Paralleled DC-DC Converters Using LC Circuits to Suppress Circulating Current
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Solution Overview
Problem
In paralleled DC-DC converters, circulating currents develop due to asynchronous control of switching circuits and voltage ripple, leading to inefficiencies and increased costs with conventional large inductance solutions.
Innovation Solution
The implementation of inductor-capacitor (LC) circuits tuned to the switching frequency, either in series or parallel configurations, to shunt or block circulating currents at the switching frequency, reducing noise and impedance in the forward path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional large inductance solutions are used to suppress circulating currents, then circulating current suppression is improved, but device complexity and cost increase
Solution Approach 1:
The patent changes the impedance characteristics of the circuit by introducing LC resonant circuits tuned to the switching frequency. Instead of using large inductance values across all frequencies, the patent creates frequency-selective impedance by adjusting the resonant frequency of LC circuits to match the switching frequency, thereby suppressing circulating currents at that specific frequency without requiring large inductance values across the entire frequency spectrum.
Solution Approach 2:
The patent introduces LC resonant circuits as intermediary elements between the paralleled converters. These LC circuits act as frequency-selective mediators that block circulating currents at the switching frequency while allowing other frequencies to pass, thereby suppressing the harmful circulating currents without requiring large inductors directly in the converter paths.
2Reliability
If conventional large inductance solutions are used to suppress circulating currents, then circulating current suppression is improved, but cost increases
Solution Approach 1:
The patent changes the impedance characteristics of the circuit by introducing LC resonant circuits tuned to the switching frequency. Instead of using large inductance values across all frequencies, the patent creates frequency-selective impedance by adjusting the resonant frequency of LC circuits to match the switching frequency, thereby suppressing circulating currents at that specific frequency without requiring large inductance values across the entire frequency spectrum.
Solution Approach 2:
The patent introduces LC resonant circuits as intermediary elements between the paralleled converters. These LC circuits act as frequency-selective mediators that block circulating currents at the switching frequency while allowing other frequencies to pass, thereby suppressing the harmful circulating currents without requiring large inductors directly in the converter paths.
3Reliability
If large inductance is introduced to suppress circulating currents, then circulating current suppression is improved, but impedance in the forward path increases
Solution Approach 1:
The patent changes the impedance characteristics from being frequency-independent (large inductance at all frequencies) to frequency-dependent (LC resonant circuits with low impedance at DC and specific frequencies, high impedance only at the switching frequency). This allows the circuit to suppress circulating currents at the switching frequency while maintaining low impedance for the forward power path at other frequencies.
Solution Approach 2:
The patent applies frequency-selective impedance suppression only at the specific switching frequency where circulating currents occur, rather than introducing high impedance across all frequencies. The LC resonant circuits provide high impedance locally at the switching frequency while maintaining low impedance for the forward power path at other frequencies, thus suppressing circulating currents without harming the forward power transmission.
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
Effectively suppresses circulating currents around the switching frequency without introducing large impedances, improving efficiency and reducing costs by using LC circuits that resonate at or near the switching frequency.
Implementation Method 1
Each of the plurality of LC series circuits has a resonant frequency at or around a switching frequency for the plurality of switches of the associated paralleled converter
Implementation Method 2
Each of the plurality of LC parallel circuits has a resonant frequency at or around a switching frequency for the plurality of switches of the associated paralleled converter
Data Source
AI summary
A converter includes a DC bus, a first DC-DC converter, a second DC-DC converter, and a plurality of circulating current suppression circuits. The first DC-DC converter is coupled to the DC bus and includes a first plurality of switches. The second DC-DC converter is coupled to the DC bus in parallel with the first DC-DC converter. The second DC-DC converter includes a second plurality of switches. The plurality of circulating current suppression circuits are coupled to the DC bus and are further respectively coupled to the first DC-DC converter and the second DC-DC converter. Each of the plurality of circulating current suppression circuits has a resonant frequency at or around a switching frequency for the first and second pluralities of switches. The plurality of circulating current suppression circuits is configured to suppress current at or around the switching frequency and pass at least direct current.