Capacitive Isolation Level Shifter for Common-Mode Noise Immunity
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Solution Overview
Problem
Level shifters face interference from common mode noise, particularly asynchronous common mode noise, which can cause distortion and disrupt the accurate shifting of signals between circuits with different grounds, leading to potential misfire or damage in systems relying on these signals.
Innovation Solution
A level shifter utilizing bidirectional signaling through a capacitive isolation barrier, where a low voltage circuit provides a differential signal to a high voltage circuit, and the high voltage circuit provides feedback through the same isolation barrier, allowing for galvanic isolation while avoiding the need for a dedicated isolation barrier for feedback, thus reducing noise interference and system costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dedicated isolation barrier is used for feedback signal, then galvanic isolation and noise immunity are improved, but device complexity and cost increase
Solution Approach 1:
The patent combines the forward signal path and feedback signal path into a single shared capacitive isolation barrier. The feedback circuit shares the same isolation capacitor (C1) used for the forward control signal, eliminating the need for a separate isolation barrier for feedback. This merging approach maintains galvanic isolation while reducing component count and system complexity.
Solution Approach 2:
The capacitive isolation barrier is designed to serve multiple functions: it provides galvanic isolation for the forward control signal from the low-voltage circuit to the high-voltage circuit, and simultaneously serves as the isolation path for the feedback signal returning from the high-voltage circuit to the low-voltage circuit. This multi-functionality reduces the need for dedicated isolation components.
2Ease of operation
If traditional level shifting approaches are used, then signal level conversion is achieved, but asynchronous common mode noise causes distortion and interference
Solution Approach 1:
The patent introduces a capacitive isolation barrier as an intermediary element between the low-voltage control circuit and the high-voltage power circuit. This capacitor-based isolation barrier blocks common mode noise and ground potential differences while allowing AC signal transmission. The feedback circuit uses this same intermediary to return signals immune to the noise present in traditional direct-coupled level shifters.
3Reliability
If separate isolation barriers are used for forward and feedback signals, then isolation performance is improved, but cost and footprint increase
Solution Approach 1:
The patent merges the isolation function for both forward and feedback signals into a single capacitive isolation barrier. The same capacitor C1 that isolates the forward control signal also serves as the isolation path for the feedback signal, reducing the total number of isolation components from two separate barriers to one shared barrier.
Solution Approach 2:
The capacitive isolation barrier is designed to handle bidirectional signaling - it provides galvanic isolation for the forward control signal from low-voltage to high-voltage circuit, and simultaneously provides isolation for the feedback signal returning from high-voltage to low-voltage circuit, making a single component serve dual isolation functions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively reduces distortion caused by asynchronous common mode noise, ensuring accurate signal shifting and maintaining system functionality while lowering the overall cost and footprint of the level shifter by enabling bidirectional signaling through shared capacitive isolation barriers.
Implementation Method 1
level shifter utilizing bidirectional signaling through a capacitive isolation barrier
Data Source
AI summary
According to an exemplary implementation, a level shifter includes a low voltage circuit and a high voltage circuit. The low voltage circuit is configured to provide a differential signal to the high voltage circuit through a capacitive isolation barrier. The high voltage circuit is configured to receive the differential signal from the low voltage circuit through the capacitive isolation barrier so as to level shift the differential signal from a first ground of the low voltage circuit to a second ground of the high voltage circuit. The high voltage circuit is further configured to provide a feedback signal to the low voltage circuit through the capacitive isolation barrier. The low voltage circuit can be configured to receive the feedback signal from the low voltage circuit between edges of the differential signal.