I have couple of lead acid battery reserved power supplies with output voltage from 9.5 (battery discharge cutoff) up to 13.9 (while charging the battery), intended for use with CCTV cameras, but current cameras and DVR allow only 12V+-10% and can't tolerate 13.9V.

What type of DC-DC converter can work with input both lower and higher than output?

Each camera draws up to 0.7A and, there are 8 of them connected to first PSU + DVR drawing 4A on second PSU.

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    \$\begingroup\$ FWIW: 9.5V sounds dangerously low for 12V lead acid. \$\endgroup\$ – Russell McMahon Aug 6 '14 at 17:42

There are lots of possibilities:

A buck-boost (which inverts the polarity unless it's of the 4 switch type), a SEPIC, a CUK (also inverting) and many transformer coupled topologies. For your purposes I would look at the 4 switch type of buck-boost- You can go to any of the major power semi vendors' websites and see if they have an evaluation board that is similar to what you need. TI, Linear Tech, Maxim, ON Semi and Fairchild all should have products available that are close to what you want.

Here's a board from TI that is very close to what you want, a little modification should get you the 4A+ output that you need:


You might be able to find something commercially available as well, but if that's the purpose maybe the question is off-topic for this forum.


DROK boost/buck converters on Amazon:

[Adding extra detail, per request from Dave Tweed]

Example 1: DROK DC/DC Synchronous Auto Boost Buck Converter DC 5-32V to 1.25-20V 12V 5A Car Voltage Regulator Adjustable Power supply Module

Example 2: DROK 600W 12A Constant Current/Voltage 12-60V to 12-80V DC Car Power Converter Battery Charger LED Driver Regulated Laptop Power Supply

Example 3: DROK 150W/15A 12/24V 6-32V to 0.8-28V DCDC Converter Up/Down Car Laptop Regulated Power Supply

These and others have some utility for the poster. There are also smaller boost/buck converters to be found on Amazon or EBay. Lower power converters might be used to run fewer cameras per converter, and perhaps provide some flexibility or redundancy.


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