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    Here is an interesting circuit of a true-portable and cute solid-state bright light built with LT1932. The light can be operated from two AA size dry/rechargeable pen-light cells.
    There is no housing included so that you can use your own imagination as to what you would like to do with this light circuit. A search light, cupboard light, pathway light or an inspection head light!

    The LED Bright Light circuit is realised using a small 6 pin integrated circuit in SMD package LT1932 (IC1) from Linear Technologies. The LT1932 is a fixed frequency step-up DC to DC converter designed to operate as a constant-current source.
    Because it directly regulates output current, the LT1932 is ideal for driving light emitting diodes (LEDs) whose light intensity is proportional to the current passing through them, not the voltage across their terminals.

    The LT1932 accurately regulates LED current even when the input voltage is higher than the LED voltage, greatly simplifying battery powered designs. A single external resistor sets LED current between 5mA and 40mA. In this circuit the LED current is set to 15mA with R1=1.5Kilo Ohm. Here IC1 is configured as a two cell driver for three white LEDs(D2-D4). This design strictly follows the LT application data of LT1932.

    Portable High LED Light Circuit Schematic

    handy bright led light circuit schematic

    A small SMD prototyping board may be used for construction of the whole circuit.As with all switching regulators, careful attention must be paid to the PCB board layout and SMD component placement.To prevent radiation and high frequency resonance problems, proper layout of the high frequency switching path is essential. Minimize the length and area of all traces connected to pin 1, and always use a ground plane under the switching regulator to minimize interplane coupling.

    The signal path including pin 1, output diode D1 and output capacitor C2, contains nanosecond rise and fall times and should be kept as short as possible. In addition, the ground connection for the resistor R1 should be tied directly to pin 2 and not be shared with any other component, ensuring a clean, noise-free connection.

    Low ESR (equivalent series resistance) capacitor should be used as C2 to minimize the output ripple voltage. Similarly, D1 must be a Schottky diode, with low forward voltage drop and fast switching speed. Make sure that the diode has a voltage rating greater than the output voltage.

    MBR0540 (500mA/40V) is a good selection for D1. The value and type of the power inductor (L1) also plays an important role in the overall system efficiency. As core losses at 1.2MHz are much lower for ferrite cores than for the cheaper powdered-iron ones, ferrite core inductor should be used to obtain the best efficiency. Choose a 4.7 micro-henry inductor that can handle at least 500mA.

    Lab Note: If you wish to use only one LED at the output, Just connect its anode to the cathode terminal of D1 and its cathode terminal to pin 3 of IC1.No additions/deletions required!

    ask a question

    10 Responses to "Handy Bright Light Circuit"

    1. what will be the change if I will use AC current.

      • T.K.Hareendran says: on January 9, 2011 at 4:57 am

        I regret,ur comment is not very clear.I think you ask about the use of an ac adapter.Yes,any ac adaptor with a dc output of 3V can be used instead of the 3V battery.More doubts? feel free to write again.Thanks!

    2. Yes I am clear that I can use a adepter instead of 3 V battery . But how it will possible to make 3V dc output from 220V , 50hz AC .

      • T.K.Hareendran says: on January 9, 2011 at 12:09 pm

        Build your own AC 220V to DC 3V battery eliminator using a 220V-3V step-down transformer.If you have no such circuits in hand,just look for it on web.Or you can procure a ready-made 3V adaptor from a component vendor near you!

    3. There are 3 Led , is it possible to set 22 Led in the circuit? what will be the change?
      Can I use 4.5 V adapter for 22 Led?

      • T.K.Hareendran says: on January 9, 2011 at 5:27 pm

        By using IC LT3466,it is possible to drive upto 20 LEDs from 4.5 Volt dc supply.Refer LT3466 datasheet ( from Linear Technology) for more info.Till now,I’ve not tested such a circuit.The component is a very hard to find item in my location!

    4. I want to make complete handy light that we can charge from AC. After charge we will ran Handy Bright Light by Dc battery . To do that I need more a adepter and a charging circuit with this circuit. Is it ok?

      • T.K.Hareendran says: on January 10, 2011 at 3:35 am

        Yes,you are right! First of all replace the 3V battery with 3 Ni-Cd cells in series (1.2Vx3=3.6V).Then add a simple Ni-Cd battery charger circuit with the main circuit.After,you can re-charge the battery pack using an external ac mains adaptor.Go on with your complete handy light.All the bset!

    5. Sorry but what is L1?

    6. Is this can be used for converting cheep China torch , which is working with 4v lead acid cell?

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