Multi-channel constant current source and illumination source

A multi-channel circuit having respective channels powered through transformers having primary windings connected in series allows substantially equal constant currents to be provided through all channels by cross-regulation while only a single channel need be monitored and controlled. The variation in current between channels is generally small and largely insensitive to imbalances between voltages on loads due, for example, to different numbers of LEDs in series connected strings in illumination devices and can be further reduced by inverse coupling between inductors in respective channels. Efficiency is improved through reduction in the number of stages of the constant current source since the respective channels provided both DC-to-DC conversion and constant current regulation.