* SPICE netlist
XU1 N015 N012 N014 MP_01 N010 N008 N004 0 0 N011 N006 N009 0 N005 N004 0 LT1950 ;pnba Comp)FB)Rosc))Slope)Ref)_SHDN)GND)Blank)Isense)Vin2)Gate)PGND)Boost)Vin)Vsec
R1 N012 0 4.99K
R2 N016 N015 4.7K
C1 N012 N016 .01
MQ1 N007 N009 N011 N011 IRF7413
R3 N011 0 .015
L1 N001 N007 100 Rpar=10K
L2 N002 0 100 Rpar=10K
V1 N001 0 54
D1 N002 N003 UPSC600
D2 0 N003 UPSC600
L3 N003 OUT 47 Rpar=2K
C2 OUT 0 47 Rser=.2
R4 OUT N012 100K
V2 N004 0 4
R5 N014 0 249K
L4 N004 N005 4.7 Rpar=2K
D3 N005 N006 1N5817
C3 N006 0 4.7
C4 N013 N012 1000p
R6 OUT N013 10K
Rload OUT 0 20
.tran 2m startup
K1 L1 L2 1

* LTspice schematic (.asc)
Version 4
SHEET 1 1328 560
WIRE -40 -280 -88 -280
WIRE 104 -280 40 -280
WIRE 232 -280 152 -280
WIRE 344 -280 296 -280
WIRE 424 -280 344 -280
WIRE 536 -280 504 -280
WIRE 568 -280 536 -280
WIRE 664 -280 568 -280
WIRE 568 -264 568 -280
WIRE 664 -264 664 -280
WIRE 104 -248 104 -280
WIRE 152 -248 152 -280
WIRE 344 -232 344 -280
WIRE -552 -216 -664 -216
WIRE -456 -216 -552 -216
WIRE -424 -216 -456 -216
WIRE -328 -216 -344 -216
WIRE -296 -216 -328 -216
WIRE -200 -216 -232 -216
WIRE -168 -216 -200 -216
WIRE -88 -216 -104 -216
WIRE -664 -200 -664 -216
WIRE -456 -168 -456 -216
WIRE -328 -168 -328 -216
WIRE -200 -168 -200 -216
WIRE 568 -168 568 -200
WIRE 664 -168 664 -184
WIRE 152 -136 152 -168
WIRE 344 -136 344 -168
WIRE -664 -104 -664 -120
WIRE 104 -104 104 -168
WIRE -552 -88 -552 -216
WIRE -520 -88 -552 -88
WIRE -136 -88 -152 -88
WIRE -520 -24 -536 -24
WIRE 56 -24 -152 -24
WIRE -520 40 -536 40
WIRE 104 40 104 -8
WIRE 104 40 -152 40
WIRE 104 56 104 40
WIRE 344 72 328 72
WIRE 424 72 408 72
WIRE 536 72 536 -280
WIRE 536 72 504 72
WIRE -616 104 -632 104
WIRE -520 104 -536 104
WIRE -136 104 -152 104
WIRE -40 104 -56 104
WIRE 40 104 24 104
WIRE -520 168 -536 168
WIRE -104 168 -152 168
WIRE 40 168 40 104
WIRE 40 168 -104 168
WIRE 328 168 328 72
WIRE 328 168 40 168
WIRE 392 168 328 168
WIRE 536 168 536 72
WIRE 536 168 472 168
WIRE -104 184 -104 168
WIRE -408 264 -408 232
WIRE -264 264 -264 232
WIRE -104 280 -104 264
FLAG -408 264 0
FLAG -264 264 0
FLAG -104 280 0
FLAG 104 136 0
FLAG -88 -280 0
FLAG 344 -136 0
FLAG 152 -136 0
FLAG 568 -168 0
FLAG -664 -104 0
FLAG -536 168 0
FLAG -632 104 0
FLAG 664 -168 0
FLAG -136 -88 0
FLAG -88 -216 0
FLAG 664 -280 OUT
SYMBOL PowerProducts\\LT1950 -328 40 R0
SYMATTR InstName U1
SYMBOL res -120 168 R0
SYMATTR InstName R1
SYMATTR Value 4.99K
SYMBOL res -40 88 R90
SYMATTR InstName R2
SYMATTR Value 4.7K
SYMBOL cap 24 88 R90
SYMATTR InstName C1
SYMATTR Value .01
SYMBOL nmos 56 -104 R0
SYMATTR InstName Q1
SYMATTR Value IRF7413
SYMBOL res 88 40 R0
SYMATTR InstName R3
SYMATTR Value .015
SYMBOL ind2 88 -264 R0
SYMATTR InstName L1
SYMATTR Value 100
SYMATTR Type ind
SYMATTR SpiceLine Rpar=10K
SYMBOL ind2 168 -264 M0
SYMATTR InstName L2
SYMATTR Value 100
SYMATTR Type ind
SYMATTR SpiceLine Rpar=10K
SYMBOL voltage 56 -280 R90
SYMATTR InstName V1
SYMATTR Value 54
SYMBOL schottky 232 -264 R270
SYMATTR InstName D1
SYMATTR Value UPSC600
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL schottky 328 -168 M180
SYMATTR InstName D2
SYMATTR Value UPSC600
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL ind 408 -264 R270
SYMATTR InstName L3
SYMATTR Value 47
SYMATTR SpiceLine Rpar=2K
SYMBOL cap 552 -264 R0
SYMATTR InstName C2
SYMATTR Value 47
SYMATTR SpiceLine Rser=.2
SYMBOL res 488 152 R90
SYMATTR InstName R4
SYMATTR Value 100K
SYMBOL voltage -664 -216 R0
SYMATTR InstName V2
SYMATTR Value 4
SYMBOL res -520 88 R90
SYMATTR InstName R5
SYMATTR Value 249K
SYMBOL ind -440 -200 R270
SYMATTR InstName L4
SYMATTR Value 4.7
SYMATTR SpiceLine Rpar=2K
SYMBOL schottky -296 -200 R270
SYMATTR InstName D3
SYMATTR Value 1N5817
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL cap -168 -200 R270
SYMATTR InstName C3
SYMATTR Value 4.7
SYMBOL cap 408 56 R90
SYMATTR InstName C4
SYMATTR Value 1000p
SYMBOL res 520 56 R90
SYMATTR InstName R6
SYMATTR Value 10K
SYMBOL res 648 -280 R0
SYMATTR InstName Rload
SYMATTR Value 20