Magnetically Isolated Feedback Circuit for Radiation-Hardened Power Supplies
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Solution Overview
Problem
Conventional feedback circuits in regulated power supplies require electrical isolation, which is not feasible in environments with high radiation levels, such as space, and often rely on optocouplers that may not be suitable for all applications.
Innovation Solution
A magnetically isolated feedback circuit comprising an isolated gate drive circuit and a forward converter circuit that produces bi-polar pulses to sample the load voltage and provide feedback to a pulse width modulator, eliminating the need for secondary-side oscillator ICs and reducing stress on the gate drive of the feedback transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optocouplers are used to provide electrical isolation in feedback circuits, then electrical isolation is achieved, but the circuit becomes unsuitable for high radiation environments such as space
Solution Approach 1:
The patent replaces the optocoupler-based optical isolation mechanism with a magnetic isolation mechanism using a feedback transformer. The transformer provides galvanic isolation through magnetic coupling between primary and secondary windings, eliminating the need for optocouplers and making the circuit suitable for radiation-hardened applications while maintaining electrical isolation functionality.
2Reliability
If feedback windings are incorporated in the main transformer, then isolation is provided, but the transformer design becomes more complex and stressful
Solution Approach 1:
The patent separates the isolation function from the main power transformation function by using a dedicated feedback transformer. This segmentation allows the main transformer to focus on power conversion while the feedback transformer handles isolation and feedback signal transmission, reducing stress and design complexity on the main transformer.
Solution Approach 2:
The feedback transformer serves multiple functions: providing galvanic isolation, transmitting feedback signals, and enabling voltage sampling. This multi-functionality consolidates what would otherwise require separate components, simplifying the overall design while maintaining isolation performance.
3Reliability
If a conventional feedback circuit is used, then electrical isolation is achieved, but the gate drive of the feedback transistor experiences high stress
Solution Approach 1:
The patent introduces an isolated gate drive circuit as an intermediary between the feedback transformer and the feedback transistor. This intermediate stage buffers and conditions the feedback signal, reducing stress on the gate drive while maintaining the isolation capability provided by the transformer.
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 solution provides stable and tightly regulated output voltage, is rad/SEE-hardened, and can be used in space and nuclear applications, offering improved performance and reliability without the need for feedback windings in the main transformer.
Implementation Method 1
an isolated gate drive circuit operable to receive a plurality of pulses, wherein the isolated gate drive circuit produces a plurality of isolated bi-polar pulses from the plurality of pulses
Implementation Method 2
The plurality of isolated bi-polar pulses causes the forward converter circuit to sample a voltage at the load as a sampled voltage
Data Source
AI summary
Magnetically isolated feedback circuits and regulated power supplies are disclosed. In some embodiments, a magnetically isolated feedback circuit includes an isolated gate drive circuit and a forward converter circuit. The isolated gate drive circuit is operable to receive a plurality of pulses, wherein the isolated gate drive circuit produces a plurality of isolated bi-polar pulses from the plurality of pulses. The forward converter circuit is electrically coupled to the isolated gate drive circuit and is operable to be electrically coupled to a load. The plurality of isolated bi-polar pulses causes the forward converter circuit to sample a voltage at the load as a sampled voltage. The forward converter circuit is operable to provide the sampled voltage to a feedback input of a pulse width modulator.