Here's a little programmable voltage regulator to go with that 1200 volt power supply that I posted somewhere above.
The R4-D2-G1-D1 mess approximates a Hitachi photovoltaic optocoupler.
It's possible that not everyone has the "universal opamp" in their LT Spice. We've had that problem recently.
Version 4 SHEET 1 880 796 WIRE 304 -272 224 -272 WIRE 432 -272 304 -272 WIRE 432 -240 432 -272 WIRE 224 -128 224 -272 WIRE 432 -112 432 -160 WIRE -544 -48 -672 -48 WIRE -448 -48 -544 -48 WIRE -112 -48 -368 -48 WIRE 80 -48 -112 -48 WIRE 176 -48 80 -48 WIRE -672 0 -672 -48 WIRE -544 0 -544 -48 WIRE -368 0 -368 -48 WIRE -112 0 -112 -48 WIRE -448 16 -448 -48 WIRE -416 16 -448 16 WIRE 80 48 80 -48 WIRE -416 64 -448 64 WIRE 224 64 224 -32 WIRE -112 96 -112 64 WIRE -816 112 -928 112 WIRE -672 112 -672 80 WIRE -672 112 -816 112 WIRE -544 112 -544 80 WIRE -448 112 -448 64 WIRE -448 112 -544 112 WIRE -672 160 -672 112 WIRE -544 160 -544 112 WIRE -368 224 -368 80 WIRE -112 224 -112 176 WIRE -112 224 -368 224 WIRE 80 224 80 128 WIRE 80 224 -112 224 WIRE 224 224 224 144 WIRE 224 224 80 224 WIRE 416 224 224 224 WIRE 544 224 416 224 WIRE 608 224 544 224 WIRE -672 272 -672 224 WIRE 416 272 416 224 WIRE -368 288 -368 224 WIRE 224 304 224 224 WIRE -544 336 -544 224 WIRE -496 336 -544 336 WIRE -464 336 -496 336 WIRE -848 352 -864 352 WIRE -816 352 -848 352 WIRE -48 384 -80 384 WIRE 0 384 -48 384 WIRE 176 384 0 384 WIRE 416 384 416 336 WIRE -816 400 -816 352 WIRE -672 416 -672 352 WIRE -672 416 -784 416 WIRE -368 416 -368 368 WIRE -368 416 -672 416 WIRE -928 432 -928 112 WIRE -848 432 -928 432 WIRE 224 432 224 400 WIRE 336 432 224 432 WIRE -672 448 -784 448 WIRE -368 464 -368 416 WIRE 0 480 0 384 WIRE 224 480 224 432 WIRE 336 480 336 432 WIRE -672 496 -672 448 WIRE -816 512 -816 464 WIRE 512 528 400 528 WIRE 560 528 512 528 WIRE 592 528 560 528 WIRE 512 592 512 528 WIRE -672 624 -672 576 WIRE -368 624 -368 544 WIRE 0 624 0 560 WIRE 224 624 224 560 WIRE 336 624 336 576 WIRE 512 720 512 672 WIRE 256 752 224 752 WIRE 336 752 336 704 WIRE 336 752 256 752 FLAG 544 224 OUT FLAG 432 -112 0 FLAG 0 624 0 FLAG 416 384 0 FLAG -368 624 0 FLAG -816 512 0 FLAG -672 624 0 FLAG 304 -272 V+ FLAG -816 112 ERR FLAG 256 752 ERR FLAG 224 624 0 FLAG -48 384 +10 FLAG -848 352 +10 FLAG 512 720 0 FLAG 560 528 +5 FLAG -496 336 +5 SYMBOL nmos 176 -128 R0 WINDOW 0 125 31 Left 2 WINDOW 3 74 65 Left 2 SYMATTR InstName M1 SYMATTR Value STN3N45K3 SYMBOL nmos 176 304 R0 WINDOW 0 -106 -26 Left 2 WINDOW 3 -154 11 Left 2 SYMATTR InstName M2 SYMATTR Value STN3N45K3 SYMBOL res 352 720 R180 WINDOW 0 -52 73 Left 2 WINDOW 3 -50 40 Left 2 SYMATTR InstName R1 SYMATTR Value 5K SYMBOL res 208 48 R0 WINDOW 0 66 35 Left 2 WINDOW 3 68 64 Left 2 SYMATTR InstName R2 SYMATTR Value 3K SYMBOL voltage 432 -256 R0 WINDOW 0 66 41 Left 2 WINDOW 3 55 75 Left 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value PULSE(0 1200 0 1m) SYMBOL voltage 0 464 R0 WINDOW 0 -103 38 Left 2 WINDOW 3 -102 73 Left 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V2 SYMATTR Value 10 SYMBOL cap 400 272 R0 WINDOW 0 59 17 Left 2 WINDOW 3 55 49 Left 2 SYMATTR InstName C1 SYMATTR Value 22n SYMBOL res 64 32 R0 WINDOW 0 -60 50 Left 2 WINDOW 3 -75 85 Left 2 SYMATTR InstName R3 SYMATTR Value 1Meg SYMBOL g -368 -16 R0 WINDOW 0 31 113 Left 2 WINDOW 3 32 143 Left 2 SYMATTR InstName G1 SYMATTR Value 1m SYMBOL res -560 -16 R0 WINDOW 0 50 41 Left 2 WINDOW 3 57 70 Left 2 SYMATTR InstName R4 SYMATTR Value 1 SYMBOL res -384 272 R0 WINDOW 0 66 54 Left 2 WINDOW 3 48 92 Left 2 SYMATTR InstName R5 SYMATTR Value 10Meg SYMBOL res -384 448 R0 WINDOW 0 65 45 Left 2 WINDOW 3 59 85 Left 2 SYMATTR InstName R6 SYMATTR Value 50K SYMBOL Opamps\\UniversalOpamp -816 432 M0 WINDOW 0 45 35 Left 2 SYMATTR InstName U1 SYMBOL res -688 256 R0 WINDOW 0 -64 33 Left 2 WINDOW 3 -82 77 Left 2 SYMATTR InstName R7 SYMATTR Value 3Meg SYMBOL cap -688 160 R0 WINDOW 0 -65 19 Left 2 WINDOW 3 -63 55 Left 2 SYMATTR InstName C2 SYMATTR Value 1n SYMBOL res -656 96 R180 WINDOW 0 64 72 Left 2 WINDOW 3 60 38 Left 2 SYMATTR InstName R8 SYMATTR Value 200 SYMBOL voltage -672 480 R0 WINDOW 0 99 28 Left 2 WINDOW 3 -140 190 Left 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V3 SYMATTR Value PULSE(1 4 25m 10u 10u 25m) SYMBOL LED -560 160 R0 WINDOW 0 90 57 Left 2 WINDOW 3 33 93 Left 2 SYMATTR InstName D2 SYMATTR Value NSPW500BS SYMBOL diode -128 0 R0 WINDOW 0 51 24 Left 2 WINDOW 3 56 54 Left 2 SYMATTR InstName D1 SYMBOL voltage -112 80 R0 WINDOW 0 -85 44 Left 2 WINDOW 3 -77 75 Left 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V5 SYMATTR Value 8 SYMBOL res 208 464 R0 WINDOW 0 -69 36 Left 2 WINDOW 3 -79 72 Left 2 SYMATTR InstName R9 SYMATTR Value 50K SYMBOL npn 400 480 M0 WINDOW 0 -78 -29 Left 2 WINDOW 3 -100 3 Left 2 SYMATTR InstName Q1 SYMATTR Value 2N4401 SYMBOL voltage 512 576 R0 WINDOW 0 58 36 Left 2 WINDOW 3 65 72 Left 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V4 SYMATTR Value 5 TEXT -312 -8 Left 2 ;PV COUPLER TEXT -408 -256 Left 2 ;KILOVOLT REGULATOR TEXT -408 -208 Left 2 ;J Larkin June 28, 2015 TEXT -344 -152 Left 2 !.tran 100m TEXT -624 552 Left 2 ;HV SETPOINT TEXT 248 -24 Left 2 ;IXTY02N120P TEXT 16 352 Left 2 ;IXTY02N120P TEXT -296 32 Left 2 ;TLP191B TEXT -624 592 Left 2 ;0 to 5 VOLTS