Boris Landoni @ open-electronics.org presents their second version of Torpedo, a kind of DC-DC converter able to provide 5V output from a variety of sources. He writes:
Some time ago we had introduced you to the Torpedo switching power supply, a particular kind of DC/DC power supply called SEPIC capable of supplying 5 V from several external supply sources, such as an external voltage between around 3.5 and 20 V, the 5 V coming from a USB connector or the 3 to 7 V supplied by a LiPo battery. The very small power supply also had a circuit capable of charging the battery up through external sources, where available.
- triple power source: USB, LiPo battery and an external source;
- a wide range of input voltage values: 6,5 – 18 V;
- can supply a maximum current of 3 A;
- high efficiency, even over 85-90%;
- built-in charger for LiPo single cells;
- can switch from battery-powered to another source without interruption;
- 5 V output with high stability when load varies and low ripple;
- possibility to turn off the only output leaving the step-down converter and the charger active;
- possibility to automatically deactivate the output if power supply comes from the USB connector which is limited to 500 mA current by the specs; if there is a battery, power supply is granted by that;
- status LEDs indicating charge, the power supply used, output activation and so on.
Torpedo 2 – a cheap & powerful 3A DC/DC converter with built-in charger – [Link]