External Charger for Determining Alignment with an Implantable Medical Device Using One or More Sense Coils

A method for wirelessly providing energy to an implantable medical device (IMD), comprising:

• energizing a charging coil in an external charger using a drive signal to produce a magnetic field to wirelessly provide energy to the IMD during a charging session;
• adjusting a frequency of the drive signal to a resonant frequency during the charging session;
• and
• storing an initial value of the adjusted frequency and thereafter continuing to receive the adjusted frequency, and
• determining an alignment between the charging coil and the IMD by assessing a difference between the received adjusted frequency and the initial value.

A computer readable medium comprising instructions executable in an external charger for wirelessly providing energy to an implantable medical device (IMD), wherein the instructions when executed are configured to:

• energize a charging coil in the external charger using a drive signal to produce a magnetic field to wirelessly provide energy to the IMD during a charging session;
• adjust a frequency of the drive signal to a resonant frequency during the charging session;
• and
• store an initial value of the adjusted frequency and thereafter continue to receive the adjusted frequency, and
• determine an alignment between the charging coil and the IMD by assessing a difference between the received adjusted frequency and the initial value.