 PWM calculation
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IamSmooth
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Fri Jan 29 2010, 01:24PM
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Registered Member #190
Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567
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The frequency of the pulse wave is 490hz
How do I determine the right R and C values so, so a low-pass filter yields a 25% duty = 0.25 of Vmax and a 50% duty = 0.5 of Vmax?
Does the RC time constant equal less than 1/5th of 490hz, or something to this effect?
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Steve Conner
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Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
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IamSmooth wrote ...
The frequency of the pulse wave is 490hz
How do I determine the right R and C values so, so a low-pass filter yields a 25% duty = 0.25 of Vmax and a 50% duty = 0.5 of Vmax?
Does the RC time constant equal less than 1/5th of 490hz, or something to this effect?
The average voltage will always obey the law you gave above, so you can't calculate the required RC time constant from that law. The RC time constant just affects the amount of ripple on the voltage. Generally you want it as long as possible.
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