Isolated Resistive Voltage Sensing for Accurate Mains Monitoring
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Solution Overview
Problem
Conventional voltage sensors used in UL 60950-1 compliant systems for measuring AC mains voltage are large, expensive, and inaccurate due to their reliance on transformers and opto-couplers, which fail to meet the requirements of safety and isolation standards effectively.
Innovation Solution
A voltage sensor design utilizing a resistor network configured as a voltage divider, ensuring proper clearance and creepage spacing, with series-coupled resistors and shunt resistances to maintain isolation and accuracy, eliminating the need for transformers and opto-couplers, while meeting UL 60950-1 safety standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional voltage sensors using transformers and opto-couplers are used, then primary to secondary isolation requirements are met, but the sensors become large, expensive, and inaccurate
Solution Approach 1:
The patent extracts the isolation function from traditional transformers and opto-couplers, replacing it with a capacitive coupling mechanism. The sensing circuit directly measures primary voltage through a capacitor that provides sufficient isolation while maintaining measurement accuracy, eliminating the need for bulky transformer-based isolation components.
Solution Approach 2:
The patent replaces the magnetic field-based isolation mechanism of transformers with an electric field-based capacitive coupling system. This substitution enables more accurate voltage sensing while maintaining isolation compliance, as the capacitive system introduces minimal measurement error compared to magnetic coupling methods.
2Reliability
If conventional voltage sensors using transformers and opto-couplers are used, then primary to secondary isolation requirements are met, but the sensors become large and expensive
Solution Approach 1:
The patent removes the bulky transformer and opto-coupler components from the sensor design, retaining only the essential capacitive coupling element. This extraction dramatically reduces the physical size and component count while maintaining the required isolation functionality, resulting in a more compact and cost-effective sensor.
Solution Approach 2:
The patent changes the isolation mechanism from magnetic coupling (transformers) to electric field coupling (capacitors). This parameter change enables the use of smaller, cheaper components that provide sufficient isolation for UL 60950-1 compliance without the size and cost penalties of traditional transformer-based designs.
3Measurement precision
If a resistor network is used for voltage sensing across isolation boundaries, then accuracy and cost-effectiveness improve, but safety isolation requirements must be carefully met
Solution Approach 1:
The patent introduces a capacitor as an intermediary element between the primary and secondary circuits. This capacitor provides the necessary electrical isolation while allowing the resistor network to accurately sense voltage. The capacitive coupling acts as a mediator that maintains safety isolation boundaries while enabling precise measurements.
Solution Approach 2:
The patent segments the voltage sensing function into distinct components: a capacitive isolation element and a resistive sensing network. This segmentation allows each component to perform its specialized function optimally - the capacitor provides isolation while the resistor network provides accurate voltage division and sensing, together meeting both safety and accuracy requirements.
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
The resistor network-based voltage sensor is highly accurate, cost-effective, and compact, providing reliable measurements across isolation boundaries, reducing power consumption, and adhering to safety standards, thus overcoming the limitations of conventional sensors.
Implementation Method 1
a resistor network having an input for receiving a first sensed voltage from a first of the voltage nodes of the primary side circuit, traversing an isolation boundary between the primary side circuit and the secondary side circuit while adhering to a safety specification
Data Source
AI summary
Methods and apparatus provide for a primary side circuit including one or more voltage nodes; and a monitoring circuit operating to monitor one or more parameters of the primary side circuit, and including at least one sensing circuit and at least one processing circuit within a secondary side circuit, where the sensing circuit includes a resistor network having an input for receiving a first sensed voltage from a first of the voltage nodes of the primary side circuit, traversing an isolation boundary between the primary side circuit and the secondary side circuit while adhering to a safety specification, which includes a primary-secondary isolation requirement, and having an output for providing a first modified sensed voltage to the processing circuit.