Implantable medical device comprising a DC-DC converter

A step-up converter with a plurality of levels disposed in a subcutaneous implantable defibrillator, the step-up converter comprising:

• a transformer comprising a single primary winding and at least two secondary windings;
• a primary circuit comprising the single primary winding and a switching device, and
• a secondary circuit comprising the secondary windings and a plurality of step-up levels, the plurality of step-up levels comprising a first plurality of step-up levels associated with a first one of the at least two secondary windings and a second plurality of step-up levels associated with a second one of the at least two secondary windings, each step-up level comprising a first diode, a second diode, a first capacitor, and a second capacitor interconnected such that:
• an anode of the first diode is connected to a terminal of the first capacitor and to a cathode of the second diode;
• a terminal of the second capacitor is connected to a cathode of the first diode;
• and
• another terminal of the second capacitor is connected to an anode of the second diode;
• and
• wherein second capacitors of the plurality of step-up levels are connected in series and are surge capacitors configured to store energy for delivery of a shock by the subcutaneous implantable defibrillator;
• wherein first capacitors of the first plurality of step-up levels are connected in parallel with one another, and first capacitors of the second plurality of step-up levels are connected in parallel with one another.

A method for operating a step-up converter with a plurality of levels disposed in an implantable defibrillator

• the step-up converter comprising:
• a transformer having a single primary winding and a single secondary winding;
• a primary circuit including the single primary winding, a primary power source connected in series with the single primary winding, and a switching device connected in series with the single primary winding, and an inductor connected in series with the single primary winding and the switching device;
• and
• a secondary circuit comprising the single secondary winding and a plurality of step-up levels, each step-up level comprising a first diode, a second diode, a first capacitor, and a second capacitor interconnected such that (i) an anode of the first diode is connected to a terminal of the first capacitor and to a cathode of the second diode, (ii) a terminal of the second capacitor is connected to a cathode of the first diode, and (iii) another terminal of the second capacitor is connected to an anode of the second diode;
• and wherein second capacitors of the plurality of step-up levels are connected in series and are surge capacitors configured to store energy for delivery of a shock by the implantable defibrillator,
• the method comprising the steps of:
• a) closing the switching device during a first period such that the single primary winding stores energy according to a peak value of current in the primary circuit and the first capacitors are charged via the second diodes to voltages of the respective second capacitors;
• b) opening the switching device during a second period immediately after the first period such that energy is transferred from the first capacitors and the single secondary winding to the second capacitors;
• and
• (c) repeating steps a) and b) until a predefined output voltage is provided by the series-connected second capacitors;
• wherein closing the switching device establishes a current path including the primary power source, the inductor, the single primary winding, and the switching device, and opening the switching device interrupts the current path;
• wherein, during the repeating, the inductor reduces a current surge occurring when the switching device is closed;
• and
• wherein, over all or part of the repeating, at least one of (i) a duration of the first period or (ii) the peak value of current in the primary circuit progressively increases.