I don't think there's anything odd going on with your dimmer. The circuit inside a dimmer is often a simple RC filter (with variable R) to delay the arrival of the trigger voltage at the triac gate. These things are made as cheap as possible so precision components are out.
The poor designer has to come up with something that will work in the worst possible case using parts with a very wide tolerance. The result is that some dimmers do not use all of their available knob movement. I bought a cheap one from s***wf*x which does exactly the same - and the mechanical construction is rubbish too! I'll be getting a new one.
Incidentally, with this simple kind of dimmer the minimum load exists because a triac has a minimum hold-on current. Once triggered, a traic stays on until the current drops below this limit (unless the trigger voltage is still present). If the load is too small the triac can switch off early.
The poor designer has to come up with something that will work in the worst possible case using parts with a very wide tolerance. The result is that some dimmers do not use all of their available knob movement. I bought a cheap one from s***wf*x which does exactly the same - and the mechanical construction is rubbish too! I'll be getting a new one.
Incidentally, with this simple kind of dimmer the minimum load exists because a triac has a minimum hold-on current. Once triggered, a traic stays on until the current drops below this limit (unless the trigger voltage is still present). If the load is too small the triac can switch off early.
