Output Driver Waveform Shaping for EMI-Reduced Signaling
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Solution Overview
Problem
Designing output drivers for electronic devices to meet specific electromagnetic interference (EMI) emission standards can be challenging, as existing solutions often result in irregular behavior of other devices due to EMI emissions.
Innovation Solution
The output driver reduces EMI emissions by tailoring the signal shape of the output signal from a square wave to a sine wave through progressive reduction of drive strength, using parallel circuit paths and control circuits to vary current values, and employing comparators and logic gates to adjust voltage levels and control signal segments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional output drivers are used to provide electrical signals, then signal transmission function is achieved, but electromagnetic interference emissions occur causing irregular behavior in other devices
Solution Approach 1:
The output driver is divided into multiple parallel circuit paths (first circuit path with first output driver, second circuit path with second output driver). Each path can be independently controlled to adjust the overall signal characteristics and reduce EMI emissions through distributed signal transmission
Solution Approach 2:
The patent changes the signal waveform parameter from square wave to sine wave by adjusting the drive strength and circuit operation. This parameter change reduces the high-frequency harmonics inherent in square waves that cause EMI, while maintaining the essential signal transmission function
2Object-affected harmful factors
If output drivers are designed to meet EMI emission standards, then EMI emissions are reduced, but device complexity increases
Solution Approach 1:
Multiple circuit paths are merged into a single output structure that works together to produce the desired sine wave output. The parallel drivers and their control logic are integrated to function as a unified EMI-reduced output system, achieving complexity reduction through functional integration
Solution Approach 2:
The output driver employs dynamic control where the drive strength is progressively reduced and circuit paths are selectively activated or deactivated based on signal requirements. This dynamic operation allows the system to adaptively reduce EMI while maintaining signal integrity, avoiding the need for overly complex static EMI filtering structures
Data Source
AI summary
Some embodiments include an output driver having a first circuit to provide a plurality of first parallel circuit paths between an output node and a first supply node, a second circuit to provide a plurality of second parallel circuit paths between the output node and a second supply node, and a control circuit responsive to a voltage at the output node to vary a value of a current in the plurality of first parallel circuit paths and a value of a second current in the plurality of second parallel circuit paths to control a signal shape of the output signal. Additional apparatus, systems, and methods are disclosed.