A negative pressure wound therapy device includes at least one piezoelectric pump and a control circuit. The control circuit is configured to generate a first control signal to control operation of the at least one piezoelectric pump, the control signal having a first root mean square (RMS) voltage, transmit the first control signal to the at least one piezoelectric pump, identify at least one of a change of state of the at least one piezoelectric pump or an expiration of a duration of time associated with operation of the at least one piezoelectric pump, responsive to identifying the at least one of the change of state or the expiration of the duration of time, generate a second control signal having a second RMS voltage less than the first RMS voltage, and transmit the second control signal to the at least one piezoelectric pump.

The invention in question pertains to the technological field of refrigeration compressors. A hermetic compressor for positive displacement is disclosed whose airtight housing is specially altered so that its natural frequencies of vibration are distributed at frequencies above 4200 Hz and whose “capacitance density” is greater than 160 W/L.

A negative pressure wound therapy device includes at least one piezoelectric pump and a control circuit. The control circuit is configured to generate a first control signal to control operation of the at least one piezoelectric pump, the control signal having a first root mean square (RMS) voltage, transmit the first control signal to the at least one piezoelectric pump, identify at least one of a change of state of the at least one piezoelectric pump or an expiration of a duration of time associated with operation of the at least one piezoelectric pump, responsive to identifying the at least one of the change of state or the expiration of the duration of time, generate a second control signal having a second RMS voltage less than the first RMS voltage, and transmit the second control signal to the at least one piezoelectric pump.

A linear compressor and methods of operation, for example, to control a setpoint and vary cooling capacity of the linear compressor, are provided herein. An appliance may include a linear compressor having a reciprocating piston movable in a negative axial direction toward a chamber and positive axial direction away from the chamber. The appliance may further include a motor operatively coupled to the reciprocating piston, the motor having a resting setpoint, an inverter configured to supply a variable frequency waveform to the motor, and a controller configured to control the variable frequency waveform. The controller may be configured to direct a positive DC voltage to the motor to shift the resting setpoint to increase a cooling capacity of the linear compressor.

A hermetic compressor for positive displacement is disclosed whose airtight housing is specially altered so that its natural frequencies of vibration are distributed at frequencies above 4200 Hz and whose capacitance density is greater than 160 W/L.