What is the idea behind this circuit?

Simple Current Source (real loaded)

Idea: Depreciating the losses by significant additional losses and energy.

The combination of a voltage source and a voltage-to-current converter acts as a simple current source.

The simple current source becomes imperfect when a real load (e.g. having a varying ohmic resistance or voltage) is applied.

Observing the odd idea above, we add significant additional losses than the ones caused by the load and also increase the input voltage. As a result, the load's losses are depressed. Now, both the voltage source and the voltage-to-current converter define the output current predominantly.

Implementation: Increasing the resistance Ri and the voltage V.

The simple current source sonsists of a voltage source and a humble resistor connected in series.  If the output is shortened, a constant current will flow through the circuit. Click to view full-size picture.

We may see this idea in the beginning of any book on basic electricity where the resistance Ri and the voltage V are increased so that Ri >> RL and V >> VRL. As a result, an almost constant current I=V/Ri flows through the circuit.

If we continue increasing these quantities up to infinity, we will get the classic ideal current source. Only, this simple circuit has a big disadvantage - a whole lot of energy dissipates over the internal resistance Ri.