Integrated Onboard Charger with EMIT for G2V and V2G Applications
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Solution Overview
Problem
Existing onboard chargers for plug-in electric vehicles (PEVs) face inefficiencies due to the integration of non-isolated single-stage chargers and require more components, increasing size, weight, and cost, while lacking bidirectional capabilities and compliance with IEC 61851-1 Standard for isolation between HV traction batteries and LV dc loads.
Innovation Solution
An integrated and isolated onboard charger with a dual-output DC-DC resonant converter using a three-winding electromagnetically integrated transformer (EMIT) for both HV traction batteries and LV loads, capable of unidirectional or bidirectional operation, including grid-to-vehicle (G2V) and vehicle-to-grid (V2G) applications, with a CLLLC resonant converter integrated with an LLC converter for enhanced power density and reduced component count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If non-isolated single-stage chargers are integrated, then device complexity is reduced, but isolation requirements per IEC 61851-1 Standard are not met
Solution Approach 1:
The patent combines the isolation function and charging function into a single integrated onboard charger unit. The isolated dual-output DC-DC converter integrates the isolation transformer and rectifier circuits into one unified structure, achieving both galvanic isolation (meeting IEC 61851-1) and charging functionality without requiring separate independent devices, thus reducing overall system complexity while maintaining safety compliance.
Solution Approach 2:
The onboard charger is designed with dual-output capability that can simultaneously or independently charge both the high-voltage traction battery and the low-voltage auxiliary battery. This multi-functional design allows a single device to perform multiple charging tasks, reducing the need for separate charging systems and simplifying the overall vehicle electrical architecture while maintaining proper isolation.
2Reliability
If multiple independent converters are used, then isolation requirements are met, but size and weight increase
Solution Approach 1:
The patent merges multiple converter functions into a single isolated dual-output DC-DC converter unit. By integrating the isolation transformer, high-voltage rectifier, and low-voltage converter circuits into one unified structure, the design achieves necessary galvanic isolation while significantly reducing the total weight compared to using separate independent converters for each battery system.
3Reliability
If multiple independent converters are used, then isolation requirements are met, but component count increases
Solution Approach 1:
The isolated dual-output DC-DC converter integrates multiple functions including the isolation transformer, rectifier circuits, and converter stages into a single unified structure. This merging reduces the total component count by eliminating the need for separate independent converters and their associated mounting hardware, while maintaining full isolation compliance through the integrated transformer design.
4Reliability
If traditional isolated chargers are used, then isolation requirements are met, but power density is reduced
Solution Approach 1:
The patent employs a nested structure where the low-voltage converter and rectifier circuits are integrated within the magnetic structure of the isolation transformer. This nesting allows the converter components to share the transformer's magnetic core and physical space, achieving high power density while maintaining galvanic isolation through the transformer's inherent isolation properties.
5Device complexity
If unidirectional chargers are used, then device simplicity is maintained, but bidirectional capabilities are lost
Solution Approach 1:
The onboard charger is designed with bidirectional power flow capability, allowing it to dynamically adapt between charging modes (grid-to-vehicle) and discharging modes (vehicle-to-grid). The isolated dual-output DC-DC converter can operate in different configurations to enable both unidirectional charging and bidirectional energy transfer, providing versatility without requiring multiple separate devices.
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 reduces the size and weight of the charger, enhances charging efficiency across a wide range of battery voltages, and provides bidirectional charging capabilities, meeting isolation requirements while minimizing component count and cost.
Implementation Method 1
a dual-output isolated DC-DC converter that includes a bridgeless interleaved boost power factor correction (PFC) converter and an electromagnetically integrated transformer (EMIT)
Implementation Method 2
a dual-output isolated DC-DC converter that includes a bridgeless interleaved boost power factor correction (PFC) converter and an electromagnetically integrated transformer (EMIT) for both main high-voltage (HV) traction batteries and auxiliary low-voltage (LV) loads
Data Source
AI summary
An integrated and isolated onboard charger for plug-in electric vehicles, includes an ac-dc converter and a dual-output dc-dc resonant converter, for both HV traction batteries and LV loads. In addition, the integrated and isolated onboard charger may be configured as unidirectional or bidirectional, and is capable of delivering power from HV traction batteries to the grid for vehicle-to-grid (V2G) applications. To increase the power density of the converter, the dual-output DC-DC resonant converter may combine magnetic components of resonant networks into a single three-winding electromagnetically integrated transformer (EMIT). The resonant converter may be configured as a half-bridge topology with split capacitors as the resonant network components to further reduce the size of converter. The integrated charger may be configured for various operating modes, including grid to vehicle (G2V), vehicle to grid (V2G) and high voltage to low voltage, HV-to-LV (H2L) charging.