Sensorless Motor Control Circuit Startup Noise Reduction
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Solution Overview
Problem
Conventional sensorless motor control circuits face inefficiencies due to the need to power off the coil to detect induced electromotive force, leading to power consumption errors and high noise during startup, which decreases motor efficiency and increases noise levels.
Innovation Solution
A control circuit with a first and second coil, a first and second switch circuit, and an auxiliary switch circuit that alternates between half-bridge and full-bridge driving modes to manage current flow, using the auxiliary switch circuit to minimize noise during startup and enhance efficiency once the motor reaches stable speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the coil is powered off to detect induced electromotive force, then the magnetism of the silicon steel sheets can be determined, but the motor efficiency decreases and power is consumed
Solution Approach 1:
The control circuit predicts the rotating speed of the motor at the next time when the motor starts to operate again, and adjusts the time from powering off to starting switching the current based on this prediction. This preliminary action allows the system to optimize the detection timing to minimize power loss while still accurately detecting the induced electromotive force.
2Measurement precision
If the coil is powered off to detect induced electromotive force, then the magnetism of the silicon steel sheets can be determined, but noise of the motor increases
Solution Approach 1:
The control circuit predicts the rotating speed of the motor at the next time when the motor starts to operate again, and adjusts the time from powering off to starting switching the current based on this prediction. This preliminary action allows the system to optimize the detection timing to minimize noise while still accurately detecting the induced electromotive force.
3Measurement precision
If the current cannot be immediately cut off due to control error, then the induced electromotive force detection can be performed, but power is consumed
Solution Approach 1:
The control circuit continuously monitors the motor's operating state and uses feedback to adjust the timing of current cutoff. By predicting the rotating speed and adjusting the detection timing based on this feedback, the system minimizes unnecessary power consumption while ensuring accurate detection of the induced electromotive force.
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 proposed solution effectively reduces startup noise and improves motor efficiency by transitioning from half-bridge to full-bridge driving modes, allowing for smoother operation and reduced power consumption.
Implementation Method 1
the currents flow through the coil 15 via different directions so that the silicon steel sheets generate different magnetic forces to repel a magnetic pole of a rotor of the motor so as to push the rotor
Implementation Method 2
the induced electromotive force is detected from two ends A and B of the coil 15 so that the magnetism of the magnetic pole corresponding to the coil 15 can be determined
Data Source
AI summary
A control circuit of a sensorless motor includes a first coil, a second coil, a first switch circuit, a second switch circuit and an auxiliary switch circuit. The first switch circuit is electrically connected to the first coil and controls a direction of a current flowing through the first coil. The second switch circuit is electrically connected to the second coil and controls a direction of a current flowing through the second coil. The auxiliary switch circuit is electrically connected to and between the first coil and the second coil and controls the directions of the currents flowing through the first coil and the second coil by cooperating with the first switch circuit and the second switch circuit. A control method of a sensorless motor is also disclosed.