BLDC Motor Braking Control with Busbar Voltage Feedback
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Solution Overview
Problem
Existing brushless DC motor braking systems face issues with high phase current during braking, leading to circuit damage and unstable transitions, and continuous busbar voltage increase, which can exceed withstand voltage values, damaging components.
Innovation Solution
A brushless DC motor braking system with a controller that monitors busbar voltage through a voltage sampling module, using PWM modulation to control duty cycles of transistors to maintain busbar voltage within safe thresholds, ensuring smooth and efficient braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If three-phase lower transistor PWM modulation is used for motor braking, then braking control is achieved, but busbar voltage continuously increases and can exceed withstand voltage values causing circuit damage
Solution Approach 1:
The patent implements a feedback mechanism by sampling the busbar voltage in real-time during braking and using this information to dynamically adjust the PWM duty cycle of the lower transistors. When the busbar voltage approaches the withstand voltage threshold, the system automatically reduces the PWM duty cycle to prevent voltage overload, thus resolving the contradiction between achieving braking control and preventing busbar voltage damage.
2Reliability
If three upper transistors are controlled to close and three lower transistors to conduct for motor braking, then braking is achieved, but phase short circuit current becomes large causing circuit component damage and unstable transition
Solution Approach 1:
The patent applies dynamic control by continuously adjusting the PWM duty cycle of the lower transistors based on real-time busbar voltage sampling during braking. Instead of maintaining a fixed conduction state, the system dynamically modulates the transistor switching duty cycle to limit phase short circuit current while achieving effective braking, thus resolving the contradiction between braking function and current damage.
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 prevents circuit damage by controlling busbar voltage within safe limits, providing stable transitions and improved user experience through slow braking.
Implementation Method 1
a voltage sampling module electrically connected between positive and negative poles of the DC power supply for collecting a busbar voltage value of the busbar circuit when the brushless DC motor brakes
Implementation Method 2
The brake control module controls the busbar voltage value to be between the high threshold of the busbar voltage and the low threshold of the busbar voltage
Data Source
AI summary
The present disclosure discloses a brushless DC motor braking system and method. during the braking process of the brushless DC motor, the busbar voltage value is controlled to always be between the high threshold of the busbar voltage and low threshold of the busbar voltage through the brake control module; and different PWM modulation signals are used to control the brushless DC motor 4 to perform slow braking until stopping based on different busbar voltage states. Thus, in the present disclosure, the method not only ensures that the busbar voltage value continues to be maintained between the high threshold of the busbar voltage and low threshold of the busbar voltage, thereby protecting electronic components and circuits and extending their service life; but also avoids the hard braking method of direct conduction of the three lower transistors of the three-phase inverter in related arts.