Abstract: A start-up delay circuit for an electronic ballast for "instant-start" type fluorescent lamps of the type having an electronic converter powered by an active electronic preregulator. The converter is an inductive-capacitive parallel-resonant push-pull circuit or other type of current-fed power-resonant circuit. The preregulator may be a boost-type. The start-up circuit may be either a resistor and zener diode or resistor, capacitor and diac network or programmable unijunction transistor circuit connected between the preregulator output and an oscillation-enabling input of the converter.