Active implantable medical device which includes a circuit of RF telemetry
An active implantable medical device having an RF telemetry circuit. The device is in particular a stimulation, resynchronization, defibrillation and/or cardioversion device. It includes a principal circuit, an RF telemetry auxiliary circuit and a supply battery for the principal and auxiliary circuits. It is envisaged to have between the supply battery and the auxiliary circuit a regulating circuit including an accumulator of electric power coupled with the auxiliary circuit to deliver a current ready to feed the auxiliary circuit, and a load circuit coupled with the supply battery to maintain the accumulator on a predetermined level of load.
1. An active implantable medical device, comprising:
a principal circuit;
an auxiliary RF telemetry circuit;
a supply battery having an internal resistance;
a voltage multiplying stage comprising a plurality of condensers connected by a plurality of switches for multiplying a voltage delivered by the supply battery by charging the plurality of condensers; and
a regulating circuit comprising an accumulator, the accumulator having a load level and being connected to a load circuit,
wherein the supply battery, while providing power to the principal circuit with a first voltage, charges the plurality of condensers of the voltage multiplying stage during a first phase of a variable period and charges the accumulator to a second voltage by changing connectivity among the plurality of condensers using the plurality of switches during a second phase of the variable period;
wherein the load circuit detects a terminal voltage of the accumulator; and
wherein the accumulator delivers power with the second voltage to the auxiliary RF telemetry circuit, and the load circuit maintains the accumulator at a predetermined load level by varying the variable period and/or controlling at least one switch of the plurality of switches of the regulating circuit in response to the detected terminal voltage of the accumulator.
2. The device of claim 1 , wherein said accumulator is a rechargeable battery.
3. The device of claim 1 , wherein said accumulator is a condenser.
4. The device of claim 1 , wherein a voltage corresponding to the predetermined load level is higher than the voltage delivered by the supply battery.
5. The device of claim 4 , wherein the voltage multiplying stage delivers an exit voltage higher than the voltage delivered by the supply battery to the accumulator.
6. The device of claim 1 , wherein the load circuit is configured for intermittent and cyclic operation having a cyclic report/ratio.
7. The device of claim 6 , wherein the cyclic report/ratio is a variable report/ratio function of the internal resistance of the supply battery, and wherein a relative duration of the variable period of the time cycle decreases when the internal resistance increases.
8. The device of claim 6 , wherein the cyclic report/ratio is a variable report/ratio function of the load level of the accumulator, and wherein a relative duration of the variable period of the time cycle decreases when the load level increases.
9. The device of claim 1 , wherein the load circuit can stop the load of the accumulator when a level of terminal voltage of the accumulator reaches a predetermined upper limit.
10. The device of claim 1 , wherein the load circuit can stop the load of the accumulator when a charging current of the accumulator reaches a predetermined lower limit.
11. The device of claim 1 , wherein the load circuit can stop the load of the accumulator after completion of a given maximum duration.
12. The device of claim 1 , wherein the plurality of condensers comprises a first condenser, a serial condenser comprising a second condenser and a third condenser,
wherein, during the first phase of the variable period, the first condenser is parallelly connected to the serial condenser between a ground terminal and a high voltage terminal, the second condenser and the third condenser of the serial condenser are serially connected at a midpoint, and the high voltage terminal of the serial condenser is connected to the high voltage terminal of the supply battery using a first switch of the plurality of switches, and
wherein, during the second phase of the variable period, the ground terminal of the first condenser is connected to the midpoint of the serial condenser using a second switch of the plurality of switches, and the high voltage terminal of the serial condenser is opened using the first switch of the plurality of the switches.
13. The device of claim 1 , wherein the load circuit comprises a comparator and a plurality of serially connected voltage divider resistors.
14. The device of claim 13 , wherein the comparator compares the terminal voltage of the accumulator with a reference voltage.
15. The device of claim 14 , wherein the regulating circuit stops charging the accumulator if the terminal voltage of the accumulator reaches an upper threshold voltage.
16. The device of claim 14 , wherein the regulating circuit resumes charging the accumulator if the terminal voltage of the accumulator falls below a lower threshold voltage.