24V-300V, 1000W DC-DC Push-pull simulation with precharge 90% efficient

That's what the marketing types say. In reality one has to contend with sending all the current across a tiny source pin. In your case I see an average current of almost 50A. So if you absolutly have to use this brute force method use many FETs.

Also, take a look at the dissipation in M3 peak around 5.1msec. This peak is half a millisecond wide and goes to almost a kilowatt. That can greatly exceed the SOA of many devices.

Why can't you do the soft-start with the controller? Just make short pulses in the beginning. There should also be an inductor between D10 and C3, right now you are cramming large current spikes into C3 which causes increases losses in that cap and the diodes.

--
Regards, Joerg

http://www.analogconsultants.com/

Hooo boy.

Take a look at the output current waveform, before it hits the zener/cap/load.

Take a look at the primary current waveform.

All energy transfer occurs in the first 15uSec of the switching phase period. No energy transfer occurs in the later part of the switching phase, as primary current ramps linearly.

You've made a push-pull flyback. Yeesh.

This is where you hope that the simulation reflects real hardware, after you've gone over all the nodes to check for realistic stress levels.

Those 120V drain spikes might be possible, if the fets's withstand them without clipping - if they do clip, thats an unanticipated fet loss and a reduction in the di/dt of the associated circuitry.

The ringing during actual energy transfer may be more lossy than expected, and include unanticipated harmonics, if any clipping or snubber/rectifier current reversal actually results.

re: volts per turn. This is a very loose expression but usually applies as rms/N. You are unlikely to come across a practical example of 60V/turn in your work. RMS and average values of a displayed period are easily extracted by your current simulator software GUI by cntrl/clicking any plotted item.

Higher volts per turn will generate core losses in an exponential relationship. Peak flux, and proximity to saturation will exhibit an inverse relationship. Below 40KHz, most ferrite cores are saturation limited, in commercially available sizes.

RL

Actually I had meant to do this simulation using the tape wound silicon=20 steel toroid that I used in my original design. The 60 V/turn was=20 extrapolated from that and I was trying to see if a transformer with one = or=20 two primary turns of bus bar might be feasible.

So I changed the transformer to my actual measured toroid which I have=20 tested at 16 kHz, and I ran the simulation again, with 10 nH as the = leakage=20 inductance. The results were actually much better. The power into the = load=20 went up to almost 1200 watts and the efficiency was about 99%. Here are = the=20 plots and ASC files:

.asc ition.png c.png

I do see some problems at the transition, but otherwise things seem to = be=20 OK. But I thought 10nH might be too low for the transformer, so I used=20

100nH. It seemed even better, perhaps. And I slowed down the transition = by=20 increasing the gate capacitor on M3, and it reduced the peak power = spikes to=20 more reasonable levels. I'll probably use two or more MOSFETs for that=20 switch, as well as the push-pull drivers. But I was very surprised to = find=20 that they apparently dissipate only about 3 watts each. Here's an = updated=20 plot over 40 mSec:

_40mSec.png

I still need to look more closely at the waveforms at critical points = and=20 see what I may need to do to reduce the high power transients which will =

exceed the SOA.

Thanks.

Paul=20

I admire your consistency of getting the inverter to work. If more people would put that much effort in their work, the world would be a better place! :)

But may I suggest something? I have made such an inverter in the past and suffered as you are with the high wheeling voltage using power fets.

That type of Push Pull inverter works well as long as you keep some current in the primary field between alternations. This saturation current or where ever the current maybe at the time helps to reduce the effects (dump), have you played with over lapping gate signals?

I made one before that simply had delayed trigger on the reference where each ending cycle would trigger the start of the next for the other phase however, I used a PIC chip to control that because I also was doing current monitoring via a ADC to set output demands for soft ramps and the frequency naturally varied. As current demand drops off, the overlap got narrow and as current demands increased, I would increase the overlap time. This made it so that when the secondary side was up where it belong (low PI error), the current damned on the primary was low and there was no need for a over lap to speak of, which makes for low quiescence current.

Have you considered using a "Buck Boost" type of supply? We made one that had to operate from a 36 volt system and generate ~480 volts DC for a AC drive on a battery operating equipment. The AC motor was small,only 1/4 so we didn't need a lot there however, we used high voltage fets,

500V (Yes, very close but they worked) types that handles 18 Amps.

The system at 36 volts needed no more than 10 amps from the battery. We used 4 of those MOSFETS on a widely spread heat sink to keep things cools. It was most likely over kill but it worked find. Btw, we used 4 separate coils, one for each MosFet and a switching diode on each one all tied to gather to the HV cap output side filter.

We also used current mode sensing on that, too. The only trick there is, to make sure your full magnetizing current has a maximum time limit before it switches, incase the feed back loop error is greater than the supply can deliver. Cases like low battery and out of parameter range, otherwise, you'll get a latch up. Ect..

Have a good day..

Jamie

So you're back into straight DC-DC transformer territory.

If all of your inrush is due to the output filter cap, as you propose, then why not stick the switched inrush limiter in series with 'it' ? That way it only has to deal with this specific inrush path, and doesn't have to deal with continuous power train current, just the ripple.

Such a control can be on the low side, tailored by whatever small signal bells and whistles you desire. This isn't an isolated application, after all.

RL

On Sat, 14 Jul 2012 21:06:45 -0400, "P E Schoen" wrote:

Like this, as a starting point, anyways: ............................ 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512 WIRE -608 528 -656 528 WIRE -496 528 -496 464 WIRE -496 528 -608 528 WIRE -400 528 -496 528 WIRE -336 528 -336 448 WIRE -336 528 -400 528 WIRE -112 528 -336 528 WIRE -400 560 -400 528 WIRE -320 560 -400 560 WIRE -176 560 -176 480 WIRE -176 560 -240 560 WIRE -96 560 -176 560 WIRE 0 560 0 512 WIRE 0 560 -96 560 WIRE 32 560 32 336 WIRE 96 560 96 512 WIRE 96 560 32 560 WIRE 176 560 176 512 WIRE 176 560 96 560 WIRE 704 560 704 480 WIRE 752 560 752 496 WIRE 752 560 704 560 WIRE 784 560 752 560 WIRE 896 560 896 512 WIRE 896 560 784 560 WIRE -112 592 -112 528 WIRE 32 592 32 560 WIRE 32 592 -112 592 WIRE 752 592 752 560 WIRE -656 608 -656 528 FLAG -656 608 0 FLAG 752 336 0 FLAG 720 80 Vout FLAG 592 240 in FLAG -128 144 m1 FLAG 112 368 m2 FLAG -288 464 g1 FLAG -96 288 g2 FLAG -96 560 s FLAG 400 80 a FLAG 400 224 b FLAG -640 240 batt FLAG 544 352 0 FLAG 752 592 0 SYMBOL ind2 272 128 R0 SYMATTR InstName L1 SYMATTR Value 180µ SYMATTR Type ind SYMATTR SpiceLine Rser=100u SYMBOL ind2 272 240 R0 WINDOW 0 45 35 Left 0 WINDOW 3 41 61 Left 0 SYMATTR InstName L2 SYMATTR Value 180µ SYMATTR Type ind SYMATTR SpiceLine Rser=100u SYMBOL ind2 400 128 M0 WINDOW 0 21 -5 Left 0 WINDOW 3 -9 113 Left 0 SYMATTR InstName L3 SYMATTR Value 32m SYMATTR Type ind SYMATTR SpiceLine Rser=10m SYMBOL nmos -224 384 R0 SYMATTR InstName M1 SYMATTR Value IPB019N08N3 SYMBOL nmos -48 416 R0 SYMATTR InstName M2 SYMATTR Value IPB025N10N3 SYMBOL voltage -608 416 R0 WINDOW 123 0 0 Left 0 WINDOW 39 24 132 Left 0 SYMATTR InstName V1 SYMATTR Value 24 SYMBOL diode 512 240 M270 WINDOW 0 32 32 VTop 0 WINDOW 3 0 32 VBottom 0 SYMATTR InstName D2 SYMATTR Value MUR460 SYMBOL diode 448 176 R270 WINDOW 0 32 32 VTop 0 WINDOW 3 0 32 VBottom 0 SYMATTR InstName D3 SYMATTR Value MUR460 SYMBOL res 736 144 R0 WINDOW 0 -26 33 Left 0 WINDOW 3 -29 65 Left 0 SYMATTR InstName R1 SYMATTR Value 80 SYMBOL voltage -496 368 R0 WINDOW 123 0 0 Left 0 WINDOW 39 -43 57 Left 0 WINDOW 3 -31 242 Left 0 SYMATTR SpiceLine Rser=10 SYMATTR Value PULSE(0 10 0 50n 50n 32u 66u 1000) SYMATTR InstName V2 SYMBOL voltage -336 352 R0 WINDOW 123 0 0 Left 0 WINDOW 39 -43 57 Left 0 WINDOW 3 -188 285 Left 0 SYMATTR SpiceLine Rser=10 SYMATTR Value PULSE(0 10 33u 50n 50n 32u 66u 1000) SYMATTR InstName V3 SYMBOL diode 448 96 R270 WINDOW 0 32 32 VTop 0 WINDOW 3 0 32 VBottom 0 SYMATTR InstName D1 SYMATTR Value MUR460 SYMBOL diode 512 336 M270 WINDOW 0 32 32 VTop 0 WINDOW 3 0 32 VBottom 0 SYMATTR InstName D4 SYMATTR Value MUR460 SYMBOL res -224 544 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R3 SYMATTR Value .001 SYMBOL cap -752 352 R0 SYMATTR InstName C10 SYMATTR Value 40µ SYMATTR SpiceLine V=250 Rser=1m SYMBOL ind 224 128 R90 WINDOW 0 5 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName L5 SYMATTR Value 20n SYMATTR SpiceLine Rser=50u SYMBOL ind 256 352 R90 WINDOW 0 5 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName L6 SYMATTR Value 20n SYMATTR SpiceLine Rser=50u SYMBOL schottky 784 240 M180 WINDOW 0 24 64 Left 0 WINDOW 3 24 0 Left 0 SYMATTR InstName D10 SYMATTR Value UPSC600 SYMATTR Description Diode SYMATTR Type diode SYMBOL res -592 352 R180 WINDOW 0 36 76 Left 0 WINDOW 3 36 40 Left 0 SYMATTR InstName R2 SYMATTR Value .008 SYMBOL cap 16 144 R0 SYMATTR InstName C1 SYMATTR Value 47n SYMATTR SpiceLine V=250 Rser=1m SYMBOL res 48 352 R180 WINDOW 0 36 76 Left 0 WINDOW 3 36 40 Left 0 SYMATTR InstName R4 SYMATTR Value 10 SYMBOL cap 80 368 R0 SYMATTR InstName C2 SYMATTR Value 47n SYMATTR SpiceLine V=250 Rser=1m SYMBOL res 112 528 R180 WINDOW 0 36 76 Left 0 WINDOW 3 36 40 Left 0 SYMATTR InstName R5 SYMATTR Value 10 SYMBOL schottky 80 272 M0 SYMATTR InstName D5 SYMATTR Value MBRB2545CT SYMATTR Description Diode SYMATTR Type diode SYMBOL schottky 192 448 M0 SYMATTR InstName D6 SYMATTR Value MBRB2545CT SYMATTR Description Diode SYMATTR Type diode SYMBOL cap 640 144 R0 WINDOW 0 -26 5 Left 0 WINDOW 3 -25 59 Left 0 SYMATTR InstName C3 SYMATTR Value 40µ SYMATTR SpiceLine V=250 Rser=11m SYMBOL ind -624 320 R0 SYMATTR InstName L4 SYMATTR Value 100n SYMATTR SpiceLine Rser=50u SYMBOL res 608 352 R180 WINDOW 0 28 80 Left 0 WINDOW 3 33 42 Left 0 SYMATTR InstName R6 SYMATTR Value 40 SYMBOL nmos 656 288 R0 WINDOW 3 -49 -5 Left 0 SYMATTR Value IPP200N25N3 SYMATTR InstName M3 SYMBOL res 800 576 R180 WINDOW 0 -33 86 Left 0 WINDOW 3 -26 54 Left 0 SYMATTR InstName R7 SYMATTR Value 5k SYMBOL zener 624 480 M180 WINDOW 0 27 62 Left 0 WINDOW 3 -59 -17 Left 0 SYMATTR InstName D7 SYMATTR Value BZX84C10L SYMATTR Description Diode SYMATTR Type diode SYMBOL res 896 384 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R8 SYMATTR Value 150k SYMBOL res 544 96 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 0 56 VBottom 0 SYMATTR InstName R9 SYMATTR Value .01 SYMBOL cap 736 432 R0 WINDOW 0 -22 8 Left 0 WINDOW 3 -24 64 Left 0 SYMATTR InstName C4 SYMATTR Value 1µ SYMATTR SpiceLine V=250 Rser=1m SYMBOL cap 880 448 R0 SYMATTR InstName C5 SYMATTR Value 4.7E-7 SYMATTR SpiceLine Rser=.01 TEXT 32 88 Left 0 !K1 L1 L2 L3 1 TEXT -648 576 Left 0 !.tran 0 10m 1u 1u startup TEXT 48 656 Left 0 ;Leakage 20nH, 47nF+10R TEXT 48 688 Left 0 ;Load Rl=80, Vout=308, 1191W/1214W = 98.1% .......................

Some wrapping text strings are removed.

That is a good idea, and I tried the simulation you provided in the = other=20 post. The only problem is that the output needs to connect to a VFD, = which=20 normally contains some hefty capacitors on the DC link. But that just = means=20 using a high-side MOSFET. Actually it may be easier to use a simple = relay=20 which can fairly easily handle 320VDC at 3 to 5 amps. There may be some=20 inrush on the battery side but I really don't need large capacitors. The =

40=20 uF capacitor was chosen for low ESR and high surge currents. 603

It is 40 uF 400V with 1.4 mOhm for about $14 and handles 29A RMS:

I really think the DC-DC transformer topology is the way to go. The = major=20 problem was the high current, high voltage, and high power transients. I =

still don't know if the steel core toroid will really work well with a =

16=20 kHz square wave, but my earlier testing showed reasonably low core = losses of=20 just about Vin^2/16, so 9W at 12V and estimated 36W at 24V.

But the transformer worked OK at 2kHz with 24V, so I would think it = would=20 work about as well at 16kHz with 1/8 the number of turns, which is where = I=20 got the idea for the single turn primaries. Wouldn't that reduce the = core=20 losses? It would reduce the magnetizing inductance but the current = should=20 stay about the same at the higher frequency. Let's see, it has about=20

3.2uH/sqrt(T) so 1 turn is 3.2uH which is 0.32 ohms at 24 volts is 75A.=20 Oops! But 8 turns is 180uH and at 2kHz that's 2.26 ohms and about 12A at =

24V. Looks like I'd need 2 turns for 12.8uH and 1.28 ohms or 24A, or go = to 3=20 turns and 28.8uH and 2.89 ohms and about 8.3A.

I see that I've not been figuring this correctly. I had always thought = V/t=20 was constant for a given core (yes) and was linear with frequency (no).=20 Actually it must go by the square root of frequency, so the transformer = that=20 had 3 volts/turn at 2 kHz would have 8.5 volts/turn at 16 kHz. My = initial=20 estimate was based on about 0.25 V/t at 60Hz and thus 2.5 V/t at 600Hz. = I=20 should have used 0.8 V/t, and 1.44 V/t at 2kHz. In that case, it would = be 4=20 V/t at 16 kHz and my 8 turns is just about right for 24V. AHA!!! That = makes=20 more sense, so that's my theory and I'm sticking to it!

Thanks,

Paul=20

If You want versatility in choice of load, you'll need to use a smarter converter than unregulated DC transformer.

As previously mentioned, filtering requirements of the unregulated DC transformer re modest - that includes ripple current rating of the capacitors. Ideally, no capacitors are needed.

You've been exposed to other opinions re DC-DC transformer and have spent some time dealing with the issues involved. If this isn't enough to convince you otherwise........

At lower voltages, the siren call of the single turn winding is hard to ignore. You've already run into the mechanical and coupling issues it raises. These are separate from issues related to the use of the topology and are a side-tracking obfuscation.

As turns are reduced incrementally, approaching one (why stop there - why not half or other fractional turns?), it's like moving to another planet, due to the specific problems involved and differing solutions available in each iteration. You can end up having to build the core around the winding, rather than vice-versa - and this is notoriously less flexible. Check out 'Matrix transformer'.

RL

Doesn't the VFD already incorporate inrush limiting?

Many do, though sometimes on a timer, rather than actual precharge sensing.

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

I suggested that, a while back.

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

Not for me to make the horse drink. I might have done it, but couldn't find a triac model that reflects real life. Using an FET.driven as shown, produces a nasty dissipation burst in M3, as it goes through its active region, at 2.5ms. Not helped by Cgs.

Depends on how well you model things. I always check a modeled curve trace of a new device model against a real life one. I sometimes check device capacitances, too. I've known models where they were way out.

Useful for proof-of-concept. No substitute for hardware.

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

- but didn't do the 'work' for him. 'fait accomplis' tends to sell.

The whole simulation business gives me the squitters, when no hardware is being built. It takes effort to make a simulation represent real hardware, even after it's built.

Only really useful to demonstrate basic priciples or to predict iterations of subcircuits - and even then you need to add salt.

RL

Well, in this case I actually have built the hardware, and it worked for = a=20 while but suffered from certain problems such as high voltage spikes and =

extreme current surges. So with the help of some more experienced people =

here, I was able to see where my design had issues, and now after = another=20 round of simulation, I think I am ready to rebuild the hardware and try=20 again.

There are some things that do not lend themselves well to simulation. I = plan=20 to use a PIC, probably the PIC16F684 or PIC16F616, but their PWM modules = are=20 not suited to a push-pull topology except at 50% duty cycle. I may be = able=20 to use a low duty cycle PWM to reduce the high current surges from the=20 output capacitance, and I don't think the small 2HP VFD has a precharge=20 built in. Some, I think, use SCRs as part of the input rectifier bridge, = but=20 that obviously will work only on AC and not where the DC link is being=20 powered directly.

There were certainly clues to the problems of the original circuits. = When I=20 powered them using a 5A current limited supply, the current limit always =

kicked in until the output came up to near the target voltage. But I was =

expecting a surge of up to 50 amps when using the battery. The first=20 circuit, using a 12V battery, seemed to work OK and the 30A circuit = breaker=20 did not usually trip when turned on. But it used the output of an LM324 = to=20 drive the MOSFETs, so the gate drive was "soft" and that probably = reduced=20 some of the high voltage spikes. Also, for 12V I was using a doubler = output=20 configuration, which may or may not have reduced the stress on the=20 components. And I was also using 500 Hz.

I think it was when I added proper gate drivers and went up to a 24V = supply=20 and 2 kHz that one of the MOSFETs failed. But that could have been = because=20 of a software bug where I had forgotten about the change to inverting = gate=20 drivers and the start-up code turned both ON for maybe 500 mSec. They = might=20 have survived the current limited supply, but maybe not. I had a 5,000 = uF=20 capacitor on the output of the supply so the surge currents were = essentially=20 unlimited.

There is still much work that can be done using the simulator. I can try =

running a low duty cycle for start-up and see if there are any high = current=20 or high power transients. I could use several gate drive sources and set = the=20 delays so that they use increasing duty cycle as the output voltage = ramps=20 up. Or I could make a variable duty cycle driver using a ramp function = and a=20 comparator and perhaps use the current through the MOSFETs to cut the = PWM=20 short, cycle by cycle. Even with the PIC, this may be the best approach, = and=20 I might be able to use the PIC's comparator and an interrupt to end the = ON=20 cycles. This will probably work OK at 16 kHz.

The main objective at this point is to ascertain that the steel core = toroid=20 design will work at the power level I want. Once that has been = accomplished=20 I want to be able to "button up" this unit and just use it for my = electric=20 tractor project as I take other measurements to see what power levels = are to=20 be expected under various conditions. For that, I have made a PIC = project=20 that displays various parameters on an LCD display and streams serial = data=20 to a laptop computer for later analysis.

Eventually, I want to come up with a complete solution, with battery = charger=20 and monitor, DC-DC converter, VFD, and an overall vehicle controller and =

dashboard display. I want to use 2 or 3 lead-acid deep-cycle batteries, =

105=20 A-H, 62 lb and $85 each, which should give me a safely usable 1800 W-Hr, = and=20 able to operate at an average of 1-2 HP for up to two hours.

But another option is to use LiPo batteries, and get enough of them for = a=20

300V nominal link voltage without the DC-DC. They are expensive, but I = found=20 some where 30 pieces at $240 would give me 732 W-Hr. Since they are more =

efficient and can be discharged and charged up to 10C or even 30C, they=20 might give me 45 minutes at 1 HP and 5-10 HP peak if needed.

OK, enough discussion for now. Gotta get stuff done.

Thanks,

Paul=20

Well, in this case I actually have built the hardware, and it worked for = a=20 while but suffered from certain problems such as high voltage spikes and =

extreme current surges. So with the help of some more experienced people =

here, I was able to see where my design had issues, and now after = another=20 round of simulation, I think I am ready to rebuild the hardware and try=20 again.

There are some things that do not lend themselves well to simulation. I = plan=20 to use a PIC, probably the PIC16F684 or PIC16F616, but their PWM modules = are=20 not suited to a push-pull topology except at 50% duty cycle. I may be = able=20 to use a low duty cycle PWM to reduce the high current surges from the=20 output capacitance, and I don't think the small 2HP VFD has a precharge=20 built in. Some, I think, use SCRs as part of the input rectifier bridge, = but=20 that obviously will work only on AC and not where the DC link is being=20 powered directly.

There were certainly clues to the problems of the original circuits. = When I=20 powered them using a 5A current limited supply, the current limit always =

kicked in until the output came up to near the target voltage. But I was =

expecting a surge of up to 50 amps when using the battery. The first=20 circuit, using a 12V battery, seemed to work OK and the 30A circuit = breaker=20 did not usually trip when turned on. But it used the output of an LM324 = to=20 drive the MOSFETs, so the gate drive was "soft" and that probably = reduced=20 some of the high voltage spikes. Also, for 12V I was using a doubler = output=20 configuration, which may or may not have reduced the stress on the=20 components. And I was also using 500 Hz.

I think it was when I added proper gate drivers and went up to a 24V = supply=20 and 2 kHz that one of the MOSFETs failed. But that could have been = because=20 of a software bug where I had forgotten about the change to inverting = gate=20 drivers and the start-up code turned both ON for maybe 500 mSec. They = might=20 have survived the current limited supply, but maybe not. I had a 5,000 = uF=20 capacitor on the output of the supply so the surge currents were = essentially=20 unlimited.

There is still much work that can be done using the simulator. I can try =

running a low duty cycle for start-up and see if there are any high = current=20 or high power transients. I could use several gate drive sources and set = the=20 delays so that they use increasing duty cycle as the output voltage = ramps=20 up. Or I could make a variable duty cycle driver using a ramp function = and a=20 comparator and perhaps use the current through the MOSFETs to cut the = PWM=20 short, cycle by cycle. Even with the PIC, this may be the best approach, = and=20 I might be able to use the PIC's comparator and an interrupt to end the = ON=20 cycles. This will probably work OK at 16 kHz.

The main objective at this point is to ascertain that the steel core = toroid=20 design will work at the power level I want. Once that has been = accomplished=20 I want to be able to "button up" this unit and just use it for my = electric=20 tractor project as I take other measurements to see what power levels = are to=20 be expected under various conditions. For that, I have made a PIC = project=20 that displays various parameters on an LCD display and streams serial = data=20 to a laptop computer for later analysis.

Eventually, I want to come up with a complete solution, with battery = charger=20 and monitor, DC-DC converter, VFD, and an overall vehicle controller and =

dashboard display. I want to use 2 or 3 lead-acid deep-cycle batteries, =

105=20 A-H, 62 lb and $85 each, which should give me a safely usable 1800 W-Hr, = and=20 able to operate at an average of 1-2 HP for up to two hours.

But another option is to use LiPo batteries, and get enough of them for = a=20

300V nominal link voltage without the DC-DC. They are expensive, but I = found=20 some where 30 pieces at $240 would give me 732 W-Hr. Since they are more =

efficient and can be discharged and charged up to 10C or even 30C, they=20 might give me 45 minutes at 1 HP and 5-10 HP peak if needed.

OK, enough discussion for now. Gotta get stuff done.

Thanks,

Paul=20

And that's exactly where the main problems is. Every mundane switcher IC worth its salt has a soft-start feature. Other than a little ceramic cap it requires zero in additional parts.

I don't know what it is with these PICs. They are ok as a uC but why are people using them as switcher chips? It makes no sense. I've seen designs where they were used (against my advice) and very painful compromises resulted. These things cannot do proper current mode control, there is no good dead time control, there is no easy soft-start solution, any loop that was being attempted was bog-slow, and to top it all off the uC cost a lot more than a switcher chip that could have done a much better job.

[...]

--
Regards, Joerg

http://www.analogconsultants.com/

Yep, they're lifesavers.

To show that they can? Playtime? First do no harm.

Looks better on a resume.

RL

The one time I considered it (with an AVR) the AVR was for something else. And it was hey, look, I can take this bit away, and that bit, and do this in software, and even the power supply chip could go if i wanted.

--

John Devereux

[...]

But micro controllers can't. That's the problem. Unless you have a nearly infinite horsepower in the thing which will results in high cost, a fat chip and wasteful power consumption.

--
Regards, Joerg

http://www.analogconsultants.com/