BLDC Commutation Switching for Fast Residual Current Extinction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for driving brushless direct current (BLDC) motors under high load conditions fail to effectively extinguish residual current, leading to loss of electrical position sensing and potential driving failures due to residual current masking the induced voltage.
Innovation Solution
A method using unipolar pulse width modulation (ON_PWM) to drive the BLDC motor, monitoring residual current through a voltage observer, and applying a switching pattern that maximizes voltage in the open phase to accelerate residual current extinction, involving opening the switch of the phase maintained driven and closing the switch related to the previously driven phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional six-step driving method is used, then the BLDC motor operates under high load conditions, but the residual current extinction time is prolonged causing loss of electrical position sensing
Solution Approach 1:
The patent applies dynamic switching patterns that adapt during the commutation process. Specifically, it dynamically changes the switching states of phases: first turning off the newly activated phase switch to accelerate residual current extinction, then turning it back on after a predetermined time, and finally turning off the previously activated phase switch. This dynamic adjustment optimizes both high load operation and residual current extinction speed.
Solution Approach 2:
The patent changes the electrical parameters during commutation by applying voltage to the open phase for a predetermined time period after turning off the switch. This parameter change (applying voltage to accelerate current decay) directly addresses the contradiction by reducing extinction time while maintaining the ability to operate under high load conditions.
2Reliability
If residual current is not quickly extinguished, then the motor continues to operate, but the residual current masks the induced voltage causing loss of electrical position sensing
Solution Approach 1:
The patent performs preliminary actions to clear the measurement path before detection is needed. By turning off the switch of the newly activated phase and applying voltage to accelerate residual current extinction before the induced voltage measurement phase, it ensures that when measurement occurs, the residual current has already decayed sufficiently to not mask the induced voltage signal.
Solution Approach 2:
The patent rushes through the residual current extinction phase by applying voltage to the open phase for a predetermined time, accelerating the current decay process. This allows the system to quickly transition from a state where residual current masks measurements to a state where induced voltage can be accurately detected, thus resolving the measurement precision issue while maintaining continuous operation.
3Reliability
If switch timing is extended to ensure complete current extinction, then electrical position sensing is preserved, but the motor response time is delayed
Solution Approach 1:
The patent uses periodic switching actions with predetermined time intervals. It turns off the newly activated phase switch, applies voltage for a specific duration, then turns the switch back on and finally turns off the previously activated phase switch. This periodic, time-controlled sequence ensures position sensing accuracy is maintained while limiting the total time extension, thus preserving motor response speed.
4Productivity
If a switching pattern is applied to accelerate residual current extinction, then current extinction speed is improved, but the switching complexity increases
Solution Approach 1:
The patent segments the commutation process into distinct sequential steps: (1) turn off newly activated phase switch, (2) apply voltage to open phase for predetermined time, (3) turn on the switch back, (4) turn off previously activated phase switch. This segmentation makes the complex switching pattern manageable by breaking it into discrete, controllable actions with clear timing relationships.
Data Source
AI summary
Method of accelerated extinguishing of residual current of a phase that opens when changing an electric position during the driving of a BLDC motor (10), under high load conditions, comprising:using the unipolar pulse width modulation pattern ON_PWM to drive the BLDC motor (10);determining if there is residual current by means of monitoring the voltage of the phases that opens using a voltage observer (40);while there is residual current, applying a switching pattern, on the switches (S1-S6) of the BLDC motor (10), which superimposes the pulse width modulation pattern used and maximizes the voltage in the open phase for the accelerated extinguishing of said residual current,said switching pattern comprising:opening the switch of the phase maintained driven when changing the electrical position; andclosing the switch related to the phase that was driven when changing the electric position.