A control device for an ultrasonic piezoelectric actuator including a first stage supplied by a DC voltage source and including a mechanism forming a second DC voltage above that voltage delivered by the DC voltage source, and a second stage including a mechanism amplifying the second voltage and chopping the voltage obtained by excitation of the actuator with the chopped voltage, under control of a computer. The amplifying mechanism includes an inductor in electrical resonance with the piezoelectric actuator. The inductor is connected to the first stage so as to constitute, during formation of the second voltage, a secondary winding of a transformer forming part of a flyback voltage converter introduced into the first stage to develop the second voltage. The control device may find application to control of a fuel injector in an internal combustion engine.