Modular DC-DC Converter Architecture for AC Loss Reduction
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Solution Overview
Problem
Conventional DC-DC boost converters face efficiency degradation due to various loss mechanisms, particularly AC losses, which increase with switching frequency, and are thermally limited, leading to reduced output power and increased costs per watt, with inefficiencies also evident at lower output powers and voltages.
Innovation Solution
A modular DC-DC converter architecture incorporating a DC transformer (DCX) module and multiple converter modules, such as boost and buck modules, operating in pass-through modes to reduce AC losses, employ lower-voltage semiconductor devices, and share voltage stresses, thereby reducing capacitor and inductor sizes and improving efficiency across a range of conversion ratios and output powers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional DC-DC boost converter is used to increase output voltage, then voltage conversion is achieved, but efficiency degrades due to AC losses increasing with switching frequency
Solution Approach 1:
The converter is divided into multiple modular units (first converter module, second converter module, DC transformer module) that can operate independently or in combination. This segmentation allows the system to achieve voltage conversion while distributing AC losses across multiple lower-frequency operating units, thereby improving overall efficiency.
Solution Approach 2:
The DC transformer module serves as an intermediary component between the first and second converter modules. It provides galvanic isolation and voltage transformation with reduced AC losses compared to conventional direct conversion, acting as a mediator that enables efficient high-voltage output without proportionally increasing AC losses.
2Power
If higher switching frequency is used to increase output power, then power delivery capability improves, but thermal limits are exceeded and cooling system size increases
Solution Approach 1:
The power conversion function is segmented across multiple modules operating at different switching frequencies. The DC transformer module operates at a lower frequency with reduced losses, while the converter modules operate at higher frequencies for responsive control. This segmentation allows high output power capability while distributing thermal generation across multiple smaller heat sources that are easier to manage.
3Power
If conventional boost converter topology is used, then voltage conversion is achieved, but efficiency at lower output powers is significantly reduced
Solution Approach 1:
The system dynamically switches between different operational modes: the converter modules can operate in pass-through mode at lower powers to maintain high efficiency, while the DC transformer module provides voltage transformation. This dynamic operational flexibility allows the system to maintain high efficiency across a wide range of output power levels from partial to full load.
4Speed
If higher voltage semiconductor devices are used to handle increased voltage stress, then voltage conversion ratio improves, but device cost and performance degrade
Solution Approach 1:
The voltage stress is segmented and distributed across multiple semiconductor devices in different modules. Each device only needs to handle a portion of the total voltage stress, allowing the use of lower-voltage-rated, lower-cost semiconductor devices while still achieving high overall voltage conversion ratios through the cascaded modular architecture.
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 modular architecture achieves high efficiency over a wide range of operating points, reduces capacitor size and AC losses, and allows the use of lower-voltage semiconductor devices, resulting in increased output power and reduced costs per watt while maintaining high efficiency at both maximum and lower power levels.
Implementation Method 1
a DC transformer (DCX) module and multiple converter modules, such as boost and buck modules
Implementation Method 2
When the transistor Q is ON, energy from an input source is stored in the inductor L. When the transistor Q is OFF, the diode D becomes forward-biased by an inductor current, and energy stored in the inductor L is released to the output.
Implementation Method 3
When the transistor Q is OFF, the diode D becomes forward-biased by an inductor current, and energy stored in the inductor L is released to the output.
Data Source
AI summary
A modular dc-dc boost converter system is provided that can substantially improve efficiency over a wide range of input and output voltages. The system includes three modules: a buck module, a boost module, and a dc transformer module. These modules are interconnected such that the system output voltage is equal to the sum of the output voltages of adc-dc converter module and a dc transformer module. Depending on the operating point, one or more modules may operate in passthrough mode, leading to substantially reduced ac losses. The required capacitor size and the transistor voltage ratings are also substantially reduced, relative to a conventional single dc-dc boost converter operating at the same input and output voltages.