Four-Switch Buck-Boost Converter Control for Low-Ripple Charging
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Solution Overview
Problem
Conventional methods for operating a four-switch buck-boost converter in charging stations are not efficient in terms of producing output current, especially when the charger battery voltage is relatively close to the EV battery voltage, leading to inefficiencies in energy transfer.
Innovation Solution
A controller operates the four-switch buck-boost converter in buck, boost, and buck-boost modes based on voltage differences between the source and target batteries, optimizing switch operations to minimize inductor current ripple and achieve highest efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional methods are used to operate a four-switch buck-boost converter in buck-boost mode, then the converter can transfer power between batteries with similar voltages, but the efficiency is reduced due to higher average inductor current and larger current ripple
Solution Approach 1:
The patent implements dynamic switching control where the controller selectively activates different switch configurations based on real-time voltage differential conditions. When voltage difference exceeds a threshold, the system transitions to a more efficient switching pattern, dynamically adapting to operating conditions to minimize losses while maintaining power transfer capability.
Solution Approach 2:
The system changes operational parameters by adjusting which switches are active based on the voltage differential between batteries. By monitoring the voltage difference and transitioning between different switching states, the system optimizes the inductor current characteristics, reducing both average current and ripple to improve overall efficiency.
2Adaptability or versatility
If all four switches operate within the same switching cycle in buck-boost mode, then the converter handles voltage transitions between batteries, but the inductor current ripple increases leading to higher losses
Solution Approach 1:
The patent segments the switching cycle into distinct phases with different switch configurations. Instead of all four switches operating simultaneously in the same cycle, the system divides operation into separate switching intervals where different switch pairs are activated, reducing overlapping current paths and minimizing inductor current ripple.
Solution Approach 2:
The system employs periodic switching patterns where different switch combinations are activated in alternating cycles based on voltage differential conditions. This periodic variation in switching states allows the converter to handle voltage transitions while creating a more favorable current waveform with reduced ripple and lower RMS current.
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 optimized switch control results in the lowest average inductor current and peak-to-peak ripple, enhancing the efficiency of energy transfer between the charging station and EV batteries.
Implementation Method 1
a four-switch buck-boost converter configured to couple to the source battery and the target battery and including an inductor
Data Source
AI summary
A four-switch buck-boost converter configured to couple to a source battery and a target battery includes an inductor and switches S1, S2, S3, and S4 connected so as to define (i) a buck mode in which the switch S3 is always ON, and the switches S1 and S2 control charging and discharging of the inductor, (ii) a boost mode in which the switch S1 is always ON, and the switches S3 and S4 control the charging and the discharging of the inductor, and (iii) a buck-boost mode in which all of the switches S1, S2, S3, and S4 control the charging and the discharging of the inductor. A controller operates the converter in the buck mode, the boost mode, and the buck-boost mode, when it turns the switch S1 ON at a beginning of a switching cycle, and turns the switch S4 ON at an end of the switching cycle.