Source Buffer Switch Slew-Rate Control for Display EMI
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Solution Overview
Problem
The rapid switching of source buffer output switches in high-resolution display devices leads to electromagnetic interference (EMI) due to sudden voltage changes, which affects image quality.
Innovation Solution
A source buffer output switch control circuit that includes a switch driver, current limiter, and bias block to control the slew rate of switch control signals by limiting driving currents, using PMOS and NMOS transistors and bias voltages to manage the switching times of source buffer output switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If source buffer output switches are turned on or off quickly to transmit source signals simultaneously from thousands of source buffers, then transmission speed is improved, but electromagnetic interference occurs due to sudden voltage changes
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the slew rate of switch control signals based on the number of simultaneously operating source buffers. When many source buffers operate simultaneously, the slew rate is reduced to minimize voltage changes and EMI. This is achieved through a control circuit that monitors buffer operation counts and adjusts signal transition parameters accordingly, resolving the contradiction between fast switching and EMI reduction.
Solution Approach 2:
The patent implements dynamics by making the switch control signal characteristics adaptive rather than fixed. The slew rate control circuit dynamically modifies signal transition parameters in real-time based on system state (number of active buffers). This dynamic adjustment allows the system to optimize switching speed when needed while reducing EMI when multiple buffers operate simultaneously, eliminating the need for fixed compromise settings.
2Object-generated harmful factors
If the slew rate of switch control signals is reduced to minimize electromagnetic interference, then EMI is decreased, but switching time increases
Solution Approach 1:
The patent resolves this contradiction through dynamic slew rate adjustment rather than using a fixed low slew rate. The control circuit monitors the number of simultaneously operating source buffers and adjusts the slew rate accordingly - using lower slew rates only when necessary (many simultaneous buffers) and higher slew rates when fewer buffers operate. This dynamic approach minimizes EMI when needed while preserving fast switching performance during normal operation, eliminating the permanent time penalty of fixed low-slew-rate designs.
Data Source
AI summary
A source buffer output switch control circuit for controlling operations of a source buffer output switch configured to transmit a source signal output from a source buffer to a display panel or block the source signal includes: a switch driver configured to generate a switch control signal for controlling the operations of the source buffer output switch based on a switch operation input signal; a current limiter configured to limit a driving current applied to the switch driver in order to control a slew rate of the switch control signal; and a bias block configured to supply the current limiter with a bias voltage for controlling a magnitude of the driving current.