Motor Control Circuit With Limit-Switch Feedback for EMI-Free Stopping
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Solution Overview
Problem
Existing motor control circuits for direct current motors in medical devices face reliability and security issues due to electromagnetic interference and sparks caused by inductive loads when power is cut off, and they struggle with real-time feedback and position control, leading to potential motor burnout and inconsistent feedback signals.
Innovation Solution
A motor control circuit that uses a switch drive circuit to receive feedback signals from limit switches and directly control the power supply, bypassing relays and software delays, thereby preventing electromagnetic interference and ensuring reliable and secure motor control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a relay or contactor is used to cut off power supply when limit switch is triggered, then the motor can be stopped, but electromagnetic interference and sparks occur due to inductive load switching
Solution Approach 1:
The patent replaces the mechanical relay/contactor switching system with an electronic switch drive circuit that uses triodes (transistors) to control power supply to the motor. This substitution eliminates the arc and electromagnetic interference problems associated with mechanical contactors when switching inductive loads, while maintaining the ability to stop the motor when the limit switch is triggered.
Solution Approach 2:
The patent introduces a switch drive circuit as an intermediary between the limit switch and the motor power supply. This intermediary circuit processes the limit switch signal and controls the triode switches to cut off power supply in a controlled manner, preventing direct switching of the inductive load that causes sparks and electromagnetic interference.
2Loss of information
If software or programs are used to control relay or contactor, then feedback signal can be processed, but control delay occurs reducing real-time performance
Solution Approach 1:
The patent replaces software-based control with a hardware-based logic circuit system. The switch drive circuit directly processes feedback signals from the limit switch through hardware logic operations, eliminating the processing delays inherent in software execution while maintaining the ability to control the relay or contactor for feedback signal acquisition.
3Speed
If limit switch directly cuts off power supply, then motor stops immediately, but feedback signal cannot be provided to controller
Solution Approach 1:
The patent introduces a switch drive circuit as an intermediary that receives the limit switch signal and coordinates two functions: controlling the power supply cutoff to the motor and enabling feedback signal transmission to the controller. This intermediary ensures both immediate motor stopping and proper feedback signal provision without conflict.
Solution Approach 2:
The switch drive circuit is designed to process the limit switch signal in advance, preparing the circuit state to allow feedback signal transmission before completely cutting off power supply. This preliminary action ensures that the feedback signal can be captured and transmitted to the controller before the motor power is fully disconnected.
4Adaptability or versatility
If relay or contactor is used for direction control, then power supply direction can be switched, but electromagnetic interference and sparks occur
Solution Approach 1:
The patent replaces mechanical relay/contactor switching for direction control with an electronic switch drive circuit using triodes. This electronic system controls power supply direction to the motor without the arc and electromagnetic interference problems of mechanical contactors, while maintaining full direction control capability.
Data Source
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AI summary
The present disclosure relates to a motor control circuit, including: a switch circuit section, powered by a power supply to drive a motor to output a motion; a switch drive circuit section, capable of sending a drive signal in a valid state to the switch circuit section, to enable the switch circuit section to drive the motor to output the motion; and a limit switch section, including at least one limit switch that is associated with at least one position of the motion outputted by the motor, to enable the motor to generate a feedback signal when the motor outputs the motion to the position in a direction, and the feedback signal is received by the switch drive circuit section, so that the switch drive circuit section cuts off power from the power supply to the switch circuit section, and the motor stops outputting. The motor control circuit provides a mechanism for feeding from the limit switch back to a controller, and when the direction of the motion outputted by the motor is switched, the power from the power supply to the switch circuit section is turned off by using the feedback signal, resolving problems of electromagnetic interference and sparks generated by turning off the power supply of the motor with simplicity and higher security.