Bidirectional DC-DC Backup Power for EV Battery Management
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Solution Overview
Problem
Electric vehicles face challenges in maintaining a reliable power supply to their battery management systems, particularly when the primary low voltage power supply is lost, leading to potential damage from unintended disconnection and lack of information about current flow through relays.
Innovation Solution
A bidirectional power supply system that includes a low voltage board net, a high voltage board net, a bidirectional DC-DC converter, a measurement element to detect power loss, and a switching element to switch from primary power supply to high voltage traction battery as a backup, ensuring continuous power to the battery management system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate high voltage power supply is provided for the battery management system, then reliability of power supply is improved, but device complexity and cost increase
Solution Approach 1:
The bidirectional DC-DC converter is designed to perform multiple functions: during normal operation it steps down voltage from the low voltage board net to power high voltage components, and during fault conditions it reverses direction to step up voltage from the low voltage backup battery to power the battery management system, eliminating the need for a separate dedicated power supply
2Reliability
If a separate high voltage power supply is provided for the battery management system, then power supply reliability is improved, but manufacturing cost increases
Solution Approach 1:
The bidirectional DC-DC converter serves dual purposes as both a voltage step-down converter during normal operation and a voltage step-up converter during fault conditions, replacing the need for expensive separate high voltage power supply hardware and reducing overall system manufacturing costs
3Adaptability or versatility
If a bidirectional DC-DC converter is used for power conversion, then power supply flexibility and reliability are improved, but device complexity increases
Solution Approach 1:
The DC-DC converter implements dynamic bidirectional power flow capability, automatically switching between forward mode (stepping down voltage) during normal operation and reverse mode (stepping up voltage) during fault conditions, providing adaptability to different operational states while using a single unified converter design
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 system provides an uninterrupted power supply to the battery management system by automatically switching to the high voltage traction battery as a backup, preventing damage and ensuring continuous operation, while also being cost-efficient by using a shared transformer for galvanic isolation.
Implementation Method 1
a bidirectional DC-DC converter, in which a low voltage side is coupled to the low voltage board net, and a high voltage side is coupled to the high voltage board net
Data Source
AI summary
A bidirectional power supply system receives power from a low voltage (LV) primary power supply, providing power to a control unit of a LV board net in a first mode of operation. A high voltage (HV) board net is coupled to a HV traction battery. A DC-DC converter, in the first mode, transfers energy from the LV board net to the HV board net to power components of the HV board net via the primary power supply, and, in a second mode of operation, transfers energy from the HV board net to the LV board net to power the control unit via the traction battery. The bidirectional power supply system includes a measurement element to detect whether the primary power supply is lost, and a switching element to switch operation of the DC-DC converter from the first mode to the second mode, when the primary power supply is lost.