Motor Drive Device PWM Control for Voltage Precision
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Solution Overview
Problem
Conventional motor drive devices face limitations in effectively controlling the drive voltage applied to motor coils, leading to inefficient use of power supply voltage and slow response times due to the use of bipolar transistors, and existing solutions either consume excessive power or require expensive components.
Innovation Solution
A motor drive device incorporating a PWM signal generating circuit and control circuit that adjusts the duty cycle of the drive voltage based on the ratio between the power supply voltage and control voltage, using field effect transistors in an H-bridge configuration to maintain the drive voltage at a desired value, allowing for wide-range control and efficient power use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If bipolar transistors are used as switch elements in an H-bridge circuit with a dropper-type regulator configuration, then the drive voltage can be controlled to a desired value, but the response time is slow and the power supply voltage range cannot be effectively utilized
Solution Approach 1:
The patent changes the switching element from bipolar transistor to field effect transistor, and changes the control method from analog dropper-type regulation to PWM digital control. This parameter change enables both precise voltage control and fast response time, as PWM control can quickly adjust the duty cycle to achieve desired voltage levels without the slow analog adjustment limitations of the dropper configuration.
Solution Approach 2:
The patent replaces the analog dropper-type regulator mechanism with a digital PWM control system. Instead of using continuous analog voltage adjustment through transistor base current control, the system uses pulse width modulation with field effect transistors switching at high frequency, achieving both precision and speed through digital control methods.
2Measurement precision
If bipolar transistors are used as switch elements in an H-bridge circuit, then drive voltage control is achieved, but the response time is slow
Solution Approach 1:
The patent changes the switching element from bipolar transistor to field effect transistor, which has faster switching characteristics. Combined with PWM control, this enables rapid adjustment of the drive voltage while maintaining precise control, directly addressing the response time issue without sacrificing voltage control accuracy.
3Measurement precision
If conventional dropper-type regulator configuration is used, then drive voltage can be controlled, but power supply voltage range utilization is inefficient
Solution Approach 1:
The patent changes from analog dropper regulation to PWM control, which allows the system to efficiently utilize the full power supply voltage range. By varying the duty cycle of the PWM signal, the system can achieve any desired average voltage from 0 to the full supply voltage, maximizing voltage range utilization while maintaining precise control.
4Speed
If PWM control with field effect transistors is implemented, then response time is improved and power supply voltage range is effectively utilized, but control circuit complexity increases
Solution Approach 1:
The patent divides the control function into separate modules: PWM signal generation, duty cycle control based on back electromotive voltage detection, and H-bridge switching control. This segmentation allows each module to perform its function efficiently while keeping the overall system manageable, reducing the complexity burden despite the advanced control methods used.
5Measurement precision
If bridge servos or proportional current servos are used to maintain motor rotation speed, then speed control is achieved, but power consumption is excessive
Solution Approach 1:
The patent uses PWM control which operates by periodic switching of the power supply to the motor through the H-bridge circuit. This periodic action allows the motor to receive power in pulses rather than continuous DC, reducing average power consumption while maintaining precise speed control through duty cycle adjustment based on detected back electromotive voltage.
Data Source
AI summary
A motor drive device of the present invention includes: an output circuit provided with a switch element connected to a motor; a PWM signal generating circuit for generating a PWM signal having a duty corresponding to a ratio between a power supply voltage applied to the motor and a predetermined control voltage; a control circuit for performing on/off control of the switch element according to the PWM signal; and a control voltage generating circuit for generating the control voltage such that the back electromotive voltage of the motor is maintained at a desired value.