PWM/Linear Motor Driver Control Without Cross-Over Distortion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Motor controllers with fully-differential switch/amplifier arrangements face cross-over distortion when operating in both pulse-width modulated (PWM) and linear control modes, as class-B biasing introduces distortion that is not fully eliminated.
Innovation Solution
The motor driver system includes a mode selection control circuit that allows operation in either PWM or linear mode without cross-over distortion, using a push-pull driver configuration where one driver is pulse-width modulated and the other supplies a fixed voltage in PWM mode, and both drivers supply current in linear mode, ensuring a continuous feedback loop with equivalent transfer functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If class-B biasing is used in push-pull driver configuration, then power efficiency is improved, but cross-over distortion is introduced
Solution Approach 1:
The patent dynamically adjusts the biasing mode of the push-pull driver based on operating conditions. In PWM mode, class-B biasing is used for high efficiency, while in linear mode, class-AB biasing is applied to eliminate cross-over distortion. The system transitions between these dynamic states based on the selected operating mode, resolving the contradiction between efficiency and distortion.
Solution Approach 2:
The patent changes the biasing parameter (class-B vs class-AB) depending on the operating mode. When switching from PWM to linear mode, the biasing is adjusted from class-B to class-AB to eliminate cross-over distortion. This parameter change allows the system to optimize for efficiency in PWM mode and for low distortion in linear mode.
2Adaptability or versatility
If mode switching between PWM and linear control is implemented, then system versatility is improved, but output discontinuity and distortion are introduced
Solution Approach 1:
The patent applies preliminary action by pre-conditioning the output signal and biasing state before mode transitions occur. The system prepares the push-pull driver and feedback loop in advance to ensure smooth switching between PWM and linear modes, preventing output discontinuity and maintaining stability during mode changes.
Solution Approach 2:
The patent uses feedback control to maintain output continuity during mode transitions. The feedback loop continuously monitors the output and adjusts the control signals to ensure seamless transitions between PWM and linear modes, eliminating distortion and maintaining stable operation throughout the switching process.
3Manufacturing precision
If class-B biasing is used to match PWM closed-loop feedback transfer function, then transfer function matching is improved, but cross-over distortion cannot be eliminated
Solution Approach 1:
The patent dynamically changes the biasing approach based on operating mode. In PWM mode, class-B biasing maintains transfer function matching, while in linear mode, the system switches to class-AB biasing that eliminates cross-over distortion. This dynamic adaptation allows the system to achieve both transfer function matching and distortion elimination at different operational states.
Data Source
AI summary
An electronic motor control system provides selectable linear and pulse-width modulated (PWM) operation without generating cross-over distortion. The system includes an output stage that has a pair of push-pull drivers each coupled to a terminal of the motor. The electronic motor control system also includes a pulse-width modulated (PWM) driver for providing pulse-width modulated drive signals to an input of the output stage when the pulse-width modulated mode is selected and a linear amplifier stage that provides a linear analog signal to the input of the output stage in linear mode, so that both drivers are operated to supply the current to the motor. In pulse-width modulated mode, a driver is selected for PWM operation, while the other driver is operated to supply a fixed voltage. A feedback control loop senses motor current and provides outputs to the pulse-width modulator and the linear amplifier stage.