Current Sensor Isolation via Polyimide Film Insulation
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Solution Overview
Problem
Current sensors with integrated current conductors and magnetic field transducers face challenges in achieving adequate safety isolation, particularly in designs that require galvanic isolation between primary and secondary conductors, as existing insulation thickness and spacing requirements are not consistently met, posing risks of electrical shock.
Innovation Solution
A current sensor integrated circuit design featuring a lead frame with a primary conductor and secondary leads, where a non-conductive insulative material encloses the semiconductor die and insulation structure, ensuring a minimum distance of 0.4 mm between conductors through insulation and a creepage distance of at least 7.2 mm, using polyimide film and adhesive layers for reinforced isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If insulation thickness and spacing are increased to meet safety standards, then electrical shock protection is improved, but device size and complexity increase
Solution Approach 1:
The patent combines multiple insulation functions into a single integrated insulation structure that provides both basic insulation and supplemental insulation simultaneously. The insulation structure includes an insulation layer and an extension layer that work together to provide the required creepage distance and electrical shock protection without requiring separate insulation components, thereby reducing device complexity while maintaining high reliability.
Solution Approach 2:
The insulation structure serves multiple functions: it provides basic insulation between primary and secondary conductors, provides supplemental insulation through its extension layer, establishes the required creepage distance of at least 7.2 mm, and prevents electrical shock. This multi-functional design eliminates the need for separate insulation components for each safety requirement.
2Device complexity
If basic insulation alone is used, then device complexity is reduced, but electrical shock protection is insufficient for user-accessible circuits
Solution Approach 1:
The patent merges basic insulation and supplemental insulation into a single integrated insulation structure. The insulation layer provides basic insulation while the extension layer provides supplemental insulation, together achieving the protection level required for user-accessible circuits without requiring separate insulation components.
Solution Approach 2:
The insulation structure uses thin film insulation layers that extend beyond the primary conductor to provide both basic and supplemental insulation. This flexible film-based approach achieves the required double insulation protection while maintaining a compact and simple device structure.
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 design achieves reinforced isolation for high working voltages up to 500 VRMS, meeting safety standards by ensuring adequate insulation thickness and spacing, thereby reducing the risk of electrical shock and enhancing the safety of the current sensor.
Implementation Method 1
a magnetic field sensing circuit to sense a magnetic field associated with a current through the primary conductor and to generate a secondary signal indicative of the current
Data Source
AI summary
A current sensor integrated circuit includes a lead frame having a primary conductor and at least one secondary lead, a semiconductor die disposed adjacent to the primary conductor, an insulation structure disposed between the primary conductor and the semiconductor die, and a non-conductive insulative material enclosing the semiconductor die, the insulation structure, a first portion of the primary conductor, and a first portion of the at least one secondary lead to form a package. The first portion of the at least one secondary lead (between a first end proximal to the primary conductor and a second end proximal to the second, exposed portion of the at least one secondary lead) has a thickness that is less than a thickness of the second, exposed portion of the least one secondary lead. A distance between the second, exposed portion of the primary conductor and the second, exposed portion of the at least one secondary lead is at least 7.2 mm.