Motor Drive Control with Speed-Current Mode Switching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional motor control devices excessively limit the drive current, leading to unsatisfied air flow-static pressure characteristics due to the reliance on peak current detection for overcurrent protection, which results in inadequate current threshold settings.
Innovation Solution
A motor drive control device that includes a control circuit unit capable of switching between speed feedback control and current feedback control modes, with the power control unit setting a current threshold based on power supply voltage, allowing for precise management of drive current to maintain desired air flow-static pressure characteristics without over-limiting the motor current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If peak current detection is used for overcurrent protection, then motor damage is prevented, but the current threshold must be set smaller in advance, causing excessive current limitation and unsatisfied air flow-static pressure characteristics
Solution Approach 1:
The invention changes the detection parameter from peak current to average current. By detecting the average value of the absolute current over one period rather than the peak instantaneous current, the system can set a higher current threshold that satisfies both motor protection requirements and air flow-static pressure characteristics. This parameter change eliminates the need to set the threshold smaller in advance.
Solution Approach 2:
The invention implements feedback control by continuously detecting the average current and comparing it with the threshold, then adjusting the drive control signal accordingly. The control circuit switches between speed feedback control mode and current feedback control mode based on whether the average current exceeds the threshold, enabling dynamic adjustment that satisfies both protection and performance requirements.
2Stability of the object's composition
If speed feedback control is performed to maintain constant rotation speed, then motor speed stability is improved, but drive current increases at high static pressure points, risking motor and drive circuit damage
Solution Approach 1:
The invention makes the control mode dynamic by switching between speed feedback control mode and current feedback control mode based on operating conditions. When the average current exceeds the threshold at high static pressure points, the system switches to current feedback control mode to limit the drive current, preventing motor and drive circuit damage while maintaining speed stability when conditions permit.
Data Source
AI summary
To satisfy a desired air flow-static pressure characteristic while satisfying constraints of a power supply capacity and without over-limiting the drive current. A motor drive control device includes: a control circuit unit configured to generate a drive control signal (Sd) for controlling an actual rotation speed of a motor based on a speed command signal indicating a target rotation speed of the motor; and a motor drive unit configured to drive the motor based on the drive control signal (Sd). The control circuit unit includes a power control unit configured to enable selection of one of: a speed feedback control mode to generate the drive control signal (Sd) so that the actual rotation speed of the motor matches the target rotation speed; and a current feedback control mode to generate the drive control signal (Sd) so that a drive current of the motor matches a target current. The power control unit sets a current threshold corresponding to a power supply voltage (Vdd) supplied from the outside as the target current, and when detecting that the drive current is not less than the current threshold, switches from the speed feedback control mode to the current feedback control mode.