That's my first post here, so hello everyone
I'm designing a dynamo light for my bike and need a little bit of help. To explain my problem very simply :
- dynamo power goes through some impedance matching and switching regulator, so I get about 10V to power my 3 white LEDs in series.
- a LiIon battery (3 .. 4.1V) needs to power the LEDs when stopped and is recharged when riding
Now I have to choose between two topologies :
1) Vin => buck => Vbattery => boost => VLED
Pros : Works on any Vin since Vbattery is small, so even at very low speeds some power will be harvested, easy to do, good efficiency
Cons : When running on dynamo power, two converters in series reduce efficiency ; high currents at low voltages
2) Vin => buck => VLed <= 2quadrant buck/boost => VBattery
Here a 2-quadrant buck boost transfer power to the battery when the dynamo provides more than needed, and transfer power from the battery to the LEDs when the dynamo doesn't provide enough.
I'd like to explore this solution but I can't find any chips to fit the 2 quadrant buck/boost role. So if you guys can advise me on this, I'd be grateful. Basically the converter needs to transfer power :
- from about 7-11V (LEDs) to about 3-4V (battery) and the other way around
- at about 5W max
It's a synchronous buck but the datasheets don't say wether the chips handle the other quadrant (and how).
Regards, Pierre
I'm designing a dynamo light for my bike and need a little bit of help. To explain my problem very simply :
- dynamo power goes through some impedance matching and switching regulator, so I get about 10V to power my 3 white LEDs in series.
- a LiIon battery (3 .. 4.1V) needs to power the LEDs when stopped and is recharged when riding
Now I have to choose between two topologies :
1) Vin => buck => Vbattery => boost => VLED
Pros : Works on any Vin since Vbattery is small, so even at very low speeds some power will be harvested, easy to do, good efficiency
Cons : When running on dynamo power, two converters in series reduce efficiency ; high currents at low voltages
2) Vin => buck => VLed <= 2quadrant buck/boost => VBattery
Here a 2-quadrant buck boost transfer power to the battery when the dynamo provides more than needed, and transfer power from the battery to the LEDs when the dynamo doesn't provide enough.
I'd like to explore this solution but I can't find any chips to fit the 2 quadrant buck/boost role. So if you guys can advise me on this, I'd be grateful. Basically the converter needs to transfer power :
- from about 7-11V (LEDs) to about 3-4V (battery) and the other way around
- at about 5W max
It's a synchronous buck but the datasheets don't say wether the chips handle the other quadrant (and how).
Regards, Pierre