johnsmith1261
New Member
Hi!
Imagine a simple DC power supply: transformer secondary, diode bridge, filtering cap, regulator.
Many books calculate power dissipation in the regulator this way:
P = (Vin - Vout) * Imax.
where:
- Vin: the filtered unregulated DC volatage
- Vout: the regulator's output voltage
- Imax: maximum current draw
I think it's correct only when regulating ripple-free DC voltages, but NOT in the case of unregulated DC's that have considerable ripple.
Wouldn't it be more correct to calculate with the mean value of the input voltage (something like rms)?
Let's label bottom and top of ripple with Vrb and Vrt, respectively.
Then I would calculate dissipation this way:
((Vrb + (Vrt-Vrb)/2) - Vout) * Imax
Is this a more proper way or am I missing something?
Thanks,
j
Imagine a simple DC power supply: transformer secondary, diode bridge, filtering cap, regulator.
Many books calculate power dissipation in the regulator this way:
P = (Vin - Vout) * Imax.
where:
- Vin: the filtered unregulated DC volatage
- Vout: the regulator's output voltage
- Imax: maximum current draw
I think it's correct only when regulating ripple-free DC voltages, but NOT in the case of unregulated DC's that have considerable ripple.
Wouldn't it be more correct to calculate with the mean value of the input voltage (something like rms)?
Let's label bottom and top of ripple with Vrb and Vrt, respectively.
Then I would calculate dissipation this way:
((Vrb + (Vrt-Vrb)/2) - Vout) * Imax
Is this a more proper way or am I missing something?
Thanks,
j