Dual Active Bridge Converter Timing Control for Hard Switching Loss
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Solution Overview
Problem
Commonly used DAB converters experience reactive current issues and hard switching due to energy transfer from both the primary and secondary DC power sources, especially under light load conditions, leading to inefficiencies and energy loss.
Innovation Solution
A bidirectional insulated DC-DC converter design featuring a first and second bridge circuit connected in parallel, with an insulated transformer and a control circuit that manages switching elements to prevent reactive current by controlling phase differences and using synchronous rectification, thereby reducing conduction losses and hard switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a commonly-used DAB converter charges the reactor from both primary and secondary DC power sources, then power transfer capability is achieved, but reactive current is produced and hard switching occurs leading to energy loss
Solution Approach 1:
The patent segments the power transfer process into distinct phases: a first period where only the primary DC power source charges the reactor, and a second period where only the secondary DC power source charges the reactor. This segmentation prevents simultaneous charging that causes reactive current, while maintaining bidirectional power transfer capability through controlled phase alternation.
Solution Approach 2:
The patent implements periodic action by alternating between two distinct operating periods: a first period for primary-side power transfer and a second period for secondary-side power transfer. This periodic switching eliminates continuous reactive current flow while maintaining the ability to transfer power in both directions, resolving the contradiction between power transfer capability and energy loss.
2Power
If phase difference control is used to regulate output power, then power control is achieved, but conduction losses increase under light load conditions
Solution Approach 1:
The patent dynamically adjusts the operating mode based on load conditions. Under light load conditions, it switches to a mode where the reactor is charged exclusively from one DC power source during dedicated periods, minimizing conduction losses. Under heavier load conditions, it transitions to utilizing both power sources. This dynamic adaptation resolves the contradiction between maintaining power control capability and reducing conduction losses.
Solution Approach 2:
The patent changes the operating parameters by switching between different charging configurations: single-source charging for light loads to minimize losses, and dual-source charging for heavier loads to maintain power transfer capability. This parameter change strategy allows the system to optimize efficiency across different operating conditions while maintaining effective power control.
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 solution achieves a highly efficient power conversion by minimizing reactive power and conduction losses, enhancing the overall efficiency of the DC-DC converter and preventing hard switching, making it suitable for bidirectional power transfer across a wide voltage range.
Implementation Method 1
an insulated transformer connected between the first bridge circuit and the second bridge circuit
Implementation Method 2
Diodes are connected or formed in antiparallel to the first switching element-the eighth switching element, respectively
Data Source
Figure 1
Figure 2A~2F
Figure 3A~3B
AI summary
For power transfer from a first DC part to a second DC part in a dual active bridge (DAB) converter by stepping down a voltage, a first bridge circuit 11 includes a period in which the first DC part and a primary winding n1 of an insulated transformer TR1 conduct and a period in which ends of a primary winding n1 of the insulated transformer TR2 are short-circuited in the first bridge circuit 10. A second bridge circuit 12 includes a rectification period. A control circuit 13 variably controls a phase difference between a first leg a the second leg, variably controls a simultaneous off period of a fifth switching element and a sixth switching element, and variably controls a simultaneous off period of a seventh switching element and an eighth switching element.