Bidirectional CLLC Converter Bridge Switching for Wide Voltage Range
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Solution Overview
Problem
Bidirectional CLLC converters face challenges in efficiently managing wide output voltage ranges during charging and discharging modes, particularly in applications like EV on-board chargers, vehicle-to-grid, and vehicle-to-load operations, where the required output voltage range can vary significantly.
Innovation Solution
A bidirectional power converter design that includes a first switch circuit coupled to a second switch circuit via a transformer, where the first switch circuit operates in a half bridge configuration during charging and a full bridge synchronous rectifier configuration during discharging, allowing for flexible control and reduced switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed transformer turns ratio is designed for CLLC converter, then the converter can achieve zero voltage switching (ZVS) operation at resonant frequency, but the converter cannot efficiently handle widely-varying output voltage ranges in charging and discharging modes
Solution Approach 1:
The patent implements dynamic configuration switching of the switch circuits between half-bridge and full-bridge modes based on operating conditions (charging/discharging). This allows the transformer turns ratio to be effectively adjusted dynamically without physical changes, enabling the system to adapt to widely-varying output voltage ranges while maintaining ZVS operation and avoiding complex multi-ratio transformer designs
2Adaptability or versatility
If a two-stage structure with buck/boost converter followed by CLLC converter is used, then the output voltage range can be extended, but the system cost and complexity increase
Solution Approach 1:
The patent makes the same switch circuits perform multiple functions by dynamically switching between half-bridge and full-bridge configurations. During charging mode, the first switch circuit operates as half-bridge while the second operates as full-bridge synchronous rectifier, and vice versa during discharging mode. This multi-functional approach eliminates the need for separate buck/boost converter stages, reducing system complexity and cost while maintaining wide output voltage range capability
3Adaptability or versatility
If relay-based flexible control is used to change transformer turns ratio, then the converter can adapt to different operation modes, but the system cost and efficiency are negatively impacted
Solution Approach 1:
The patent replaces mechanical relay-based turns ratio adjustment with electronic configuration switching of the switch circuits. By controlling the switching states of the power switches, the system achieves flexible adaptation to different operation modes (charging/discharging) without mechanical components. This eliminates relay contact resistance and switching losses associated with mechanical relays, improving overall system efficiency while maintaining adaptability
4Power
If full bridge configuration is used during both charging and discharging modes, then the power handling capability is maximized, but the turn-off losses increase when gain is less than resonant frequency gain
Solution Approach 1:
The patent applies different bridge configurations to different switch circuits based on the specific operating mode and power requirements. During charging mode, the first switch circuit uses half-bridge configuration for lower power operations with reduced turn-off losses, while the second switch circuit uses full-bridge synchronous rectifier configuration. During discharging mode, the configurations are reversed. This localized optimization allows the system to minimize turn-off losses when gain is less than resonant frequency gain while maintaining adequate power handling capability
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
This design enhances the gain range of the system, simplifies the transformer ratio and resonant tank design, and reduces turn-off losses, leading to improved system efficiency, power density, and cost-effectiveness compared to two-stage or relay-based solutions.
Implementation Method 1
a first switch circuit coupled to a second switch circuit via a transformer, wherein the first switch circuit is configured to transfer power to the second switch circuit during a charging mode, the second switch circuit is configured to transfer power to the first switch circuit during a discharging mode
Implementation Method 2
As used herein, 'CLLC' refers to the resonant combination of circuit elements including capacitance (C) and inductance (L)
Implementation Method 3
As used herein, 'CLLC' refers to the resonant combination of circuit elements including capacitance (C) and inductance (L)
Data Source
AI summary
A bidirectional power converter includes a first switch circuit coupled to a second switch circuit via a transformer, wherein the first switch circuit is configured to transfer power to the second switch circuit during a charging mode, the second switch circuit is configured to transfer power to the first switch circuit during a discharging mode, and the first switch circuit is configured to operate in a half bridge configuration during a first portion of the charging mode.