Bidirectional DC/DC Converter with Active Switch Bridge
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Solution Overview
Problem
Existing AC fast chargers for electric vehicles are limited to mono-directional power transfer, unable to efficiently transfer power back to the electrical grid, which is necessary for applications like vehicle-to-grid systems.
Innovation Solution
A bidirectional LLC resonant DC/DC converter is introduced, utilizing a capacitor for DC-bias current blocking and active switches in a bridge configuration, controlled by a microcontroller to enable bi-directional power flow through a control algorithm that manages switching frequency for efficient power transfer in both charging and discharging directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If diodes are used in the secondary side AC/DC rectifier, then the charger can operate in mono-directional mode with simple circuit design, but it becomes incapable of transferring power back to the electrical grid
Solution Approach 1:
The patent replaces the traditional diode-based rectifier with an active switch bridge configuration that can operate in reverse mode. By inverting the conventional diode rectifier approach and using controllable switches instead, the system enables bidirectional power flow while maintaining the same physical hardware, thus resolving the contradiction between adaptability and device complexity.
Solution Approach 2:
The active switch bridge circuit serves multiple functions: it can rectify AC to DC for battery charging, and it can also enable DC to AC conversion for power feedback to the grid. This multi-functional design eliminates the need for separate circuits for charging and discharging, achieving bidirectional capability without proportionally increasing device complexity.
2Adaptability or versatility
If active switches are used instead of diodes, then bidirectional power transfer is enabled, but control complexity increases
Solution Approach 1:
The patent combines the rectifier and inverter functions into a single active switch bridge circuit controlled by a unified control system. By merging these functions and using coordinated control of the switches, the system achieves bidirectional power transfer without requiring separate control systems for charging and discharging, thus managing control complexity while enabling versatility.
3Loss of energy
If high efficiency components are used, then overall charger efficiency exceeds 94%, but the system remains limited to mono-directional operation
Solution Approach 1:
The patent introduces dynamic controllability to the rectifier circuit by replacing fixed diode elements with controllable active switches. This dynamic design allows the system to adapt its operation mode (charging or discharging) while maintaining high efficiency through optimized switching control, thus resolving the contradiction between efficiency and versatility.
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 enables efficient bidirectional power transfer, maintaining high efficiency and allowing for vehicle-to-grid systems by effectively controlling power flow between the electrical grid and the electric vehicle battery, supporting applications like demand response services.
Implementation Method 1
a capacitor that performs DC-bias current blocking
Implementation Method 2
a transformer T that transfers power to a secondary side
Implementation Method 3
ensuring the active switches operate under soft switching
Data Source
AI summary
In one embodiment, a bidirectional DC/DC converter includes a DC/AC inverter having active switches (e.g., MOSFETs), and an AC/DC rectifier having a capacitor that performs DC-bias current blocking and active switches (e.g., MOSFETs) arranged in a bridge configuration. A microcontroller is coupled to the active switches of the DC/AC inverter and AC/DC rectifier and configured to provide control signals thereto according to a control algorithm that, when power is to flow in a forward direction, sends control signals to operate the active switches of the DC/AC inverter at a duty cycle and to disable the active switches of the AC/DC rectifier, and when power is to flow in a reverse direction, sends control signals to operate the active switches of the DC/AC inverter to disable the active switches of the DC/AC inverter and operates the active switches of the AC/DC rectifier at a duty cycle.