Pulse Width Modulation (PWM) Implementation Using Microprocessor

Saad Mekhilef and N.A.Rahim

Faculty of Engineering, Universti Malaya

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Manuscript received January 25, 2000

Revised May 29, 2000.




A theoretical analysis and practical implementation of the natural and regular (symmetric, asymmetric) sampled three-phase PWM waveform has been presented in this paper, which was digitally implemented on an MC68000 microprocessor, and the essential considerations involved in the feasibility of using a microprocessor software-based calculation to generate PWM. All the necessary microprocessor hardware/software techniques and algorithms required to implement and generate three-phase Pulse Width Modulation (PWM) are developed in detail, and demonstrated using practical results from an experimental microprocessor board. The techniques developed and presented in this paper are readily applicable to other currently available microprocessors, with minor modifications to reflect the special features of the particular microprocessor used. Particular emphasis has been placed on the basic concepts and principles, rather than concentrating on the details of a particular microprocessor.

List of Principal Symbols

     = P.W.M modulation index (0£M£1)

fR        = fc/fm = frequency ratio

fc        = frequency of carrier signal

fm        =  frequency of modulating signal

wm       = angular frequency of modulating signal   

T        = time period

t1, t2 = Switching instants

j       = phase angle



Keywords : PWM, controller, power electronics


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