initial commit
This commit is contained in:
Joseph Hopfmüller
59
examples/Educational/FRA/Eg1.asc
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59
examples/Educational/FRA/Eg1.asc
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Version 4
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SHEET 1 4156 1252
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|
||||
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|
||||
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|
||||
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|
||||
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|
||||
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|
||||
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|
||||
WINDOW 0 -32 56 VBottom 2
|
||||
WINDOW 3 32 56 VTop 2
|
||||
SYMATTR InstName V3
|
||||
SYMATTR Value SINE(0 10m {Freq})
|
||||
SYMATTR Value2 ac 1
|
||||
SYMBOL Opamps\\UniversalOpamp2 1792 656 R0
|
||||
SYMATTR InstName U1
|
||||
SYMBOL voltage 1936 560 R0
|
||||
SYMATTR InstName V1
|
||||
SYMATTR Value 5
|
||||
SYMBOL voltage 2032 560 R0
|
||||
SYMATTR InstName V2
|
||||
SYMATTR Value -5
|
||||
SYMBOL res 1792 528 R90
|
||||
WINDOW 0 0 56 VBottom 2
|
||||
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|
||||
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|
||||
SYMATTR Value 10K
|
||||
SYMBOL res 1520 528 R90
|
||||
WINDOW 0 0 56 VBottom 2
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||||
WINDOW 3 32 56 VTop 2
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||||
SYMATTR InstName R2
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||||
SYMATTR Value 1K
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||||
TEXT 2200 560 Left 2 !.tran 0 {5/Freq+.1m} .1m\n.step oct param Freq .1 10Meg 3
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TEXT 1504 752 Left 2 !.measure Aavg avg V(a)\n.measure Bavg avg V(b)\n.measure Are avg (V(a)-Aavg)*cos(360*time*Freq)\n.measure Aim avg -(V(a)-Aavg)*sin(360*time*Freq)\n.measure Bre avg (V(b)-Bavg)*cos(360*time*Freq)\n.measure Bim avg -(V(b)-Bavg)*sin(360*time*Freq)\n.measure GainMag param 20*log10(hypot(Are,Aim) / hypot(Bre,Bim))\n.measure GainPhi param mod(atan2(Aim, Are) - atan2(Bim, Bre)+180,360)-180
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TEXT 2200 448 Left 2 !.save V(a) V(b)\n.option nomarch\n.option plotwinsize=0 numdgt=15
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TEXT 2200 648 Left 2 ;.ac oct 10 .1 10Meg\n.param freq=0
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TEXT 1856 248 Center 2 ;This example shows the basic principle of extracting\nthe small signal AC characteristics from time domain simulation.\n \nAfter running the simulation, execute menu command\nView=>SPICE Error Log. Then right click and select\n"Plot .step'ed .meas data". Press "yes" to the dialog\nasking if it should combine the data to complex numbers.
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TEXT 2200 784 Left 2 ;To use this technique in your\nown simulations, include these\n.measure statements
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RECTANGLE Normal 2608 976 1488 720 2
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182
examples/Educational/FRA/Eg2.asc
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examples/Educational/FRA/Eg2.asc
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||||
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||||
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||||
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||||
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||||
SYMATTR Value 4.99K
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||||
SYMBOL schottky 960 384 M180
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||||
WINDOW 0 41 53 Left 2
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WINDOW 3 24 0 Left 2
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||||
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||||
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||||
SYMBOL cap 960 416 R0
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||||
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||||
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||||
SYMATTR Value 4.7<EFBFBD>
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||||
SYMBOL ind 1072 240 R270
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
SYMATTR InstName C5
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||||
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||||
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||||
SYMBOL res 976 624 R270
|
||||
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|
||||
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|
||||
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|
||||
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||||
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||||
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||||
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||||
SYMBOL cap 896 624 R0
|
||||
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||||
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||||
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||||
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||||
WINDOW 3 32 56 VTop 2
|
||||
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||||
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||||
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||||
SYMATTR InstName U1
|
||||
SYMBOL res 256 432 R270
|
||||
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|
||||
WINDOW 3 0 56 VBottom 2
|
||||
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|
||||
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|
||||
SYMBOL res 368 432 R0
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||||
SYMATTR InstName R5
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||||
SYMATTR Value 39.2K
|
||||
SYMBOL res 272 96 R0
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||||
SYMATTR InstName R6
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||||
SYMATTR Value 249K
|
||||
SYMBOL res 368 -32 R0
|
||||
SYMATTR InstName R7
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||||
SYMATTR Value 15.0K
|
||||
SYMBOL res 368 80 R0
|
||||
SYMATTR InstName R8
|
||||
SYMATTR Value 4.99K
|
||||
SYMBOL cap 1456 240 R0
|
||||
SYMATTR InstName C8
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||||
SYMATTR Value 50<35>
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||||
SYMATTR SpiceLine Rser=1.5m Lser=.24n
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||||
SYMBOL res 1552 224 R0
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||||
SYMATTR InstName Rload
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||||
SYMATTR Value 0.25
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||||
TEXT 1672 192 Left 2 !.measure Aavg avg V(a)\n.measure Bavg avg V(b)\n.measure Are avg (V(a)-Aavg)*cos(360*time*Freq)\n.measure Aim avg -(V(a)-Aavg)*sin(360*time*Freq)\n.measure Bre avg (V(b)-Bavg)*cos(360*time*Freq)\n.measure Bim avg -(V(b)-Bavg)*sin(360*time*Freq)\n.measure GainMag param 20*log10(hypot(Are,Aim) / hypot(Bre,Bim))\n.measure GainPhi param mod(atan2(Aim, Are) - atan2(Bim, Bre)+180,360)-180
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TEXT 1680 560 Left 2 ;Loop crossover frequency: 125KHz\nPhase Margin: 92<39>
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||||
TEXT 1664 32 Left 2 !.param Freq=125K ; iterate to 0dB gain or use the .step statement below\n.step oct param freq 50K 200K 5\n.save V(a) V(b) I(L1)\n.option plotwinsize=0 numdgt=15
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TEXT 1672 472 Left 2 !.param t0=.2m\n.tran 0 {t0+25/freq} {t0}
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162
examples/Educational/FRA/Eg3.asc
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162
examples/Educational/FRA/Eg3.asc
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||||
Version 4
|
||||
SHEET 1 2936 1904
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||||
WIRE 1120 768 912 768
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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|
||||
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|
||||
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||||
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||||
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||||
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|
||||
FLAG 2192 1312 0
|
||||
FLAG 2480 1232 0
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||||
FLAG 2320 1232 0
|
||||
FLAG 912 880 0
|
||||
FLAG 1728 1216 0
|
||||
FLAG 848 1312 0
|
||||
FLAG 2480 1088 OUT
|
||||
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|
||||
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|
||||
FLAG 1616 1392 B
|
||||
FLAG 1776 1392 A
|
||||
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|
||||
SYMBOL RES 960 1168 R90
|
||||
WINDOW 0 0 56 VBottom 2
|
||||
WINDOW 3 32 56 VTop 2
|
||||
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|
||||
SYMATTR Value 10K
|
||||
SYMBOL res 2176 1088 R0
|
||||
SYMATTR InstName R2
|
||||
SYMATTR Value 20K
|
||||
SYMBOL res 2176 1200 R0
|
||||
SYMATTR InstName R3
|
||||
SYMATTR Value 10K
|
||||
SYMBOL res 2000 1104 R270
|
||||
WINDOW 0 32 56 VTop 2
|
||||
WINDOW 3 0 56 VBottom 2
|
||||
SYMATTR InstName R4
|
||||
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|
||||
SYMBOL cap 1024 1168 R90
|
||||
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||||
WINDOW 3 32 32 VTop 2
|
||||
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|
||||
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||||
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||||
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||||
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||||
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|
||||
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|
||||
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||||
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||||
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||||
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|
||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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||||
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|
||||
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|
||||
SYMBOL nmos 1680 1104 R0
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||||
SYMATTR InstName Q2
|
||||
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|
||||
SYMBOL cap 1648 816 R0
|
||||
SYMATTR InstName C5
|
||||
SYMATTR Value 4.7<EFBFBD>
|
||||
SYMBOL cap 1520 1008 R0
|
||||
SYMATTR InstName C6
|
||||
SYMATTR Value .22<EFBFBD>
|
||||
SYMBOL schottky 1520 848 R0
|
||||
SYMATTR InstName D1
|
||||
SYMATTR Value 1N5818
|
||||
SYMBOL schottky 1856 1184 M180
|
||||
WINDOW 0 24 64 Left 2
|
||||
WINDOW 3 24 0 Left 2
|
||||
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|
||||
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|
||||
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|
||||
SYMATTR InstName U1
|
||||
SYMBOL voltage 1760 1392 R90
|
||||
WINDOW 0 -32 56 VBottom 2
|
||||
WINDOW 3 32 56 VTop 2
|
||||
WINDOW 39 53 56 VTop 2
|
||||
WINDOW 123 74 56 VTop 2
|
||||
SYMATTR InstName V2
|
||||
SYMATTR Value SINE(0 10m {Freq})
|
||||
SYMBOL res 2464 1104 R0
|
||||
SYMATTR InstName Rload
|
||||
SYMATTR Value .5
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||||
TEXT 1856 1624 Left 2 !.param t0=.5m\n.tran 0 {t0+10/Freq} {t0} 10n
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||||
TEXT 1856 1536 Left 2 !.ic V(out)=2.4\n.save V(a) V(b) I(L1)
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TEXT 800 1480 Left 2 !.measure Aavg avg V(a)\n.measure Bavg avg V(b)\n.measure Are avg (V(a)-Aavg)*cos(360*time*Freq)\n.measure Aim avg -(V(a)-Aavg)*sin(360*time*Freq)\n.measure Bre avg (V(b)-Bavg)*cos(360*time*Freq)\n.measure Bim avg -(V(b)-Bavg)*sin(360*time*Freq)\n.measure GainMag param 20*log10(hypot(Are,Aim) / hypot(Bre,Bim))\n.measure GainPhi param mod(atan2(Aim, Are) - atan2(Bim, Bre)+180,360)-180
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TEXT 1856 1464 Left 2 !.param freq=21K ; iterate to 0dB gain or use the .step statement below\n.step oct param Freq 15K 30K 4
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||||
TEXT 2256 1576 Left 2 ;Loop crossover frequency: 21KHz\nPhase Margin: 66<36>
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||||
68
examples/Educational/FRA/ReadMe.txt
Normal file
68
examples/Educational/FRA/ReadMe.txt
Normal file
@@ -0,0 +1,68 @@
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Frequency Response Analysis
|
||||
|
||||
These examples show to how to extract the small-signal, AC open-loop
|
||||
gain from time-domain, closed-loop simulations. The technique is a
|
||||
subset of the method shown in ../LoopGain.asc and ../LoopGain2.asc.
|
||||
The method assumes that the input impedance of the error amplifier is
|
||||
infinite so that the loop gain can be computed solely by the voltage
|
||||
loop gain.
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||||
|
||||
The open-loop gain is computed from the closed-loop system by inserting
|
||||
a perturbing voltage source in the loop and measuring how well the
|
||||
perturbation is servoed out of the the loop via the feedback. The
|
||||
open-loop gain is given by the ratio of complex voltages at either side
|
||||
of the perturbing voltage source.
|
||||
|
||||
But since the SMPS macromodels are implemented as time-domain models
|
||||
that include detailed switching information but don't include
|
||||
continuous-time(average) equivalents, the complex voltage is determined
|
||||
from Fourier analysis of a time-domain sine wave perturbation.
|
||||
|
||||
A script of .measure statements is used to perform the Fourier analysis
|
||||
and computer the open-loop response. To use this script into your own
|
||||
SMPS design, follow these steps:
|
||||
|
||||
1. Place these .measure statements on your circuit as a SPICE
|
||||
directive:
|
||||
|
||||
.measure Aavg avg V(a)
|
||||
.measure Bavg avg V(b)
|
||||
.measure Are avg (V(a)-Aavg)*cos(360*time*Freq)
|
||||
.measure Aim avg -(V(a)-Aavg)*sin(360*time*Freq)
|
||||
.measure Bre avg (V(b)-Bavg)*cos(360*time*Freq)
|
||||
.measure Bim avg -(V(b)-Bavg)*sin(360*time*Freq)
|
||||
.measure GainMag param 20*log10(hypot(Are,Aim) / hypot(Bre,Bim))
|
||||
.measure GainPhi param mod(atan2(Aim,Are)-atan2(Bim,Bre)+180,360)-180
|
||||
|
||||
2. Insert a voltage source in the feedback loop under analysis. Give
|
||||
this voltage sourse the value SINE(0 5m {Freq})
|
||||
|
||||
3. Place a SPICE directive on the schmatic that defines Freq:
|
||||
|
||||
.param Freq=10K
|
||||
|
||||
4. Run a .tran command to see how long it takes your circuit to come to
|
||||
steady state and then edit the .tran command so that data isn't saved
|
||||
until this time.
|
||||
|
||||
5. Rerun the .tran command to do the analysis at the frequency defined
|
||||
with the .param statement of step 3.
|
||||
|
||||
6. Execute menu command View=>SPICE Error Log to see the results of this
|
||||
analysis. The open-loop response magnitude is given by GainMag[dB]
|
||||
and the phase is given by GainPhi[<5B>].
|
||||
|
||||
You can iterate the param Freq to zero dB. That frequency is the loop
|
||||
crossover frequency and phase margin will be reported as GainPhi in the
|
||||
error log.
|
||||
|
||||
You can set up a .step statement to sweep the parameter Freq. Then you
|
||||
can plot the open-loop response be executing menu command
|
||||
View=>SPICE Error Log, and then right mouse clicking and executing menu
|
||||
command "Plot .step'ed .meas data" Answer yes to the dialog that asks
|
||||
if LTspice should combine the real .meas data to complex data. Then you
|
||||
can plot the quanity gain to get a Bode plot the open-loop response of
|
||||
the system.
|
||||
|
||||
--Mike
|
||||
Reference in New Issue
Block a user