Coreless PCB Transformer for Tamper-Resistant Meter Power
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Solution Overview
Problem
Existing utility-grade electrical energy meters using isolated shunt resistor current sensors face issues with tampering due to magnetic saturation in ferrite-cored transformers and inefficiency and electromagnetic emissions in air-cored transformers, necessitating a tamper-resistant and cost-effective power supply for isolated shunt circuitry.
Innovation Solution
A radio-frequency (RF) power supply system using a coreless transformer with a primary coil and a secondary coil electromagnetically coupled for galvanic isolation, where the RF energy is modulated with a pseudorandom bit sequence to prevent tampering, and a voltage regulator circuit provides DC power to the power measurement front end.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If ferrite-cored transformer is used in SMPS, then power supply efficiency is improved, but the meter becomes susceptible to magnetic tampering
Solution Approach 1:
The patent removes the ferrite core from the transformer, extracting the harmful magnetic properties while retaining the electromagnetic induction functionality. This eliminates the vulnerability to magnetic tampering while maintaining power transfer capability through air-cored electromagnetic coupling.
Solution Approach 2:
The patent converts the potential harm of magnetic field exposure into a benefit by using the electromagnetic field for wireless power transfer through the PCB transformer, eliminating the need for physical magnetic cores that are susceptible to tampering while maintaining efficient power transfer.
2Object-affected harmful factors
If air-cored transformer is used in SMPS, then magnetic saturation and tampering susceptibility are reduced, but the device becomes bulky and produces significant EM emissions
Solution Approach 1:
The patent merges the primary and secondary windings into a single PCB structure with integrated magnetic shielding, combining multiple functions (power transfer, shielding, compact form factor) into one unified component that reduces overall EM emissions while maintaining air-cored benefits.
Solution Approach 2:
The patent uses thin magnetic shielding films integrated into the PCB structure to contain electromagnetic emissions while maintaining the compact, flat form factor. This allows effective EM containment without adding significant bulk or complexity.
3Loss of energy
If conventional SMPS with ferrite core is used, then power delivery efficiency is maintained, but the device requires screening to contain EM emissions
Solution Approach 1:
The patent combines the transformer windings and magnetic shielding into a single integrated PCB structure, eliminating the need for separate screening components. This integration maintains efficient power delivery while inherently containing EM emissions within the PCB structure itself.
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 RF power supply system offers tamper-resistance and cost-effectiveness by reducing electromagnetic emissions and preventing unauthorized access to the power measurement circuit, while maintaining efficient power delivery to the energy meter.
Implementation Method 1
a first transformer coil and a second transformer coil that are formed on opposite sides of the PCB and that are electromagnetically coupled
Data Source
AI summary
An apparatus. The apparatus includes a source of radio-frequency energy and a first transformer coil coupled to the source of RF energy. A second transformer coil, the second transformer coil electromagnetically coupled to the first transformer coil. A modulator is coupled to the source of radio frequency energy, wherein the modulator is configured to receive a modulating signal comprising a pseudorandom bit sequence. The apparatus further includes a power receiver coupled to the second transformer coil.