LED Driving Stage with Coupled Coils Without Capacitors

An LED driver with the possibility to control the illumination and at the same time send out information is treated. The converter is very simple and does not need capacitors for the energy transfer. The storage medium of the energy is a tapped inductor or two magnetically coupled windings. The function of the converter is explained. The current is controlled by a very simple two-point controller. The input current ripple is determined by the hysteresis of the two-point controller. Hints on dimensioning are given and the influence of the parasitic inductances at the input and at the output and the leakage of the coupled coils is studied and a remedy is shown to avoid pronounced overvoltage and ringing at the components. The dynamics of the converter are treated. Variants of the converter are shown and discussed. The considerations are proved with the help of LTSpice.