Mild Hybrid Unidirectional DC/DC Converter Bypass
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Solution Overview
Problem
Existing mild hybrid systems face limitations in fuel efficiency due to limited electrical energy recovery during regenerative braking, increased electrical loads, and the need for bidirectional DC/DC converters, which raise costs and inefficiencies.
Innovation Solution
A mild hybrid system utilizing a unidirectional DC/DC buck converter with a bypass function to manage electrical energy flow, allowing for bidirectional electricity flow in bypass states and eliminating the need for a bidirectional converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a bidirectional DC/DC converter is used to manage electrical energy flow in both charging and discharging modes, then the system can handle high electrical loads and ensure reliable energy management, but the manufacturing cost increases and the device complexity increases
Solution Approach 1:
The patent divides the electrical energy management system into two separate unidirectional DC/DC converters: one dedicated to charging the electrical energy storage device and another dedicated to discharging. This segmentation allows each converter to be optimized for its specific function, reducing overall system complexity while maintaining the ability to handle high electrical loads effectively.
2Loss of energy
If the capacity of the motor-alternator is increased to recover more electrical energy during regenerative braking, then the fuel efficiency improves, but the device complexity and cost increase
Solution Approach 1:
The patent introduces an electrical energy storage device (such as a capacitor or battery) as an intermediary between the motor-alternator and the vehicle's electrical loads. This intermediary allows the motor-alternator to operate at a smaller, more cost-effective capacity while still enabling significant energy recovery during regenerative braking, as the storage device buffers and manages the energy flow.
3Device complexity
If a unidirectional DC/DC buck converter is used instead of a bidirectional converter, then the manufacturing cost decreases and device complexity reduces, but the ability to manage bidirectional energy flow is limited
Solution Approach 1:
The patent combines two separate unidirectional DC/DC buck converters into the energy management system - one configured for charging mode and another for discharging mode. This merging approach maintains the simplicity and cost-effectiveness of unidirectional converters while collectively achieving bidirectional energy flow management capability through parallel operation of the two converters.
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 configuration enhances fuel efficiency by optimizing energy use during varying electrical loads, reduces manufacturing costs, and ensures reliable engine start-ups without additional cooling needs or a separate starter system.
Implementation Method 1
the motor-alternator 1 converts the rotational kinetic energy of the wheels into electrical energy
Implementation Method 2
an inverter for controlling electrical energy flow to and from the motor-alternator
Implementation Method 3
a DC/DC converter for connecting a high voltage of about 30 V and a vehicle electrical load
Data Source
AI summary
A mild hybrid system according embodiments of the invention may include: a motor-alternator; an inverter for controlling electrical energy flow to and from the motor-alternator; an electrical energy storage for storing electrical energy generated by the motor-alternator; and a unidirectional DC/DC buck converter including a bypass means for providing a physical connection between the motor-alternator and a vehicle electrical load. With the system, the manufacturing cost can be reduced, packaging process can be simplified, and an additional cooling device is not required.