* SPICE netlist
R1 N018 0 .67
C1 N019 0 220p
C2 N016 0 .1
C3 N015 N014 .005
R2 N014 N011 100K
R3 N016 N019 12K
R4 N011 0 20K
R7 N018 N017 1K
MQ1 N006 N013 N018 N018 IRF7303
R8 N013 N012 12
R9 N007 N011 152K
C4 N007 0 .0022
C5 N008 0 100p
D1 N008 N007 BAT54
C6 N005 0 22
R10 N010 N005 39
D2 N009 N010 BAT54
R13 IN N017 1.32Meg
R14 IN N003 660K
C7 IN N003 470p
L1 N001 0 16 Rser=.05 Rpar=10K
L3 N009 0 18.8 Rser=.1 Rpar=10K
L2 N006 IN 100 Rser=.05 Rpar=10K
D3 N001 N002 MBRS340
C8 N002 0 20
L4 N002 +20V 1
C9 +20V 0 3.3 Rser=.1
R15 +20V 0 750
V1 IN 0 200
D4 N004 N005 BZX84C15L
Rload +20V 0 20
D5 N006 N003 MURS320
R17 N009 N008 510
R18 IN N005 400K
XU1 N015 N011 N017 N019 0 N012 N005 N016 LT1242 ;pnba COMP)FB)Isense)Rt/Ct)GND)Output)Vcc)Vref
D6 0 N004 BZX84C6V2L
C10 N017 0 50p
.tran 2m
K1 L1 L2 L3 1

* LTspice schematic (.asc)
Version 4
SHEET 1 1936 832
WIRE -424 -416 -584 -416
WIRE -232 -416 -424 -416
WIRE -8 -416 -232 -416
WIRE 104 -416 -8 -416
WIRE 232 -416 104 -416
WIRE -584 -400 -584 -416
WIRE -8 -400 -8 -416
WIRE 104 -400 104 -416
WIRE -424 -368 -424 -416
WIRE 232 -368 232 -416
WIRE 280 -368 232 -368
WIRE 440 -368 344 -368
WIRE 536 -368 504 -368
WIRE 584 -368 536 -368
WIRE 712 -368 664 -368
WIRE 840 -368 712 -368
WIRE 968 -368 840 -368
WIRE 280 -352 280 -368
WIRE 344 -352 344 -368
WIRE 536 -352 536 -368
WIRE 712 -352 712 -368
WIRE 840 -352 840 -368
WIRE 968 -352 968 -368
WIRE -232 -320 -232 -416
WIRE -584 -304 -584 -320
WIRE -8 -304 -8 -336
WIRE 104 -304 104 -320
WIRE 104 -304 -8 -304
WIRE 104 -288 104 -304
WIRE -696 -256 -744 -256
WIRE -536 -256 -632 -256
WIRE -424 -256 -424 -288
WIRE -424 -256 -472 -256
WIRE 280 -256 280 -272
WIRE 280 -256 232 -256
WIRE 344 -256 344 -272
WIRE 536 -256 536 -288
WIRE 536 -256 344 -256
WIRE 712 -256 712 -288
WIRE 712 -256 536 -256
WIRE 840 -256 840 -272
WIRE 840 -256 712 -256
WIRE 968 -256 968 -272
WIRE 968 -256 840 -256
WIRE 968 -240 968 -256
WIRE 104 -208 104 -224
WIRE 232 -208 232 -256
WIRE 232 -208 104 -208
WIRE -824 -128 -952 -128
WIRE -760 -128 -824 -128
WIRE -632 -128 -696 -128
WIRE -552 -128 -632 -128
WIRE 40 -128 -472 -128
WIRE 280 -128 40 -128
WIRE -824 -112 -824 -128
WIRE -632 -112 -632 -128
WIRE 280 -112 280 -128
WIRE -952 -96 -952 -128
WIRE -424 -64 -424 -256
WIRE -200 -64 -424 -64
WIRE -136 -64 -200 -64
WIRE -40 -64 -56 -64
WIRE 40 -64 40 -128
WIRE 40 -64 24 -64
WIRE -200 -48 -200 -64
WIRE -824 -16 -824 -48
WIRE -632 -16 -632 -48
WIRE 280 -16 280 -32
WIRE -424 0 -424 -64
WIRE 104 16 104 -208
WIRE -200 48 -200 16
WIRE -952 64 -952 -16
WIRE -584 64 -952 64
WIRE -136 96 -264 96
WIRE 56 96 -56 96
WIRE -952 128 -952 64
WIRE -824 128 -952 128
WIRE -696 128 -744 128
WIRE -584 128 -632 128
WIRE -952 144 -952 128
WIRE -728 192 -840 192
WIRE -584 192 -728 192
WIRE -728 208 -728 192
WIRE -840 224 -840 192
WIRE -232 224 -232 -240
WIRE -232 224 -264 224
WIRE -200 224 -232 224
WIRE 104 224 104 112
WIRE 104 224 -120 224
WIRE -952 240 -952 224
WIRE 104 240 104 224
WIRE -584 256 -632 256
WIRE -232 272 -232 224
WIRE -728 288 -728 272
WIRE -840 320 -840 304
WIRE -632 320 -632 256
WIRE -632 320 -840 320
WIRE -840 336 -840 320
WIRE 104 336 104 320
WIRE -424 368 -424 320
WIRE -232 368 -232 336
WIRE -840 416 -840 400
FLAG 104 336 0
FLAG -840 416 0
FLAG -728 288 0
FLAG -952 240 0
FLAG -424 368 0
FLAG -824 -16 0
FLAG -632 -16 0
FLAG -200 48 0
FLAG 280 -16 0
FLAG -584 -304 0
FLAG -744 -256 0
FLAG 968 -368 +20V
FLAG 968 -240 0
FLAG -232 368 0
FLAG -584 -416 IN
SYMBOL RES 88 224 R0
SYMATTR InstName R1
SYMATTR Value .67
SYMBOL cap -856 336 R0
SYMATTR InstName C1
SYMATTR Value 220p
SYMBOL cap -744 208 R0
SYMATTR InstName C2
SYMATTR Value .1
SYMBOL cap -632 112 R90
SYMATTR InstName C3
SYMATTR Value .005
SYMBOL res -728 112 R90
SYMATTR InstName R2
SYMATTR Value 100K
SYMBOL res -856 208 R0
SYMATTR InstName R3
SYMATTR Value 12K
SYMBOL res -968 128 R0
SYMATTR InstName R4
SYMATTR Value 20K
SYMBOL res -104 208 R90
SYMATTR InstName R7
SYMATTR Value 1K
SYMBOL NMOS 56 16 R0
SYMATTR InstName Q1
SYMATTR Value IRF7303
SYMBOL res -40 80 R90
SYMATTR InstName R8
SYMATTR Value 12
SYMBOL res -968 -112 R0
SYMATTR InstName R9
SYMATTR Value 152K
SYMBOL cap -840 -112 R0
SYMATTR InstName C4
SYMATTR Value .0022
SYMBOL cap -648 -112 R0
SYMATTR InstName C5
SYMATTR Value 100p
SYMBOL schottky -696 -144 R90
SYMATTR InstName D1
SYMATTR Value BAT54
SYMBOL cap -216 -48 R0
SYMATTR InstName C6
SYMATTR Value 22
SYMBOL res -40 -80 R90
SYMATTR InstName R10
SYMATTR Value 39
SYMBOL schottky 24 -80 R90
SYMATTR InstName D2
SYMATTR Value BAT54
SYMBOL res -248 -336 R0
SYMATTR InstName R13
SYMATTR Value 1.32Meg
SYMBOL res 88 -416 R0
SYMATTR InstName R14
SYMATTR Value 660K
SYMBOL cap -24 -400 R0
SYMATTR InstName C7
SYMATTR Value 470p
SYMBOL ind2 360 -368 M0
SYMATTR InstName L1
SYMATTR Value 16
SYMATTR SpiceLine Rser=.05 Rpar=10K
SYMBOL ind2 264 -128 R0
SYMATTR InstName L3
SYMATTR Value 18.8
SYMATTR SpiceLine Rser=.1 Rpar=10K
SYMBOL ind2 264 -256 M180
SYMATTR InstName L2
SYMATTR Value 100
SYMATTR SpiceLine Rser=.05 Rpar=10K
SYMBOL schottky 440 -384 M90
SYMATTR InstName D3
SYMATTR Value MBRS340
SYMBOL cap 520 -352 R0
SYMATTR InstName C8
SYMATTR Value 20
SYMBOL ind2 568 -352 R270
SYMATTR InstName L4
SYMATTR Value 1
SYMATTR Type ind
SYMBOL polcap 696 -352 R0
SYMATTR InstName C9
SYMATTR Value 3.3
SYMATTR SpiceLine Rser=.1
SYMBOL res 824 -368 R0
SYMATTR InstName R15
SYMATTR Value 750
SYMBOL VOLTAGE -584 -416 R0
SYMATTR InstName V1
SYMATTR Value 200
SYMBOL zener -536 -240 R270
SYMATTR InstName D4
SYMATTR Value BZX84C15L
SYMBOL res 952 -368 R0
SYMATTR InstName Rload
SYMATTR Value 20
SYMBOL diode 88 -224 M180
SYMATTR InstName D5
SYMATTR Value MURS320
SYMBOL res -456 -144 R90
SYMATTR InstName R17
SYMATTR Value 510
SYMBOL res -440 -384 R0
SYMATTR InstName R18
SYMATTR Value 400K
SYMBOL PowerProducts\\LT1242 -424 160 R0
SYMATTR InstName U1
SYMBOL zener -696 -240 R270
SYMATTR InstName D6
SYMATTR Value BZX84C6V2L
SYMBOL cap -248 272 R0
SYMATTR InstName C10
SYMATTR Value 50p