J
Jon Slaughter
- Jan 1, 1970
- 0
How is the duty cycle and current capacity generally related? linear,
exponential, logarithmic? (approximate ofcourse)
Maybe if they specified an exponential approximation Ae^(-Bx) + C then only
3 parameters would need to be given(which is just one more) for a
description of an arbitrary(within reason) of any duty cycle.
This assumes that a linear approximation is not very good.
Right now I'm trying to figure out if a linear interpolation is good enough.
1/10 duty has a current of 100mA and duty of 1(average) is 25mA.
This gives the linear equation -83.3x + 108.3 where x is the duty cycle.
So at 50% duty I would expect that I could have a current capacity of 66mA.
This seems aweful high though? (for some reason I guess I'm expecting to
double it from 25mA to 50mA since I cut the duty in half)
It also seems that there would then be an optimal duty cycle for a given
device. If f(x) is the current capacity given duty cycle x then x*f(x) is
the average current. If f(x) is approximately linear then this has a
maximum.
For my example above it occurs at a duty cycle of .65 and gives a maximum
current capacity of 54mA and average current of 35mA. An increase of 15mA(a
40% increase)!!!
Also, since at the maximum it is somewhat "flat" the duty doesn't have to be
perfect. A variation of 10%, i.e. 55% to 75% duty, gives a variation of <
1mA in the average current capacity.
I expect though that the curve is not linear but exponential... can anyone
verify this?
exponential, logarithmic? (approximate ofcourse)
Maybe if they specified an exponential approximation Ae^(-Bx) + C then only
3 parameters would need to be given(which is just one more) for a
description of an arbitrary(within reason) of any duty cycle.
This assumes that a linear approximation is not very good.
Right now I'm trying to figure out if a linear interpolation is good enough.
1/10 duty has a current of 100mA and duty of 1(average) is 25mA.
This gives the linear equation -83.3x + 108.3 where x is the duty cycle.
So at 50% duty I would expect that I could have a current capacity of 66mA.
This seems aweful high though? (for some reason I guess I'm expecting to
double it from 25mA to 50mA since I cut the duty in half)
It also seems that there would then be an optimal duty cycle for a given
device. If f(x) is the current capacity given duty cycle x then x*f(x) is
the average current. If f(x) is approximately linear then this has a
maximum.
For my example above it occurs at a duty cycle of .65 and gives a maximum
current capacity of 54mA and average current of 35mA. An increase of 15mA(a
40% increase)!!!
Also, since at the maximum it is somewhat "flat" the duty doesn't have to be
perfect. A variation of 10%, i.e. 55% to 75% duty, gives a variation of <
1mA in the average current capacity.
I expect though that the curve is not linear but exponential... can anyone
verify this?