US 5,317,248 AGranted

Micro-controller based PWM waveform generation for a multiple phase AC machine

AssigneesGeneral Motors Corporation, Delco Electronics Corporation

InventorsDaniel E. Utley, Kevin M. Deasy, Gordon D. Cheever, Jr.

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Abstract

A multi-processor AC motor control system having a timer processor which generates multiple synchronized PWM waveforms while minimizing software latency effects. The timer processor generates a 50% PWM duty cycle sync signal at the PWM frequency, creating a logic level transition (leading edge) in each PWM period. At each such transition, the timer processor interrupts the host processor for the purpose of updating a multi-byte timer data register with PWM on-time data stored in nonvolatile memory as a function of machine position and requested current. A separate timer channel is provided for each PWM waveform to be generated, and the timer processor sets off-to-on and on-to-off transitions of each waveform in accordance with the updated PWM on-time data such that respective off-to-on and on-to-off transitions in each waveform are centered about the leading edges of the sync signal. If the on-time is 0% or 100%, the timer processor overrides the normal instruction set and forces the logic state of the waveforms to a full-off or full-on logic state.

Claims6

Dependent claims

In a control system for a multiple phase AC machine including an array of switching devices defining an inverter, a timer data register for storing PWM on-time data for respective switching devices of said inverter, a host processor interruptable to update said PWM on-time data based on a machine position encoder signal and a requested machine current, and a timer processor for generating conduction control signals for the switching devices of said inverter based on the PWM on-time data stored in said timer data register, a method of operation for said timer processor comprising the steps of:

generating a sync signal having leading edges occurring once per PWM cycle;
interrupting said host CPU at successive leading edges to initiate periodic updating of the PWM on-time data stored in said timer data register;
setting off-to-on and on-to-off transitions of said conduction control signals in accordance with the updated PWM on-time data such that said transitions are centered about a succeeding leading edge of said sync signal;
and
controlling the switching devices of said inverter in accordance with respective conduction control signals.

2 more elements

Dependencies are inferred from the claim text.