On 7/6/2015 12:39 AM, rickman wrote:
On 7/5/2015 4:45 PM, Jerry Stuckle wrote:

Actually, it doesn't matter if it's a fixed or a variable output voltage
- maximum power transfer always occurs when there is an impedance match.

How about we quit with the speculation and come up with some numbers?

Here is a simulation of a 50 ohm load with a 50 ohm matched series
output impedance and a voltage source of 200 VAC peak. Power into the
load is 100 W.

http://arius.com/sims/Matched%20Load%20Power.png

Same exact circuit with the series impedance of just 1 ohm, power into
the load is 385 W.

http://arius.com/sims/UnMatched%20Load%20Power.png

I'd say that is pretty clear evidence that matched loads are not the way
to maximize power transfer when the load impedance is fixed and the
output impedance is controllable.

In case anyone wants to duplicate the simulation...

Version 4
SHEET 1 880 680
WIRE 48 48 0 48
WIRE 144 48 48 48
WIRE 304 48 224 48
WIRE 336 48 304 48
WIRE 0 80 0 48
WIRE 336 80 336 48
WIRE 0 192 0 160
WIRE 336 192 336 160
WIRE 48 304 0 304
WIRE 144 304 48 304
WIRE 304 304 224 304
WIRE 336 304 304 304
WIRE 0 336 0 304
WIRE 336 336 336 304
WIRE 0 448 0 416
WIRE 336 448 336 416
FLAG 0 192 0
FLAG 336 192 0
FLAG 48 48 V1
FLAG 304 48 Vload1
FLAG 0 448 0
FLAG 336 448 0
FLAG 48 304 V2
FLAG 304 304 Vload2
SYMBOL voltage 0 64 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V1
SYMATTR Value SINE(0 200 100K)
SYMBOL res 320 64 R0
SYMATTR InstName RL1
SYMATTR Value 50
SYMBOL res 128 64 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName RS1
SYMATTR Value 50
SYMBOL voltage 0 320 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value SINE(0 200 100K)
SYMBOL res 320 320 R0
SYMATTR InstName RL2
SYMATTR Value 50
SYMBOL res 128 320 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName RS2
SYMATTR Value 1
TEXT -34 472 Left 2 !.tran 10us


--

Rick