Method and apparatus for supplying energy to a medical device

Abstract

In a method and apparatus for supplying wireless energy to a medical device implanted in a patient, wireless energy is transmitted from an external energy source located outside a patient and is received by an internal energy receiver located inside the patient, for directly or indirectly supplying received energy to the medical device. An energy balance is determined between the energy received by the internal energy receiver and the energy used for the medical device, and the transmission of wireless energy is then controlled based on the determined energy balance. The energy balance thus provides an accurate indication of the correct amount of energy needed, which is sufficient to operate the medical device properly, but without causing undue temperature rise.

1 .- 220 . (canceled) 
     
     
         221 . A method for controlling transmission of wireless energy supplied to an electrically operable medical device when implanted in a patient, wherein the method comprises transmitting said wireless energy from an external energy source located outside the patient, and receiving said wireless energy by an internal energy receiver located inside the patient, the internal energy receiver being connected to the medical device for directly or indirectly supplying received energy thereto, the method further comprising:
 determining an energy balance between the energy received by the internal energy receiver and the total energy used for the medical device,   determining the energy balance, by an internal control unit or external control unit, during the transmission of wireless energy,   transmitting feedback information from inside the body to be able to control the wireless energy supply sent by the external energy source,   and   controlling the transmission of wireless energy from the external energy source, based on the determined energy balance, the transmission of wireless being controlled in accordance with at least one of:
 an energy reception rate in the internal energy receiver compared to an total rate of used energy being consumption rate, storage rate or combined consumption and storage rate, and 
 directly or indirectly measuring over time the difference between the total amount of energy received by the internal energy receiver and the total amount of used energy being consumed, stored or combined consumed and stored energy, and determining the energy balance based on at least one of: said difference and a detected change in said difference. 
   
     
     
         222 . The method according to  claim 221 , wherein the wireless energy is transmitted inductively from a primary coil in the external energy source to a secondary coil in the internal energy receiver. 
     
     
         223 . The method according to  claim 221 , further comprising detecting at least one of:
 a change in said energy balance, and controlling the transmission of wireless energy based on said detected energy balance change, wherein the amount of transmitted wireless energy is decreased if the detected energy balance change implies that the energy balance is increasing, or increased if the detected energy balance change implies that the energy balance is decreasing, wherein the decrease/increase of energy transmission corresponds to a detected change rate, and   a difference between energy received by said internal energy receiver and energy used for the medical device, and controlling the transmission of wireless energy based on said detected energy difference, wherein the amount of transmitted wireless energy is decreased if the detected energy difference implies that the received energy is greater than the used energy, or increased if the detected energy balance change implies that the energy balance is decreasing, wherein the decrease/increase of energy transmission corresponds to the magnitude of said detected energy difference.   
     
     
         224 . The method according to  claim 223 , wherein the energy used for the medical device is handled in at least one of the following alternatives: a) consuming substantially all energy used for the medical device to operate the medical device, b) storing substantially all energy used for the medical device in at least one energy storage device and c) partly consuming the energy used for the medical device to operate the medical device and partly store the energy in said at least one energy storage device. 
     
     
         225 . The method according to  claim 224 , wherein the energy is consumed or stored after being stabilized in at least one energy stabilizing unit of the medical device. 
     
     
         226 . The method according to  claim 225 , wherein the wireless energy is first transmitted with a predetermined energy rate, and then transmitted based on the energy balance, which is determined by detecting the direction and rate of change in the current amount of accumulated energy in the energy stabilizing unit. 
     
     
         227 . The method according to  claim 225 , wherein said energy stabilizing unit includes at least one of: an accumulator, a capacitor or a semiconductor adapted to stabilize the received energy. 
     
     
         228 . The method according to  claim 224 , wherein the energy balance is determined based on a detected change followed over time in the amount of consumed, stored or consumed and stored energy. 
     
     
         229 . The method according to  claim 228 , wherein the change in the amount of consumed, stored or consumed and stored energy is detected by determining over time the derivative of a measured electrical parameter related to said amount of consumed, stored or consumed and stored energy, the derivative at a first given moment corresponding to the rate of the change at the first given moment, wherein the rate of change includes the direction and speed of the change. 
     
     
         230 . The method according to  claim 229 , wherein said derivative is determined based on a detected rate of change of the electrical parameter. 
     
     
         231 . The method according to  claim 221 , wherein the energy received by the internal energy receiver is supplied to the medical device with at least one of; at least one constant voltage, wherein the constant voltage is created by a constant voltage circuitry and at least one constant current, wherein the constant current is created by a constant current circuitry. 
     
     
         232 . The method according to  claim 231 , wherein the energy is supplied with at least one of: at least two different voltages, including the at least one constant voltage and at least two different currents, including said at least one constant current. 
     
     
         233 . The method according to  claim 223 , wherein said detected difference being related to the integral over time of at least one measured electrical parameter related to said energy balance, wherein said integral of the electrical parameter relates to the energy balance as an accumulated difference between the total amount of energy received by said internal energy receiver and the total amount of consumed energy, stored energy or consumed and stored energy. 
     
     
         234 . The method according to  claim 223 , wherein values of said electrical parameter are plotted over time as a graph in a parameter-time diagram, and wherein said integral is determined from the size of the area beneath the plotted graph. 
     
     
         235 . The method according to  claims 223 , wherein an energy storage device is provided comprising at least one of: a rechargeable battery, an accumulator or a capacitor. 
     
     
         236 . The method according to  claim 221 , further comprising:
 providing a first electric circuit to supply electrical pulses to the external transmitting device, said electrical pulses having leading and trailing edges, said transmitting device adapted to supply wireless energy, wherein
 the electrical circuit being adapted to vary the lengths of at least one of:
 first time intervals between successive leading and trailing edges of the electrical pulses, and 
 second time intervals between successive trailing and leading edges of the electrical pulses, and 
 
   providing the transmitted wireless energy, generated from the electrical pulses having a varied power, the power depending on the lengths of the first, second or first and second time intervals.   
     
     
         237 . The method according to  claim 236 , wherein the frequency of the electrical pulses is substantially constant when varying the first, second or first and second time intervals, wherein the amplitude of the electrical pulses is substantially constant when varying the first, second or first and second time intervals, when applying electrical pulses, so that the electrical pulses remain unchanged, except for varying the first, second or first and second time intervals. 
     
     
         238 . The method according to  claim 236 , further comprising:
 supplying a train of two or more electrical pulses in a row, said train having a first electrical pulse at the start of the pulse train and having a second electrical pulse at the end of the pulse train, and   supplying two or more pulse trains in a row, wherein the lengths of the second time intervals between successive trailing edge of the second electrical pulse in a first pulse train and leading edge of the first electrical pulse of a second pulse train are varied.   
     
     
         239 . The method according to  claim 238 , wherein, when electrical pulses are applied, at least one of: the electrical pulses within the pulse trains, and the pulse trains themselves having at least one of: a substantially constant frequency, a substantially constant current and a substantially constant voltage. 
     
     
         240 . The method according to  claim 236 , wherein the wireless energy is transmitted in a substantially inductive way from the external energy source to the receiver and wherein the electrical pulses are released from the first electrical circuit with at least one of: a frequency and time period between leading edges of the consecutive pulses, so that when the lengths of the first, second or first and second time intervals are varied, the resulting transmitted energy varied. 
     
     
         241 . The method according to  claim 240 , wherein the circuit formed by the first electric circuit and the external energy source has a first characteristic time period or first time constant, and when effectively varying the transmitted energy, such frequency time period is in the range of the first characteristic time period or time constant or shorter.