ip65 would normally be used outside, there is no need for that level in doors, most down lights are MR16 which means multifaceted reflector 16 1/8th of an inch across or 2 inch or 50 mm. It does not refer to voltage or pin configuration. In the main G5.3 are 12 volt and GU10 are 230 volt but that's not written in stone, with GU10 there are three versions GZ10 allows heat to travel through the reflector, it only reflects light used to stop over heating item in front of them, the GZ10 holder will take all lamps, GU10 it reflects both heat and light, and a GZ10 lamp will not fit in a GU10 holder. And GU10L2 is a special to comply with building regulations and the holder will only take energy saving bulbs.
On to 12 volt, there was nothing to stop you fitting bulb with a dichroic coating instead of an aluminium reflector. So you could fit wrong bulb and over heat the space behind the bulb. There were two ways of getting 12 volt, one was a wire wound transformer which was heavy, lasted for years and years, but had no voltage correction, however would work zero to rated watts, so LED can be used instead of tungsten without any change to power supply.
Then we have the switch mode power supply, far better with tungsten as had voltage compensation, often called electronic transformers also much lighter and cheaper, however they often have an output window like 35 - 105 VA (VA as far as you need to know is same as watts) so fitting a bulb under 35 watt and they would close down, so not suitable for LED.
Quartz bulbs should never be dimmed, the temperature of the quartz is that hot the tungsten will not stick to it, so returns to the filament, so with a quartz replacement often they also can't be dimmed, with LED there are three ways to limit the current, simple resistor, a capacitor or a switch mode module. So some are AC only and AC at 50 Hz, some are AC/DC and some DC only the latter normally more expensive and really designed for boats and caravans with a voltage 10 to 30, so DC types not found in most shops. The AC type normally state 50 Hz on them and you need a wire wound transformer for them.
For the MR16 replacement LED bulb it is rare that they need DC so not a driver, but a transformer. Driver should mean current regulated, however same name often used for voltage regulated. So have to be careful even with a 10 to 30 volt DC MR16 they may not work with a voltage regulated driver as often out put is not smoothed.
Old house has some 12 volt (extra low voltage) pods in the bathroom with a wire wound transformer where I have some Lidi 50 Hz LED lamps and works fine, new house are all 230 volt (low voltage) GU10 lamps.
Note in USA 12 volt is low voltage, every where else it's called extra low voltage, and 230 volt is low voltage, but some times lamps are incorrectly labelled.
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