Re: High current LED driver circuit
- From: Piotr Curious Gluszenia Slawinski <curious@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Tue, 21 Oct 2008 00:49:50 +0200
electronic.piaf@xxxxxxxxx wrote:
Hello,key question is - what is capacity of their junction. with this knowledge,
Does anyone have some simple circuit design that will handle 16 high
power leds from 220V power source?
The idea would be to control the current from 320 to 700ma for the
you can connect them safely in parallel and use step down DC-DC regulators
commonly used for driving small transformers . there are various chips like
that avail, i do not want to advertise anything, try querying part
databases for 400-600V rated , single chip DC-DC converters or mosfet
drivers. you need just a cap and rectifier bridge for them, and instead of
transformer winding you just connect your LEDs via small coil. capacitance
of LEDs is issue here, like you need to at least basically know it, to
choose proper oscillating freq , rising edge time, and coil.
or, you can use bit dangerous but xtremely cheap way and use plain
thyristors. there will be significant stroboscopic effect, and your LEDS
can be destroyed by voltage spikes in power grid. thyristors should be
turned on on falling slope of AC sine wave , when voltage is rated for
diodes, or better , but bit less efficient - intermediate voltage can be
used, then regulated thyristor rectifier just charges intermediate voltage
cap, and current is then limited by plain passive element like small
resistor.
minus might be relative complexity, like even it's simple circuit , it is
not 'one chip' design like lm or dc-dc chip.
russian designers often use small capacitor in series to device which acts
as load as current limiter. it works quite well if AC is 50hz, there are no
abrubt spikes and you plan to never use device with i.e. trapezoid AC
inverter. calculation for such capacitor might be bit tricky in case of
assymetric load (diode), you could though connect half of diodes in one
direction, and another half - in opposite. this will equalize current
flowing back and forth cap, and thus simplify impedance calculations.
if you do not mind cost, you could use LC filter, with or without rectifier.
it is not very efficient, and calculations might be tricky (you also have to
wind quite large coil), but you get decent protection against voltage
spikes, totally simple design (rectifier and LC filter, or just one simple
coil in series to diodes). minuses - you must use 50hz, as with series cap,
otoh trapezoid AC source will not destroy your lamps, but just make them
shine dimmer.
i wish you luck
--
.
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