White LED Array Lamp

Posted on Feb 6, 2014

To make a battery operated LED lamp, it may better to use a cluster of low power discrete LED array rather than a single high power LED. The light produced will be scattered and It considerably reduces irritation or damages to a naked eye, if accidentally looked on it. Also the light spreads nicely so it is good for room lighting and no heat sink required

White LED Array Lamp
Click here to download the full size of the above Circuit.

for the LEDs! The circuit is designed to operate 3W, 5 x 7 white LED array powered from four NiMH cells. The design is straight forward DC to DC boost circuit using a LM3410 which includes a 170 m © NMOS switch. The circuit is completes with few external components. The switching frequency is internally set to either 525 kHz for LM3410-Y devices or 1. 60 MHz for LM3410-X, allowing the use of extremely small inductors and capacitors. The 525 kHz switching frequency is selected due to the availability of suitable ferrite having lower core losses. The inductor value needed for the circuit depends upon the voltage and current output needed. A detailed calculation is described in the datasheet of the LM3410. A higher efficiency of approximately 88% is achieved. The IC is featured with an external shutdown and the standby current of only 80 nA. The operating current for a single branch the LED array is ~25mA, and since there are 7 parallel paths a total output current of 190mA is drawn from the DC to DC convertors. This current is set by the 1O resistor R4 (I = 0. 19/R4). An optional output over voltage protection is provided using a 22V zener diode D23 and a resistor R3. This will protect the IC if the LED load becomes an open circuit. Since the absolute maximum input voltage to the IC is 5. 5 V, a voltage regulator using R1 and zener diode D31 is required if the circuit is operated from a voltage source more than 5. 5 V. The...

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