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White LED (White Light Emitting Diodes) Circuits
White LEDs: #-B C - K L - P
Q - V W - Z LED
Circuits
Last Updated on:
Wednesday, December 03, 2008 04:22 PM
| Circuits Designed by Dave Johnson, P.E. : |
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Ramping LED Driver
The circuit below was designed to drive a LED with an intensity
ramping mode. Two 555 timers generate two different triangle waveforms.
The upper device generates a 10KHz signal while the lower unit produces a
1Hz signal. The two signals are fed to a voltage comparator. The result
is a pulse width modulation (PWM) signal, which with the aid of the FET,
drives the LED in such a way that its average light output slowly ramps
from about zero light to maximum and then slowly dims back down. The
circuit should operate over a supply voltage ranging from 3v to 12v. You
can easily vary the ramping time by changing the value of the 1M
resistor. For an interesting effect, you can place a 1N4148 diode in
parallel with the 1M resistor, with the cathode (banded end) side
connected to pin 3.
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| Links to electronic schematics, circuits, designs and diagrams for engineers,
hobbyists, students & inventors |
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Scheme Provides
High Side Current Sensing for White LED Drivers: 02/19/04 EDN Design Ideas / (added 1/05) White LEDs find wide use in backlighting color-LCD screens in
most portable devices, such as cellular phones, PDAs, and MP3 players. Multiple LEDs often connect in series to ensure that the same current flows through every LED. To forward-bias these
LEDs, a voltage of 10 to 16V comes from an inductor-based boost regulator, such as an SP6690.... |
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Series Connected Voltage Boost Circuit for a Battery Operated LED Lantern: A circuit that goes in series with a
white LED and a 1.5 volt cell to make > 3 Volts to drive a white LED...(schematic / circuit added 6/07) |
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Series White LED Driver: National Semiconductor Application Note LM3590 November 2003 (app note added 02/05) |
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Simplified PC Connections for Gpib Instruments:
Aligent Application Note (app note added4/08) |
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Single and Two Cell White LED Drivers Without Inductors : The operating voltage of white LEDs coupled with my
emotional need for low cost for a given function, motivates me to make LED drivers suitable for battery operated lanterns that can run from a small number of cells. White and Ultraviolet LEDs
available at the time of this writing, require higher voltages than colored LED's. In the case of the ones I bought most recently, from 2.8 to 4 volts, depending upon operating current and the
individual device....(schematic / circuit added 6/07) |
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Single Cell Flashes White LED: 12/11/03 EDN Design Ideas / (added 2/06) Many portable appliances and other products that must operate from a single cell
are restricted to working at very low voltages. It is thus difficult to drive white LEDs that typically have a forward voltage of 3 to 5V. The ability to flash the LED with a supply voltage as
low as 1V presents additional complications. |
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Special Lighting : experiments with white LEDs (added 4/02) |
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Synchronous Buck/Boost High Power White LED Driver: Linear Technology LT3453 (app note added 2/05) |
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Synchronous Step-Up DC/DC Converter for White LED Application: National Semiconductor Application Note LM3500 February 05 (app note added 02/05) |
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TB060: Drive High Intensity White LEDs Efficiently using the PIC16C781: Microchip Application Note Published
17-Jul-02 (app note added 6/06) |
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Tiny Regulators Drive White LED Backlights: DN231 Design Notes (Linear Technology) (app note added 2/06) |
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Voltage to Current Converter Drives White LEDs: 06/27/02 EDN Design Ideas / (added 6/07) You sometimes need to drive a white LED from one 1.5V battery.
Unfortunately, the forward voltage of a white LED is 3 to 4V. So, you would need a dc/dc converter to drive the LED from one battery. Using the simple circuit in Figure 1, you can drive one
white LED or two series-connected green LEDs, using only a few components.... |
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White LEDs: #-B
C - K L - P Q - V
W - Z LED Circuits |
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