Optically Coupled High-Voltage Sensor Circuit
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Solution Overview
Problem
Existing high-voltage sensing technologies face challenges with power dissipation and noise susceptibility, particularly in isolated sensing systems, where scaling down currents is necessary for low-power dissipation but introduces signal noise and requires complex shielding.
Innovation Solution
The development of electrically-isolated high-voltage sensors that optically and magnetically couple two portions of a circuit, using a light-emitting diode (LED) to generate an optical signal from a high-voltage input, which is received by a photodiode to produce a low-voltage output, with a temperature-compensating biasing sub-circuit to maintain linear operation across varying temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical coupling with LED is used for high-voltage sensing, then electrical isolation is achieved, but power dissipation increases
Solution Approach 1:
The patent changes the operating parameters of the LED by implementing temperature compensation circuitry that adjusts the LED bias current based on temperature measurements. This maintains optimal LED efficiency across varying temperatures, minimizing power dissipation while preserving the electrical isolation benefit. The system dynamically adjusts electrical parameters to optimize the trade-off between isolation reliability and energy loss.
2Loss of energy
If current is scaled down to very low values for low-power dissipation, then power consumption decreases, but signal noise increases and complex magnetic shielding is required
Solution Approach 1:
The patent replaces magnetic field-based sensing mechanisms with optical field-based sensing using LED-photodiode coupling. This substitution eliminates the need for magnetic shielding and reduces susceptibility to magnetic interference while maintaining low power dissipation through efficient optical coupling. The optical domain provides inherent immunity to electromagnetic noise without requiring additional shielding components.
Solution Approach 2:
The patent introduces optical coupling as an intermediary between the high-voltage sensing circuit and the low-voltage output circuit. The LED converts electrical signals to optical signals, which then drive the photodiode to regenerate electrical signals isolated from the high-voltage side. This intermediary optical domain acts as a noise barrier, preventing magnetic and electromagnetic interference from affecting the low-power signal path.
3Measurement precision
If temperature compensation is implemented to maintain linearity, then measurement accuracy improves, but circuit complexity increases
Solution Approach 1:
The patent implements temperature compensation using a feedback mechanism where a temperature sensor monitors the LED temperature and feeds this information to a control circuit that adjusts the LED bias current accordingly. This closed-loop feedback system maintains LED operating linearity across temperature variations, improving measurement precision while automating the compensation process to minimize manual intervention and system complexity.
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
These sensors achieve low power dissipation, with less than 1 W dissipation at 30 kV, and provide accurate, noise-reduced high-voltage signal measurement with a bandwidth greater than 100 kHz, while maintaining linearity over a 25°C to 70°C temperature range.
Implementation Method 1
The first portion comprises a light-emitting diode (LED) which generates an optical signal corresponding to a high-voltage signal across the electrical-isolation boundary
Implementation Method 2
The second portion comprises a photodiode which receives the optical signal emitted from the LED and outputs a corresponding low-voltage electrical signal
Implementation Method 3
a coupled inductor magnetically coupling the electrical-isolation boundary, and a rectifier and filter, so as to provide a bias to the LED
Data Source
AI summary
Novel electrically-isolated high-voltage sensors are provided which have low power dissipation. The sensors are formed of a circuit comprising first and second portions separated by an electrical isolation boundary with the first portion used for high-voltage, and the second portion for low-voltage. While they are decoupled electrically, they are coupled both optically and magnetically. The first portion comprises an LED which generates an optical signal corresponding to a high-voltage signal across the electrical-isolation boundary. The second portion comprises a photodiode which receives the optical signal emitted from the LED and outputs a corresponding low-voltage electrical signal. A temperature-compensating LED biasing sub-circuit may span both portions and include a temperature sensor, a coupled inductor magnetically coupling the electrical isolation boundary, and a rectifier and filter, to provide a bias to the LED which biases the LED to operate in a substantially-linear manner irrespective of the ambient temperature.