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Forum Index : Electronics : Variable input voltage bat charger
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| BjBlaster Regular Member  Joined: 04/04/2008 Location: AustraliaPosts: 55 |
I just bought a new powersupply (Thermaltake) and it claims 85% and is certified to be better than 80% as per the new green rules.... My old 350W one it was replacing is supposed to be 60% - but that is at it's full loaded output. My little Jaycar meter says 85W idle with this new supply instead of 115W with the old supply. that's enough proof for me :) Bj Check out my projects here in: Bj's Shed |
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GWatPE Senior Member  Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi Bj, I can only assume this is the computer that is idle, and not the power supply alone. My whole computer 22inch screen, 250GB, 4GBram, dual core 2.1GHz,DVD burner, runnning Vista[0-2%cpu usage] etc operating while typing this post, is consuming 45W, so there are still some way to go with a normal PC. This is the power supplied to the plugpac, so the actual computer would be using even less. My old PC's are taking up space in a cupboard. Gordon. become more energy aware |
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| davef Guru  Joined: 14/05/2006 Location: New ZealandPosts: 499 |
Gordon, LCD or OLED screen? Which CPU? Impressive power consumption! Dave |
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oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Gordon, They don't provide fans half the size of the box because they are efficient.  They have a poor power/crest factor as well... 
But they are very good to use if you need good regulation. .........oztules Village idiot...or... just another hack out of his depth |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi oztules, the purpose of using these units was as the interface between the windmill and the battery, for charging purposes. I would not justify wasting 1/3 of the harvested power as heat in the converter. This amounts to needing a windmill 50% bigger. Hi Dave, I really didn't want to describe the computer here, but why not. my computer is like a big tablet PC. touch screen LCD and wireless everything, like a really big laptop. Will be good when travelling. Does prettywell everything media wise. HDTV, PVR, DVD player. Instant sleep and recover, no hibernate though. One problem so far is that tiny bugs that may land on the screen at night can turn the unit on. The touch screen can detect the position of your finger, or anything else, without even touching the glass. Have set the sleep mode timer to 5 mins. Sleep Power down consumption is only 2W. No real need to worry about powering OFF. I can just walk away, and come back an hour or so later, shake the mouse and continue on. This has not much to do with the topic, but it seems a lot neeeds to be done to SMPSU to make them suitable as power/voltage converters in RE systems. Gordon. become more energy aware |
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| BjBlaster Regular Member Joined: 04/04/2008 Location: AustraliaPosts: 55 |
Gordon, That I have got to see. I just built two machines for the kids, and they are core2 - 2.8Ghz machines with a 200GB HDD 2GB RAM and a 19" LCD monitor. each of them chew 75W @ 100% PF idle, so I find that 45W value you are getting very interesting.. Something is wrong with someones numbers. My jaycar meter shows 101W running a 100W lamp, so I would have thought it was fairly accurate - the PF could have something to do with this then when running the PC... What are you using to measure this? Cheers Bj (edit - Oh it's a laptop! that's different :) Check out my projects here in: Bj's Shed |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Yes, I read the numbers again. The Energy meter with the special 4 quadrant multiplier chip reads 57.45W and the Jaycar plugin power meter reads between 39-45W. The consumption is so low that my inverter goes in and out of standby mode trying to operate it by itself. I now run it from the grid. BTW: it is not a laptop, but like a laptop, made by HP. The energy meter reads the consumption of the neon indicator lights on some GPO's as 0.02W per neon Gordon. become more energy aware |
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| Janne Senior Member Joined: 20/06/2008 Location: FinlandPosts: 121 |
Update, I tested the 3 atx boxes i had in hand.. of the 3 psu's only one turned out to be operational, the other one of the 2 just didn't want to turn on by grounding the green wire, and the other just blew the new fuse i put in it.. Shame, for the 2 doa psu's i was able to find datasheets for the pwm ic, the other had UC3843 and the other has SG6105D The 3rd one that turned out to be working was a nexus 300W PSU. I tested it with a variac, and with the switch in 230V position it turned on with load with 70VAC(the load on 12V line was a 6 ohm resistor = 2 amps at full voltage) and achieved full power at 105VAC. By adjusting the pot i was able to adjust the 12V line from 11V to 12.7.. now the bad news is that the pwm IC chip in it is something i can't find the datasheets for.. the numbers on the IC chip are 3528 (i assume this is the part number), followed by (on the next line) 342 J4810 (or J481C , i can't make it out for sure).. the manufacturer's logo on it is something i haven't seen, a far "F" letter on some odd shaped background. It's a 20pin pdip casing, pin number confirmed by finger binary counting system 
I'd appreciate the help if anyone recognizes this ic chip, otherwise i think i'm better off finding more PSU's to test. If at first you don't succeed, try again. My projects |
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| BjBlaster Regular Member Joined: 04/04/2008 Location: AustraliaPosts: 55 |
Gordon, It really does go to show how inefficient the PC SMPS is in a desktop. It's like the age old fuel efficiency thing for cars... We won't make it better because we don't need/have to. On a laptop / portable desktop battery life has driven design and efficiency up for longer run time, but on the standard 240V desktop it was never the case. Only this year have they really started to push 80+ standard for PSUs. Check out my projects here in: Bj's Shed |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
The voltages you record on the output for the wide range of input voltages are what the computer supply is designed to do. Not the way to load a windmill however. I have found that the units are pretty rudimentary with the overload detection. Not really current limiting like I had thought, so any mods would need to have some current sensing element and feedback control put in as well as the mixing of the input voltage signal before the unit can be made to load a windmill correctly. Gordon. become more energy aware |
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| Janne Senior Member Joined: 20/06/2008 Location: FinlandPosts: 121 |
Hello Gordon, Yeah I understand that the PSU is not a "proper" way of loading the turbine.. But lets assume for a moment that we get current controlling to work, we could then couple the PSU, or charger, to the mill at say 80 volts, and by the time the generator reaches 105 volts the turbine is already able to make more than 300W, so the charger wouldn't stall the turbine.. so the charger could just work full power all the time, limited by battery charge state. The battery charger overall in this system is only a small portion of the load, the main load are the heating elements. I think I haven't mentioned the turbine, it's an axial flux turbine with 5.2m diameter rotor, and the generator giving approximately 1Volt/Rpm between phases. The nexus psu I fiddled with yesterday might not prove totally useless either, even if finding datasheets seems impossible.. It could well be used as the "slave" psu in oztules' 2 psu's in series idea. edit. by current control earlier i meant to say current limiting. If at first you don't succeed, try again. My projects |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Janne The supply using the 3842 may be quite useful anyway. Just fix it.... this will provide some hands on for modifying it later  easy to say when your 12000 miles away 
If you can get the 3842 running, you can use the current input pin (see data sheet pin 3 or 5 (8 or 14 pin)), as your current limit point. That chip is a current mode chip, unlike the tl494 (voltage mode) So rather than narrowing the pulse, it truncates it on over current, and starts the next cycle on the next clock. Easier to find a AT supply with a 494. Or....... a useful device instead like this one. Fairly cheap and pretty bullet proof. I found changing 1 resistor, the unit runs well at 300w but may require a fan at these settings for extended periods. It is about 80% efficient and is a very tough customer I can say. Would easily do what you want I suspect. I use it for all kinds of terrible things. (change another resistor, and the output caps and go 48v no problems.  )
.........oztules Village idiot...or... just another hack out of his depth |
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| Janne Senior Member Joined: 20/06/2008 Location: FinlandPosts: 121 |
Hello oztules, The device you posted a link indeed would sound like a good starting point. however, computer psu's have the advantage, that they can be had for free, so it won't hurt me too much if i happen to accidentally fry one :P . While looking at the UC3842 datasheet more closely, i have to admit that I'm in a bit of loss, how the IC behaves in the psu fundamentally. I assume, that the output voltage is connected to the error amplifier via some kind of voltage diversion circuit, so that it just stops "swiching" as the voltage goes up to the setpoint.. and then start switching again as the voltage in the secondary circuit drops. Can't check anything on the psu right now, have to look at the circuit board more closely when i get the chance. From the 2 defect psu's the one with the UC3842 is the one that just doesn't want to turn on. The aux 5V line in it is working, but i've yet to investigate further. It might be easier just to find an AT power with tl494, but i seem to have too much fun with these also to stop, at least yet :) If at first you don't succeed, try again. My projects |
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| Janne Senior Member Joined: 20/06/2008 Location: FinlandPosts: 121 |
Okay i gave up trying to bring the UC3842 psu alive, at least for now. Might try it later when i've gained more confidence with these buzzers. Yesterday instead i got 2 AT powers to play with.. the other with tl494 based control circuit, and the other with some other ic, but based on the pin configuration and other stuff on the board i suspect it's just a clone for tl494. Both tested with variac were able to deliver full power at 130VAC to the dummy load, 40W 12V incandescend bulb. To the tl494 psu i put in a new 5k trim pot to replace the 2 resistors that went to ground from pin 1.. With that mod the output voltage was adjustable from 8.8V to at least 15V, i didn't dare to try anything higher just yet. Next thing i'll try to figure if it's safe to free up the second error amp for current monitoring purposes. I drew up the schematic on the control board, but it's not helping much on that part, as many of the wires from it disappear somewhere else inside the rest of the psu, so i guess i'll have to trace it too. If at first you don't succeed, try again. My projects |
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| Janne Senior Member Joined: 20/06/2008 Location: FinlandPosts: 121 |
How lucky can one get? As i traced where the pin 15 from the tl494 was going, I noticed it disappeared through 2 resistors somewhere into the transformer.. a quick measurement with multimeter indicated that as current went up, voltage on pin 15 went down.. extrapolating from the measurements it looked like the original current limit was set pretty high, over 30A.. So i calculated that if I'd add some 500k-1M trimmer to the now 100k pull-up resistor i could make the current limit into a sensible level. I added 2 more 470k trimmers in series with the line, and hey presto at a little over 500k the 45W 12V bulb started dimming. Current stayed stable as i added more load on the 12V line. Now the problem that arised with this new mod is that with the current limit set low the bulb will just flash briefly on startup and the psu doens't want to start until the caps on it have bleeded empty, and power is then re-applied. I guess the next step is to figure out if that pesky LM339 onboard has something to do with the shutdown... If at first you don't succeed, try again. My projects |
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| Dinges Senior Member Joined: 04/01/2008 Location: AlbaniaPosts: 510 |
[quote=Janne] I guess the next step is to figure out if that pesky LM339 onboard has something to do with the shutdown...[/quote] Yes it does... in the supplies I played with, the LM339 controlled the TL494 via its pin nr. 4 (Dead-time control). Usually there are two small diodes (1N4148-like) that have both their cathodes connected to TL494-pin4, whereas their anodes go to the LM339. I usually disconnect both diodes, which basically disconnects/eliminates the entire LM339 circuit. Removing the two diodes to pin-4 of the TL494 has always done the trick for me, and eliminated messing with the protection circuit around the LM339 directly. You will then rely on your own over-current protection (which in your case already seems to be present? Nice...) to protect the PSU from nasty situations. The fact that the PSU briefly flashes before switching itself off (into protection) makes me wonder whether in your case current is really limited; if it did limit current to a safe value, it shouldn't turn itself off, I think. You may want to make double sure that current regulation really works, because if it doesn't, eliminating the LM339 (via the two diodes to pin 4/TL494) may cause any fault-condition to blow things up (if you're lucky, just the fuse; if not, the switching transistors and/or input rectifier bridge; been there-done that). You could try to limit current even further to, say, 1A or less, as a test. If anything in the above is incorrect, no doubt Oztules will gladly point that out to you .
Peter. Edit: apart from the two diodes, you don't want to mess with any other components to pin-4 of the TL494. There is likely also a resistor and capacitor connected to it that increases dead-time during startup. This is to give all PSU signals/voltages a chance to stabilize before the TL494 turns on completely. You do NOT want to remove this resistor/capacitor combination, as it is essential for protection of the PSU during start up. |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
I have been force fed red wine.... in excess ....by a well meaning neighbor. I have nothing sensible to add at this time....... except I agree with Dinges summation of the situation. Make certain you have real current control... the PSU should not go into protection mode like that if A control is functional.... as best as I can recall.... which doesn't say much really.... been a while. ............oztules Ps......Hic.... Village idiot...or... just another hack out of his depth |
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| Dinges Senior Member Joined: 04/01/2008 Location: AlbaniaPosts: 510 |
[quote=Oztules]I have been force fed red wine.... in excess ....[/quote] Sure... maybe you can fool the others... but the symptoms as I see them are more likely to indicate (*gasp!*) SWINEFLU!  
Peter (runs around in circles, screams and shouts, pulls out hairs) |
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| Janne Senior Member Joined: 20/06/2008 Location: FinlandPosts: 121 |
Hello, I fiddled a little more with the psu, i think the problem now lies with the undervoltage lockout. When turning the voltage down below 7 Volts (doesn't matter if i do this with the voltage pot or current pot, with load), the psu trips into failsafe mode. I assume there would be no adverse consequences if I disabled the undervoltage lockout, right? The tl494 and lm339 seem to get their power from an auxiliary 20VDC line. This psu seems to use pin 3 to shut down the psu instead of the dead time control. The LM339 latches on to do this. The pin 4 is just connected to a voltage divider between Vref and ground.. which leads me to another question, how is the soft start in this psu handled? There is a place for a cap in the pin 4 resistor circuit in the pcb, but there is no cap in it(it would make sense if there were a cap, as it is in paraller with the pullup resistor). Only soft start i see in this is the cap in paraller with the resistor feeding the pin1 on tl494. Another thing also i need to do, currently the psu takes the reference measurement from +5V line, i'll have to change this to the 12V line. A few pics below, sorry about the not so great pic quality. 
Notice how nicely the control board is in there, attached with 2 screws and the cord is easily removed = easy to take the board out for soldering :) 
PSU & some of the equipment. I'll also upload the schematic of the psu control board, both in dxf and in diptrace work file, in case anyone is interested to look, or even happens to have a similar unit. 2009-05-05_014653_schematic.zip 2009-05-05_014706_hakkuri.zip For anyone that might be interested doing some similar stuff, I'll post some links that i found useful. Also oztules's and dinges's diaries in FL are very worth while to read. http://www.smps.us/ http://www.users.on.net/~endsodds/smps.htm http://focus.tij.co.jp/jp/lit/an/slva001d/slva001d.pdf If at first you don't succeed, try again. My projects |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Hmmm... The designer obviously attacked this with a different bent than most others I have seen. The 393 seems to kill off the pulse at the feedback point. Works I guess, but not as I would have done. Controlling soft start by drowning the control voltage is as good as any I guess, but usually done by pulling pin4 high with a cap, and letting a bleed resistor pull it back down again.... ie cap in series with b+, resistor pin4 to ground. In the ones I have played with, an aux diode simply rectifies the 12v rail directly from the transformer, and feeds the 494 with that. Keeps it fairly independent from the main rectified voltage. (seems to run on ripple when short on the secondary is in place, and current control keeps current at exact levels when Vout=0 I am unable to see the dxf files of the circuit. Are you able to screen catch and post a jpeg or similar? The physical layout is very different to what I have seen, but at least it is not as messy as an ATX. "I assume there would be no adverse consequences if I disabled the undervoltage lockout, right? ".... providing the current control is real, and not imagined. By this I mean, if you lower the current into a globe, is it the lower voltage giving you lower current reading, or is it the lower current giving you a lower voltage??...... lower the current and then double the load at that point. Does the current remain stable. If it increases, you haven't got current control yet. If it stays stable, then you may feel more confident to toss the 393 out of the equation without smoke. ............oztules The world seems a little blurry this morning. Village idiot...or... just another hack out of his depth |
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