Pre-drive Controller Oscillator Synchronization
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Solution Overview
Problem
In motor driver systems with redundant motors or windings, internal oscillators can have manufacturing tolerances leading to frequency differences, causing torque ripple, vibration, and noise due to unsynchronized pulse-width modulated signals.
Innovation Solution
A drive circuit with a pre-drive controller that synchronizes internal oscillators using an external clock reference and synchronization signal, ensuring pulse-modulated switching signals are synchronized across multiple drivers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple internal oscillators are used in redundant motor drivers, then each driver can operate independently, but frequency differences due to manufacturing tolerances cause torque ripple and vibration
Solution Approach 1:
An external clock reference signal is introduced as an intermediary to synchronize multiple internal oscillators. The clock reference acts as a mediator that aligns the timing of PWM signals across redundant motor drivers, eliminating frequency differences while preserving independent operation capability
Solution Approach 2:
The oscillators are designed to be adjustable in frequency. By changing the operating parameters of the oscillators to match a common reference frequency, the system eliminates frequency mismatches between redundant drivers while maintaining the ability to operate independently when needed
2Ease of manufacture
If internal oscillators operate at different frequencies, then manufacturing tolerances are accommodated, but pulse-width modulated signals become unsynchronized causing noise and harshness
Solution Approach 1:
The external clock reference serves as an intermediary that reconciles manufacturing tolerances. Instead of requiring precise matching of internal oscillators, the system uses the external clock as a mediator to synchronize all PWM signals, accommodating component variations while eliminating noise
Solution Approach 2:
All oscillators are brought to the same frequency potential by referencing them to a common external clock. This creates equipotential conditions across all motor drivers, ensuring synchronized operation and eliminating the harmful effects of frequency mismatches
3Object-generated harmful factors
If synchronization is implemented using external clock reference, then torque ripple and vibration are reduced, but system complexity increases
Solution Approach 1:
The external clock reference serves multiple functions simultaneously: it synchronizes oscillators, provides a timing reference for PWM generation, and can be used for diagnostic purposes. This multi-functionality reduces the need for separate synchronization circuits, thereby limiting the increase in system complexity
Data Source
AI summary
A drive circuit includes an internal oscillator and a pre-drive controller coupled to the internal oscillator. The pre-drive controller can have a switch control output configured to be coupled to a switch input. The pre-drive controller can receive switch control data, receive a clock signal, receive a synchronization signal, synchronize the internal oscillator based on the clock signal and the synchronization signal, and generate a pulse modulated switching signal at the switch control output based on the switch control data and the internal oscillator.