Detector for electromagnetic fields
A battery-powered electrical device is disclosed, which may be implemented as an implantable medical device, wherein the device contains at least one battery voltage monitoring unit which is designed to monitor a voltage profile at a battery during the charging of a capacitor, via a transformer in a charging circuit, and which on the basis of the voltage characteristic is able to specify a magnetic presaturation of the transformer, and one control unit which terminates the charging process whenever a predefined threshold value for the magnetic presaturation of the transformer is exceeded.
1. A battery-powered electrical device, comprising:
a battery voltage monitoring unit configured to
monitor a voltage profile at a battery during charging of a capacitor, via a transformer in a charging circuit, and
specify a magnetic presaturation of the transformer based on the voltage profile; and
a control unit configured to terminate charging of the capacitor whenever a predefined threshold value of the magnetic presaturation of the transformer is reached or exceeded;
wherein the device is configured to be placed in an MRI-safe state by programming; and
wherein the control unit is further configured to place the battery-powered electrical device in the MRI-safe state for a prescribed period of time.
2. The battery-powered electrical device according to claim 1 , wherein the exceedance of the threshold value of the magnetic presaturation of the transformer is configured to be detected by measuring a minimum battery voltage during charging.
3. The battery-powered electrical device according to claim 1 , wherein the exceedance of the threshold value of the magnetic presaturation of the transformer is configured to be detected by measuring a maximum battery voltage gradient dU/dt at a start of the charging.
4. The battery-powered electrical device according to claim 1 , wherein the exceedance of the threshold of the magnetic presaturation of the transformer is configured to be detected by measuring a maximum voltage difference before and during charging.
5. The battery-powered electrical device according to claim 1 , wherein the exceedance of the threshold of the magnetic presaturation of the transformer is configured to be detected by measuring a minimum battery voltage during charging, and a maximum voltage difference before and during charging.
6. The battery-powered electrical device according to claim 1 , wherein a charging current when charging is configured to be limited such that the battery voltage is not less than a minimum value.
7. The battery-powered electrical device according to claim 1 , wherein when charging is terminated, the charging circuit is configured to be deactivated for a first period of time.
8. The battery-powered electrical device according to claim 7 , wherein the charging circuit is deactivated by a series of time intervals.
9. The battery-powered electrical device according to claim 1 , wherein transition to the MRI-safe state is configured to be transmitted by telemetric remote monitoring.
10. The battery-powered electrical device according to claim 1 , wherein the device is an implantable medical device (IMD).
11. The battery-powered electrical device according to claim 10 , wherein the IMD is an implantable defibrillator/cardioverter (ICD).
12. The battery-powered electrical device according to claim 11 , wherein said MRI-safe state includes suppression of delivery of high-voltage shocks.
13. The battery-powered electrical device according to claim 11 , wherein said MRI-safe state includes patient dependent stimulation modes.