An apparatus for driving a resonant circuit is disclosed. The apparatus comprises: a first drive circuit, the first drive circuit arranged to provide a drive current to said resonant circuit and a controller coupled to said first drive circuit, the first drive circuit further comprising: a first input adapted to receive a current from a power supply a switch a second input adapted to receive from said controller a signal to control said switch an output coupled to said resonant circuit a first inductor, which acts to set the drive current through said resonant circuit when the switch is closed and a first diode coupled across said first inductor, said first diode arranged to enable current to continue to flow in the first inductor when the switch is open, wherein the controller is adapted to receive from a sensor a signal derived from the current flowing in said resonant circuit, wherein said sensor is coupled to said controller, and said controller is configured to close said switch to enable the drive current to flow through said resonant circuit when said signal derived from said sensor satisfies a first condition and said controller is further configured to open said switch to cause the drive current to stop flowing through the resonant circuit when said signal derived from said sensor satisfies a second condition. In a preferred embodiment, the apparatus also comprises a forward diode in series with the switch, so as to allow the resonance to be driven to a greater amplitude than otherwise possible.La présente invention porte sur un appareil dexcitation dun circuit résonant. Lappareil comprend : un premier circuit dexcitation, le premier circuit dexcitation étant conçu pour fournir un courant dexcitation audit circuit résonant et un dispositif de commande couplé audit premier circuit dexcitation, le premier circuit dexcitation comprenant en outre : une première entrée conçue pour recevoir un courant provenant dune alimentation électrique un interrupteur une sec
