12v regulator for tft monitor

[affinite]

Im about to fit a small 12v tft monitor as part of the boat navstation (with a laptop buried safely under the chart table). I have a dc-dc converter for the laptop as it is 18v but I cant decide if I should fit some sort of voltage regulator to keep dc down to 12v for the monitor or if I should allow the onboard alternator regulation to keep dc to a tolerable level.
Any thoughts ?

 

[wragges]

I ran a 15" TFT in the cockpit on my previous boat for more than 3 years without any kind of regulation in the circuit and it worked just fine, in fact I had the opposite problem at first, it took a little more current than expected so I had to beef-up the power cable a litte otherwise the backlight invertor kept switching off.

Most TFT's have some basic voltage clean-up circuit inside the unit as the crud and spikes that would come thought from the mains adaptor are not so nice either.

However, if you want to be belt and braces then go for a 12v DC-to-DC convertor that can output atleast 4 amps.

 

[William_H]

If you decide you want regulated power to your monitor the only way to go is the switch mode DC to Dc converter similar to what you have for your laptop.
The problem is that your battery voltage will vary from 14 volts unnder charge to 11 volts nearly discharged.

It is simple to set up a series regulator to give precisely 12 volts. This is a transistor which automatically varies its resistance withb a feed back arangement. Most conveneientlky in a single integrated circuit. The problem is that once inn circuit it will drop several volts regardless. So it needs min 13 or 14 volts to give 12. That is possibly OK if engine is charging the batteries but no good when engine is off.

The DC to Dc converter actually is able to transform the voltage up as well as down to give 12 v from 11 to 15 or more input but at a loss of efficiency.

Only for very low currents is it practical to use a shunt regulator. Again very simple but allows a current to flow through a resistor of lowish value to your device. If the voltage rises a device begines to pass current to ground such that the resistor drops the voltage to 12 volts. This type will give 11 volts straight through until the battery reaches 12v where upon it limits the volltage to 12 v and gets to waste (ie gets hot) a lot of power with 14 v input.

Just a bit of background waffle regards ollewill