Motor Controller PWM Duty Cycle Inverse Voltage Regulation
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Solution Overview
Problem
Existing motor controller circuits face challenges in efficiently controlling motor speed across varying supply voltages and maintaining speed stability, especially during motor braking and low-speed conditions, due to continuous high current draw from transistor pairs in H-bridge configurations.
Innovation Solution
A motor controller circuit incorporating a PWM control circuit with a duty cycle control mechanism, a timer, and comparator circuitry to generate a PWM output signal with a duty cycle inversely proportional to the supply voltage, enabling precise speed control and reducing current consumption by periodically disconnecting transistors and adjusting duty cycles based on rotor commutation signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous high current is drawn from transistor pairs in H-bridge configuration to maintain motor speed, then motor speed stability is improved, but energy consumption increases and efficiency decreases
Solution Approach 1:
The patent implements periodic PWM (pulse-width modulation) switching of transistor pairs instead of continuous conduction. The control circuit periodically activates different transistor pairs (Q1-Q4, Q2-Q3, Q3-Q6, Q4-Q5) in sequence, creating pulsed current delivery to the motor windings. This periodic action maintains motor speed stability through controlled current pulses while significantly reducing overall energy consumption by allowing transistors to remain off between pulses.
Solution Approach 2:
The patent dynamically adjusts the duty cycle of PWM signals based on motor operating conditions. The control circuit modifies the proportion of time transistor pairs remain on versus off, optimizing current delivery timing. This dynamic adjustment enables the system to maintain speed stability across varying loads while minimizing energy waste by adapting the switching pattern to actual motor needs rather than using fixed continuous conduction.
2Speed
If 100% duty cycle is used to achieve fastest motor startup, then motor acceleration is improved, but current consumption is excessive during normal operation
Solution Approach 1:
The patent uses PWM periodic switching to control motor acceleration and steady-state operation. During startup, the control circuit can initially use higher duty cycles for faster acceleration, then transition to lower duty cycles for efficient steady-state operation. The periodic on-off switching of transistor pairs enables this dynamic control, replacing continuous 100% duty cycle operation with timed pulses that provide acceleration when needed and conserve energy during normal operation.
Solution Approach 2:
The control circuit dynamically adjusts PWM duty cycle based on motor speed and load conditions. During acceleration phases, the duty cycle is increased to deliver higher current for faster speed-up. Once the motor reaches the desired speed, the duty cycle is reduced to maintain speed with minimal current consumption. This dynamic adaptation resolves the contradiction between acceleration performance and ongoing energy efficiency.
3Stability of the object's composition
If transistor pairs remain continuously conducting to maintain motor operation, then motor running stability is improved, but heat generation and energy loss increase
Solution Approach 1:
The patent implements periodic PWM switching that turns transistor pairs on and off in controlled sequences. Instead of continuous conduction, each transistor pair conducts only during specific PWM pulses when current is needed to maintain motor rotation. The periodic nature of this switching maintains motor running stability through consistent pulsed current delivery while minimizing heat generation and energy loss during the off periods when transistors are non-conducting.
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 allows for stable motor speed regulation across voltage variations, reduces current consumption during braking and low-speed operations, and prevents motor stalling by dynamically adjusting the duty cycle and transistor operation, thereby enhancing energy efficiency and motor performance.
Implementation Method 1
The speed of the motor may be determined from a rotor commutation signal that is generated by converting the magnetic field generated by a rotating motor element, such as an alternating pole ring magnet, to an electrical signal with the use of a magnetic field-to-voltage transducer, such as a Hall effect element.
Data Source
AI summary
In one aspect, a control circuit to control a speed of a motor includes a PWM oscillator configured to generate a PWM output signal having a duty cycle. The speed of the motor is controlled by the PWM output signal to be proportional to the duty cycle. The control circuit also includes a duty cycle control circuit responsive to a duty cycle selection signal and coupled to the PWM oscillator. The duty cycle control circuit is configured to compare a voltage reference and a supply voltage. The duty cycle control circuit controls the duty cycle of the PWM output signal to be inversely proportional to the supply voltage.