Re: 12V to 20V 2-Phase DC-DC Boost
Sooo... do you suppose the flux reversal is complete at what duty cycle.
what about two seperate cores?
N-Channel said:Luka, et.al,
Here is the schematic, FINALLY!.....
As you can see, the SG3525 drives the two MOSFETS in a 2-F topology, at 50kHz each (100kHz clock).
Inductor L1 is 24T of #18AWG wound bi-filar on a T-80-26 powdered-iron toroid colored yellow-white. L2 was lifted from an old ATX psu, and was the output inductor for the +12V section. Since the max voltage either MOSFET will ever have to stand off is 40V (2 x the 20V boost on the 2-winding coil), I thought 60V units would suffice. Switch S1 switches the output between 16v & 20V, beacuse the converter originally was for two different laptops. As this need change, and then went away all together, I decided to still leave it in, in case my needs ever changed (again!).
Last night, I loaded it down to about 6A using 3- 10W 10W resistors paralleled. IC1 stayed cool, the Q1 &Q2 barely got warm (probably because their Rds(on) is only 9mW); L1 heated up then stabilized out just like before; D2 was moderately warm, though not as warm as L1, and L2's temp did not change perceptably.
Next, I will post my single-F boost, controlled by a UC3843BN current-mode PWM chip. I have not yet built this one, and it may take a back seat as other, more important projects take precedence.
Ask me any question you may have, PLEASE!
Sooo... do you suppose the flux reversal is complete at what duty cycle.
what about two seperate cores?
so do you suppose kemppainen's booster would do 18v at 50 amps? with a little rewind and heavier parts peices?
http://www.arrl.org/files/qst-binaries/
http://www.arrl.org/files/qst-binaries/
Jimbo,
I contacted N8XJK directly about a year back, and told him my intentions: 19V @ ~5-6A. He said No Problem, just make the appropriate changes to the transformer windings and the output voltage feedback sense section. As for 18V @ 50A, voltage-wise there's no problem, but for 50A current, you will definitely need to beef up all the power traces- if you're using his boards. Even if you're doing your own board, I would recommend augmenting wide power traces with the following trick I learned a while back: Take ordinary magnet wire (#12 AWG should do OK for 50A), lay it down along the trace(s) to be beefed up, then solder it in place directly on the trace. Obviously, at least a 100W soldering gun will be needed to avoid the thick wire from heatsinking the heat away from the junction before solder melt, but it should work.
His converter utilizes a true transformer very efficiently, and still allows battery voltage to flow through even if the boost ckt is off, by referencing the secondary's centertap to B+ instead of ground. My design utilizes the interleaved inductor in an "auto-former" fashion, also allowing battery voltage to be present when the booster is off.
Steve
I contacted N8XJK directly about a year back, and told him my intentions: 19V @ ~5-6A. He said No Problem, just make the appropriate changes to the transformer windings and the output voltage feedback sense section. As for 18V @ 50A, voltage-wise there's no problem, but for 50A current, you will definitely need to beef up all the power traces- if you're using his boards. Even if you're doing your own board, I would recommend augmenting wide power traces with the following trick I learned a while back: Take ordinary magnet wire (#12 AWG should do OK for 50A), lay it down along the trace(s) to be beefed up, then solder it in place directly on the trace. Obviously, at least a 100W soldering gun will be needed to avoid the thick wire from heatsinking the heat away from the junction before solder melt, but it should work.
His converter utilizes a true transformer very efficiently, and still allows battery voltage to flow through even if the boost ckt is off, by referencing the secondary's centertap to B+ instead of ground. My design utilizes the interleaved inductor in an "auto-former" fashion, also allowing battery voltage to be present when the booster is off.
Steve
Well, mine is definitely simpler, smaller, and less expensive, but but his seems more rubust in the protection and power capacity departments. If you don't need the RF detect and other radio-associated circuits, then perhaps you should give mine a try.
If you go his route, the complete kit, including transformer core and powdered-iron toroid are included for something like $27 or $39 (I can't remember which) from FASR ckts. Don't forget S/H.
What topology/controller/core did you use for your isolated ckt?
Steve
If you go his route, the complete kit, including transformer core and powdered-iron toroid are included for something like $27 or $39 (I can't remember which) from FASR ckts. Don't forget S/H.
What topology/controller/core did you use for your isolated ckt?
Steve
What freq? At 50kHz, the FT-240-77 should be able to handle about 250W, if I rember correctly, from the Amidon datasheets.
I assume you're using a TL494/SG3525/MC33025/SG1846 for the controller? What MOSFETs and output rectifier(s)?
I still gravitate back to the toroids, 'cuz that's where I have the most experience......................
I assume you're using a TL494/SG3525/MC33025/SG1846 for the controller? What MOSFETs and output rectifier(s)?
I still gravitate back to the toroids, 'cuz that's where I have the most experience......................
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.