12V to 5V: How efficient is this?

[Avi8tor]

front:
http://www.pbase.com/avi8tor/russia/Lighter plug PCB component side_640.jpg

back:
http://www.pbase.com/avi8tor/russia/Lighter plug PCB back.jpg

(try clicking on the 'medium' link if these don't display)

I intend to power an iQ from an external battery.

This is the innards of a lighter plug adapter from pc-mobile (www.pc-mobile.com). The outside label says it accepts input voltages from 12-24 V and outputs 850ma @ 5V. I haven't measured it yet.

I'm no EE - or anything close. Can anyone say with some certainty whether this type of design wastes most of the input (as heat?), or is it efficient at converting the input to 5V out?

Thanks,

Avi8tor

[Moose Man]

Based upon my limited automotive electronics (ASE certified) this should be efficient and not generate a lot of waste. It really makes little difference if it wastes anyway other than the heat factor but it looks like you'll not generate excessive heat. 850 milliamps won't generate a lot of heat.

Now if it was flowing 5 full amps - then stand back with the fork and marshmellows and watch them catch flame. :D

As long as the output is 850 milliamps - you should generate very little heat and almost no measurable waste.

[jonasolof]

There is a principal difference between voltage regulators and switching circuits. I think the latter are somewhat more efficient - and more expensive

You should be able to identify the chip by the printed text ang get get to understand more what the circuit is. I think it is a voltage regulator (uneducated guess).

What kind of battery do you intend to use?

The forum has had rather extensive discussions on switching circuits to power the iQue previously. You can find switching circuits at www.tracopower.com among others. The one JohnVA used did not need any additional components to feed 5V from a 7.2 V LiIon video battery.

[jonasolof]

There is a principal difference between voltage regulators and switching circuits. I think the latter are somewhat more efficient - and more expensive

You should be able to identify the chip by the printed text ang get get to understand more what the circuit is. I think it is a voltage regulator (uneducated guess).

What kind of battery do you intend to use?

The forum has had rather extensive discussions on switching circuits to power the iQue previously. You can find switching circuits at www.tracopower.com among others. The one JohnVA used did not need any additional components to feed 5V from a 7.2 V LiIon video battery.

[Avi8tor]

Thanks for the replies. I'm driving this circuit with a 12V 12AH battery. But it's powering other electronics besides the iQ - a Garmin 76s, an aircraft-band VHF radio and a variometer (sensitive rate-of-climb instrument) - all 12V input.

I fly a sailplane and plan to use Soaring Pilot (www.soaringpilot.org) running on the iQ as a flight computer / logger, with the 76s as a backup. Primary navigation is still pilotage.

On a good day, soaring flights can last five or six hours (!) and cover hundreds of miles, and the battery is the sole source of power. If this particular unit is inefficient, I'll replace it.

I'll try to find the IC on-line and determine what it is, but I'm hoping someone with more electronics background might beat me to it. :p

[jonasolof]

I'd recommend this:

tracopower TEN5-1211 9-18 V in 5 V 1000 mA max out, 85 % efficiency. See www.tracopower.com

"Line regulation: ±0.3% max.
Load regulation: ±1.0% max.
Ripple & noise: <50 mVpk-pk (20 MHz BW)
Conducted EMI: EN 55022, class A and FCC, level A (internal filter)
Short circuit protection: continuous
Efficiency: 85% typ.
3.3 VDC models: 79% typ.
Operating temperature range: -40°C ... +75°C (no derating)
I/O isolation voltage: 1'500 VDC
Safety standards/ approvals: cUL/UL 1950, IEC/EN 60950
MTBF: >1 Mio. h @ +25°C
Case: metal with insulated baseplate "

If you want to feed more 5 V devices, you can find units with higher output in other product ranges within Tracopower. Eg the TEN8-1211 which gives you 1500 mA at 5V also at > 80 percent efficency.

No further components necessary.