I left for Chandni Chowk (a place in Kolkata, India where you can get tonnes of electronic parts of all kinds) determined to buy a MAX 756 ic. But to my dismay, even after searching a few shops, i coudnt find it. I also tried to buy those linear-technology chips-LT 1073 and LT 1111, but still could not get it. I could not order it online too, beacuse it is costly and adding the shipping charges, it's just too much for a single chip. So my plans of making the minty boost shattered.
One day, an idea came to my mind. I thought to myself, why do i even need a costly chip, all i need to make is a charge pump, for which i needed a oscillating current source.
So i choose the very cheaply available NE 555 timer chip, made a schematic and tried my luck with it. Bingo! i recieved the same result. The project costed me less than 1$ or less than 60 INR. My joy knew no bounds ! I had made a variant of the minty boost with NE 555.
Step 1: Materials Required
1)NE 555 timer ic x1 ( any 555 will do).
2)Transistor- BC 547 x1
i) 0.01 uF(105) x2
i) 1N4148 x1
ii) 5.1 volt zener
5) Inductor - 100uH
6) USB port female
7)A DIP 8 Pin socket for NE 555
9) Soldering kit and some basic skills of soldering.
Step 2: Working Principle
There is nothing to explain as such of the working principle. It is the same old concept of charge pump. Here the 555 timer ic provides a constant oscillating current source which feeds the oscillating current to the transistor. The inductor takes stage, boosts the current and dumps it back in the circuit. At last there is a rectification stage where the oscillating current is rectified back to get a dc output. The circut it simple but effective.
The current output is not so much, around 20mA. But its good for trickle charging.