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In this paper, a low cost electronic ballast with power factor correction for 250 W high pressure sodium vapour lamps is presented. The electronic ballast is based on a two-stage scheme. The first stage realises the power factor correction by using a CC/CC buck converter operating in discontinuous conduction mode (DCM) and constant duty cycle meeting the standard IEC 1000 3-2 with a very low cost circuit. The second stage is based on a resonant full-bridge LCC series-parallel inverter with resonant current mode control and optimum commutations. This current mode control minimises the losses in the switches and the return of power to the input power supply.