See the MSD7342-224ml for coupled inductor. The IRF9640 is overkill but only SC3 model available. The control loop should be pretty straight forward. What is the input voltage range desired?
I would copy in that neat net + wiring list that you guys use but do not know how. Just learning LTSPICE.
To post your ASC file, you can put it on the web site as you have done.
There is also an option on the web site to provide a direct download link. For example, your ASC file is at
formatting link
You can also load the ASC file into an ascii editor and paste it into your newsgroup client. This creates the problem of line wrap when you have anything that extends past column 70 or so. It also creates havoc with some news clients that wish to change symbols to hex. For example, the equal sign, "=", becomes "=3D". This creates problems in LTspice since it cannot deciper lines like
SYMATTR SpiceLine Rser=3D0.02 Rpar=3D5000
Some newsgroups allow you to post an ASC file as an attachment. This is convenient since the newsreader usually saves the attachment to a folder. This eliminates the problem of wrapping long lines in the newsreader.
There are a number of ways of conveying your circuit to the newsgroup. Try to pick one that causes the least amount of problems for your readers.
There is a bit of overshoot in your circuit on startup. You might consider lowering the on time of the IRF9640. You can set V2 to around
50% duty cycle. Try
PULSE(0 10 10N 10N 10N 5U 10U)
It needs just a tad more on time to come up exactly on the target voltage. However, this will change with the load.
After seeing the group's 45V power supply kludge, I would like to enter mine into the competition.
Version 4 SHEET 1 1108 900 WIRE -816 -256 -1200 -256 WIRE -576 -256 -816 -256 WIRE -80 -256 -576 -256 WIRE -1632 -240 -1680 -240 WIRE -1504 -240 -1552 -240 WIRE -1488 -240 -1504 -240 WIRE -576 -192 -576 -256 WIRE -816 -176 -816 -256 WIRE -864 -160 -944 -160 WIRE -1856 -128 -1952 -128 WIRE -1680 -128 -1680 -240 WIRE -1456 -128 -1680 -128 WIRE -80 -128 -80 -256 WIRE -944 -112 -944 -160 WIRE -256 -112 -288 -112 WIRE -128 -112 -176 -112 WIRE -1200 -80 -1200 -256 WIRE -1952 -64 -1952 -128 WIRE -576 -48 -576 -112 WIRE -1456 -16 -1456 -128 WIRE -1360 -16 -1456 -16 WIRE -992 16 -1040 16 WIRE -864 16 -864 -112 WIRE -864 16 -992 16 WIRE -816 16 -816 -96 WIRE -688 16 -816 16 WIRE -288 16 -288 -112 WIRE -288 16 -688 16 WIRE -1680 48 -1680 -128 WIRE -1632 48 -1680 48 WIRE -1520 48 -1568 48 WIRE -1408 48 -1440 48 WIRE -1360 48 -1408 48 WIRE -1680 80 -1680 48 WIRE -768 96 -816 96 WIRE -752 96 -768 96 WIRE -432 96 -464 96 WIRE -320 96 -368 96 WIRE -192 96 -240 96 WIRE -1440 112 -1472 112 WIRE -1376 112 -1440 112 WIRE -1360 112 -1376 112 WIRE -80 112 -80 -32 WIRE -1472 128 -1472 112 WIRE -816 128 -816 96 WIRE -1024 144 -1040 144 WIRE -976 144 -1024 144 WIRE -912 144 -976 144 WIRE -864 144 -864 16 WIRE -1360 176 -1392 176 WIRE -464 208 -464 96 WIRE -464 208 -576 208 WIRE -352 208 -464 208 WIRE -192 208 -192 96 WIRE -192 208 -288 208 WIRE -80 208 -80 112 WIRE 32 208 -80 208 WIRE 192 208 96 208 WIRE 288 208 192 208 WIRE -1472 224 -1472 208 WIRE -1392 224 -1392 176 WIRE -1392 224 -1472 224 WIRE -1472 240 -1472 224 WIRE -576 240 -576 208 WIRE -192 240 -192 208 WIRE -80 240 -80 208 WIRE 288 240 288 208 WIRE -464 256 -464 208 WIRE 192 256 192 208 WIRE -912 272 -912 144 WIRE -1200 288 -1200 240 WIRE -816 288 -816 224 WIRE -736 288 -816 288 WIRE -816 352 -816 288 WIRE -816 352 -864 352 WIRE -576 368 -576 320 WIRE -464 368 -464 320 WIRE -192 368 -192 320 WIRE -80 368 -80 320 WIRE 192 368 192 320 WIRE 288 368 288 320 WIRE -1376 384 -1376 112 WIRE -1312 384 -1376 384 WIRE -1024 384 -1024 144 WIRE -1024 384 -1232 384 WIRE -1024 400 -1024 384 FLAG -576 -48 0 FLAG -80 368 0 FLAG 192 368 0 FLAG -192 368 0 FLAG -464 368 0 FLAG -576 368 0 FLAG 288 368 0 FLAG -80 112 VS FLAG 288 208 NO FLAG -576 208 PO FLAG -1200 288 0 FLAG -992 16 DV FLAG -688 16 DN FLAG -1472 304 0 FLAG -1472 224 FR FLAG -736 368 0 FLAG -1024 464 0 FLAG -912 368 0 FLAG -1440 112 VR FLAG -768 96 VR FLAG -976 144 IS FLAG -944 -112 0 FLAG -1680 160 0 FLAG -1504 -240 PO FLAG -1408 48 CP FLAG -1952 16 0 FLAG -1792 -128 CP SYMBOL ind2 -96 224 R0 WINDOW 0 50 51 Left 2 WINDOW 3 60 86 Left 2 SYMATTR InstName L1 SYMATTR Value 220µ SYMATTR Type ind SYMATTR SpiceLine Rser=1.72 SYMBOL cap -480 256 R0 SYMATTR InstName C1 SYMATTR Value 1µ SYMBOL schottky 96 224 M270 WINDOW 0 32 32 VTop 2 WINDOW 3 -3 -7 VBottom 2 SYMATTR InstName D1 SYMATTR Value MBRS1100 SYMATTR Description Diode SYMATTR Type diode SYMBOL voltage -576 -208 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value 16 SYMBOL schottky -288 224 M270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D3 SYMATTR Value MBRS1100 SYMATTR Description Diode SYMATTR Type diode SYMBOL cap 208 320 R180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C6 SYMATTR Value 1µ SYMBOL res -592 224 R0 WINDOW 3 25 4 Left 2 SYMATTR Value 2.2k SYMATTR InstName R2 SYMBOL res 272 224 R0 SYMATTR InstName R4 SYMATTR Value 2.2k SYMBOL res -160 -128 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R1 SYMATTR Value 20 SYMBOL ind2 -208 336 M180 WINDOW 0 36 80 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName L2 SYMATTR Value 220µ SYMATTR Type ind SYMATTR SpiceLine Rser=1.72 SYMBOL pmos -128 -32 M180 SYMATTR InstName M2 SYMATTR Value IRF9640 SYMBOL e -816 -192 R0 SYMATTR InstName E1 SYMATTR Value -1 SYMBOL res -1488 112 R0 SYMATTR InstName R3 SYMATTR Value 30K SYMBOL cap -1488 240 R0 SYMATTR InstName C2 SYMATTR Value 470p SYMBOL res -1216 368 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R6 SYMATTR Value 30K SYMBOL cap -1040 400 R0 SYMATTR InstName C3 SYMATTR Value 1n SYMBOL pmos -864 224 M180 SYMATTR InstName M1 SYMATTR Value BSS84 SYMBOL nmos -864 272 M0 SYMATTR InstName M3 SYMATTR Value 2N7002 SYMBOL res -752 272 R0 SYMATTR InstName R5 SYMATTR Value 2K SYMBOL res -1696 64 R0 SYMATTR InstName R7 SYMATTR Value 10K SYMBOL res -1536 -256 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R8 SYMATTR Value 170K SYMBOL cap -1568 32 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C4 SYMATTR Value 100n SYMBOL res -1424 32 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R9 SYMATTR Value 68K SYMBOL PowerProducts\\LT1242 -1200 80 R0 SYMATTR InstName U1 SYMBOL voltage -1952 -80 R0 WINDOW 3 -49 325 Left 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR Value PULSE(0 4 5n 2m 10n 10M 30m) SYMATTR InstName V2 SYMBOL diode -1792 -144 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName D2 SYMBOL res -224 80 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 37 48 VTop 2 SYMATTR InstName R11 SYMATTR Value 220 SYMBOL cap -368 80 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C5 SYMATTR Value 120p TEXT -912 -352 Left 2 !.tran 0 4MU 0 100N TEXT -216 424 Left 2 !K L1 L2 0.9965 TEXT -216 472 Left 2 ;MSD7342-224
The design still needs a soft start, high side driver and stability analysis. Once the input voltage range is known the design can be completed. The magnetics is an OTS coupled choke from Coilcraft. The MOSFET needs replacement by a
Very nice indeed. I just plugged it into PSpice, reduced the output caps to 100nF and induced a step response. It seems quite stable, allthough I have not dug very deep
Increasing the value of the inductor L1 to 150uH does introduce ringing with C4 and C7 which makes is unstable during startup and transients due to the ringing sense current in R1.
No, mine was a buck-boost, whereas John has posted a few capacitively coupled boosts, of which this is one.
The nice thing about doing it his way is that you get some cross-regulation, because one polarity adjusts the voltage swing on the inductor, whereas I get the full input voltage variation impressed on the HV and have to get rid of it afterwards.
The efficiency is comparatively poor for some reason that I haven't looked into very deeply--if you filter the current draw from V1 using a
100 milliohm/1 millifarad RC lowpass to get rid of the spikes, and compute
(V(VP)*I(R5)+V(VN)*I(R6))/(-16*I(V1)), it never gets above about 0.3.
The nice thing about doing it my way is that you only need one switching regulator instead of two (one inverter and one AC-coupled boost), and that it's simpler and more efficient.
The OP's circuit also has the nice cross-regulation feature, but needs a lot of parts, including a $2.50 regulator chip, and a transformer that would need to be a toroid to make me happy, at least at this stage of my education in how to combine SMPSes with ultrasensitive instruments.
Defeating the current-sense like that seems a bit counterproductive as well.
It has tons of switching losses. It needs a smaller fet and needs to run at lower frequency. I hacked that fast and had to go to Safeway. I'm running a similar thing, my 9-to-48 booster, and it sims over 90% and runs about 85 in real life.
formatting link
(3 kilowatt laser driver)
I like these schmitt-trigger switchers. You get to turn all the knobs yourself.
--
John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com
That is Ok for a bench top tweak but will not make it in the production world. Your efficiency is poor due to 750KHz operation. C4 can be replaced with a short and D4 removed. C1,6 need be
So what magic Smitt-Trigger IC do you use that operates in this unit over temp and lot to lot? I admit that I use lots of ST but not in apps. like this. Looks like something JF would use with his 555s.
NC7WZ17 dual, 5 cents, and I'm only using half here. I've done it with schmitt gate drivers too, like LM5112.
The schmitt thresholds are plenty stable for a switcher like this. The operating range is from the upper switch threshold down to close to ground, so the specified hysteresis doesn't itself matter.
I've sold zillions of things like this. No problems. I *have* had a nunber of problems with a couple of the LTC parts; weird startups, subcycle oscillation, failures, latchups, model inaccuracies. Not to mention cost. You hacked around an LTC part pretty seriously so have created even more complexity hence potential hazards. The schmitt thing is elegantly simple.
John
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John Larkin Highland Technology, Inc
jlarkin at highlandtechnology dot com
Your suitable-for-production circuit used LT1242, $1.95 at 1K. Plus a bunch of other parts. The UC3842 still needs a bunch of added parts... as many as 12 in some of the datasheet examples, not even including the inductor/diodes/filter caps.
--
John Larkin Highland Technology, Inc
jlarkin at highlandtechnology dot com
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