12V TO 12V SMPS circuit topology choices - diyAudio
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Old 10th November 2014, 01:56 AM   #1
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Question 12V TO 12V SMPS circuit topology choices

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.........
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Old 13th November 2014, 05:00 PM   #2
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12.2*70 = 854W on secondary side.
854*80% = 1100W on primary.

I would go fullbridge.
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Old 14th November 2014, 10:30 PM   #3
JMFahey is offline JMFahey  Argentina
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Quote:
Originally Posted by palstanturhin View Post
12.2*70 = 854W on secondary side.
854*80% = 1100W on primary.

I would go fullbridge.
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
Quote:
non-fluctuating 12V
Is it really that critical?
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Old 25th December 2014, 10:27 PM   #4
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Quote:
Originally Posted by JMFahey View Post
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.
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Old 26th December 2014, 04:40 AM   #5
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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?
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Old 26th December 2014, 05:40 AM   #6
DUG is offline DUG  Canada
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Take a look at synchronous rectification...used to reduce rectifier losses...significantly.

Also take a look at multi-phase controllers.
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