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Many of the newer bike lights use LEDs. Although I understand basic electronics it has been some years since I learned electronic theory. Although I understand the basics of buck and boost drivers I have some questions about how they operate.

Question one: Is it possible that a driver can supply more current to a load than the current that is delivered to the driver from the battery ( or voltage source )? This has been something that I have wondered about for some time. I always thought that the max. current supplied by the voltage source was the same as the max. current supplied and delivered through the load powered by the driver. I've heard that this is not so and that a driver can deliver more current ( depending on the design and components used to build the driver ). Is this possible?

Put another way; Is there such a thing as a boost driver that not only regulates current but boosts current as well?

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  • \$\begingroup\$ what do you mean by driver, versus the load? Why do you think one's supply limits the other? \$\endgroup\$ – KyranF Oct 20 '14 at 8:18
  • \$\begingroup\$ if the only load is your LED or whatever, then that is where the current is going to go, supplied by the battery. The "driver" just turns on/off the load very faster in order to regulate voltage (or current) \$\endgroup\$ – KyranF Oct 20 '14 at 8:25
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There are two ways that a LED driver can supply more current than it draws from its power source.

1) If the source is at a higher voltage than the load needs, a "buck converter" can translate high voltage, low current to a higher current at a lower voltage. The product (voltage * current) is the same on input and output (minus some losses in the converter) So a 3 cell LiPo (11.4V) supplying 1 amp could be translated into 3 Amps into a white LED (about 3.2 to 3.5V)

2) You can draw a continuous current from the source, store it (e.g. in a large capacitor), and release it as a short burst of high current. A bright flashing light can be more visible than a steady light while consuming less average power.

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  • \$\begingroup\$ @ B.D.; Your answer ( #2 ) seems to confirm what I had been told before, namely that a boost driver basically is an equivalent voltage/current source configured to meet the users demand. I'm assuming there is a limitation on how much ( boost ) current can be produced depending on the values of the coil and capacitors used. \$\endgroup\$ – Rob W Oct 21 '14 at 8:26

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