Droplet spray generation device

Abstract

An electronic drive system for a droplet spray generation device (10) has a droplet generator (II) with a perforate membrane (32) driven by a piezoelectric transducer (31). An electronic circuit controls a power supply (21) to control the charging of a capacitor (22) to a supply voltage providing power to a power amplifier (23) connected to receive electric power from the capacitor and supply a drive signal to the piezoelectric transducer. The electronic circuit is also arranged to control the operation of the power amplifier (23) including the drive signal operating frequency at substantially its resonant frequency, where the resonant frequency is calculated by measuring and/or timing changes to the voltage across the capacitor when the droplet generator is operated in a plurality of bursts at different frequencies, by charging the capacitor (22) to a given voltage, and either actuating the droplet generator for a given time and either measuring the voltage drop across the capacitor at the end of the given time or the time taken to recharge the capacitor to the set value thereafter, or actuating the droplet generator and measuring the time taken for the voltage to fall to a known value, and determining as the resonant frequency of the droplet generator, the frequency at which respectively the time to recharge is the greatest, or the voltage drop is the greatest, or the time taken for the voltage to fall to the known value is shortest, and to set the drive signal operating frequency at the resonant frequency thus determined.

Dependencies are inferred from the claim text.