* SPICE netlist
R1 N018 0 .67
C1 N019 0 220p
C2 N016 0 .1
C3 N015 N014 .01
R2 N014 N011 100K
R3 N016 N019 12K
R4 N011 0 20K
R5 N018 N017 1K
MQ1 N004 N013 N018 N018 IRF7303
R6 N013 N012 12
R7 N007 N011 152K
C4 N007 0 .0022
C5 N008 0 100p
D1 N008 N007 BAT54
C6 N006 0 22
R8 N010 N006 39
D2 N009 N010 BAT54
R9 IN N017 1.32Meg
R10 IN N003 660K
C7 IN N003 470p
L1 N001 0 16 Rser=.05
L2 N009 0 18.8 Rser=.1
L3 N004 IN 100 Rser=.05
D3 N001 N002 MBRS340
C8 N002 0 10
L4 N002 +20V 1 Rpar=100
C9 +20V 0 3.3
R11 +20V 0 750
V1 IN 0 200
D4 N005 N006 BZX84C15L
D5 N004 N003 MURS320
R12 N009 N008 510
R13 IN N006 400K
XU1 N015 N011 N017 N019 0 N012 N006 N016 LT1244 ;pnba COMP)FB)Isense)Rt/Ct)GND)Output)Vcc)Vref
D6 0 N005 BZX84C6V2L
C10 N017 0 50p
Rload +20V 0 50
.tran 750u
K1 L1 L2 L3 1

* LTspice schematic (.asc)
Version 4
SHEET 1 1856 912
WIRE -416 -456 -576 -456
WIRE -224 -456 -416 -456
WIRE -32 -456 -224 -456
WIRE 80 -456 -32 -456
WIRE 208 -456 80 -456
WIRE -576 -440 -576 -456
WIRE -32 -440 -32 -456
WIRE 80 -440 80 -456
WIRE -416 -424 -416 -456
WIRE 208 -392 208 -456
WIRE 272 -392 208 -392
WIRE 416 -392 336 -392
WIRE 544 -392 480 -392
WIRE 592 -392 544 -392
WIRE 720 -392 672 -392
WIRE 816 -392 720 -392
WIRE 928 -392 816 -392
WIRE -224 -376 -224 -456
WIRE 272 -376 272 -392
WIRE 336 -376 336 -392
WIRE 544 -376 544 -392
WIRE 720 -376 720 -392
WIRE 816 -376 816 -392
WIRE 928 -376 928 -392
WIRE -576 -344 -576 -360
WIRE -32 -344 -32 -376
WIRE 80 -344 80 -360
WIRE 80 -344 -32 -344
WIRE 80 -312 80 -344
WIRE 272 -280 272 -296
WIRE 272 -280 208 -280
WIRE 336 -280 336 -296
WIRE 544 -280 544 -312
WIRE 544 -280 336 -280
WIRE 720 -280 720 -312
WIRE 720 -280 544 -280
WIRE 816 -280 816 -296
WIRE 816 -280 720 -280
WIRE 928 -280 928 -296
WIRE 928 -280 816 -280
WIRE 928 -264 928 -280
WIRE -672 -248 -736 -248
WIRE -528 -248 -608 -248
WIRE -416 -248 -416 -344
WIRE -416 -248 -464 -248
WIRE 80 -232 80 -248
WIRE 208 -232 208 -280
WIRE 208 -232 80 -232
WIRE -816 -120 -912 -120
WIRE -752 -120 -816 -120
WIRE -624 -120 -688 -120
WIRE -544 -120 -624 -120
WIRE 16 -120 -464 -120
WIRE 272 -120 16 -120
WIRE -816 -104 -816 -120
WIRE -624 -104 -624 -120
WIRE 272 -104 272 -120
WIRE -416 -56 -416 -248
WIRE -192 -56 -416 -56
WIRE -160 -56 -192 -56
WIRE -64 -56 -80 -56
WIRE 16 -56 16 -120
WIRE 16 -56 0 -56
WIRE -192 -40 -192 -56
WIRE -912 -24 -912 -120
WIRE -816 -24 -816 -40
WIRE -624 -24 -624 -40
WIRE 272 -8 272 -24
WIRE -416 8 -416 -56
WIRE 80 24 80 -232
WIRE -192 40 -192 24
WIRE -912 72 -912 56
WIRE -576 72 -912 72
WIRE -128 104 -256 104
WIRE 32 104 -48 104
WIRE -912 136 -912 72
WIRE -816 136 -912 136
WIRE -688 136 -736 136
WIRE -576 136 -624 136
WIRE -912 152 -912 136
WIRE -720 200 -832 200
WIRE -576 200 -720 200
WIRE -720 216 -720 200
WIRE -832 232 -832 200
WIRE -224 232 -224 -296
WIRE -224 232 -256 232
WIRE -112 232 -224 232
WIRE 80 232 80 120
WIRE 80 232 -32 232
WIRE -912 248 -912 232
WIRE -224 248 -224 232
WIRE 80 248 80 232
WIRE -576 264 -624 264
WIRE -720 296 -720 280
WIRE -224 328 -224 312
WIRE 80 344 80 328
WIRE -832 360 -832 312
WIRE -624 360 -624 264
WIRE -624 360 -832 360
WIRE -832 376 -832 360
WIRE -416 376 -416 328
WIRE -832 456 -832 440
FLAG 80 344 0
FLAG -832 456 0
FLAG -720 296 0
FLAG -912 248 0
FLAG -416 376 0
FLAG -816 -24 0
FLAG -624 -24 0
FLAG -192 40 0
FLAG 272 -8 0
FLAG -576 -344 0
FLAG -736 -248 0
FLAG 928 -392 +20V
FLAG 928 -264 0
FLAG -576 -456 IN
FLAG -224 328 0
SYMBOL RES 64 232 R0
SYMATTR InstName R1
SYMATTR Value .67
SYMBOL cap -848 376 R0
SYMATTR InstName C1
SYMATTR Value 220p
SYMBOL cap -736 216 R0
SYMATTR InstName C2
SYMATTR Value .1
SYMBOL cap -624 120 R90
SYMATTR InstName C3
SYMATTR Value .01
SYMBOL res -720 120 R90
SYMATTR InstName R2
SYMATTR Value 100K
SYMBOL res -848 216 R0
SYMATTR InstName R3
SYMATTR Value 12K
SYMBOL res -928 136 R0
SYMATTR InstName R4
SYMATTR Value 20K
SYMBOL res -16 216 R90
SYMATTR InstName R5
SYMATTR Value 1K
SYMBOL NMOS 32 24 R0
SYMATTR InstName Q1
SYMATTR Value IRF7303
SYMBOL res -32 88 R90
SYMATTR InstName R6
SYMATTR Value 12
SYMBOL res -928 -40 R0
SYMATTR InstName R7
SYMATTR Value 152K
SYMBOL cap -832 -104 R0
SYMATTR InstName C4
SYMATTR Value .0022
SYMBOL cap -640 -104 R0
SYMATTR InstName C5
SYMATTR Value 100p
SYMBOL schottky -688 -136 R90
SYMATTR InstName D1
SYMATTR Value BAT54
SYMBOL cap -208 -40 R0
SYMATTR InstName C6
SYMATTR Value 22
SYMBOL res -64 -72 R90
SYMATTR InstName R8
SYMATTR Value 39
SYMBOL schottky 0 -72 R90
SYMATTR InstName D2
SYMATTR Value BAT54
SYMBOL res -240 -392 R0
SYMATTR InstName R9
SYMATTR Value 1.32Meg
SYMBOL res 64 -456 R0
SYMATTR InstName R10
SYMATTR Value 660K
SYMBOL cap -48 -440 R0
SYMATTR InstName C7
SYMATTR Value 470p
SYMBOL ind2 352 -392 M0
SYMATTR InstName L1
SYMATTR Value 16
SYMATTR SpiceLine Rser=.05
SYMBOL ind2 256 -120 R0
SYMATTR InstName L2
SYMATTR Value 18.8
SYMATTR SpiceLine Rser=.1
SYMBOL ind2 256 -280 M180
SYMATTR InstName L3
SYMATTR Value 100
SYMATTR SpiceLine Rser=.05
SYMBOL schottky 416 -408 M90
SYMATTR InstName D3
SYMATTR Value MBRS340
SYMBOL cap 528 -376 R0
SYMATTR InstName C8
SYMATTR Value 10
SYMBOL ind2 576 -376 R270
SYMATTR InstName L4
SYMATTR Value 1
SYMATTR Type ind
SYMATTR SpiceLine Rpar=100
SYMBOL polcap 704 -376 R0
SYMATTR InstName C9
SYMATTR Value 3.3
SYMBOL res 800 -392 R0
SYMATTR InstName R11
SYMATTR Value 750
SYMBOL VOLTAGE -576 -456 R0
SYMATTR InstName V1
SYMATTR Value 200
SYMBOL zener -528 -232 R270
SYMATTR InstName D4
SYMATTR Value BZX84C15L
SYMBOL diode 64 -248 M180
SYMATTR InstName D5
SYMATTR Value MURS320
SYMBOL res -448 -136 R90
SYMATTR InstName R12
SYMATTR Value 510
SYMBOL res -432 -440 R0
SYMATTR InstName R13
SYMATTR Value 400K
SYMBOL PowerProducts\\LT1244 -416 168 R0
SYMATTR InstName U1
SYMBOL zener -672 -232 R270
SYMATTR InstName D6
SYMATTR Value BZX84C6V2L
SYMBOL cap -240 248 R0
SYMATTR InstName C10
SYMATTR Value 50p
SYMBOL res 912 -392 R0
SYMATTR InstName Rload
SYMATTR Value 50