* SPICE netlist
XU1 0 N010 NC_01 Vcc N018 N010 N008 Vcc NE555 ;pnba GND)TRIG)OUT)RST)CV)THRS)DIS)Vcc
R1 Vcc N008 270
R2 N008 N010 2k7
C1 N010 0 2.2n
C2 N018 0 100n
R3 Vcc N016 4k
R4 N016 0 4k
R6 Vcc N014 10k
V1 Vcc 0 5
XU2 N016 N010 Vcc 0 N014 LTC6702 ;pnba In+)In-)V+)GND)OUT
Q1 N011 N015 0 0 NPN
R7 N015 N014 1k
V2 N006 0 2.5
C3 N012 0 1000p
R8 N012 N011 500k
R9 N006 N011 100
XU3 N012 N009 Vcc 0 N009 AD712 ;pnba In+)In-)V+)V-)OUT
XU4 N013 N007 Vcc 0 Vcontrol AD712 ;pnba In+)In-)V+)V-)OUT
R10 N007 N009 10k
R11 Vcontrol N007 10k
R12 0 N013 10k
V3 N017 0 5V
R13 N013 N017 10k
V4 N020 0 24
R14 FB_IN N020 102k
R15 0 FB_IN 10k
XU5 FB_IN N019 Vcc 0 N019 AD712 ;pnba In+)In-)V+)V-)OUT
R5 N016 N019 1k5
V5 N005 N001 8
M1 N005 N002 0 0 IRLH5036
D1 N004 0 BZX84B20VLY
R16 N001 N002 100k
R17 N001 0 1
R18 N003 N002 1k
D2 N003 N004 D
.tran 0 5m 0 1n

* LTspice schematic (.asc)
Version 4
SHEET 1 3040 1776
WIRE -144 -888 -496 -888
WIRE 304 -888 -144 -888
WIRE -144 -824 -144 -888
WIRE -496 -792 -496 -888
WIRE 304 -792 304 -888
WIRE -144 -696 -144 -744
WIRE -112 -696 -144 -696
WIRE 64 -696 -32 -696
WIRE 176 -696 128 -696
WIRE 176 -632 176 -696
WIRE -144 -600 -144 -696
WIRE -496 -552 -496 -712
WIRE -224 -552 -496 -552
WIRE 176 -552 176 -568
WIRE 176 -552 -128 -552
WIRE 304 -552 304 -712
WIRE 304 -552 176 -552
WIRE 304 -536 304 -552
WIRE 368 -296 256 -296
WIRE -1088 -216 -1088 -280
WIRE 256 -216 256 -296
WIRE 1344 -136 1296 -136
WIRE 1472 -136 1424 -136
WIRE 368 -120 368 -296
WIRE -1088 -104 -1088 -136
WIRE -496 -104 -1088 -104
WIRE 256 -104 256 -136
WIRE 1040 -56 816 -56
WIRE -816 -24 -912 -24
WIRE -544 -24 -592 -24
WIRE -912 -8 -912 -24
WIRE -16 -8 -16 -56
WIRE 912 -8 912 -72
WIRE 816 8 816 -56
WIRE 880 8 816 8
WIRE 1360 8 1360 -24
WIRE 1040 24 1040 -56
WIRE 1040 24 944 24
WIRE 1184 24 1040 24
WIRE 1296 24 1296 -136
WIRE 1296 24 1264 24
WIRE 1328 24 1296 24
WIRE -816 40 -928 40
WIRE -496 40 -496 -104
WIRE -496 40 -592 40
WIRE 368 40 368 -40
WIRE 480 40 368 40
WIRE 688 40 560 40
WIRE 880 40 688 40
WIRE 1472 40 1472 -136
WIRE 1472 40 1392 40
WIRE 1520 40 1472 40
WIRE -1088 56 -1088 -104
WIRE 1328 56 1296 56
WIRE -208 72 -208 40
WIRE 368 72 368 40
WIRE 688 88 688 40
WIRE 912 88 912 56
WIRE -544 104 -592 104
WIRE -240 104 -544 104
WIRE 1360 104 1360 72
WIRE -16 120 -16 72
WIRE -16 120 -160 120
WIRE 128 120 -16 120
WIRE 304 120 208 120
WIRE -240 136 -288 136
WIRE 1152 136 1088 136
WIRE 1296 136 1296 56
WIRE 1296 136 1232 136
WIRE -816 168 -864 168
WIRE -512 168 -592 168
WIRE 1088 168 1088 136
WIRE 1296 168 1296 136
WIRE 688 184 688 152
WIRE -208 200 -208 168
WIRE -1408 216 -1408 168
WIRE 368 216 368 168
WIRE -512 232 -512 168
WIRE -1088 280 -1088 136
WIRE -928 280 -928 40
WIRE -928 280 -1088 280
WIRE -544 280 -544 104
WIRE -544 280 -928 280
WIRE 1088 280 1088 248
WIRE 1296 280 1296 248
WIRE -1088 312 -1088 280
WIRE -1408 328 -1408 296
WIRE -512 328 -512 296
WIRE -368 360 -368 328
WIRE -640 392 -864 392
WIRE -1088 424 -1088 376
WIRE -768 440 -768 376
WIRE -864 456 -864 392
WIRE -800 456 -864 456
WIRE -640 472 -640 392
WIRE -640 472 -736 472
WIRE -560 472 -640 472
WIRE -368 472 -368 440
WIRE -368 472 -480 472
WIRE -288 472 -288 136
WIRE -288 472 -368 472
WIRE -800 488 -912 488
WIRE -368 504 -368 472
WIRE -768 536 -768 504
WIRE -368 616 -368 584
WIRE -1408 696 -1520 696
WIRE -1280 696 -1280 600
WIRE -1280 696 -1328 696
WIRE -1216 696 -1280 696
WIRE -1072 696 -1136 696
WIRE -1520 760 -1520 696
WIRE -1072 776 -1072 696
WIRE -1520 888 -1520 840
FLAG -1088 424 0
FLAG -912 -8 0
FLAG -512 328 0
FLAG -1088 -280 Vcc
FLAG -544 -24 Vcc
FLAG -864 168 Vcc
FLAG -208 200 0
FLAG -208 40 Vcc
FLAG -16 -56 Vcc
FLAG -368 616 0
FLAG -368 328 Vcc
FLAG -1408 328 0
FLAG -1408 168 Vcc
FLAG 256 -104 0
FLAG 368 216 0
FLAG 688 184 0
FLAG 912 88 0
FLAG 912 -72 Vcc
FLAG -912 488 FB_IN
FLAG 1088 280 0
FLAG 1296 280 0
FLAG 1520 40 Vcontrol
FLAG 1360 104 0
FLAG 1360 -24 Vcc
FLAG -1072 776 0
FLAG -1520 888 0
FLAG -1280 600 FB_IN
FLAG -768 536 0
FLAG -768 376 Vcc
FLAG 304 -536 0
SYMBOL Misc\\NE555 -704 72 R0
SYMATTR InstName U1
SYMBOL res -1104 -232 R0
SYMATTR InstName R1
SYMATTR Value 270
SYMBOL res -1104 40 R0
SYMATTR InstName R2
SYMATTR Value 2k7
SYMBOL cap -1104 312 R0
SYMATTR InstName C1
SYMATTR Value 2.2n
SYMBOL cap -528 232 R0
SYMATTR InstName C2
SYMATTR Value 100n
SYMBOL res -384 344 R0
SYMATTR InstName R3
SYMATTR Value 4k
SYMBOL res -384 488 R0
SYMATTR InstName R4
SYMATTR Value 4k
SYMBOL res -32 -24 R0
SYMATTR InstName R6
SYMATTR Value 10k
SYMBOL voltage -1408 200 R0
SYMATTR InstName V1
SYMATTR Value 5
SYMBOL Comparators\\LTC6702 -208 120 R0
SYMATTR InstName U2
SYMBOL npn 304 72 R0
SYMATTR InstName Q1
SYMBOL res 224 104 R90
SYMATTR InstName R7
SYMATTR Value 1k
SYMBOL voltage 256 -232 R0
SYMATTR InstName V2
SYMATTR Value 2.5
SYMBOL cap 672 88 R0
SYMATTR InstName C3
SYMATTR Value 1000p
SYMBOL res 576 24 R90
SYMATTR InstName R8
SYMATTR Value 500k
SYMBOL res 352 -136 R0
SYMATTR InstName R9
SYMATTR Value 100
SYMBOL OpAmps\\AD713 912 -40 R0
SYMATTR InstName U3
SYMBOL OpAmps\\AD713 1360 -24 R0
SYMATTR InstName U4
SYMBOL res 1280 8 R90
SYMATTR InstName R10
SYMATTR Value 10k
SYMBOL res 1440 -152 R90
SYMATTR InstName R11
SYMATTR Value 10k
SYMBOL res 1312 264 R180
SYMATTR InstName R12
SYMATTR Value 10k
SYMBOL voltage 1088 152 R0
SYMATTR InstName V3
SYMATTR Value 5V
SYMBOL res 1248 120 R90
SYMATTR InstName R13
SYMATTR Value 10k
SYMBOL voltage -1520 744 R0
SYMATTR InstName V4
SYMATTR Value 24
SYMBOL res -1312 680 R90
SYMATTR InstName R14
SYMATTR Value 102k
SYMBOL res -1120 680 R90
SYMATTR InstName R15
SYMATTR Value 10k
SYMBOL OpAmps\\AD713 -768 408 R0
SYMATTR InstName U5
SYMBOL res -464 456 R90
SYMATTR InstName R5
SYMATTR Value 1k5
SYMBOL voltage -496 -696 R180
SYMATTR InstName V5
SYMATTR Value 8
SYMBOL nmos -224 -600 M90
SYMATTR InstName M1
SYMATTR Value IRLH5036
SYMBOL zener 160 -632 R0
SYMATTR InstName D1
SYMATTR Value BZX84B20VLY
SYMBOL res -160 -840 R0
SYMATTR InstName R16
SYMATTR Value 100k
SYMBOL res 288 -808 R0
SYMATTR InstName R17
SYMATTR Value 1
SYMBOL res -16 -712 R90
SYMATTR InstName R18
SYMATTR Value 1k
SYMBOL diode 64 -680 R270
SYMATTR InstName D2