Motor Input Voltage Control Using Duty Cycle Feedback
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Solution Overview
Problem
Conventional brushless motor circuits without large electrolyte capacitors experience voltage fluctuations due to non-polarity capacitors, leading to unstable input voltage and potential current protection triggers, especially under varying loads.
Innovation Solution
A motor control circuit with two rectifier circuits connected in parallel, a voltage detection circuit, and a controller that adjusts the target duty cycle and voltage value based on bus current and voltage values to stabilize the input voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a large electrolyte capacitor is used to stabilize voltage, then voltage stability is improved, but circuit board size increases
Solution Approach 1:
The patent changes the control parameters by introducing a duty cycle adjustment mechanism. The controller dynamically adjusts the duty cycle based on the relationship between input voltage and reference voltage, transforming the voltage stabilization problem from a passive capacitor-based solution to an active control-based solution. This allows voltage stabilization without requiring large capacitors.
Solution Approach 2:
The patent implements a feedback control system where the controller continuously monitors the input voltage and adjusts the duty cycle accordingly. By comparing the actual input voltage with the reference voltage and adjusting the PWM duty cycle in real-time, the system achieves voltage stabilization without needing large electrolyte capacitors, thus reducing circuit board size while maintaining voltage stability.
2Area of stationary object
If a small capacitance capacitor is used to reduce circuit board size, then circuit board size is reduced, but voltage fluctuation increases
Solution Approach 1:
The controller uses feedback control to monitor input voltage and adjust the duty cycle in real-time. By continuously comparing the actual input voltage with the reference voltage and modifying the PWM signal accordingly, the system compensates for voltage fluctuations caused by small capacitance capacitors, maintaining voltage stability while keeping the circuit board compact.
Solution Approach 2:
The patent introduces dynamic adjustment of the duty cycle parameter. Instead of using fixed passive components, the system dynamically changes the PWM duty cycle based on real-time voltage conditions. This dynamic control approach allows the use of smaller capacitors while maintaining voltage stability through active compensation.
3Device complexity
If voltage after rectification is not controlled, then circuit complexity is reduced, but control effect of motor deteriorates
Solution Approach 1:
The controller performs multiple functions: it not only controls the motor but also regulates the input voltage by adjusting the PWM duty cycle. This multi-functional approach allows the same control unit to handle both motor control and voltage stabilization, avoiding the need for separate voltage regulation circuits and maintaining control effectiveness without significantly increasing circuit complexity.
4Area of stationary object
If non-polarity capacitor is used to reduce size, then circuit board size is reduced, but current protection is easily triggered
Solution Approach 1:
The controller uses feedback control to monitor both voltage and current conditions. By adjusting the duty cycle based on real-time measurements, the system prevents current spikes that would otherwise trigger protection circuits. This feedback mechanism ensures stable operation with small non-polarity capacitors by actively compensating for voltage fluctuations that could lead to current protection triggers.
Data Source
AI summary
An input voltage control method includes: a power supply, a first rectifier circuit and a second rectifier circuit connected between the positive terminal and the negative terminal of the power supply. The first rectifier circuit and the second rectifier circuit are connected in parallel with each other, an output end of the first rectifier circuit is connected to the motor via a driver circuit. An output end of the second rectifier circuit is connected to a controller through a voltage detection circuit. The controller collects a bus current value and collects a bus voltage value. The controller stores a target duty cycle value and a target voltage value. The controller determines a corresponding target voltage value based on the collected bus current value and obtains an output control duty cycle to drive the motor.