Single-Stage Buck-Boost AC-DC Charger With Input PFC
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Solution Overview
Problem
Conventional UPS systems face challenges in efficiently charging batteries while maintaining power factor correction without using isolation transformers, leading to increased complexity, cost, and lower efficiency, especially when dealing with varying AC input voltages and non-isolated battery connections.
Innovation Solution
A single-stage AC-DC battery charger using a buck-boost converter is integrated with a PFC stage, allowing direct power draw from the AC mains and avoiding processing through the PFC stage, thereby achieving high efficiency, low cost, and high power density with PFC capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional two-stage AC-DC converter with isolation transformer is used for battery charging, then power factor correction is achieved, but device complexity and cost increase
Solution Approach 1:
The patent combines the PFC function and battery charging function into a single integrated AC-DC converter stage, eliminating the need for separate PFC circuitry and isolation transformers. The single-stage converter directly charges the battery from AC mains while maintaining power factor correction, thereby reducing component count and system complexity while achieving both PFC capability and reliable battery charging.
Solution Approach 2:
The single-stage AC-DC converter is designed to perform multiple functions simultaneously: it provides power factor correction, performs rectification, and charges the battery. This multi-functional design eliminates the need for dedicated PFC circuitry and isolation transformers, reducing overall system complexity while maintaining all required capabilities.
2Reliability
If a conventional two-stage AC-DC converter with isolation transformer is used for battery charging, then power factor correction is achieved, but manufacturing cost increases
Solution Approach 1:
The patent merges the PFC stage and battery charging stage into a single AC-DC converter, eliminating the need for expensive isolation transformers and separate PFC circuitry. This integration reduces component count, simplifies manufacturing, and lowers overall system cost while maintaining power factor correction capability.
Solution Approach 2:
The patent extracts and eliminates the isolation transformer from the conventional two-stage architecture, realizing that it is not necessary for battery charging applications where galvanic isolation is not required. This removal of unnecessary components directly reduces manufacturing cost and complexity.
3Reliability
If a conventional two-stage AC-DC converter is used for battery charging, then power factor correction is achieved, but conversion efficiency decreases
Solution Approach 1:
The patent combines PFC and battery charging into a single conversion stage, eliminating the intermediate DC link and associated losses. The direct single-stage conversion reduces the number of power conversion steps, minimizing energy losses and improving overall conversion efficiency while maintaining power factor correction.
Solution Approach 2:
The single-stage converter enables continuous direct power transfer from AC mains to battery charging without interruption or energy-wasting intermediate stages. This continuous power conversion path eliminates the inefficiencies associated with two-stage conversion, improving overall energy efficiency.
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 provides high efficiency, low cost, and reduced complexity in charging batteries with PFC, suitable for a wide range of AC input voltages, without the need for isolation transformers.
Implementation Method 1
A single-stage AC-DC battery charger using a buck-boost converter is integrated with a PFC stage
Data Source
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AI summary
A power converter includes a battery (104) having a positive terminal and a negative terminal, a first power input (112, 114) to receive AC input power, a second power input to receive DC input power from the battery, a first power output to charge the battery, a second power output to provide power to a load, a rectifier circuit (210) coupled to the first power input (112, 114), and a non-isolated single-stage power conversion circuit (200) having an input and configured as a buckboost converter. The power at the second power output is derived from the first power input and/or the second power input. The single-stage power conversion circuit is configured to convert an AC voltage to a DC voltage using a common energy storage element (228), and is coupled to the first power output and the rectifier circuit (210).