Buck-Boost PFC Converter for Wide Voltage EV Charging
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Solution Overview
Problem
Commercially available on-board battery chargers for electric vehicles have limited output voltage ranges, requiring separate chargers for different electric vehicles and resulting in inefficient magnetic component usage and reduced charging efficiency at lower voltage ranges.
Innovation Solution
A battery charger with a power factor correction converter that dynamically operates in buck, boost, or intermediate buck and boost modes to generate a wide output voltage range, using a buck-boost PFC converter to accommodate lower DC-link voltages and minimize the size and weight of magnetic components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a boost PFC converter is used to generate high fixed DC-link voltage, then input power quality is maintained, but the size and weight of magnetic components in the second stage increase and charging efficiency decreases at lower voltage ranges
Solution Approach 1:
The PFC converter dynamically switches between boost mode and buck mode based on the relationship between instantaneous rectified AC input voltage and reference output voltage. This dynamic operation allows the DC-link voltage to vary within a wide range (50-500V) rather than maintaining a fixed high voltage, thereby reducing magnetic component size and weight while maintaining power quality
Solution Approach 2:
The invention changes the operating parameters of the PFC converter by introducing variable DC-link voltage operation. The controller adjusts the DC-link voltage based on battery voltage requirements, enabling the system to operate efficiently across different voltage ranges (36-72V, 72-150V, 200-450V) without requiring separate chargers or large magnetic components designed for fixed high voltage
2Reliability
If separate battery chargers are used for different electric vehicle voltage requirements, then each charger is optimized for its specific voltage range, but device complexity and the number of required chargers increase
Solution Approach 1:
The battery charger is designed with universal adaptability to charge multiple types of electric vehicles with different voltage requirements (36-72V, 72-150V, 200-450V). The PFC converter's dynamic buck-boost operation and the DC-DC converter's variable ratio work together to provide a single charger solution that replaces multiple dedicated chargers, maintaining charging efficiency across all voltage ranges
3Use of energy by moving object
If high fixed DC-link voltage is generated, then power factor correction is achieved, but the operation of the second stage becomes less efficient at lower voltage ranges
Solution Approach 1:
The system dynamically adjusts the DC-link voltage to match the battery voltage requirements. When charging lower voltage batteries (36-72V, 72-150V), the PFC converter operates in buck mode or intermediate mode to generate lower DC-link voltages, thereby improving the efficiency of the second stage DC-DC converter and reducing energy losses
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
Enables efficient charging across a wide voltage range (50-500 V) with improved power quality and reduced size and weight of the charger, allowing a single charger to support various electric vehicle types without the need for multiple chargers.
Implementation Method 1
a power factor correction converter configured to receive a rectified alternating-current (AC) input voltage and generate a direct-current (DC) output voltage, the power factor correction converter comprising: a boost circuit having at least one boost switch; a buck circuit, cascaded with the boost circuit, and having a buck switch
Data Source
AI summary
Various embodiments of a two-stage on-board battery charger that can generate a wide range of output voltages is described herein. Generally, the battery charger employs a first stage buck and boost Power Factor Correction (PFC) converter, and a second stage DC-DC converter. The buck and boost PFC converter is capable of generating variable intermediate DC-link voltages which allow the on-board battery charger to efficiently generate the wider range of output voltages.