Display Data Driver Output Amplifier Without Output Switch Noise
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Solution Overview
Problem
In large-screen liquid crystal display devices, the increased load capacitance and higher resolution lead to insufficient driving speed, increased power dissipation, and heat generation due to the on-resistance of the output switch, which also results in area inefficiencies and noise generation.
Innovation Solution
An output amplifier circuit with a shared differential circuit, comprising a main amplifier and a sub-amplifier, where the input signal is received by both in a voltage follower configuration initially, and then by the main amplifier alone to drive the load, eliminating the need for an output switch, thereby reducing on-resistance and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If an output switch is used to drive the data line, then the circuit can control signal output, but the on-resistance of the output switch causes insufficient driving speed and power dissipation
Solution Approach 1:
The patent removes the output switch from the circuit by using a buffer amplifier configuration where the output stage directly drives the data line without switching elements. This extraction of the problematic component eliminates on-resistance losses while maintaining signal output capability through the buffer amplifier's direct drive mechanism.
Solution Approach 2:
The patent replaces the mechanical switching action (output switch) with an electrical buffer amplifier configuration. The buffer amplifier uses voltage follower topology to provide direct drive capability without mechanical switches, substituting the switching mechanism with an amplifier-based solution that eliminates on-resistance losses.
2Speed
If the output switch size is increased to reduce on-resistance, then driving speed improves, but the circuit area increases
Solution Approach 1:
By removing the output switch entirely from the circuit architecture, the patent eliminates the need to size this component. The buffer amplifier configuration provides direct drive capability without requiring a switch, thereby avoiding the area penalty that would result from increasing switch size to reduce on-resistance.
Solution Approach 2:
The patent substitutes the output switch with a buffer amplifier configuration that provides direct drive capability. This replacement eliminates the need for large switch elements, as the buffer amplifier's voltage follower topology inherently provides the necessary drive strength without requiring oversized switching components.
3Ease of operation
If an output switch is used, then signal output control is possible, but noise is generated during switching operations
Solution Approach 1:
The patent removes the output switch from the circuit, eliminating the source of switching noise. The buffer amplifier configuration provides continuous signal output control without the discrete switching action that generates noise, thereby maintaining ease of operation while eliminating harmful noise generation.
Solution Approach 2:
The patent replaces the switching mechanism with a buffer amplifier configuration that provides continuous signal output. This substitution eliminates the mechanical switching action that generates noise, while the buffer amplifier maintains signal output control capability through its voltage follower topology.
4Area of stationary object
If the data line capacitance is increased to drive larger displays, then display size increases, but driving speed becomes insufficient
Solution Approach 1:
The patent uses a buffer amplifier configuration with voltage follower topology to provide high current drive capability directly into the data line. This amplifier-based approach can charge and discharge the increased capacitance of larger display data lines much faster than a simple switch could, thereby maintaining driving speed despite increased display size and capacitance.
Data Source
AI summary
Disclosed is an output amplifier circuit including a differential stage, a first output stage that receives outputs of the differential stage, and a second output stage having an output thereof electrically connected to a load. The differential stage receives an input signal at a non-inverting input thereof. In the first connection configuration, an output of the first output stage is electrically disconnected from the output of the second output stage, outputs of the differential stage are electrically disconnected from inputs of the second output stage, and a second input of the differential stage is electrically connected to the output of the first output stage. In the second connection configuration, the output of the first output stage is electrically connected to the output of the second output stage, and the outputs of the differential stage is electrically connected to the inputs of the second output stage.