Current Lightning | Electronic Project Circuits

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Li-Ion White LED Driver by LT1618

In addition to providing an accurate input current limit, the
LT1618 can also be used to provide a regulated output
current for current-source applications. {View Led driver Image} White LED drivers
are one such application for which the LT1618 is
ideally suited. With an input voltage range of 1.6V to 18V,
the LT1618 can provide LED drive from a variety of input
sources, including two or more alkaline cells, or one or
more Li-Ion cells. The circuit in Figure 7 is capable of
driving six white LEDs from a single Li-Ion cell. LED
brightness can be adjusted using a pulse width modulated
(PWM) signal, as shown, or by using a DC voltage to drive
the IADJ pin directly, without the R3/C3 lowpass filter. If
brightness control is not needed, simply tie the IADJ pin to
ground. Typical output voltage with the LEDs shown is
around 22V, and the R1, R2 output divider sets the
maximum output voltage to around 26V to protect the
LT1618 if the LEDs are disconnected. The LT1618â€™s
constant-current loop regulates 50mV across the 2.49W
sense resistor, setting the LED current to 20mA.

Be the first to comment - What do you think? Posted by admin - June 14, 2008 at 1:17 pm

Categories: Lighting Tags: current lightning, Led current limit, li ion battery charger, lithium battery

Low volt LED Flasher

In the circuit diagram for the Joule Thief, the common point of the toroid is the connection at the top of the hand-wound ferrite toroid, in the upper right of the diagram. This goes to the positive end of the battery. The other two wires from the toroid go to the resistor and to the intersection of the transistor with the LED.
One other detail that you may need to know is the symbol and pinout of the 2N3904 transistor. In the symbol, the part with the arrow is the “emitter”, the “collector” is the end above it, that also connects to the LED, and the “base” is the wire leading off to the left, between the collector and emitter. (Also remember that the end of the LED with the flat side and short lead is the end that has the flat bar in the diagram.)

Read More Source: http://www.evilmadscientist.com/article.php/joulethief
Thank you.