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scuzt |
Voltage matters in regards to percentage. You can tolerate more ripple voltage at a higher absolute voltage. Besides, it gets inconvienient to use a 2000uF capacitor for your 2000V 1A supply. (2kV on 2000uF is 4 kilojoules!)Obviously, more current discharges the capacitor faster, and more frequency recharges the capacitor faster, so all told we have an equation that looks like:C = K * I / (V * F), where K is some 'k'onstant. Let's solve for it... Let's say C = 2000uF, V = 12V, I = 1A and F = 60Hz. Incidentially the units are coulombs per volt = K * (coulombs/second) / (volt * cycle per second), or s * V * C / (s * V * C) = K, seconds cancel, volts cancel, coulombs cancel too, so K is dimensionless. Convienient. Well anyways, K = C * V * F / I = 0.002 * 12 * 60 / 1 = 1.44 (C in farads, V in volts, I in amps, F in hertz).I think that's for around 1Vrms ripple, I'm not sure. Obviously, ripple voltage changes roughly in inverse proportion to capacitance, so you can estimate from there.Tim |
2008/9/3 21:03 |
