High-Voltage Generator Phase-Shifted Inverter Stray Inductance
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Solution Overview
Problem
High-voltage generators for X-ray devices face challenges in compact design due to high stray inductance, leading to voltage drops that require overdimensioned transformers and increased semiconductor current stress, complicating regulation and increasing production costs.
Innovation Solution
A high-voltage generator design featuring two-phase inverters and rectifiers with a 90° phase offset, transforming inverter voltages into rectifier voltages that are proportional to their sum and difference, reducing output capacitance and allowing soft switching, and achieving favorable regulation dynamics similar to a first-order system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a compact transformer design is used, then the device size is reduced, but the stray inductance increases causing voltage drop
Solution Approach 1:
The patent divides the single primary winding into two separate primary windings (first primary winding and second primary winding) that are operated with phase shift. This segmentation allows the transformer to achieve compact dimensions while reducing the effective stray inductance impact through phased operation, resolving the contradiction between compact size and low stray inductance.
Solution Approach 2:
The patent employs dynamic phase-shifting operation of the two primary windings, where the windings are activated cyclically with different phases. This dynamic operation mode enables the transformer to maintain compact physical dimensions while the phased activation reduces the effective stray inductance, preventing excessive voltage drop under load.
2Reliability
If the transformation ratio is overdimensioned to compensate for voltage drop, then the output voltage is maintained under load, but the inverter current rms value increases
Solution Approach 1:
The patent uses dynamic phase-shifting operation of two primary windings to reduce the rms value of inverter currents. By cyclically activating the windings with phase shift, the current waveform is optimized, reducing the rms current while maintaining adequate voltage transformation ratio, thus resolving the contradiction between voltage stability and current magnitude.
Solution Approach 2:
The patent changes the operational parameters by introducing phase-shifting between two primary windings and varying the duty cycle dynamically. This parameter optimization allows maintaining output voltage stability under load without requiring excessive transformation ratio, thereby keeping inverter currents at acceptable levels.
3Reliability
If a series resonant converter is used to compensate for stray inductance, then load-independent output voltage is achieved, but the regulation becomes complex due to second-order system behavior
Solution Approach 1:
The patent segments the single primary winding into two windings operated in parallel with phase shift, effectively transforming the second-order resonant system into a simpler control structure. This segmentation allows achieving load-independent output voltage through duty cycle control without the complexity of frequency variation required in series resonant converters.
Solution Approach 2:
The patent uses duty cycle as the primary control parameter instead of frequency variation. By dynamically adjusting the duty cycle of the phase-shifted primary windings, the system achieves load-independent output voltage with simpler first-order system behavior, avoiding the complex second-order dynamics of traditional series resonant converters.
4Object-generated harmful factors
If series resonant converter is used, then voltage drop compensation is achieved, but hard switching cannot be avoided without frequency variation and current zero-crossing measurement
Solution Approach 1:
The patent employs dynamic phase-shifting operation that naturally creates soft switching conditions. The cyclically activated primary windings with phase shift ensure that semiconductor switches turn on when voltage is zero or near-zero, eliminating hard switching losses without requiring frequency variation or complex zero-crossing detection circuits.
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 design reduces semiconductor current stress, allows for compact transformer design, and simplifies regulation by enabling soft switching, while maintaining load-independent output voltage control.
Implementation Method 1
The inverter in this case feeds two primary winding systems of the transformer with inverter voltages that the transformer transforms into two rectifier voltages
Data Source
AI summary
A high-voltage generator for an X-ray device includes an input-side inverter unit, an output-side rectifier unit and a transformer connected between the inverter unit and the rectifier unit. The inverter unit is configured to generate two inverter voltages that are phase-shifted with respect to each other. These inverter voltages are transformed by the transformer into two rectifier voltages that are fed to the rectifier unit such that in no-load operation, one of the two rectifier voltages is proportional to the sum of the inverter voltages while the other of the two rectifier voltages is proportional to the difference between the inverter voltages.