Edge Modulated PWM Signal Transport Across Capacitive Isolation Barrier
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Solution Overview
Problem
Existing methods for transmitting analog signals across isolation barriers are inefficient due to high latency and signal impairments, particularly in applications like current sensing and switching power systems, where low latency is crucial.
Innovation Solution
The use of pulse width modulation (PWM) signals is employed, where rising and falling edges are converted into pulses of specific widths and transmitted across a capacitive isolation channel, followed by edge demodulation to recreate the original PWM signal, effectively reducing latency and mitigating channel impairments such as pulse width distortion and 1/f noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If analog signals are transmitted directly across isolation barriers using conventional methods (optical or inductive), then signal transmission is achieved, but latency is high and signal impairments occur
Solution Approach 1:
The patent replaces conventional optical or inductive transmission mechanisms with a capacitive coupling mechanism. The transmitter uses a capacitive element to couple the PWM signal across the isolation barrier, and the receiver uses a capacitive element to detect the signal. This substitution of the transmission mechanism reduces latency and eliminates static pulse width distortion while maintaining signal accuracy.
Solution Approach 2:
The patent changes the signal representation from continuous analog to pulse width modulated digital signals. By encoding the analog signal as PWM with specific duty cycles, the system achieves lower latency transmission across the isolation barrier. The edge modulation technique further transforms the PWM signal into pulses with widths proportional to the duty cycle, enabling accurate reconstruction at the receiver with minimal latency.
2Device complexity
If PWM signals are transmitted across isolation barriers without edge modulation, then transmission is simpler, but static pulse width distortion and low-frequency noise impair the signal
Solution Approach 1:
The patent applies periodic edge modulation to the PWM signal, transforming it into a sequence of pulses with specific widths. Each pulse width is proportional to the PWM duty cycle at the corresponding edge. This periodic transformation with distinct pulse widths for rising and falling edges enables the receiver to accurately reconstruct the original signal while eliminating static pulse width distortion and attenuating low-frequency noise.
3Reliability
If digital conversion is used to transmit analog signals across isolation barriers, then signal transmission is reliable, but additional components and power are required
Solution Approach 1:
The patent employs a self-service approach where the PWM signal itself carries all necessary information for accurate reconstruction. The edge modulation encodes the duty cycle information directly into pulse widths, allowing the receiver to reconstruct the analog signal without requiring additional ADC or DAC components. This eliminates the need for separate conversion components while maintaining reliable signal transmission across the isolation barrier.
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 approach significantly reduces latency and improves signal accuracy by eliminating static pulse width distortion and attenuating low-frequency noise, enhancing the signal-to-noise ratio and enabling faster reaction times in control loops.
Implementation Method 1
A capacitive isolation channel is coupled to receive the edge modulated signal with the first and second edges
Data Source
AI summary
An analog signal is transported across an isolation channel using edge modulation/demodulation of a pulse width modulated (PWM) signal. An edge modulator is responsive to rising edges of the PWM signal to generate first pulses having a first predetermined pulse width and is responsive to receipt of falling edges of the PWM signal to generate second pulses having a second predetermined pulse width with the same polarity as the first pulses. On the opposite side of the isolation channel an edge demodulating circuit recreates the PWM signal using the first and second pulses. The rise and falling edges of the PWM signals can be distinguished based on the pulse width of the first and second pulses. A second order pulse width modulator may be used to generate the PWM signal.