Method of controlling an implantable medical device with optimized pump drive

Abstract

Method of controlling an implantable medical device having a power source having a voltage, a therapeutic substance pump driven by a motor, electrically coupled to the power source, supplied with a series of drive pulses having a duty cycle. The voltage of the power source is measured. The duty cycle of drive pulses to the motor are varied by increasing the duty cycle as the voltage of the power source decreases.

1 . A method for reducing energy consumption in an implantable infusion device having a stepper motor driving an infusion pump and powered by a power source having a power source voltage, said stepper motor being driven by drive pulses, comprising: 
 receiving an instruction to infuse a therapeutic substance;    measuring said power source voltage;    calculating a duty cycle of said drive pulses for delivery within a substantially fixed drive interval to operate said stepper motor;    increasing said duty cycle of said drive pulses within said substantially fixed drive interval to operate said stepper motor as said power source voltage decreases; and    infusing said therapeutic substance when said stepper motor operates said infusion pump to meter said therapeutic substance.    
   
   
       2 . A method as in  claim 1  further comprising the steps of: 
 specifying a fixed drive interval for said drive pulses to be delivered to said stepper motor to operate said infusion pump according to a therapy program; and    generating a predetermined number of drive pulses within said drive interval according to said power supply voltage to reduce motor energy consumption.    
   
   
       3 . A method as in  claim 2  wherein said predetermined number of drive pulses is in a range from about 10 to about 25 drive pulses within said substantially fixed drive interval.  
   
   
       4 . A method as in  claim 2  wherein said drive interval has a duty cycle in a range from about 75% to about 100% of the step interval.  
   
   
       5 . A method as in  claim 2  wherein said predetermined number of drive pulses is selected to operate the stepper motor while substantially maintaining motor stability and substantially avoid motor stall.  
   
   
       6 . A method as in  claim 1  further comprising the step of using logic contained in registers to configure said drive pulses.  
   
   
       7 . A method as in  claim 6  wherein said registers include a pulse interval register, a drive pulse width register, a drive pulse duty cycle register, and a drive pulse expiration register.  
   
   
       8 . A method as in  claim 1  further comprising the step of forecasting said power source voltage and adjusting said duty cycle in response thereto.  
   
   
       9 . A method of controlling an implantable medical device having a power source having a voltage, a therapeutic substance pump driven by a motor, electrically coupled to said power source, supplied with a series of drive pulses having a duty cycle, comprising the steps of: 
 measuring said voltage of said power source; and    varying said duty cycle of drive pulses to said motor by increasing said duty cycle as said voltage of said power source decreases.    
   
   
       10 . A method as in  claim 9  wherein said motor comprises a stepper motor.  
   
   
       11 . A method as in  claim 9  further comprising the step of generating said series of drive pulses in a substantially fixed drive interval.  
   
   
       12 . A method as in  claim 11  further comprising the steps of: 
 specifying said fixed drive interval according to a therapy program; and    generating a predetermined number of drive pulses within said drive interval according to said power supply voltage to reduce motor energy consumption.    
   
   
       13 . A method as in  claim 12  wherein said predetermined number of drive pulses is in a range from about 10 to about 25 drive pulses within said substantially fixed drive interval.  
   
   
       14 . A method as in  claim 12  wherein said duty cycle comprises a range from about 75% to about 100% of said drive interval.  
   
   
       15 . A method as in  claim 12  wherein said predetermined number of drive pulses is selected to operate the stepper motor while substantially maintaining motor stability and substantially avoid motor stall.  
   
   
       16 . A method as in  claim 9  further comprising the step of forecasting said power source voltage and adjusting said duty cycle in response thereto.  
   
   
       17 . A method as in  claim 9  wherein said implantable infusion device has electronics coupled to said motor and to said power source, said electronics having a processor, memory coupled to the processor and an infusion program residing in said memory, further comprising the step of modifying said infusion program once said therapeutic infusion device is implanted.  
   
   
       18 . A method as in  claim 17  further comprising the step of externally receiving therapeutic substance infusion device information.  
   
   
       19 . A method as in  claim 18  further comprising the step of externally transmitting therapeutic substance infusion device information.