufacture.
Innovation Solution
The display panel driver incorporates a dual-mode output amplifier circuit with depletion-type NMOS and enhancement-type NMOS transistors, and PMOS transistors with separated wells and back gates, allowing operation at low voltages without relying on intermediate power supply voltages, using a common output stage to manage voltage ranges and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If an intermediate power supply voltage is supplied to reduce power consumption, then power consumption is reduced, but manufacturing cost and device complexity increase
Solution Approach 1:
The output amplifier circuit dynamically switches between two operational modes: a first mode using an intermediate power supply voltage for reduced power consumption, and a second mode using only power supply voltage and ground voltage for simplified operation. This dynamic adaptability allows the circuit to optimize power consumption when intermediate voltage is available while maintaining compatibility and reduced complexity when it is not.
Solution Approach 2:
The circuit changes its operating parameters by switching between different power supply configurations. In the first mode, it operates with three voltage levels (power supply voltage, intermediate voltage, ground voltage) to minimize power consumption. In the second mode, it operates with two voltage levels (power supply voltage, ground voltage) to simplify the system and reduce manufacturing costs.
2Productivity
If the number of outputs per driver is increased to reduce the number of drivers, then productivity improves, but power consumption increases
Solution Approach 1:
The output amplifier circuit is segmented into a first output stage and a second output stage, each with dedicated pull-down transistors. This segmentation allows independent optimization of each stage's power consumption while maintaining the ability to drive multiple outputs, thus improving productivity without proportionally increasing total power consumption.
3Productivity
If the size of the display panel is increased, then productivity improves, but power consumption increases
Solution Approach 1:
The circuit employs dynamic voltage mode switching that adapts to the display panel size and capacitance requirements. For larger panels requiring higher drive capability, the circuit can switch to the second mode with full voltage swing. For smaller panels or when power consumption is critical, it operates in the first mode with reduced voltage swing, thus maintaining productivity while optimizing power consumption.
Data Source
AI summary
In a display panel driver an output amplifier circuit includes a first output stage to receive a power supply voltage and a first voltage lower thereto and to output a drive voltage in a first voltage range defined between the power supply voltage and a middle power supply voltage; and a second output stage to receive the power supply and ground voltages and to output a drive voltage between the power supply and ground voltages. In a first mode that the first voltage is set as the middle power supply voltage, the first output stage outputs a first drive voltage in the first voltage range to one of first and second output terminals. In a second mode that the first voltage is set as the ground voltage, the second output stage outputs a first drive voltage in the first voltage range to one of the first and second output terminals.