Differential Line Driver Circuit for Common-Mode Noise Suppression
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Solution Overview
Problem
Electronic circuits face significant challenges in reducing common mode noise due to mismatches in differential signal paths, which lead to excessive electromagnetic interference (EMI) and violate electromagnetic compliance (EMC) standards, especially in designs using conductor traces on substrates like printed circuit boards.
Innovation Solution
A driver system is implemented with a line driver and two amplifier stages, where the first stage biases a DC voltage and the second stage minimizes voltage differences between common mode voltages using capacitors and resistors to suppress common mode noise, effectively reducing EMI without external chokes or shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If common mode chokes or improved shielding are added to suppress EMI, then electromagnetic compliance is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the common mode noise suppression function from external components (common mode chokes and shielding) and implements it within the driver circuit itself through the amplifier stages that sense and cancel common mode voltages, thereby reducing EMI without adding external suppression components
Solution Approach 2:
The driver system performs self-service by incorporating common mode noise suppression functionality directly into the driver circuit through amplifier stages that automatically sense and cancel common mode voltages, eliminating the need for external suppression components
2Object-affected harmful factors
If mismatch in differential signal path is reduced to meet EMC standards, then EMI is suppressed, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs feedback mechanisms where amplifier stages continuously sense common mode voltages at the output and adjust the drive signals to cancel out common mode noise, thereby maintaining EMC compliance without requiring extremely tight manufacturing tolerances on the differential signal path
Solution Approach 2:
The system dynamically changes the voltage parameters (common mode voltages) through amplifier adjustment to compensate for mismatches in the differential signal path, allowing standard manufacturing tolerances while still achieving low EMI levels
3Speed
If line driver is used to enable high speed communication, then data transmission rate is improved, but common mode noise generation increases
Solution Approach 1:
The patent converts the harmful common mode noise generated by high-speed line driving into a controllable parameter by using amplifier stages to sense the common mode voltages and actively cancel them, thereby maintaining high data transmission rates while suppressing the noise they inherently generate
Data Source
AI summary
A driver system includes a non-inverting system input, an inverting system input, a non-inverting system output and an inverting system output. The driver system includes a line driver which includes a non-inverting driver input coupled to the non-inverting system input and includes an inverting driver input coupled to the inverting system input. The line driver includes an inverting driver output and a non-inverting driver output. The driver system includes a first termination resistor coupled between the non-inverting driver output and the non-inverting system output and includes a second termination resistor coupled between the inverting driver output and the inverting system output. The driver system includes a first amplifier stage coupled to the line driver and includes a second amplifier stage coupled to the line driver.