Transformerless AC Line Isolator Using SiC MOSFETs
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Solution Overview
Problem
Transformers in power converters have inefficiencies, occupy significant space, and are challenging to manufacture, limiting the design of isolated systems like flyback converters.
Innovation Solution
A transformerless AC line isolator using high-voltage, low-leakage SiC MOS-FETs and a resonant LC circuit operating in QR mode, with a synchronized four-phase control loop to provide electrical isolation without a transformer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transformer is used in power converters, then electrical isolation between input and output circuits is provided, but power losses increase and efficiency decreases
Solution Approach 1:
The patent removes the transformer component from the power converter circuit entirely, extracting the isolation function and replacing it with a resonant tank circuit operating in QR mode. This eliminates the inherent power losses associated with transformer operation while maintaining the essential electrical isolation between input and output circuits through synchronized switching of MOS-FETs.
Solution Approach 2:
The patent changes the operating parameters by using high-voltage, low-leakage MOS-FETs with specific switching characteristics and operates the resonant tank circuit in QR mode rather than traditional continuous conduction mode. These parameter changes enable achieving both isolation and high efficiency without the transformer's energy losses.
2Reliability
If a transformer is used in power converters, then electrical isolation is achieved, but the device occupies significant volume and depth space
Solution Approach 1:
The patent extracts and removes the bulky transformer component from the power converter design. By replacing it with a resonant tank circuit consisting of an inductor and capacitor along with synchronized MOS-FET switching, the patent achieves the same electrical isolation function in a significantly reduced volume, enabling miniaturization of the overall converter design.
Solution Approach 2:
The patent transitions from a magnetic isolation approach (transformer with large z-height) to an electronic isolation approach using resonant circuitry and synchronized switching. This dimensional change eliminates the need for large vertical space typically required for transformer windings and magnetic cores.
3Reliability
If a transformer is used in power converters, then electrical isolation is provided, but construction and manufacturing become very challenging
Solution Approach 1:
The patent removes the transformer, which is notoriously difficult to manufacture with precise winding ratios, tight tolerances, and complex magnetic core assemblies. The replacement resonant tank circuit with discrete inductor, capacitor, and MOS-FET components is significantly easier to manufacture, assemble, and quality-control.
Solution Approach 2:
The patent replaces the mechanical/construction-intensive transformer assembly (winding wires, stacking cores, insulation, bonding) with an electronic circuit implementation using standard discrete components. This substitution dramatically simplifies the manufacturing process while maintaining the isolation function.
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
Significantly reduces power losses and allows for miniaturization of power converter designs, achieving high efficiency conversion up to 97%.
Implementation Method 1
an inductor and a capacitor operating as a link stage resonant LC circuit
Implementation Method 2
a resonant tank circuit operating in QR mode to replace the transformer found in standard power converters
Implementation Method 3
high voltage, low leakage switches, e.g., Silicon Carbide metal-oxide-semiconductor field-effect transistor (SiC MOS-FETs)
Data Source
AI summary
Various systems, apparatuses, and methods are disclosed herein, which provide a new power conversion topology for isolated systems that does not include a transformer. Embodiments of the inventive systems comprise: a switching system utilizing high voltage, low leakage switches, e.g., Silicon Carbide (SiC) MOS-FETs; a power source; an inductor and a capacitor operating as a link stage resonant LC circuit; and a load. The switching system may be configured to be controlled in a synchronized ‘four phase’ control loop process, wherein the input switches are prevented from being closed at the same time as the output switches, thereby providing electrical isolation between the input power source and the load—without the use of a transformer. The techniques disclosed herein are applicable to any number of isolated systems that supply power to electronic systems such as: digital cameras, mobile phones, watches, personal data assistants (PDAs), portable music players, displays, and computers.