Parallel Power Conversion Modules with Cascaded Units
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Solution Overview
Problem
Conventional power systems, such as cascade and quasi-parallel-connected power structures, suffer from low overall efficiency due to the inefficiencies of individual conversion modules, particularly the buck converter, which decreases as the voltage of the DC distribution bus increases, leading to a decrease in overall efficiency.
Innovation Solution
A power device comprising a first conversion module and a second conversion module, where the second conversion module includes a cascade conversion circuit with a second and third conversion unit, allowing real-time detection and adjustment of the output voltage to maintain stability and efficiency, even as the bus voltage fluctuates, by adjusting the ratio of the input voltage to the output voltage of the second conversion unit within a predetermined range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a quasi-parallel-connected power structure with a resonant-type DC/DC converter and a buck converter is used, then the overall efficiency is higher than cascade power structure, but as the bus voltage increases, the efficiency of the buck converter decreases, leading to decreased overall efficiency
Solution Approach 1:
The second conversion module is divided into multiple conversion units (second conversion unit and third conversion unit) connected in cascade. Each unit handles a portion of the voltage conversion, allowing the system to maintain high efficiency across a wide voltage range. The second conversion unit converts the second divided voltage to an intermediate voltage, and the third conversion unit converts the intermediate voltage to the output voltage, distributing the conversion stress and maintaining buck converter efficiency.
Solution Approach 2:
The system dynamically adjusts the operating point of the buck converter by introducing an intermediate voltage stage. The third conversion unit (buck converter) receives a controlled intermediate voltage from the second conversion unit, allowing its input voltage to be optimized regardless of fluctuations in the bus voltage. This dynamic voltage staging maintains the buck converter within its high-efficiency operating range.
2Power
If the bus voltage is increased to meet higher power requirements, then more power can be supplied, but the efficiency of the buck converter and overall power structure decreases
Solution Approach 1:
The voltage conversion process is segmented into multiple stages with intermediate voltage levels. The second conversion unit handles the initial voltage reduction from the divided bus voltage, and the third conversion unit handles the final conversion to output voltage. This segmentation allows each stage to operate at optimized voltage levels, maintaining high efficiency even when the overall bus voltage is high.
Solution Approach 2:
An intermediate voltage is introduced as a mediator between the high bus voltage and the final output voltage. The second conversion unit generates this intermediate voltage, which serves as the input to the third conversion unit (buck converter). This intermediary voltage level allows the buck converter to maintain high efficiency by receiving a controlled input voltage regardless of the bus voltage level.
3Device complexity
If a fixed ratio resonant-type DC/DC converter is used in the first conversion module, then the circuit design is simplified, but the system cannot adapt to bus voltage fluctuations, causing efficiency degradation
Solution Approach 1:
The system introduces dynamic voltage adjustment through the second conversion unit, which converts the second divided voltage to an intermediate voltage that can be dynamically controlled. This allows the third conversion unit (buck converter) to receive a stabilized intermediate voltage even when the bus voltage fluctuates, maintaining high efficiency without requiring the first conversion module to be complex or adaptive.
Data Source
AI summary
A power device includes a first conversion module and a second conversion module. The first conversion module includes a first conversion unit and receives a first divided voltage of a bus voltage. The second conversion module includes a cascade conversion circuit with a second conversion unit and a third conversion unit. The input terminal of the second conversion module and the input terminal of the first conversion module are connected with each other in series. The input terminal of the second conversion module receives a second divided voltage of the bus voltage. The output terminal of the second conversion module and the output terminal of the first conversion module are electrically connected with each other in parallel so as to provide an output voltage to a load. The third conversion unit detects the output voltage to control the output voltage stable.