Motor Start-Up Dead Time Control for Back-EMF Noise Suppression
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Solution Overview
Problem
Conventional motor starting circuits for fan motors in electronic devices cause high noise and potential circuit component burnout due to high back electromotive force currents, especially when the motor is running at high speeds.
Innovation Solution
A motor starting circuit with a dead time setting mechanism that includes a rotational speed detection circuit, start-up commutation selector circuit, control circuit, driver circuit, and output stage circuit, which automatically detects motor speed and sets dead time during start-up to prevent large back electromotive force currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional motor starting circuit is used, then the motor can be started, but high noise is generated and large back electromotive force current flows back into the power supply causing component burnout
Solution Approach 1:
The patent applies dynamics by making the dead time setting variable rather than fixed. The start-up commutation selector circuit dynamically adjusts the dead time duration based on real-time detection of motor rotational speed. When motor speed exceeds a threshold, the circuit automatically shortens or eliminates dead time, thereby dynamically preventing back electromotive force current while ensuring reliable motor starting under all speed conditions.
Solution Approach 2:
The patent implements feedback through the rotational speed detection circuit that continuously monitors motor speed and feeds this information to the start-up commutation selector circuit. This feedback mechanism enables the system to automatically adjust dead time settings based on actual motor operating conditions, preventing harmful back electromotive force current while maintaining reliable operation.
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 solution effectively reduces noise and prevents circuit component damage by adjusting dead time based on motor speed, ensuring stable and efficient motor operation.
Implementation Method 1
The rotational speed detection circuit is connected to a motor and configured to detect a rotational speed of the motor to output a rotational speed detection signal
Implementation Method 2
the motor from having a dead time in the motor start-up time interval, during which a large back electromotive force current will be generated and fed back into the power supply
Data Source
AI summary
A motor starting circuit having a dead time setting mechanism is provided. The motor starting circuit includes a rotational speed detection circuit, a start-up commutation selector circuit, a control circuit, a driver circuit and an output stage circuit. The rotational speed detection circuit detects a rotational speed of a motor. The start-up commutation selector circuit determines whether or not to set a dead time within a motor start-up time interval to output a commutation instructing signal according to the rotational speed of the motor. The control circuit controls the driver circuit to drive the output stage circuit so as to start up the motor according to the commutation instructing signal.