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?

  • \$\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

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.

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.