Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Converting – per se – of an ac input to corresponding dc at an...
Patent
1996-04-22
1998-09-22
Butler, Dennis M.
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Converting, per se, of an ac input to corresponding dc at an...
395556, 327175, G06F 104
Patent
active
058128310
ABSTRACT:
A method and implementing circuit for converting a digital signal to an analog equivalent by providing a pulse width modulated (PWM) output signal in various formats which result in an analog equivalent signal with a substantially lower harmonic distortion profile. Counter circuitry (e.g. 301-305) with input registers (e.g. 307-311) are implemented to establish switching points at predetermined count values (e.g. 4C3) within the period of an output signal (PWM OUTPUT). In one embodiment, delay circuitry (303, 309) is effective to delay the beginning of an output pulse so that the pulse is centered, or otherwise selectively positioned within an output signal period to minimize harmonics, and the pulse duration is set to correspond to a digital value to be converted. In other implementations, subcycles are defined and output pulses are established within such subcycles to provide the low harmonic output signal while maintaining an analog equivalence value of a digital input. Signal edge control techniques are also implemented to insure the same number of signal transitions per output signal period, independently of the data values input to the PWM circuitry. One embodiment permits an increase of the input rates for the pulse width and positioning input signals to a rate higher than a rate corresponding to a selected output period in order to move frequency domain images of the input signals to a higher frequency level where they may be more easily filtered.
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Wright, Jeff; "Multichannel PWM TPU Function (MCPWM);" Motorola, Inc.; 1993; pp. 1-35.
Dipl.-Ing. Michael Heiss, et al; "Pulsanzahlmodulator als D/A-Umsetzer;" Elektronik; 1989; pp. 96-98.
Butler Dennis M.
Hill Susan C.
Motorola Inc.
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