RV, camping, boating, and solar power industry might have had a significant influence in developing LED blubs powered by 12V DC. The automotive industry too might have had some influence. Some of the issues that make 12V DC lighting not be practical are:
- Structural: Majority of the home are power using 110/120/220/230/240 VAC. Converting these too 12V DC for lighting is costly. There is a signification structural cost to start using 12VDC for lighting lonely.
- All other appliances in a home in most case require 110/120/220/230/240 VAC depend on the region. Therefore a home will require a 110/120/220/230/240 VAC plus a 12V DC network. This is added cost to the consumer.
- Also it might be cost prohibitive to have a 12V DC network in larger office complexes, hospitals, hospitality, airports, stadiums etc.
- The DC power drop from point to point in these larger building might be higher too.
Converting AC power to 12V DC power locally for LED (Light Emitted Diodes) bulb lighting
The fundamental building block of an LED is a Diode. A typical diode switches on at 0.7V forward voltage. Current/Voltage (I-V ) characteristic for a typical diode is shown below.
Depending on the LED color the forward voltage varies. The table below lists typical forward voltage for a different colored LED’s.
Forward voltage for a typical white LED is between 3V to 4V. Below is I-V graph for typical coloured LED's
Typical AC supply (120V in USA, 240V UK) need to be rectified to a lower DC voltage. Transmitting DC power over a long distance is inefficient. Thus AC supply is a far more efficient to transmit power. There is always an energy loss when you convert AC to DC, but current technology has overcome most of these efficiencies. There are small cost effective rectifier circuit modules available in the market.
Below is an example of one such device. (RECOM Power RAC01-05SC)
Click on image for a larger version of the image.
RECOM Power RAC01-05SC
Although converting AC to DC is efficient, the other structural cost outweigh the benefits of a separate 12V DC line in homes. The growth in technology and markets it is very likely there will be universal AC LED bulbs where the conversion will occur seamlessly regardless of input AC voltage.