I'm in the process of beginning a build on a 12V to 12V SMPS to regulate a 12V Lead-Acid battery to a steady ~12V for devices that require a non-fluctuating 12V supply but powered from a 12V battery while charging (14.4V) or discharging (10-12.6V)
Not sure which topology will be the best for a DIY project, I'm looking for efficiency, ease of parts selection, and most important.....RELIABILITY
TO make dissipation simple, I'm building the project on a large heatsink as the chassis, so no need for a fan.
I have lots of salvaged MBR3045PT (30A,45V) and also MBR4045PT Schottky diodes, and several varied MOSFETS rated 50-75A and also some 30A,600V Rectifiers with a higher voltage drop (MUR3060PT)
Preferred 10V-15V input range or better, 12.2V regulated output goal on all loads. 50-70A output.
1. Should I go a PUSH-PULL into a ferrite transformer driven by MOSFETS, winding it for higher than 12V on the secondary, rectified by schottky diodes, then PWM the output voltage down using an output inductor........
2. Would a BUCK-BOOST with just a single inductor be better instead, using MOSFETS for switching.
My issues if not being sure what to do are because I assume I may need pretty high voltage schottky diodes for a push pull, but higher voltage parts drop more volts................However, a BUCK-BOOST loses power on two voltage drops, but uses less space and doesn't require a transformer.
Decisions, decisions.........
Not sure which topology will be the best for a DIY project, I'm looking for efficiency, ease of parts selection, and most important.....RELIABILITY
TO make dissipation simple, I'm building the project on a large heatsink as the chassis, so no need for a fan.
I have lots of salvaged MBR3045PT (30A,45V) and also MBR4045PT Schottky diodes, and several varied MOSFETS rated 50-75A and also some 30A,600V Rectifiers with a higher voltage drop (MUR3060PT)
Preferred 10V-15V input range or better, 12.2V regulated output goal on all loads. 50-70A output.
1. Should I go a PUSH-PULL into a ferrite transformer driven by MOSFETS, winding it for higher than 12V on the secondary, rectified by schottky diodes, then PWM the output voltage down using an output inductor........
2. Would a BUCK-BOOST with just a single inductor be better instead, using MOSFETS for switching.
My issues if not being sure what to do are because I assume I may need pretty high voltage schottky diodes for a push pull, but higher voltage parts drop more volts................However, a BUCK-BOOST loses power on two voltage drops, but uses less space and doesn't require a transformer.
Decisions, decisions.........
I would get a BIG battery.
Just curious, what kind of circuit demands such precision in its power source?
How was it used before?
What PSU gave it
Is it really that critical?
Sorry I didn't reply back, life circumstances kept me offline , and my thread got buried in the midst............
Anyway......Yes, the 12V is very critical. High-Power-Computer use.....Even though ATX spec allows +/- 10% in reality, (10.8-13.2V) stability will be an issue, so I want much less than 5% fluctuation, or nearly none. This will also be used to power other digital 12V devices as well that need true regulated 12V, hence the high output rating as a run-all PSU.
Also the agenda is cleaner, better power than the regular Mains-Powered Computer PSU, with ease of repair and customization, being a DIY design, and I'll independently build the other 5V and 3.3V rails with their own buck converters.
My Batteries in my vehicle are TWO 115AH Deep-Cycle Marine Batteries, batteries are no issue, and I run a 1500W Power Inverter effortlessly. Using a direct 12V supply would net MUCH more efficiency than using the 120V power inverter to power the computer.
Do you have multiple loads being powered from regulated 12V? Do you know the max current ratings of all those loads?
Do any of the 12V regulated loads have a substantial periodic load current, or are the loads static? Similarly, are there other loads on the battery that have substantial periodic load current (eg. an inverter)?
How were you going to avoid flattening the battery?
Do any of the 12V regulated loads have a substantial periodic load current, or are the loads static? Similarly, are there other loads on the battery that have substantial periodic load current (eg. an inverter)?
How were you going to avoid flattening the battery?
Powerstream has something similar to what I'm about to be building, just wish I could find one of their schematics to base a design off of...........
DC/DC DC input mini-redundant industrial ATX PC power supplies 12VDC input, 400 watts with hot swap capability for solar powered server farms
12V Input PC ATX computer Power Supplies, 12VDC Input, car computer power supply, 12 volt.
The idea, is reliable backup power so computer never shuts off similar to how a laptop uses the battery, but with a desktop.
I'm stuck between using buck-boost, or just a push-pull with a huge ferrite transformer and diode rectifiers. It appears with the wide voltage range of the powerstream supplies, that they use some type of boost topology for sure.
DC/DC DC input mini-redundant industrial ATX PC power supplies 12VDC input, 400 watts with hot swap capability for solar powered server farms
12V Input PC ATX computer Power Supplies, 12VDC Input, car computer power supply, 12 volt.
The idea, is reliable backup power so computer never shuts off similar to how a laptop uses the battery, but with a desktop.
I'm stuck between using buck-boost, or just a push-pull with a huge ferrite transformer and diode rectifiers. It appears with the wide voltage range of the powerstream supplies, that they use some type of boost topology for sure.
You probably want at least real B+ isolation from the regulated bus, so a tranformer is necessary. Push pull would be the right topology there. Since this is a serious project in terms of power and complexity, you may as well go for fairly high efficiency as well, so choose a moderate switching frequency, big cores, and maybe think twice about using parts bin components. Ideally all your loads not served from USB or something would be isolated as well. Are you sure a collection of Powerstream or similar products isn't just what you need? If you're not looking for exceptional efficiency or something, whacking this up yourself probably wont be the "cheaper" way out, depending on how you value time.
hmm 2 deep cycle batteries in a car. how are you charging them?
what loads do you have and how long do you need to run them without the charger?
seems like RV forum would be a better place, they do this stuff all the time and will have practical solutions.
if it's just some simple mobile computing tasks, look into newer laptops or NUCs. then investigate mobile DC/DC 40-100W chargers. new Intel Baytrail should keep IPC ~ 7-10W and lower costs as well.
if it was for off grid type cabins with solar I would consider running multiple batts at 24V or higher, then usually you'll always have the need to run an inverter anyway.
EDIT always reduce the loads 1st! then hunt for eff. vs cost of new hardware.
if yer running older ATX hardware on mobile platforms then you have to re- examine that.
what loads do you have and how long do you need to run them without the charger?
seems like RV forum would be a better place, they do this stuff all the time and will have practical solutions.
if it's just some simple mobile computing tasks, look into newer laptops or NUCs. then investigate mobile DC/DC 40-100W chargers. new Intel Baytrail should keep IPC ~ 7-10W and lower costs as well.
if it was for off grid type cabins with solar I would consider running multiple batts at 24V or higher, then usually you'll always have the need to run an inverter anyway.
EDIT always reduce the loads 1st! then hunt for eff. vs cost of new hardware.
if yer running older ATX hardware on mobile platforms then you have to re- examine that.
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you need Boost-Buck
Simplest topology is a single MOSFET, two inductors and rectifiers. As used in one MPPT DC/DC controller that I know of. expensive stuff ! you don't really need galvanic isolation but full blown transformer gives more grounding choices should noise issues raise their head.
also DC range doesn't need to go below a flat battery ( really don't want run a SLA battery lower than 50% many times!) and reasonable drop. so 13.6 VDC nominal and range of 12.0-15.5 VDC would be better spec.
off grid stuff > if you used two batteries in series, then much simpler single Buck topology can be used.
boost-buck = Cuk' converter (inverts polarity), so you will need to isolate the input or output. I don't like "buck-boost" cuz of the inputs buck conversion losses means youll be operating at boost mode constantly IE not ideal for eff. more switch losses.
Most MPPT converter folks ignore low voltage PV panels to offer reasonable buck converters.
Most MPPT converter folks ignore low voltage PV panels to offer reasonable buck converters.
not sure I understand yer Q.
the converter I had in mind offers 12V input and 12V output at 30A they also used to offer one at 50A
Im not saying this MPPT product batt charger should be used in place of a ATX PS, mainly just for illustrating a topology example in a high rel. design. Im against using anything overly complex ( or high losses ) unless as a last resort, but look at using a simpler buck converter.
your image isn't a real Cuk' converter
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Cool, meets his requirements except for the DIY part.
You are correct that the image is not a Cuk' converter but it is a buck-boost converter and to say "boost-buck = Cuk' converter (inverts polarity)..." would mislead readers to think that a buck-boost converter is the same as a Cuk' converter and that both invert the polarity.
Just trying to clarify a statement here.
I don't think any of my statements above implied that a Cuk (boost-buck) and a buck-boost converter are the same thing or that they both invert the polarity...I think that's why they tend to use the name Cuk' converterCool, meets his requirements except for the DIY part.
You are correct that the image is not a Cuk' converter but it is a buck-boost converter and to say "boost-buck = Cuk' converter (inverts polarity)..." would mislead readers to think that a buck-boost converter is the same as a Cuk' converter and that both invert the polarity.
Just trying to clarify a statement here.
.I'm not sure his requirments would be met by the 30A part , last but least on either the form factor or the price. FWIW the 50A part I linked to is a buck converter only.
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OK
I think he needs a multi-phase controller and synchronous rectification.
I was trying to find a 4 or more phase controller.
I have used a two phase but did not know it had synchronous rectification outputs on the IC. I used two multiple winding toroids...MPP cores from Magnetics Inc.
It was a flyback design with multiple secondaries for each phase, each had its' own diode.
I designed for 1.25V @ 70A but only got 45A.
I know it is an order of magnitude away from target but I think it is the way to approach it.
The easy way would be to just start with 24V and buck convert but I don't think that is the plan.
600-700W...seems that car audio amps run that high but I don't think the DC-DC in those can run all day long.
I think he needs a multi-phase controller and synchronous rectification.
I was trying to find a 4 or more phase controller.
I have used a two phase but did not know it had synchronous rectification outputs on the IC. I used two multiple winding toroids...MPP cores from Magnetics Inc.
It was a flyback design with multiple secondaries for each phase, each had its' own diode.
I designed for 1.25V @ 70A but only got 45A.
I know it is an order of magnitude away from target but I think it is the way to approach it.
The easy way would be to just start with 24V and buck convert but I don't think that is the plan.
600-700W...seems that car audio amps run that high but I don't think the DC-DC in those can run all day long.
like I said before he needs to ditch the beige ATX desktop computer @ 300 Watts idle and use a modern laptop or NUCs @ 6 Watts. note to folks that been offline > we've come a long way in powerful mobile computing in a few years! shop for computing power you want/need ranging from BayTrail up to an i7 80W full load.
Regarding power consumption, in their review of the D54250WYK with a Haswell i5-4250, Silent PC Review concluded that "An idle power level of just 6W and typical use power barely into two digits is very impressive in one sense; in another sense, it's what you find in current Ultrabooks using similar components."
You can buy ubiquitous replacement laptop 12V DC input power bricks to power a NUC too,
Regarding power consumption, in their review of the D54250WYK with a Haswell i5-4250, Silent PC Review concluded that "An idle power level of just 6W and typical use power barely into two digits is very impressive in one sense; in another sense, it's what you find in current Ultrabooks using similar components."
You can buy ubiquitous replacement laptop 12V DC input power bricks to power a NUC too,
M4-ATX, 250w output, 6v to 30v wide input Intelligent Automotive DC-DC Car PC Power Supply
I did find this ATX 12V car solution, 12V output power /specs seem a little fuzzy. probably ~250w minus the power delivered to both the 5V & 3V buck converters.
looks like it's a buck-boost/ sure would be fun to play around with. i.e. to find out when it switches over to buck mode only. software looks useful.
I reckon the PCB needs fan cooling when you operate it near full power on hot days. ( by the ATX PS chassis thingy they offer. ) reliable gear ,who knows? buy some spares.
Vin (without Vdrop)
~ 12.0 12.8 V ign off > discharging
~ 13.5 -13.9 V standby > optional float charge
~ 14.4 Vin & ign on > charging
I did find this ATX 12V car solution, 12V output power /specs seem a little fuzzy. probably ~250w minus the power delivered to both the 5V & 3V buck converters.
looks like it's a buck-boost/ sure would be fun to play around with. i.e. to find out when it switches over to buck mode only. software looks useful.
I reckon the PCB needs fan cooling when you operate it near full power on hot days. ( by the ATX PS chassis thingy they offer. ) reliable gear ,who knows? buy some spares.
Vin (without Vdrop)
~ 12.0 12.8 V ign off > discharging
~ 13.5 -13.9 V standby > optional float charge
~ 14.4 Vin & ign on > charging
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If you look at a picture of the circuit board, it appears there are Four Devices arranged as a buck/boost for the 12V section, while the 5 and 3.3V sections use two devices as a buck.
As far as a DIY buck/boost, instead of using a bootstrap and worrying about pulse width, and adequate drive of the bootstrap for the high-side MOSFETS, I imagine just creating a small 24V-boosted section to drive the PWM chip and the MOSFETS from that, would give you the drive needed to drive the MOSFET gates 10-12V or more above the rail on all sections.
Maybe make a small 24V boost circuit using a 34063 then drive a group of TL494 or 34063 based Buck-Converters from the 24V rail to feed the MOSFETS.......... and then have the boost for the 12V section just run from the 12V...............
I have hand-drawn several different schematics, but still figuring out best option.......
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