LED charger circuit design

Introduction :

                                            A light-emitting-diode charger is a solid-state lamp that uses light-emitting   diodes(LEDs) as the source of light. Since the light output of individual light-emitting diodes is small compared to incandescent and compact fluorescent lamps, multiple diodes are often used together. In recent years, as diode technology has improved, high power light-emitting diodes with higher lumen output are making it possible to replace other charger  lights with LED charger light. As a prospect   our project is on “LED CHARGER LIGHT”.

AIMS:

                 1. To make a new LED charger capable of   some better facilities  than market products.

                 2. To provide more life time of LED charger than market products.

                 3. To give auto controlling system that always not present in market products.

                 4. To convey why   our charger is better than market chargers .

          5.    To make a cost comparison between our charger and market chargers.

   6. To transmit some future ideas about this charger , etc.                

EQUIPMENTS   WE USED :

                                          1.  POWER SUPPLY -220V, 50HZ.

                                                   2.  CAPACITOR-250V, 1UF-1 PIECE

                                  3.  DIODES (1N4007)-5 PIECES.

                                  4.  TRANSISTOR (BC557AP)-1 PIECE

                                  5.  RESISTORS-(15 KΩ, 4.7KΩ,1Ω)

                                    6.  SWITCHES

                                    7.  LED-12 PIECES.

                                  8.  CONNECTING WIRES.                         

 1. BRIDGE RECTIFIER:

                             For the led charger we need d.c supply. For that  reason we use bridge rectifier circuit. It contains   four diodes connected to form bridge. We use 1N4007 series diodes. For the positive half cycle of a.c signal diodes d1 and d2  are forward biased and d3 ,d4 are reverse biased . During the negative half cycle of a.c signal diodes d1,d2 are reverse biased and diodes d3,d4 are forward biased. As a result we get d.c output  all the time . Which is needed  for our led charger circuit.

2. FILTER CIRCUIT:

                                       Here we get d.c. output from bridge rectifier circuit but this d.c is not perfect d.c because it has ripple. For removing ripple we use a filter circuit which mainly removes ripple. For this we use a capacitor and a resistor, capacitor connected parallel. Because    capacitor   blocks  d.c and passes a.c. So when capacitor passes the a.c signal and opposes the d.c   then we get   perfect d.c.the range of the capacitor is 10 micro farade.

3. BIASING CIRCUIT:

                   The proper flow of zero signal collector current and the maintenance of proper collector-emitter voltage during the passage of signal is called transistor biasing. Here for transistor performed well we use biasing circuit.

4. SWITCHING ACTION OF TRANSISTOR:

                                           Here we use a p-n-p   transistor for switching. The base of the circuit connected with the rectified output. we give input in the emitter and get output from collector. When the power off then the base-emitter junction is forward bias and when power on then base-emitter junction is reverse bias and as a result LED is off.

5. LED connection :

                              In the circuit leds are connected in parallel connection. If we connect the leds series then if one led is damaged then the panel will be unable to illuminate because current flow from one led to another led. For removing this problem we connect the leds in parallel connection. In our circuit we used two panels of leds .

PARAMETER READINGS:

•      Input voltage- 220v 50Hz

•      Voltage drop across LED panel-  2.15v

•      Current  across LEDS- 22.5 mA