I have tested a DETA LED lighting electronic transformer. This is the one that bunnings sell. What is labelled as a constant voltage transformer is NOT a constant voltage transformer. In fact its no better than the Halogen lighting transformer voltage output. Comparing this to the Phillips ET-S 15W shows that the phillips version is a constant voltage and spot on.
The Phillips works with any number of LED MR16 lights up to the maximum wattage and holds its output voltage very well. The DETA version appears to be false advertising