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I'm building a lighting system for a bike, powered by a dynamo (typically rated 6V, 3W max). The load will include LEDs and a bit of logic (such as N555/ATTiny85 for blinking, etc.). I also plan to include some form of short-term energy storage (for red lights): either a supercapacitor or a small lithium battery.

What is an appropriate choice for rectifying the 6V AC input? Obvious choices are:

  • a full-wave diode bridge rectifier (pro: easy and cheap, exists as a single-package; con: but at a low voltage, that 1.5V loss stings a bit);
  • a Schottky diode bridge (a bit more efficient, a bit pricier, I don't believe it exists as a single package);
  • a simple MOSFET bridge, which I used in a previous iteration of this circuit, but it apparently cannot charge a capacitor (although I believe I used it successfully for that purpose in said previous circuit...), which can have a low drop but is more cumbersome;
  • a MOSFET bridge driven by a LT4320: I've never used this component, and it apparently needs at least 9V to work. Also, I've never soldered SMD yet.
  • there seems to be a dedicated chip, FDMQ8203, but that is a bit expensive (incl. shipping cost) for a chip I'm not sure to be able to solder (tiny MLP package).

Did I miss any other rectifier circuits, and is my evaluation of the pros and cons of each type of rectifier accurate?

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  • \$\begingroup\$ Technically bikes use alternators. Dynamos generate DC. Dynamo is the common (mis-)terminology however. \$\endgroup\$ – Transistor Sep 18 at 13:20
  • \$\begingroup\$ Is it for a bike or for bikes? If it's for a product in series production I wouldn't worry too much about soldering. \$\endgroup\$ – Lundin Sep 18 at 14:09
  • \$\begingroup\$ It's for one-ish bike - mine, and then maybe those of my immediate family. Definitely not a series production. (Although the complete circuit, STL, etc. might end up on Instructables or the like one day, this will be somebody else's problem). \$\endgroup\$ – Circonflexe Sep 18 at 16:08
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The question has arisen before on this site and I can't find an answer that tackles your exact question. In the meantime you may find some of the following questions and answers of interest.

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