using a synchronous rectifier in a boost circuit
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From: Joerg on 29 Jun 2010 13:04 WangoTango wrote: > In article <vtij2694kou6ap4e7j17kraavkq7ifk56b(a)4ax.com>, spam(a)spam.com > says... >> On Tue, 29 Jun 2010 11:29:05 +0300, Paul Keinanen <keinanen(a)sci.fi> >> wrote: >> >>> On Tue, 29 Jun 2010 01:02:31 GMT, Jamie <jmorken(a)shaw.ca> wrote: >>> >>>> I am making a high power boost circuit (500watts+ with 12VDC input and >>>> 13.5VDC output). >>> That is more than 42 A. >>> >>> Are you sure that the ATX power supply will deliver that amount of >>> current _at_ 12 V ? >>> >> Paul makes a good point. >> >> It's usually the 5V rail thats good fo 30 to 50A the 12V is usually >> only good for 12A to maybe 20A. At least the ones I've seen. >> >> Oh and I wouldnt count on the supply to be able to delivery it for >> extended periods of time. >> > Or do it at all with no load on the +5V > It'll cost efficiency but I agree. The 12V rail diodes in most PC supplies are sort of skimpy. Probably because 12V only has to deliver peaks and once the hard disks or CD have spun up consumption goes back down. Of course Jamie could install bigger diodes on the 12V side but then he might as well swing the regulation loop over to 12V, disable everything else and set the new voltage divider resistor so that 13.5V comes out. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Jim Thompson on 29 Jun 2010 14:04 On Tue, 29 Jun 2010 03:22:57 GMT, Jamie <jmorken(a)shaw.ca> wrote: >On 6/28/2010 6:32 PM, Vladimir Vassilevsky wrote: >> >> >> Jamie wrote: >> >>> Hi, >>> >>> I am making a high power boost circuit (500watts+ with 12VDC input and >>> 13.5VDC output). >> >> I wonder what is this for. > >Hi, > >I am using an off the shelf ATX power factor corrected 750Watt >powersupply as the 12VDC input, and then boosting this to ~13.5VDC for >charging lead acid batteries at 600watts+. This is part of my "ATX >power tower" project, a cheap home energy system in a PC case :) > [snip] Why not just tweak the ATX switcher directly to get to "13.5VDC"? Which, BTW, may not be adequate to charge a cool/cold lead acid battery. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Obama: A reincarnation of Nixon, narcissistically posing in politically-correct black-face, but with fewer scruples.
From: Tim Wescott on 29 Jun 2010 14:28 On 06/29/2010 11:04 AM, Jim Thompson wrote: > On Tue, 29 Jun 2010 03:22:57 GMT, Jamie<jmorken(a)shaw.ca> wrote: > >> On 6/28/2010 6:32 PM, Vladimir Vassilevsky wrote: >>> >>> >>> Jamie wrote: >>> >>>> Hi, >>>> >>>> I am making a high power boost circuit (500watts+ with 12VDC input and >>>> 13.5VDC output). >>> >>> I wonder what is this for. >> >> Hi, >> >> I am using an off the shelf ATX power factor corrected 750Watt >> powersupply as the 12VDC input, and then boosting this to ~13.5VDC for >> charging lead acid batteries at 600watts+. This is part of my "ATX >> power tower" project, a cheap home energy system in a PC case :) >> > [snip] > > Why not just tweak the ATX switcher directly to get to "13.5VDC"? > > Which, BTW, may not be adequate to charge a cool/cold lead acid > battery. There's certainly a voltage/temperature relationship, but I'll be damned if I can find my handy battery book! Hacking the supply sounds good, unless the intent is to have something that is wholly external to the thing, to allow you to use any old ATX supply of sufficient drive. It seems that if you're going to go to the trouble to misuse an ATX power supply by building a 600W switcher to run off of an already-regulated output, you could without too much more time and expense just build an off-line switcher. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html
From: Hammy on 29 Jun 2010 16:11 On Tue, 29 Jun 2010 10:04:27 -0700, Joerg <invalid(a)invalid.invalid> wrote: >WangoTango wrote: >> In article <vtij2694kou6ap4e7j17kraavkq7ifk56b(a)4ax.com>, spam(a)spam.com >> says... >>> On Tue, 29 Jun 2010 11:29:05 +0300, Paul Keinanen <keinanen(a)sci.fi> >>> wrote: >>> >>>> On Tue, 29 Jun 2010 01:02:31 GMT, Jamie <jmorken(a)shaw.ca> wrote: >>>> >>>>> I am making a high power boost circuit (500watts+ with 12VDC input and >>>>> 13.5VDC output). >>>> That is more than 42 A. >>>> >>>> Are you sure that the ATX power supply will deliver that amount of >>>> current _at_ 12 V ? >>>> >>> Paul makes a good point. >>> >>> It's usually the 5V rail thats good fo 30 to 50A the 12V is usually >>> only good for 12A to maybe 20A. At least the ones I've seen. >>> >>> Oh and I wouldnt count on the supply to be able to delivery it for >>> extended periods of time. >>> >> Or do it at all with no load on the +5V >> > >It'll cost efficiency but I agree. The 12V rail diodes in most PC >supplies are sort of skimpy. Probably because 12V only has to deliver >peaks and once the hard disks or CD have spun up consumption goes back down. > >Of course Jamie could install bigger diodes on the 12V side but then he >might as well swing the regulation loop over to 12V, disable everything >else and set the new voltage divider resistor so that 13.5V comes out. Only if he could parallel more windings, I doubt the cooper could take two to three times the rms current they were originally designed for without excessive losses and causing thermal runaway on the transformer. At this point it would probably be less trouble to buy an off the shelf solution or build your own llc Half-bridge converter if your feeling ambitious. ;-)
From: Michael Robinson on 29 Jun 2010 17:48
>On 6/28/2010 6:32 PM, Vladimir Vassilevsky wrote: >> >> >> Jamie wrote: >> >>> Hi, >>> >>> I am making a high power boost circuit (500watts+ with 12VDC input and >>> 13.5VDC output). >> >> I wonder what is this for. > >Hi, > >I am using an off the shelf ATX power factor corrected 750Watt >powersupply as the 12VDC input, and then boosting this to ~13.5VDC for >charging lead acid batteries at 600watts+. ------At 600 watts I'm sure you are talking about bulk charging. 13.5 volts is the wrong voltage. Bulk charging occurs about a volt higher than that. --------------------------------------- Posted through http://www.Electronics-Related.com |