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- Consider an RC circuit whose input is a PWM signal
with a period and duty cycle . Derive an
equation for the signal's steady state value as a function
of , , and the PWM signal's duty cycle and period.
- Derive an equation for the signal's ripple as a
function of , , and the PWM signal's duty cycle and
period.
- Assume that the PWM signal has a 50 percent duty cycle, is 1
milli-second. Use the preceding equations to plot the ripple and
steady state value of the capacitor's voltage as a function of the
PWM signal's period, . Use this plot to select a range of
periods for which the capacitor's voltage ripple is less than 5
percent. Use the largest value of ensuring a 5 percent ripple
and plot the average capacitor voltage as a function of the
PWM signal's duty cycle. What does this plot suggest about the
relationship between the duty cycle, , and the average
steady-state capacitor voltage?
- Before starting the In-lab task, show your pre-lab
work to the TA so we can verify the correctness of your
analysis and design.
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Michael Lemmon
2009-02-01