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arnolde · 05-31-2009, 07:27 AM

Wow, this project is really awesome :-) just what I've been looking for, and was thinking about starting my own, because I also have a problem with paying >2000 EUR for a power supply that generally does less than a 50 EUR PC power supply...

For my 500V battery pack I need a charger that can supply provide 600VDC at 5A. (Although I'd be happy with 2A output for now)

Is there an easy way to adapt your circuit to provide that high a voltage? I was thinking about doubling my 230VAC input with a voltage doubler circuit (simply a rectifier connected differently) so I'd have about 700VDC input. Then limit current by PWM and also I'd like to isolate it, but thats also optional. Also I'll add PFC on the input, one from a PC power supply should do for the beginning.

I assume I'd have less cooling problems with lower current?

Do you have a complete circuit diagram, incl. the PWM setup?

I'd be happy to contribute, i.e. by making profesional PCB's for this project. I'm located in Germany so I can cheaply supply anybody in the EU.

EDIT: I just read the complete thread and was just wondering if you ever condsidered using IGBT's instead of MOSFETs? Like this one: http://www.st.com/stonline/products/...tgf7nb60sl.pdf handles upto 20A and only dissipates (=loses) 25W!!! At 150V/20A thats a loss of 0.83% or an efficiency of over 99%. Dont ask me exactly what IGBT's are, I'm not an EE either, I only remember hearing that they only work over 100V or so, so over 100V they're often used instead of MOSFETs. Also cheaper: This one costs only about 3$, so even if you use 2 in parallel, thats still cheaper than your FET.

How do I know what value of inductivity (coil) I need? I can see that for my 5A output current I'll obviously need one with at least 5A rating, but how many mH?

About adjusting the current in fine tuning: I recommend looking at PWM controllers that are meant for SMPS design, like the US2842 (http://www.st.com/stonline/products/...99/uc3842b.pdf), they sense the current themselves and auto-regulate to keep it constant, and on the current adjust knob you can add resistors in the top and bottom of the pot (wherever necessary) to keep the full swing range of the pot inside your desired current limit range. That way you should be able to comfortably adjust between 0-25A in 0.1A steps with a normal trim pot.

As for coils, would these be ok, do you think?
http://www.vishay.com/docs/34022/ihv.pdf (30A, 150µH)

Last but not least, here is a circuit I found of a commercial ATX power supply, that may provide some interesting ideas: http://www.smpspowersupply.com/ATX_p..._schematic.pdf

After reading this paper http://www.irf.com/technical-info/wh...oosewisely.pdf which compares MOSFET and IGBT, I guess it really doesnt matter, while MOSFETS seem to me to have a very slight advantage.

05-31-2009, 07:27 AM	#72 (permalink)
arnolde EcoModding Lurker Join Date: May 2009 Location: Germany Posts: 21 Thanks: 0 Thanked 0 Times in 0 Posts	Wow, this project is really awesome :-) just what I've been looking for, and was thinking about starting my own, because I also have a problem with paying >2000 EUR for a power supply that generally does less than a 50 EUR PC power supply... For my 500V battery pack I need a charger that can supply provide 600VDC at 5A. (Although I'd be happy with 2A output for now) Is there an easy way to adapt your circuit to provide that high a voltage? I was thinking about doubling my 230VAC input with a voltage doubler circuit (simply a rectifier connected differently) so I'd have about 700VDC input. Then limit current by PWM and also I'd like to isolate it, but thats also optional. Also I'll add PFC on the input, one from a PC power supply should do for the beginning. I assume I'd have less cooling problems with lower current? Do you have a complete circuit diagram, incl. the PWM setup? I'd be happy to contribute, i.e. by making profesional PCB's for this project. I'm located in Germany so I can cheaply supply anybody in the EU. EDIT: I just read the complete thread and was just wondering if you ever condsidered using IGBT's instead of MOSFETs? Like this one: http://www.st.com/stonline/products/...tgf7nb60sl.pdf handles upto 20A and only dissipates (=loses) 25W!!! At 150V/20A thats a loss of 0.83% or an efficiency of over 99%. Dont ask me exactly what IGBT's are, I'm not an EE either, I only remember hearing that they only work over 100V or so, so over 100V they're often used instead of MOSFETs. Also cheaper: This one costs only about 3$, so even if you use 2 in parallel, thats still cheaper than your FET. How do I know what value of inductivity (coil) I need? I can see that for my 5A output current I'll obviously need one with at least 5A rating, but how many mH? About adjusting the current in fine tuning: I recommend looking at PWM controllers that are meant for SMPS design, like the US2842 (http://www.st.com/stonline/products/...99/uc3842b.pdf), they sense the current themselves and auto-regulate to keep it constant, and on the current adjust knob you can add resistors in the top and bottom of the pot (wherever necessary) to keep the full swing range of the pot inside your desired current limit range. That way you should be able to comfortably adjust between 0-25A in 0.1A steps with a normal trim pot. As for coils, would these be ok, do you think? http://www.vishay.com/docs/34022/ihv.pdf (30A, 150µH) Last but not least, here is a circuit I found of a commercial ATX power supply, that may provide some interesting ideas: http://www.smpspowersupply.com/ATX_p..._schematic.pdf After reading this paper http://www.irf.com/technical-info/wh...oosewisely.pdf which compares MOSFET and IGBT, I guess it really doesnt matter, while MOSFETS seem to me to have a very slight advantage. Last edited by arnolde; 05-31-2009 at 03:15 PM..