New Topology for DC–DC Converters Used in Fuel Cell–Electric Double Layer Capacitor Hybrid Power Source Systems for Mobile Devices

Abstract

An improved topology for dc-dc converters used in hybrid power source systems, which consist of a fuel cell (FC) and electric double-layer capacitors (EDLCs), is proposed. The new topology has three transistors, and switch timing for this topology and a control method for power management between the FC and EDLCs are discussed. This new topology overcomes the two drawbacks of the previous topology with two transistors and a diode: the slightly higher load voltage and insufficient EDLC charging under low-load conditions. The introduction of two switching modes allows for the bidirectional current of the EDLCs and enables power distribution between the FC and EDLCs. A pseudo FC and bipolar power supply that imitate the EDLCs and load are used to measure the static characteristics and show that the proposed topology with switch timing operates as designed. In addition, the dynamic characteristics are measured for actual EDLCs and a bipolar power supply into which waveforms are programmed as selected functions when an actual smartphone is operated to verify that the proposed control method can distribute power to both the FC and EDLCs and manage the state of charge of the EDLCs.