48-to-5/12 V dual output DC/DC converter for high efficiency and small form factor in electric bike applications

We propose a dual output dc/dc converter for high efficiency and small form factor in electric bike applications. To implement a converter with single input of 48 V and dual output of 5 V and 12 V, we propose the system architecture combined with a 48-to-12 V converter and a 12-to-5 V converter on single PCB. The input of the 12-to-5 V is connected to the output of the 48-to-12 V converter to obtain stable 5 V without regard to the battery voltage. For high efficiency, both converters use synchronous topologies. For small form factor, the switching frequencies of the converters are fixed to 300 kHz and 1 MHz, respectively. To minimize undesirable PCB noise, several resistors are added and signal paths are designed shortly. The proposed dual output converter was implemented to 45 mm × 42 mm size. When the input voltage of 48 V is supplied, the measure efficiency is 87.5 % under a full-load condition of 3.1 A at 5 V output and 2 A at 12 V output.