Systems and methods for driving nebulizers

Abstract

In various arrangements, a nebulizer element of a nebulizer may be energized with a drive signal. A phase offset of the drive signal may be measured. A phase delta may be determined. The phase delta may indicate a difference between a target phase offset and the measured phase offset. The target phase offset may indicate a non-zero target phase difference between the voltage of the drive signal and the current of the drive signal. A frequency of the drive signal may be changed to decrease the phase delta.

What is claimed is: 
     
         1 . A nebulizer system, the nebulizer system comprising:
 a liquid reservoir for storing liquid;   a nebulizer, comprising a nebulizer element having a plurality of apertures, wherein:
 the nebulizer element is vibrated to atomize liquid from the liquid reservoir; and 
 the nebulizer element is driven by a drive signal; 
   a driver that outputs the drive signal, the driver comprising:
 a frequency generator; 
 a phase shift detector configured to measure a phase offset indicative of a phase difference between a voltage of the drive signal and a current of the drive signal; and 
 a processing system configured to:
 determine a phase delta indicative of a difference between a non-zero target phase offset and the measured phase offset; 
 change a frequency of the drive signal that is output by the frequency generator to decrease the phase delta; and 
 adjust a voltage magnitude of the drive signal used to drive the nebulizer element, wherein adjusting the voltage magnitude compensates for a change in flow rate caused by a decrease in pressure developing within the liquid reservoir as liquid is atomized. 
 
   
     
     
         2 . The nebulizer system of  claim 1 , wherein the processing system is further configured to change the frequency of the drive signal that is output by the frequency generator to decrease the phase delta comprises the processing system being configured to:
 change the frequency of the drive signal that is output by the frequency generator to decrease the phase delta to less than a threshold phase delta in a high gain mode, wherein while in the high gain mode the processing system performs larger frequency adjustments than while operating in a low gain mode;   after changing the frequency of the drive signal in the high gain mode, determine the phase delta is less than the threshold phase delta; and   change the frequency of the drive signal that is output by the frequency generator to decrease the phase delta using the low gain mode based on determining the phase delta is less than the threshold phase delta.   
     
     
         3 . The nebulizer system of  claim 2 , wherein the processing system is further configured to determine a slope of the phase offset as the frequency of the drive signal is changed. 
     
     
         4 . The nebulizer system of  claim 3 , wherein the processing system operating in the low gain mode to change the frequency of the drive signal that is output by the frequency generator is conditioned on the slope of the phase offset being negative as frequency increases. 
     
     
         5 . The nebulizer system of  claim 1 , wherein the processing system is further configured to calculate an impedance of the nebulizer element using the voltage of the drive signal and the current of the drive signal. 
     
     
         6 . The nebulizer system of  claim 5 , wherein the processing system changing the frequency of the drive signal in the low gain mode is conditioned on the impedance of the nebulizer element being below a stored impedance threshold. 
     
     
         7 . The nebulizer system of  claim 1 , wherein the threshold phase delta is five degrees or less. 
     
     
         8 . The nebulizer system of  claim 11 , wherein the target phase offset between 25 degrees and 35 degrees. 
     
     
         9 . The nebulizer system of  claim 1 , wherein the processing system is further configured to limit changing of the voltage magnitude by a stored threshold rate such that the voltage magnitude is not decreased at a rate greater than the stored threshold rate. 
     
     
         10 . A nebulizer apparatus, the nebulizer apparatus comprising:
 a liquid storage means;   a nebulizer means comprising a vibratable means having a plurality of apertures, wherein:
 the vibratable means is vibrated to atomize liquid from the liquid storage means; and 
 the vibratable means is driven by a drive signal; 
   a driver means that outputs the drive signal, the driver means comprising:
 a frequency generation means; 
 a phase shift detection means that measures a phase offset indicative of a phase difference between a voltage of the drive signal and a current of the drive signal; and 
   a processing means configured to:
 determine a phase delta indicative of a difference between a non-zero target phase offset and the measured phase offset; 
 change a frequency of the drive signal that is output by the frequency generator to decrease the phase delta; and 
 adjust a voltage magnitude of the drive signal used to drive the vibratable means, wherein adjusting the voltage magnitude compensates for a change in flow rate caused by a decrease in pressure developing within the liquid storage means. 
   
     
     
         11 . The nebulizer apparatus of  claim 10 , wherein the processing means is further configured to change the frequency of the drive signal that is output by the frequency generator to decrease the phase delta comprises the processing means being configured to:
 change the frequency of the drive signal that is output by the frequency generation means to decrease the phase delta to less than a threshold phase delta in a high gain mode, wherein while in the high gain mode the processing means performs larger frequency adjustments than while operating in a low gain mode;   after changing the frequency of the drive signal in the high gain mode, determine the phase delta is less than the threshold phase delta; and   change the frequency of the drive signal that is output by the frequency generation means to decrease the phase delta using the low gain mode based on determining the phase delta is less than the threshold phase delta.   
     
     
         12 . The nebulizer apparatus of  claim 10 , wherein the processing means is further configured to determine a slope of the phase offset as the frequency of the drive signal is changed. 
     
     
         13 . The nebulizer apparatus of  claim 12 , wherein the processing means operating in the low gain mode to change the frequency of the drive signal that is output by the frequency generation means is conditioned on the slope of the phase offset being negative as frequency increases. 
     
     
         14 . The nebulizer apparatus of  claim 10 , wherein the threshold phase delta is five degrees or less. 
     
     
         15 . The nebulizer apparatus of  claim 14 , wherein the target phase offset between 25 degrees and 35 degrees. 
     
     
         16 . A method for atomizing liquid, the method comprising:
 storing, using a liquid reservoir of a nebulizer system, a liquid;   outputting, by a nebulizer driver to a nebulizer element, a drive signal having a frequency and a magnitude;   vibrating the nebulizer element comprising a plurality of apertures to atomize liquid from the liquid reservoir, the nebulizer element being caused to vibrate by the drive signal;   measuring a phase offset of the drive signal, the phase offset being indicative of a phase difference between a voltage of the drive signal and a current of the drive signal;   determining a phase delta indicative of a difference between a non-zero target phase offset and the measured phase offset;   changing a frequency of the drive signal to decrease the phase delta; and   adjusting a voltage magnitude of the drive signal to compensate for a change in flow rate caused by a decrease in pressure developing within the liquid reservoir as liquid is atomized by the nebulizer element.   
     
     
         17 . The method for atomizing liquid of  claim 16 , wherein changing the frequency of the drive signal to decrease the phase delta comprises:
 changing the frequency of the drive signal to decrease the phase delta to less than a threshold phase delta in a high gain mode, wherein while in the high gain mode the processing system performs larger frequency step size adjustments than while operating in a low gain mode;   after changing the frequency of the drive signal in the high gain mode, determining the phase delta is less than the threshold phase delta; and   after changing the frequency of the drive signal in the high gain mode and determining the phase delta is less than the threshold phase delta, changing the frequency of the drive signal to decrease the phase delta using the low gain mode.   
     
     
         18 . The method for atomizing liquid of  claim 16 , further comprising:
 determining a slope of the phase offset as the frequency of the drive signal is changed, wherein changing mode from the high gain mode to the low gain mode is conditioned on the slope of the phase offset being negative as frequency increases.   
     
     
         19 . The method for atomizing liquid of  claim 16 , wherein the threshold phase delta is five degrees or less. 
     
     
         20 . The method for atomizing liquid of  claim 19 , wherein the target phase offset between 25 degrees and 35 degrees.