Have some questions? What current on the 5 volt output?
How much current is available from the generator at (full speed) and (at low speed)?
Is this a cell phone charger?
Using Mr SPEC's idea:
Using a voltage doubler to get 2x higher voltage.
Using a 4 to 140 volt PWM. at 400mA
Will need a change so the PWM will output less current at low input voltage. (easy)
View attachment 96266
From what I now read, synchronous rectification is another term for swich mode voltage regulation, which is already sorted (not part of this circuit). This circuit must a) step the AC down to AC below 20V and b) rectify it to DC as efficiently as possible.
In the voltage doubler mode it will deliver 12V at 0.5A-(diode drop). Then a PWM could get you to 5V at 1.1A. approx.The dynamo is 6W/6V unsaturated, so it should give just over 1A.
Some cracking responses here!
The dynamo is 18 poles. Things have moved on in the cycle world!
There is a video of a Shimano hub on youtube being driven by a drill, and it makes just over 100v, however this is with no real load on it.
Unsure of the Hz, but it's real low, 4Hz or something at minimal speed. I'm not expecting anything to work at this speed. Probably 20Hz will be the minimal before turn on.
I'm still seeing loses at the 6V range through the use of the diodes, which is what I'm ideally trying to avoid (at the expense of high speed efficiency). Perhaps the mosfets could be used for regulation before going into a switch mode with a higher voltage rating, rather than relying on the darlington's to dump it as heat, but I can't find one that'll do it and work at 6V.
That means the frequency is 9 or 18 times the RPMs. (?)The dynamo is 18 poles
The size of the capacitor in the voltage doubler is very dependent on the frequency. 20hz is much lower than I thought.Unsure of the Hz, but it's real low, 4Hz or something at minimal speed. I'm not expecting anything to work at this speed. Probably 20Hz will be the minimal before turn on.
I need to tell a story and see if you all agree.
Years ago I designed, something like this, for a large wind generator.
The current was (mega) and the spec said the voltage was 3,000 volts. Why 3kV?
In the case of a hurricane, AND the power grid went down so there was no place to dump the current, and the AND the 'lock the blades' function also failed, the generator would run-a-way and make 3kv.
So I made electronics that worked at high current under a short. AND In a over voltage condition it dumped heat into the steel tower. This kept the voltage to less than 1kV. So I did not design for 3kv because I made a load that kept the voltage down. My design had less parts, more efficient, low cost, less failure. The design was rejected because it did not meet specifications. The design worked well under a run-a-way condition.
SO: I think the alternator will not go to 100V with a 1 watt load. Probably not 50 volts. I can add a 2 watt resistor and small transistor etc that will not function below 50V but shifts in at 50V. We need to learn more about what 1 watt of load does at full speed!
That means the frequency is 9 or 18 times the RPMs. (?)
Is the dynamo connected to the hub so one turn of the tire=one turn of the alternator?
If it helps, Shimano make a regulator which dumps anything over 6V as heat. Consuming 1A, it gets quite hot during use, which shows there is some voltage over the 6V being produced.
It works the same as my twin darlington pair in the top circuit.
https://www.rosebikes.co.uk/article/shimano-sm-dh10-overvoltage-protection/aid:196629
I didn't realise the FET's have such a high switch on voltage. I take it the internal diodes are used until those switch on?
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