BLDC Motor Bridge Driver Phase Shifting for Lower EMC Noise
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Solution Overview
Problem
Brushless DC motors experience significant current ripple due to the use of a single bridge driver, leading to electromagnetic compatibility (EMC) concerns and inefficiencies, which are not adequately addressed by existing technologies.
Innovation Solution
The implementation of two independent B6 bridge drivers with a phase shift to rectify the voltage supply, allowing current to be split across the bridges and reducing ripple current, and optionally varying slew rates to manage the rate of current change.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single bridge driver is used to rectify three-phase input voltage, then the device complexity is reduced, but significant current ripple is generated leading to EMC concerns
Solution Approach 1:
The patent divides the single bridge driver into multiple independent bridge drivers (e.g., two B6 bridge drivers). Each bridge driver handles a portion of the total current, and their outputs are combined through phase shifting. This segmentation reduces the current ripple generated by each individual driver, thereby decreasing electromagnetic compatibility issues while maintaining functional complexity at an acceptable level.
2Object-generated harmful factors
If multiple independent bridge drivers are used with phase shift, then current ripple is reduced and EMC characteristics improve, but device complexity increases
Solution Approach 1:
The patent employs periodic phase shifting between multiple bridge drivers, where each driver operates with a specific phase offset (e.g., 180 degrees for two drivers). This periodic phase modulation causes the ripple currents from different drivers to cancel each other out over time, reducing overall current ripple and improving EMC characteristics despite the increased number of drivers.
3Reliability
If bridge drivers deliver current at different slew rates, then rate of current change is managed, but control complexity increases
Solution Approach 1:
The patent implements dynamic control where each bridge driver operates with a different slew rate (rate of current change). This dynamic parameter variation allows for optimized current delivery characteristics, such as reduced di/dt stress on components and improved electromagnetic compatibility, while requiring sophisticated control synchronization to manage the varying rates effectively.
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 approach effectively eliminates current ripple, reduces the load on components, enhances EMC characteristics by decreasing noise, and allows for the use of smaller, cheaper components and improved power dissipation and cooling.
Implementation Method 1
two independent B6 bridge drivers with a phase shift to rectify the voltage supply
Data Source
AI summary
An electric motor for a vehicle includes a stator, a rotor and a plurality of independent bridge drivers. Each bridge driver supplies a portion of current to the electric motor. There may be a phase shift between each independent bridge driver. Optionally, each bridge driver delivers current at a slew rate that is different from each other independent bridge driver.