An isolated bidirectional active-half-bridge resonant DC-DC power converter
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Solution Overview
Problem
Conventional DC-DC power converters face challenges with high current stresses, higher order harmonics, difficulty in achieving zero-voltage switching (ZVS), and reduced power density due to the need for additional capacitors and complex control strategies, especially in bi-directional operations.
Innovation Solution
An isolated bidirectional active-half-bridge resonant (AHBR) DC-DC power converter with a dual compensation scheme and simplified control strategy, utilizing a controller with two control loops to manage switching frequency and phase shift, and a topology with reduced switching devices and inductors to achieve efficient bi-directional power flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional inductive impedance solutions are used, then power conversion is achieved, but current stresses and higher order harmonics increase
Solution Approach 1:
The patent changes the impedance type from pure inductive to resonant by introducing a resonant capacitor in series with the transformer primary winding, creating an LCC resonant network that operates at a specific resonant frequency to reduce current stresses and harmonics
2Power
If resonant impedance with two inductors and a capacitor (LLC) is used, then power conversion is achieved, but device complexity and control difficulty increase
Solution Approach 1:
The patent extracts one inductor from the traditional LLC resonant network, transitioning from an LCC topology with two inductors and one capacitor to a simplified LCC topology with one inductor and one capacitor in series with the transformer primary, reducing component count and control complexity
Solution Approach 2:
The single resonant inductor in the patent serves multiple functions: it provides resonant operation, limits inrush current, and enables zero-voltage switching, replacing the dual-inductor configuration's multiple functions with a more efficient single-component design
3Loss of energy
If ZVS operation is implemented, then switching efficiency is improved, but current ripple at the LV side increases requiring larger output capacitors
Solution Approach 1:
The patent changes the resonant network parameters by using a series LCC configuration with specific inductance and capacitance values that allow ZVS operation while maintaining lower current ripple at the LV side compared to conventional LLC converters, reducing the required output capacitor size
4Adaptability or versatility
If bi-directional operation is implemented in conventional solutions, then power flow flexibility is improved, but additional DC blocking capacitors are required
Solution Approach 1:
The resonant LCC network inherently provides bidirectional power flow capability through its resonant operation characteristics, allowing power to flow in both directions without requiring additional DC blocking capacitors or complex control circuitry, as the resonant tank naturally accommodates bidirectional energy transfer
5Ease of operation
If additional impedance elements are added to achieve higher order impedance, then power conversion control is improved, but power density decreases
Solution Approach 1:
The patent extracts unnecessary impedance elements from higher order configurations (such as LLCL with two inductors and one capacitor on each side), retaining only the essential LCC resonant network with one inductor and one capacitor in series with the transformer primary, thereby maintaining adequate control while improving power density
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
The converter achieves high power density, efficient zero-voltage switching, and simplified control across a wide range of operating conditions, reducing ripple currents and harmonics, and minimizing the number of components.
Implementation Method 1
A resonant inductor, a resonant capacitor, and a first winding of a transformer are connected in series between the first central node and the first negative DC node
Implementation Method 2
a first winding of a transformer are connected in series between the first central node and the first negative DC node. A first inductor and a second inductor are connected in series between a first end and a second end of a second winding of the transformer
Data Source
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AI summary
An isolated bidirectional active-half-bridge resonant DC-DC power conversion apparatus employs dual control strategies to regulate bi-directional power flow between two DC sources. The apparatus includes a first half bridge switching network configured to convert a first DC power to an AC power. A series resonant impedance transfers the AC power to a first winding of a transformer. A first inductor and a second inductor are connected in series across a second winding of the transformer, and form a positive DC node. A second half bridge switching network is connected in parallel with a first clamping capacitor, with a central node connected to the first end of the second winding. A third half bridge switching network is connected in parallel with a second clamping capacitor, with a central node connected with the second end of the second winding. The clamping capacitors are connected with a negative DC node.