Transformer Signal Transfer Across Galvanic Isolation
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Solution Overview
Problem
Existing systems face challenges in efficiently transferring analog voltage signals across galvanic isolation in transformer-based 4-20 mA devices, limiting their ability to provide proportional signals for diagnostic purposes while maintaining power transfer.
Innovation Solution
A circuit and method utilizing a variable current instead of a fixed current through a transformer's primary winding, allowing the power transferred to vary proportionally with the 4-20 mA transmitter current, enabling both power and signal transfer across galvanic isolation using a single transformer, with current-sense resistors and regulators to measure and regulate currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a fixed current is drawn through the transformer's primary winding to transfer power across galvanic isolation, then power transfer is achieved, but signal transfer capability is lost
Solution Approach 1:
The patent applies the dynamics principle by transitioning from a fixed current draw through the transformer primary winding to a variable current draw that dynamically responds to the 4-20 mA transmitter signal. The DC/DC converter is modified to allow the primary winding current to vary proportionally with the transmitter current, enabling the transformer to simultaneously transfer both power (through the varying current) and signal information (through the proportionality of current variation). This dynamic approach resolves the contradiction by making the current adaptive rather than static.
Solution Approach 2:
The patent applies the universality principle by enabling the single transformer to perform multiple functions: it transfers both power and diagnostic signal across the galvanic isolation barrier. By modifying the DC/DC converter to draw variable current proportional to the transmitter current, the transformer primary winding becomes a dual-purpose element that carries both power delivery and signal information, eliminating the need for separate power and signal transfer paths.
2Device complexity
If a single transformer is used for both power and signal transfer, then component count and cost are reduced, but measurement precision requirements increase
Solution Approach 1:
The patent applies the feedback principle by implementing a measurement system that monitors the current through the transformer primary winding and uses this information to determine the transmitter current on the isolated side. Current sense resistors are placed in series with the primary winding, and the voltage across these resistors is measured and processed to extract diagnostic information. This feedback mechanism enables precise measurement of the variable current to accurately recover the transmitter signal.
Solution Approach 2:
The patent applies the mechanics substitution principle by replacing what would traditionally require separate mechanical/electrical components (separate power and signal transformers or isolation barriers) with a single transformer operated in a variable current mode. The measurement and control functions are implemented through electronic circuitry (current sense resistors, voltage measurement, and processing) rather than additional isolation components, reducing overall system complexity while maintaining measurement capability.
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 reduces component count and cost by utilizing the same transformer for both power and signal transfer, allowing for accurate measurement and processing of the 4-20 mA transmitter current, facilitating diagnostic signals across galvanic isolation.
Implementation Method 1
a transformer having a primary winding and a secondary winding
Data Source
AI summary
The present disclosure provides a circuit comprising: a 4-20 mA transmitter; a transformer having a primary winding and a secondary winding; a first current-sense resistor connected in series with the primary winding and a current regulator, wherein the current-sense resistor is configured to measure a first voltage and provide the measured first voltage to the current regulator, the current regulator being configured to output a current proportional to the measured first voltage; and a second current-sense resistor connected in series with the secondary winding, wherein the current-sense resistor is configured to measure a second voltage such that a current associated with the 4-20 mA transmitter is determined based on the second voltage.