Partial Power Switching Converter With Series Branch Voltage Control
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Solution Overview
Problem
Partial Power Processing (PPP) converters in battery chargers face challenges in achieving high efficiency and power density while maintaining a wide output voltage range, requiring high-breakdown voltage transistors that are costly and inefficient due to the need for a significant fraction of power processing in the partial power branch.
Innovation Solution
A power conversion circuit with a first converter stage generating a DC bus voltage and a second stage comprising a main branch with a fixed conversion ratio and a partial power branch with an adjustable output, where the outputs are connected in series, and a controller adjusts both the DC bus voltage and partial power branch voltage to achieve the desired output voltage, allowing for the use of transistors with lower breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the partial power branch processes a significant fraction of power to achieve wide output voltage range, then the output voltage regulation capability is improved, but the efficiency deteriorates due to increased losses in the partial power branch
Solution Approach 1:
The power conversion system is divided into two independent converter stages: a first stage (e.g., PFC converter) that generates a high DC bus voltage, and a second stage (PP converter) that steps down the voltage to the output level. This segmentation allows each stage to operate optimally - the first stage handles power factor correction at high voltage, while the second stage provides voltage regulation with reduced losses.
Solution Approach 2:
A high-voltage DC bus acts as an intermediary between the input AC power and the output DC power. The first converter stage converts AC to this intermediate DC bus voltage, and the second stage converts it to the final output voltage. This intermediary approach enables independent optimization of each conversion stage and improves overall efficiency.
2Adaptability or versatility
If high-breakdown voltage transistors are used to handle the wide output voltage range, then the output voltage regulation capability is improved, but the cost and device complexity increase
Solution Approach 1:
The voltage conversion function is segmented across two converter stages. The first stage operates at high voltage to establish a high DC bus, while the second stage operates at reduced voltage to provide the final output. This allows the use of lower-breakdown-voltage transistors in the second stage, reducing cost and complexity while maintaining wide output voltage capability.
Solution Approach 2:
The system changes the operating voltage parameters between stages. The first converter stage operates at high voltage (e.g., several hundred volts DC bus), while the second stage operates at lower voltage levels appropriate for the output requirements. This parameter change enables the use of more economical transistors with lower breakdown voltages in the second stage.
3Device complexity
If a single converter stage is used to provide wide output voltage range, then the device complexity is reduced, but the efficiency deteriorates due to increased losses in voltage regulation
Solution Approach 1:
The voltage conversion and regulation functions are segmented into two converter stages. The first stage performs bulk voltage conversion to a high DC bus, while the second stage performs the actual voltage regulation to the output level. This segmentation concentrates regulation losses in the second stage only, improving overall efficiency compared to a single-stage design where the entire power would undergo regulation losses.
Data Source
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AI summary
A power conversion circuit is described herein. In accordance with one embodiment, the circuit includes a first converter stage configured to provide a DC bus voltage and a second converter stage configured to receive the DC bus voltage and to generate an output voltage therefrom. The second converter stage includes at least a main branch and a partial power branch, wherein the main branch is configured to provide, at its output, a first voltage from the DC bus voltage based on a fixed conversion ratio and the partial power branch is configured to provide, at its output, an adjustable second voltage from the DC bus voltage. The outputs of the main branch and the partial power branch are connected in series to provide the output voltage. The circuit further includes a controller configured to control, in order to set the output voltage, the first converter stage to adjust the DC bus voltage and to control the partial power branch to adjust the second voltage.