Isolated PCB Transformer Layout Using Triple-Insulated Wire
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Solution Overview
Problem
Conventional isolation transformer designs are impractical for high frequency and high voltage applications due to the need for large creepage distances that exceed the compact size requirements, especially when using GaN power transistors, which operate at frequencies of several hundred kHz to a few MHz and voltages of several hundred volts.
Innovation Solution
The use of separate printed circuit boards with a transformer and insulated wire connections, where the transformer windings and their connections are made using triple insulated wire, eliminating the need for traditional creepage distances by ensuring compliance through clearance requirements, thereby allowing compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional isolation transformer designs are used with solid insulation and spacers to ensure creepage distance requirements, then electrical safety is improved, but the transformer size and weight increase significantly
Solution Approach 1:
The patent changes the insulation parameter from solid insulation with spacers to triple-insulated wire, fundamentally altering how creepage distance requirements are satisfied. This parameter change enables compact design while maintaining electrical safety by embedding insulation within the wire structure itself rather than relying on external spacing components.
Solution Approach 2:
The triple-insulated wire comprises multiple insulation layers (typically three) with different material properties, creating a composite structure that provides enhanced creepage protection. This composite approach allows the wire to inherently satisfy creepage distance requirements without additional spacers or solid insulation, reducing overall transformer size and weight.
2Reliability
If creepage distance requirements are met using solid insulation and spacers in conventional designs, then tracking protection is improved, but the device complexity increases
Solution Approach 1:
The patent extracts the creepage protection function from the external structure (spacers and solid insulation layers) and embeds it directly into the wire insulation itself. This eliminates the need for separate creepage protection components, simplifying the overall isolation structure while maintaining tracking protection.
Solution Approach 2:
The patent merges the functions of conductor, insulation, and creepage protection into a single triple-insulated wire component. This consolidation eliminates the need for separate spacers and solid insulation layers, reducing device complexity while ensuring adequate tracking protection through the multi-layer insulation structure.
3Productivity
If GaN power transistors are used for high frequency operation, then productivity is improved, but the required creepage distance exceeds compact design requirements
Solution Approach 1:
The patent changes the insulation configuration parameter to triple-insulated wire, which provides sufficient creepage distance within a compact form factor. This enables the use of GaN power transistors for high-frequency operation without requiring excessive creepage distances that would compromise compact design.
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 enables high frequency and high voltage operation while meeting safety standards, reducing the size and weight of transformers by using insulated wire connections that do not require extensive creepage distances, thus facilitating the use of GaN power transistors in compact switch mode power supplies.
Implementation Method 1
The isolation between the high voltage section and the low voltage section takes place across an isolating transformer
Implementation Method 2
The creepage distance is the shortest path between two conductive parts measured along the surface of the insulation between them. A proper and adequate creepage distance protects against tracking
Implementation Method 3
The clearance distance is the shortest distance between two conductive parts measured through air. A sufficient clearance distance prevents dielectric breakdown between electrodes caused by the ionization of air
Data Source
AI summary
A circuit comprises a first printed circuit board (60) carrying a first set of components and a second printed circuit board (62) carrying a second set of components, with a clearance (64) between the first and second printed circuit boards. A transformer (66) has a primary side connected to the first set of components and a secondary side connected to the second set of components. One of the transformer windings, and its connection to a respective set of components, comprises a triple insulated wire. A glass, ceramic or mica spacer (70) mounted to the first and second printed circuit boards defines and sets the clearance (64) between the first and second printed circuit boards. The clearance requirement is met by providing separate printed circuit boards with spacing between them and the use of a triple insulated wire addresses or overcomes issues of creepage. Thus, high frequency and high voltage operation on the first printed circuit board is possible.