Conversion circuits (1) convert first signals coming from fluorescent ballasts (101) into second signals for light circuits (2) comprising light emitting diodes to replace discharge lamps (102). The conversion circuits (1) comprise input stages (11) with at least two inputs (21-24, 31-32) for receiving the first signals, output stages (13) with two outputs (71-72) for supplying the second signals, and reactive stages (12) for coupling the input and output stages (11, 13). Such relatively simple conversion circuits (1) are relatively low-cost and relatively robust. The reactive stages (12) comprise reactive circuits and reduce amplitudes of one or more of the first and second signals. The reactive circuits comprise one or more inductors (41, 42) and/or capacitors (43).The conversion circuits (1) may form part of the fluorescent ballasts (101) or may form part of the light circuits (2) or may partly form part of the fluorescent ballasts (101) and may partly form part of the light circuits (2).