Switched Battery DC–DC Converters for Low-Power Applications

DC-DC conversion at an ultralow operating frequency is one potential solution to maintain high efficiency in cases of ultralow power delivery. Switched-capacitor converters (SCCs) have an inherent limitation to operate at low frequencies due to their charge-sharing losses. To overcome this issue, this article explores a new dc-dc conversion family based on switched batteries. The so-called switched-battery converter (SBC) is derived from the SCC by replacing the flying capacitors with batteries. The particular nature of the battery introduces constraints but offers degrees of freedom that redraw the trade-offs between switching frequency, charge-sharing losses, power density, and power efficiency. We demonstrate 97% power efficiency at 27 mW with only 100 Hz switching frequency using a button cell (69 mm3) to achieve a 2:1 voltage conversion ratio. We also propose a 3:1 topology and various battery experiments to generalize the concept.