Power dissipation of voltage regulators?

[Daniel Kelly (AKA Jack)]

Please could you lend me some of your expertise?

I have a 12V 6Ah battery. I'd like to power a 5V 1Amp device for as long as
possible.

If I use a voltage regulator then will I lose a significant amount of power?
Do voltage regulators dissipate much power?

Thanks,
Jack

 

[John Popelish]

"Daniel Kelly (AKA Jack)" wrote:

Please could you lend me some of your expertise?

I have a 12V 6Ah battery. I'd like to power a 5V 1Amp device for as long as
possible.

If I use a voltage regulator then will I lose a significant amount of power?
Do voltage regulators dissipate much power?

Thanks,
Jack

There are two general classes of regulators.

Linear regulators waste all the extra voltage by acting like a
variable resistor in series with the load. Your 1 amp load will use 5
watts (5 volts times 1 amp) but the regulator will burn 7 watts (7
volts times 1 amp).

Switching regulators convert one voltage to another with out
intentional losses. They are typically 80 to 90% efficient in this
voltage and current range. So to supply 5 watts to your load, they
might draw 5.5 to 6 watts from the 12 volt battery, for a battery
current of
5.5 watt / 12 volt = .45 amp to
6 watt / 12 volt = .5 amp

The battery will last about twice as long with a switching regulator
than it will with a linear regulator.

Here is a tutorial on various regulators:
http://www.national.com/appinfo/power/files/f4.pdf
http://www.national.com/appinfo/power/files/f5.pdf

--
John Popelish