Transformers and LED drivers


12 Volt downlights require a transformer to step the voltage down from 240 volts down to 12 volts. There are two types of transformers

  1. Older inefficient iron core (or ferromagnetic) transformers (use 10 - 15 watts)

  2. Newer electronic transformers (use 2 - 10 watts)

Fittings designed for halogen MR16 lamps that use electronic transformers may need to be refitted with LED-compatible transformers (eg Redback transformer) as the lamps will flicker or just not work. The average electronic transformer will be specified for a load range of 20 to 60 watts, which means that it will operate only when connected to a lamp that draws >20watts. Because LED lights draw so little power, they will not reach the minimum voltage of an electronic tranformer.

If the lamp is incompatible with the electronic transformer then there are two options. 1) replace the transformers with one designed to drive LED bulbs specifically, or 2) rewire the fittings so that there are two fittings or more per transformer. The only problem with the latter approach is that if someone at a later date replaces the LEDs with halogens again, the transformers will be overloaded and will shut down.

Electronic transformers that are LED-compatible are usually labelled as such.

Fixtures that use an iron core (ferro magnetic) transformers can generally be used with LED-lamps without modification.

Transformers use energy to operate adding to the energy requirements of the lighting without providing additional lighting. The older iron core transformers were very inefficient, adding up to 15 watts to the 50 watts used by the globe. Electronic transformers use as little as 2 watts (eg Redback transformer).

Do I need an electrician to replace transformers?
In some cases you will need an electrician, in other cases you won't (if you are competent in the roof cavity and  rearranging plugs). If downlights were fitted with a standard appliance plug that plugs in to a power point in the roof space, then you just plug in new fittings (although you might have to fit a lead to the new fittings).
If they are hard wired, then you will need an electrician.

What am I looking for in a quality transformer or LED driver?
Transformers need to draw a small amount of power (ideally less than 4 watts) and have load range allowing them to operate at lower power demands.

LED Drivers

An LED driver is a self-contained power supply that controls the amount of current and voltage supplied to an LED light. To get the best result of high brightness and long lamp life of 80,000 hours+ from an LED light, it is highly recommended that it be used in conjunction with an LED constant current driver to deliver the exact current required by the LED that will assist the lamp work over a range of voltages.  This driver delivers the exact current required by the LED and will make the lamp work over a range of voltages. Without an LED constant current driver the lamp would be sensitive to voltage changes, by getting dim or going out if the voltage drops too low, and the lifetime of the lamp will be reduced if the voltage goes too high.

Hardware stores and lighting shops sell transformers.


41 Victoria Street
Hobart Tasmania 7000

Ph (03) 6234 8066

76 Argyle Street  Hobart
Ph (03) 6231 1273

Electricians Shed
45 Burnett St 7000 North Hobart
Ph 6231 0002

CLICK HERE to go to the List of contacts and see lighting suppliers.