Patent ID: 7550897

Claim:
An electronic drive system for a droplet spray generation device of the type having a droplet generator including a perforate membrane driven by a piezoelectric transducer, the electronic drive system comprising: a drive circuit including a programmable micro-controller and a power supply for converting, in use, a battery supply voltage to power the device, a power amplifier connected to receive electric power from the power supply and supply a drive signal to the piezoelectric generator in use, the power amplifier comprising a resonant bridge circuit; and wherein the micro-controller is connected to the power amplifier and outputs, in use, a pair of signals in anti-phase to the resonant bridge circuit to control the operation of the power amplifier, including the drive signal operating frequency at substantially its resonant frequency, and wherein the micro-controller is arranged to measure the current provided to the power amplifier by the power supply at a plurality of different input frequencies, to determine, as the resonant frequency of the droplet generator, the frequency of such different input frequencies at which the maximum power is consumed by the amplifier, and to set the drive signal operating frequency at the resonant frequency.