Monday, August 16, 2010

White LED Flood Lamp

The circuit is too simple and energy saving design. Its current consumption is practically nil but can provide light like a 20 watt CFL lamp.

The circuit uses capacitive reactance to drop high volt AC to low volt AC. This reduces power loss due to heat dissipation. The value of the AC capacitor can be calculated using the formula X c= 1/ (2 π f C) where, Xc is the reactance in ohms, C the capacitance in farads and f the mains frequency. Xc = Vrms / I where Vrms is the input voltage and I is the current flowing through LEDs. The low volt AC (around 100 volts) dropped by C1 is then rectified by a full wave rectifier formed of D1-D4.

Capacitor C2 act as a ripple remover and buffer. Zener diode ZD regulates DC to 68 volts and prevents excess reverse voltage across the LEDs during the negative half cycles.R1 is a must in the circuit to bleed the stored current from C1 when the circuit in unplugged. C1 can store more than 400 volts for many days if R1 is not connected.

Note! Do not touch any points or trouble shoot when the circuit is connected to mains.


Components Required:

R1,   470KΩ  Resistor 
R2,   100Ω  1w Resistor  
C1,    225k, 400v capacitor 
C2,    1000uF, 100v electrolyte capacitor  
BR1,   1N4007 Diodes or bridge
D2-D21,   ultra bright white LEDs 
D1,   68v 1w Zener Diode 

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