Selectable boost converter and charge pump for compliance voltage generation in an implantable stimulator device
Improved compliance voltage generation circuitry for a medical device is disclosed. The improved circuitry in one embodiment comprises a boost converter and a charge pump, either of which is capable of generating an appropriate compliance voltage from the voltage of the battery in the device. A telemetry enable signal indicating whether the implant's transmitter, receiver, or both, have been enabled is received. A “boost” signal from compliance voltage monitor-and-adjust logic circuitry is processed with the telemetry enable signal and its inverse to selectively enable either the charge pump or the boost converter: if the telemetry enable signal is not active, the boost converter is used to generate the compliance voltage; if the telemetry enable signal is active, the charge pump is used. Because the charge pump circuitry does not produce a magnetic field, the charge pump will not interfere with magnetically-coupled telemetry between the implant and an external controller. By contrast, the boost converter is allowed to operate during periods of no telemetry, when magnetic interference is not a concern, while obtaining the advantage of higher power efficiency.
1. A method for generating a compliance voltage in a medical device, comprising:
determining the status of telemetry to or from the medical device;
if such determination indicates telemetry, enabling a first converter circuit to produce a compliance voltage from a battery voltage in the device;
if such determination does not indicate telemetry, enabling a second converter circuit of a type different from the first converter circuit to produce the compliance voltage from the battery voltage in the device, wherein the first converter circuit and the second converter circuit are connected in parallel between the battery voltage and the compliance voltage; and
using the compliance voltage to power circuitry used to stimulate a patient's tissue via electrodes.
2. The method of claim 1 , wherein determining the status of telemetry comprises determining if telemetry has been enabled.
3. The method of claim 1 , wherein determining the status of telemetry comprises determining if telemetry is actually occurring.
4. The method of claim 1 , wherein the compliance voltage is adjustable depending on the power it must provide at any given time.
5. The method of claim 1 , wherein the compliance voltage produced by the first converter circuit is not adjustable, and wherein the compliance voltage produced by the second converter circuit is adjustable.
6. The method of claim 1 , wherein the first converter circuit does not contain an inductor, and wherein the second converter circuit does contain an inductor.
7. The method of claim 1 , wherein the first converter circuit generates a first amount of interference with telemetry circuitry in the medical device, wherein the second converter circuit generates a second amount of interference with telemetry circuitry in the medical device, and wherein the second amount is higher than the first amount.
8. The method of claim 1 , wherein the first converter circuit comprises a capacitor-based change pump, and wherein the second converter circuit comprises an inductor-based boost converter.
9. The method of claim 1 , wherein the medical device is an implantable medical device.
10. The method of claim 9 , wherein the implantable medical device comprises an implantable stimulation device.
11. The method of claim 1 , wherein the first converter circuit is not enabled when the second converter circuit is enabled, and wherein the second converter circuit is not enabled when the first converter circuit is enabled.