Patent ID: 6380718
Filing Date: 2002-04-30
Classification: H02J,H02P,Y02T

Abstract:
A method for use with a PWM controller that controls coil voltage within a voltage range by regulating voltage pulse widths across the coil using a PWM counter register having a register range between 0 and X and wherein 1 part in X resolution is insufficient to provide required resolution, the method for increasing output resolution and comprising the steps of;(a) receiving a high resolution voltage magnitude request signal S corresponding to a request voltage within the voltage range, the signal S having a resolution greater than 1 part in X; (b) identifying first and second consecutive counts between 0 and X corresponding to lower and upper voltage levels below and above the request voltage; (c) over the course of D PWM cycles, randomly selecting between the first and second counts such that the ratio of second to first counts over the D cycles is essentially equal to the difference between the request voltage and the lower voltage divided by the difference between the upper voltage and the lower voltage; and (d) providing the selected counts as the counter register counts.