Two-Stage Pulsed Power Supply for Smaller NMR Transformers
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Solution Overview
Problem
NMR power converters face challenges with high volume and cost due to large transformer and capacitor requirements, especially in extreme environments, as they are designed for peak power ratings that are only utilized for a small percentage of the time, leading to underutilization and reliability issues.
Innovation Solution
A two-stage power converter architecture is implemented, where the isolated converter only transfers average power, reducing the power rating and volume of the transformer, and utilizing a boost converter to maintain voltage stability, allowing for a significant reduction in energy storage capacitor size and input filter size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the power converter is designed for peak power rating, then the instantaneous power requirement is met, but the transformer volume and cost increase significantly
Solution Approach 1:
The power converter is divided into two separate stages: an isolated converter handling average power transfer and a boost converter handling peak power delivery. This segmentation allows each stage to be optimized for its specific function, with the transformer only needing to handle average power ratings rather than peak power ratings.
Solution Approach 2:
The isolated converter preliminarily converts input power to an intermediate voltage level and transfers average power to the output. This preliminary action prepares the power in advance, allowing the boost converter to efficiently handle peak power demands without requiring the transformer to be oversized for peak conditions.
2Stability of the object's composition
If large capacitance value is chosen to maintain voltage linearity, then the voltage stability is improved, but the capacitor volume and power density decrease
Solution Approach 1:
The energy storage function is segmented between the isolated converter's output capacitor and the boost converter's input capacitor. The isolated converter's capacitor handles average power ripple, while the boost converter's capacitor handles peak power demands, allowing both to use smaller capacitance values than a single large capacitor would require.
Solution Approach 2:
The system changes the operating parameters by allowing the intermediate voltage to vary within a controlled range rather than maintaining strict linearity. This parameter change enables the use of smaller capacitors while still meeting performance requirements through the coordinated operation of both converter stages.
3Stability of the object's composition
If input filter is added to reduce pulse frequency harmonics, then the input source stability is improved, but the filter volume and device complexity increase
Solution Approach 1:
The harmful pulse frequency harmonics are extracted and isolated at the output of the isolated converter, where they do not affect the input source. The boost converter's switching frequency is chosen to be different from the pulse frequency, further separating the harmonic sources from the input side.
Solution Approach 2:
The isolated converter acts as an intermediary stage between the input source and the pulsed power load. It provides galvanic isolation and transforms the pulsed power requirements into continuous average power transfer, eliminating the need for large input filters while maintaining input source stability.
4Reliability
If high temperature capacitors are used for extreme environment operation, then the reliability at high temperature is improved, but the capacitance value decreases and volume increases
Solution Approach 1:
The energy storage function is segmented between two smaller capacitors in separate converter stages rather than one large capacitor. This allows the use of smaller, more manageable capacitors that can operate reliably at high temperatures without requiring excessive volume or redundancy.
Solution Approach 2:
The system changes the operating parameters by allowing voltage ripple and intermediate voltage variation within controlled ranges. This parameter flexibility enables the use of smaller high-temperature capacitors with lower capacitance values while still meeting performance requirements.
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 increases power density, reduces the size and cost of the power converter, and enhances reliability by minimizing the volume of passive components, while maintaining efficient energy utilization and stability across varying load profiles.
Implementation Method 1
an isolated converter including a transformer. The isolated converter is configured to have a variable voltage at an output thereof
Implementation Method 2
an energy storage component. The variable voltage is input to the energy storage component, and the energy storage component is configured to allow the variable voltage to have a voltage droop
Implementation Method 3
a DC-DC converter. A variable voltage from the energy storage component is input to the DC-DC converter, and the DC-DC converter is configured to convert the variable voltage from the energy storage component to a steady output voltage
Data Source
AI summary
A nuclear magnetic resonance (NMR) power supply system and method are disclosed. The architecture adopts a two-stage topology to reduce the required capacitance by over ten times, leading to a four-fold improvement in power density. The first stage is an isolated converter that only supplies average power, therefore input filter and transformer sizes can be reduced. The second stage is a fast response DC-DC converter followed by a RF transmitter to produce a pulsed RF signal, so that the mid-point voltage after the first stage can be allowed to droop considerably, leading to much smaller sized capacitors. These and other embodiments enforce the isolated converter to only transfer average power, which reduces the power rating and the volume of the system's transformer.