Re: UC3843 power supply help needed!!!


"Genome" <ilike_spam@xxxxxxxxxxx> wrote in message
news:NSFie.9288$yY4.6628@xxxxxxxxxxxxxxxxxxxxxxx
> Then I'll spend some time dissapointing myself with the switching model.
>
> Have a poke about.
>
> Later
>
> DNA
>
>

OK, here's the switching model..... Again with the warning about component
values not translating properly. I owe Barry an apology for that one.

***
Version 4
*** 1 1068 904
WIRE -1296 -32 -1296 -352
WIRE -1296 80 -1296 48
WIRE -1296 112 -1296 80
WIRE -1296 176 -1328 176
WIRE -1296 480 -1296 176
WIRE -1296 592 -1296 560
WIRE -1296 624 -1296 592
WIRE -1264 176 -1296 176
WIRE -1136 80 -1296 80
WIRE -1136 80 -1136 -112
WIRE -1136 176 -1184 176
WIRE -1136 416 -1136 176
WIRE -1136 480 -1136 448
WIRE -1136 592 -1296 592
WIRE -1136 592 -1136 560
WIRE -1104 -160 -1136 -160
WIRE -1104 -112 -1136 -112
WIRE -1104 416 -1136 416
WIRE -1104 448 -1136 448
WIRE -1072 176 -1136 176
WIRE -1072 400 -1072 368
WIRE -1072 592 -1136 592
WIRE -1072 592 -1072 464
WIRE -1056 -352 -1296 -352
WIRE -1056 -304 -1056 -352
WIRE -1056 -176 -1056 -224
WIRE -1056 -64 -1056 -96
WIRE -1056 -32 -1056 -64
WIRE -1056 80 -1136 80
WIRE -1056 80 -1056 48
WIRE -1040 368 -1072 368
WIRE -1008 -64 -1056 -64
WIRE -944 176 -992 176
WIRE -944 432 -1040 432
WIRE -944 432 -944 176
WIRE -912 176 -944 176
WIRE -896 432 -944 432
WIRE -880 -304 -880 -352
WIRE -816 -352 -880 -352
WIRE -800 432 -832 432
WIRE -736 -224 -880 -224
WIRE -736 80 -1056 80
WIRE -736 80 -736 -224
WIRE -704 432 -736 432
WIRE -672 -352 -752 -352
WIRE -672 -304 -672 -352
WIRE -672 -128 -672 -304
WIRE -672 -32 -672 -64
WIRE -672 80 -736 80
WIRE -672 80 -672 48
WIRE -592 336 -640 336
WIRE -592 384 -592 336
WIRE -592 432 -624 432
WIRE -592 480 -592 432
WIRE -592 592 -1072 592
WIRE -592 592 -592 560
WIRE -560 384 -592 384
WIRE -560 432 -592 432
WIRE -512 -304 -672 -304
WIRE -512 -32 -512 -304
WIRE -512 80 -672 80
WIRE -512 80 -512 48
WIRE -512 208 -512 176
WIRE -512 336 -512 288
WIRE -512 368 -512 336
WIRE -512 592 -592 592
WIRE -512 592 -512 448
WIRE -480 336 -512 336
WIRE -464 -352 -672 -352
WIRE -464 -304 -512 -304
WIRE -256 336 -288 336
WIRE -256 384 -256 336
WIRE -256 480 -256 432
WIRE -256 592 -512 592
WIRE -256 592 -256 560
WIRE -208 -352 -240 -352
WIRE -208 384 -256 384
WIRE -208 432 -256 432
WIRE -160 176 -512 176
WIRE -160 208 -160 176
WIRE -160 336 -160 288
WIRE -160 368 -160 336
WIRE -160 592 -256 592
WIRE -160 592 -160 448
WIRE -128 336 -160 336
WIRE -96 -352 -128 -352
WIRE -96 -96 -96 -352
WIRE -96 -32 -96 -96
WIRE -96 80 -512 80
WIRE -96 80 -96 48
WIRE -32 -32 -32 -64
WIRE -32 80 -96 80
WIRE -32 80 -32 48
WIRE 32 -352 -96 -352
WIRE 64 -96 -96 -96
WIRE 64 -64 -32 -64
WIRE 80 336 48 336
WIRE 80 480 80 336
WIRE 80 592 -160 592
WIRE 80 592 80 560
WIRE 96 -112 96 -144
WIRE 96 80 -32 80
WIRE 96 80 96 -48
WIRE 128 -144 96 -144
WIRE 128 176 -160 176
WIRE 128 288 128 176
WIRE 160 288 128 288
WIRE 160 336 80 336
WIRE 160 592 80 592
WIRE 160 592 160 384
WIRE 224 -352 112 -352
WIRE 224 -80 128 -80
WIRE 224 -80 224 -352
WIRE 240 448 240 384
WIRE 288 -80 224 -80
WIRE 400 -176 400 -240
WIRE 432 -176 400 -176
WIRE 432 -80 368 -80
WIRE 448 224 416 224
WIRE 448 240 448 224
WIRE 448 256 448 240
WIRE 448 272 448 256
WIRE 448 448 240 448
WIRE 480 224 448 224
WIRE 480 240 448 240
WIRE 480 256 448 256
WIRE 480 272 448 272
WIRE 480 288 320 288
WIRE 496 592 160 592
WIRE 496 592 496 496
WIRE 544 432 512 432
WIRE 544 448 512 448
WIRE 544 448 544 432
WIRE 544 464 512 464
WIRE 544 464 544 448
WIRE 544 480 512 480
WIRE 544 496 512 496
WIRE 544 496 544 480
WIRE 576 240 544 240
WIRE 576 432 544 432
WIRE 576 496 544 496
WIRE 656 -240 400 -240
WIRE 656 -176 624 -176
WIRE 656 -176 656 -240
WIRE 688 -352 224 -352
WIRE 688 -240 656 -240
WIRE 688 -112 624 -112
WIRE 720 176 128 176
WIRE 720 480 720 176
WIRE 720 592 496 592
WIRE 720 592 720 560
WIRE 752 176 720 176
FLAG 240 240 0
FLAG 48 336 CLK
IOPIN 48 336 Out
FLAG 416 224 CLK
IOPIN 416 224 In
FLAG 496 288 0
FLAG 576 240 MDRV
IOPIN 576 240 Out
FLAG 576 496 PKL
IOPIN 576 496 In
FLAG 576 432 PWM
IOPIN 576 432 In
FLAG 752 176 5V
IOPIN 752 176 In
FLAG -128 336 PKL
IOPIN -128 336 Out
FLAG -480 336 PWM
IOPIN -480 336 Out
FLAG -288 336 ISNS
IOPIN -288 336 In
FLAG -640 336 ISNS
IOPIN -640 336 In
FLAG -1328 176 EMITT
IOPIN -1328 176 In
FLAG -1296 624 0
FLAG -1136 -160 MDRV
IOPIN -1136 -160 In
FLAG -464 -304 VOUT
IOPIN -464 -304 Out
FLAG -464 -352 VSNS
IOPIN -464 -352 Out
FLAG -1296 112 0
FLAG -240 -352 VSNS
IOPIN -240 -352 In
FLAG 688 -352 VSEA
IOPIN 688 -352 Out
FLAG -1040 368 5V
IOPIN -1040 368 In
FLAG 128 -144 5V
IOPIN 128 -144 In
FLAG -912 176 VPEA
IOPIN -912 176 Out
FLAG -1008 -64 ISNS
IOPIN -1008 -64 Out
FLAG 688 -240 5V
IOPIN 688 -240 In
FLAG 688 -112 EMITT
IOPIN 688 -112 Out
SYMBOL Digital\\dflop 240 240 R0
WINDOW 0 50 -20 Left 0
SYMATTR InstName A1
SYMATTR SpiceLine Trise=10n Tfall=10n Vhigh=5 Vlow=0
SYMBOL voltage 80 464 R0
WINDOW 0 -100 57 Left 0
WINDOW 3 24 104 Invisible 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName VCLK
SYMATTR Value PULSE(0 5 0 10n 10n 9u 10u)
SYMBOL Digital\\and 512 192 R0
WINDOW 0 -33 14 Left 0
SYMATTR InstName A2
SYMATTR SpiceLine Trise=10n Tfall=10n Vhigh=5 Vlow=0
SYMBOL Digital\\or 480 400 M0
WINDOW 0 -29 13 Left 0
SYMATTR InstName A3
SYMATTR SpiceLine Trise=10n Tfall=10n Vhigh=5 Vlow=0
SYMBOL sw -512 352 R0
WINDOW 0 36 40 Left 0
WINDOW 3 36 64 Left 0
SYMATTR InstName S1
SYMATTR Value COMP
SYMBOL sw -160 352 R0
WINDOW 0 41 45 Left 0
WINDOW 3 42 67 Left 0
SYMATTR InstName S2
SYMATTR Value COMP
SYMBOL voltage -256 464 R0
WINDOW 0 40 43 Left 0
WINDOW 3 40 64 Left 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName VPK
SYMATTR Value 1V
SYMBOL res -176 192 R0
SYMATTR InstName R9
SYMATTR Value 1K
SYMBOL res -528 192 R0
SYMATTR InstName R8
SYMATTR Value 1K
SYMBOL diode -896 448 R270
WINDOW 0 32 32 VTop 0
WINDOW 3 0 32 VBottom 0
SYMATTR InstName D1
SYMATTR Value 1N4148
SYMBOL diode -800 448 R270
WINDOW 0 32 32 VTop 0
WINDOW 3 0 32 VBottom 0
SYMATTR InstName D2
SYMATTR Value 1N4148
SYMBOL res -608 464 R0
WINDOW 3 36 66 Left 0
SYMATTR Value 1K
SYMATTR InstName R7
SYMBOL res -608 416 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R6
SYMATTR Value 2K
SYMBOL voltage 720 464 R0
WINDOW 0 37 44 Left 0
WINDOW 3 37 69 Left 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName VSUP
SYMATTR Value 5V
SYMBOL voltage -1136 464 R0
WINDOW 0 -99 47 Left 0
WINDOW 3 -101 67 Left 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName PREF
SYMATTR Value 2.5V
SYMBOL res -976 160 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R5
SYMATTR Value 30K
SYMBOL res -1168 160 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R4
SYMATTR Value 10K
SYMBOL res -1312 464 R0
WINDOW 0 -44 44 Left 0
WINDOW 3 -44 67 Left 0
SYMATTR InstName R3
SYMATTR Value 1K
SYMBOL sw -1056 -80 M180
WINDOW 0 -72 139 Left 0
WINDOW 3 -71 114 Left 0
SYMATTR InstName S3
SYMATTR Value MSW
SYMBOL res -1072 -48 R0
WINDOW 0 36 45 Left 0
WINDOW 3 38 69 Left 0
SYMATTR InstName RSNS
SYMATTR Value 0R5
SYMBOL ind2 -1072 -320 R0
WINDOW 0 40 41 Left 0
WINDOW 3 42 65 Left 0
SYMATTR InstName L1
SYMATTR Value 500µ
SYMATTR Type ind
SYMBOL ind2 -864 -208 R180
WINDOW 0 51 71 Left 0
WINDOW 3 41 49 Left 0
SYMATTR InstName L2
SYMATTR Value 15µ
SYMATTR Type ind
SYMBOL diode -816 -336 R270
WINDOW 0 56 32 VTop 0
WINDOW 3 61 30 VBottom 0
SYMATTR InstName DRECT
SYMATTR Value DID
SYMBOL cap -688 -128 R0
WINDOW 0 43 20 Left 0
WINDOW 3 43 45 Left 0
SYMATTR InstName CFILT
SYMATTR Value 220µ
SYMBOL voltage -1296 -48 R0
WINDOW 0 37 44 Left 0
WINDOW 3 37 69 Left 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName VBUS
SYMATTR Value 311V
SYMBOL voltage -32 -48 R0
WINDOW 0 42 46 Left 0
WINDOW 3 42 69 Left 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName SREF
SYMATTR Value 2.5V
SYMBOL res -112 -48 R0
WINDOW 0 -59 49 Left 0
WINDOW 3 -59 72 Left 0
SYMATTR InstName R10
SYMATTR Value 2K
SYMBOL res -112 -368 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R1
SYMATTR Value 9K1
SYMBOL res 272 -64 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 0 56 VBottom 0
SYMATTR InstName RLED
SYMATTR Value 220R
SYMBOL Opamps\\1pole 96 -80 R0
SYMATTR InstName U1
SYMBOL Opamps\\1pole -1072 432 R0
SYMATTR InstName U2
SYMBOL load2 -512 -32 R0
WINDOW 0 49 23 Left 0
WINDOW 3 50 50 Invisible 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName ILOAD
SYMATTR Value PULSE(0.2 2 0 10n 10n 500u 1m)
SYMBOL res -688 -48 R0
WINDOW 0 36 47 Left 0
SYMATTR InstName RESR
SYMATTR Value 23m
SYMBOL res 128 -368 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R2
SYMATTR Value 20K
SYMBOL Optos\\4N25 528 -112 R0
SYMATTR InstName U3
TEXT -1296 696 Left 0 !.MODEL COMP SW(RON=10m ROFF=1E6 VT=0 VH=10m)
TEXT -1296 720 Left 0 !.MODEL MSW SW(RON=10m ROFF=1E6 VT=2.5 VH=-1)
TEXT -1024 -344 Left 0 !K1 L1 L2 1
TEXT -1296 768 Left 0 !.tran 0 5m 1m uic
TEXT -1296 744 Left 0 !.MODEL DID D(RON=10m)
***

You'll recognise some of the bits from the linear model. The additional bits
are a 'bastardization' of what a UC3843 might look like along with the power
stage.

Yes..... it's all sort of idealised but it should match up with what's going
on in the IC.

I'll put it this way.......

Your physical power supply is sitting on the bench going 'Squeal Squeal
Squeal' or otherwise bouncing about.

You can sit with it and prod about or wibble something else on it and get
nowhere. Management likes to see you doing this because you are visibly
working... More bangs per buck.

Or, You can simulate things....

So..... obviously you go on a tree hunt for all the bits to simulate your
power supply and then you stick them in your simulator and...... the
simulation is crap as well. It's probably worse than the real thing..... So,
obviously, Simulation aint worth any bangs?

The first thing you do is remove the crap so you can see the underlying
***.

I appear to have rambled.... but you get the 'simplified' switching model.
It's a Mother Beautiful circuit diagram. When you turd about with it try not
to leave too many dingleberries.

Run that and plot V(vout) and I(iload).

When it's down at 200mA things look cool. When it stomps up to 2A, zoom in
on it, things go a bit flakey. It doesn't mess about though.... Reduce R2 to
10K and do it again....

Not so fast but happier.

I wouldn't care to argue about the reasons why but... at 2A, according to
the linear model, crossover is up at 30KHz and the phase margin has been
robbed by the delay term. Could be time to wobble?

Not so interesting is, if you just want about 14V output from the ploopy, I
have been lucky with the selection of operating levels in the circuit. It's
near enough without adding some other nerf.

DNA


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