Charge Equalization Apparatus Reducing Semiconductor Voltage Stress
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Solution Overview
Problem
Conventional battery charge equalization apparatuses induce high voltage stress on semiconductor switching elements due to diodes connected in series with secondary windings, increasing costs and limiting the implementation of secondary windings as the number of batteries increases.
Innovation Solution
A charge equalization apparatus with N first transformers connected in parallel to series-connected batteries, a charge storage device, and a voltage detection and drive signal generation unit, which reduces voltage stress on semiconductor switching elements by implementing transformers in two stages, allowing for easier secondary winding manufacturing and reduced costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If diodes are connected in series with secondary windings to enable charge equalization, then charge equalization performance is achieved, but voltage stress on semiconductor switching elements increases
Solution Approach 1:
The patent divides the single transformer into multiple transformers (first transformer and second transformer) with separate primary and secondary windings. This segmentation allows the voltage stress to be distributed across multiple components rather than concentrated on a single semiconductor switching element, thereby reducing the voltage stress while maintaining charge equalization functionality.
Solution Approach 2:
The patent introduces a capacitor as an intermediary component connected between the secondary winding and the semiconductor switching element. This capacitor acts as a voltage buffer that absorbs the high voltage stress during switching operations, protecting the semiconductor switching element from direct exposure to excessive voltage while still enabling the charge equalization function to operate effectively.
2Reliability
If diodes are connected in series with secondary windings, then charge equalization is achieved, but costs of the charge equalization apparatus increase
Solution Approach 1:
The patent replaces expensive high-voltage-rated diodes with a combination of lower-voltage-rated semiconductor switching elements and capacitors. The capacitors, being simpler and cheaper components, serve as voltage buffers, allowing the use of more cost-effective semiconductor switching elements while maintaining the required voltage handling capability for charge equalization.
3Reliability
If diodes are connected in series with secondary windings, then charge equalization is achieved, but implementation of secondary windings becomes difficult as the number of batteries increases
Solution Approach 1:
The patent divides the charge equalization system into multiple independent transformer units, each handling a subset of batteries. This segmentation allows the secondary windings to be designed with fewer turns per transformer, making implementation easier and more scalable as the number of batteries increases, while still achieving overall charge equalization across all batteries.
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 decreases the withstand voltages of semiconductor switching elements, enabling efficient and cost-effective charge equalization while simplifying the manufacturing of secondary windings, thus maintaining charge equalization performance.
Implementation Method 1
when the primary winding is turned on, energy is charged in the primary winding, whereas, when the secondary winding is turned off and the primary winding is turned off, the energy charged in the primary winding is supplied to the secondary winding by a counter electromotive force
Data Source
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AI summary
The present invention relates, in general, to a battery voltage equalization apparatus and method, and, more particularly, to a charge equalization apparatus and method, which decrease the withstand voltages of semiconductor switching elements while maintaining charge equalization performance, thus making it easy to implement the secondary windings of transformers while reducing the costs of the charge equalization apparatus. The charge equalization apparatus includes N first transformers (Tl to Tn) connected in series with N series- connected batteries (Bl to Bn) and adapted to decrease voltages of overcharged batteries among the N batteries. A charge storage device (Cdump) stores energy supplied from the first transformers. A second transformer (TS) redistributes energy stored in the charge storage device to the N series-connected batteries. A voltage detection and drive signal generation unit (20) detects voltages of N respective series-connected batteries, and generates a first drive signal and a second drive signal.