MRI Power Supply Voltage Drop Compensation Circuit
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Solution Overview
Problem
In magnetic resonance imaging (MRI) systems, voltage drops along cables between power supply units and load terminals can degrade the performance of preamplifiers due to cable losses, leading to suboptimal noise factor performance.
Innovation Solution
A power supply apparatus with a voltage comparator, counter, digital-to-analog converter, and phase inverter that compensates for voltage drops by generating a gradually decreasing reference voltage to raise the load power-feed voltage to nominal levels, ensuring consistent operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If power supply unit is distributed outside the examination room or at a side of the scanner, then device layout flexibility is improved, but cable length increases causing voltage drop and performance degradation
Solution Approach 1:
The power supply function is segmented into two parts: the main power supply unit remains outside the examination room for layout flexibility, while a separate voltage compensation circuit is installed at the load end near the scanner. This segmentation allows the power supply to be physically distributed while maintaining voltage stability through local compensation.
Solution Approach 2:
The voltage compensation circuit implements feedback by continuously monitoring the reference voltage at the load end and adjusting the compensation amount based on the detected voltage drop. The circuit compares the expected reference voltage with the actual received voltage and dynamically compensates for the difference, ensuring stable operation despite cable losses.
2Reliability
If cable length is reduced to minimize voltage drop, then voltage stability is improved, but device layout flexibility and installation options are reduced
Solution Approach 1:
The voltage compensation circuit acts as an intermediary between the power supply unit and the load. It receives the degraded voltage through the long cable, compensates for the voltage drop, and provides the corrected reference voltage to the power supply unit, thereby mediating the conflict between long cable length and voltage stability.
Solution Approach 2:
The compensation circuit changes the voltage parameter by adding a compensation voltage to the degraded reference voltage. This parameter transformation converts the unstable, dropped voltage into a stable nominal voltage, allowing the system to maintain reliability regardless of cable length.
3Device complexity
If nominal reference voltage is maintained at the power supply unit, then power supply design is simplified, but voltage drop along the cable causes load end voltage to fall below nominal levels
Solution Approach 1:
The compensation circuit performs preliminary action by pre-calculating and applying the required compensation voltage before the power supply unit uses the reference voltage. This advance compensation ensures that the voltage drop is counteracted before it affects the power supply operation, maintaining nominal voltage levels at the load end.
Solution Approach 2:
The system uses feedback to detect the actual voltage at the load end and adjusts the compensation accordingly. The compensation circuit monitors the voltage drop and dynamically modifies the compensation amount, creating a closed-loop control that maintains nominal reference voltage despite cable losses.
Data Source
AI summary
A power supply apparatus for a magnetic resonance apparatus has a power supply terminal module with a power supply unit and a reference voltage pull-down unit, and a load terminal module with a voltage comparator connected to a load power-feed terminal, which compares a nominal voltage and an actual voltage of the load power-feed terminal. A counter begins counting when the actual voltage is lower than the nominal voltage, and keeps its count unchanged when the actual voltage is equal to the nominal voltage, and emits a signal corresponding to the count to a digital-to-analog converter, connected to a phase inverter, which converts the digital signal to a positive analog voltage. A phase inverter is connected to an output voltage reference terminal of the power supply unit, and inverts the phase of the analog voltage to produce a negative analog voltage that compensates voltage drop loss on a cable between the power supply and the load power-feed terminal.