Resonant DC/DC Converter Frequency Adaptation for Current Balancing
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Solution Overview
Problem
In high-current applications, achieving homogeneous distribution of losses and balancing currents across parallel semiconductor switches is challenging due to parasitics, inhomogeneous temperatures, and semiconductor property variations, leading to reduced system reliability and increased complexity.
Innovation Solution
A resonant DC/DC converter with parallel semiconductor switches and a control method that uses split resonant capacitors and current sensing to maintain balanced current distribution and adapt switching frequency when defects occur, ensuring stable and reliable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a large number of semiconductor switches are put in parallel to handle large currents, then the current handling capability is improved, but the current distribution becomes inhomogeneous due to parasitics, temperature variations, and semiconductor property variations
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the switching frequency of parallel converter bridges based on detected current distribution deviations. When current homogeneity deteriorates, the control unit modifies the switching frequency to compensate for parasitic effects and semiconductor variations, thereby restoring balanced current distribution while maintaining high power handling capability
Solution Approach 2:
The patent implements feedback control by continuously monitoring current distribution across parallel semiconductor switches and using this information to adjust switching parameters. The control unit detects current deviations and automatically modifies operating conditions to maintain homogeneous current distribution, creating a closed-loop system that adapts to varying thermal and electrical conditions
2Reliability
If switching frequency is increased to improve current balancing in parallel switches, then current distribution homogeneity is improved, but switching losses increase
Solution Approach 1:
The patent applies dynamics by making the switching frequency adjustable rather than fixed. The system dynamically adapts the switching frequency based on real-time current distribution measurements, allowing optimal frequency selection that balances current homogeneity requirements with switching loss minimization under different operating conditions
Solution Approach 2:
The patent changes the switching frequency parameter dynamically to achieve current balancing without permanently increasing switching losses. By adjusting frequency only when and where needed based on detected imbalances, the system maintains energy efficiency while restoring current homogeneity when parasitic effects cause deviations
3Reliability
If additional balancing measures are implemented to achieve homogeneous current distribution, then current balancing is improved, but device complexity increases
Solution Approach 1:
The patent uses feedback control to achieve current balancing with minimal additional complexity. By monitoring current distribution and automatically adjusting switching frequency through existing control circuitry, the system achieves homogeneous current sharing without requiring complex active balancing circuits or additional balancing components
Solution Approach 2:
The patent enables the parallel switch system to self-correct current distribution imbalances through automatic frequency adjustment. The control unit detects deviations and autonomously modifies operating parameters to restore homogeneity, eliminating the need for external balancing interventions or complex control algorithms
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 enhances system reliability by maintaining homogeneous current distribution and adapting to switch failures, reducing the need for additional balancing measures and increasing the reliability of high-current applications.
Implementation Method 1
a resonant circuit with a resonant frequency fres, in particular comprising the first plurality of N capacitors and the plurality of M primary windings
Data Source
Figure 1a~1c
Figure 2
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AI summary
A resonant DC/DC comprises: a first DC link, preferably comprising a first DC link capacitor; a DC/AC converter comprising a first plurality of N>1 converter bridges connected in parallel to the first DC link; each converter bridge comprising a plurality of switches each of which may be switched between a conducting state and a non-conducting state; an AC intermediate circuit having an input connected to an output of the DC/AC converter and comprising: a transformer, preferably a medium frequency transformer, having a primary side and a secondary side; with the primary side comprising at least one primary winding; a first plurality of N capacitors, wherein for each converter bridge, a different one from the first plurality of capacitors is connected between said converter bridge and the at least one primary winding; a control unit configured to switch semiconductor switches of the inverter bridges between the conducting and the non-conducting state or vice versa with a predetermined first switching frequency to supply an AC current and/or voltage to the AC intermediate circuit; a plurality of N current sensing means, wherein for each inverter bridge a different one of the plurality of current sensing means is provided for monitoring a current through said inverter bridge; wherein the control unit is configured to determine whether a current through one of the inverter bridges deviates from an expected value; and to adapt, in particular increase, the predetermined first switching frequency the current through one of the inverter bridges deviates from the expected value.