A couple of simple boost converter circuts are explained in this post, whch can be build and applied by any hobbyists for their own specific requiremenet.
What is a Boost Converter
A DC boost converter circuit is designed for stepping-up or boosting a small input voltage levels to a desired higher output voltage level, hence the name "boost" converter. Since these circuits basically step up a low voltage to a higher voltage levels, they are also know as step-up converters.
Although a boost converter circuit may involve many complex stages and calculations, here we will see how the same could be built using minimum number of components, and with effective results.
Basically a boost converter works by oscillating current though a coil or inductor, wherein the voltage induced in the inductor is transformed into a boosted voltage whose magnitude is dependent on the number of turns and PWM of the oscillation frequency.
Simple Boost Converter using a single BJT
R1 = 1K 1/4 watt
D1 = 1N4148 or a Schottky diode such as FR107 or BA159
T1 = any NPN power BJT such as TIP31, 2N2222, 8050 or BC139 (on heatsink)
C1 = 0.0047uF
C2 = 1000uF/25V
Inductor = 20 turns each of super enameled copper wire on a ferrite torroid T13. Wire thickness can be as per the output current requirement.
1.5V to 30V Converter
In the above design a single BJT and an inductor is all that's needed for visualizing an incredible 1.5V to upto 30V boost.
Using a flyback concepts allows the two side of the transformer isolated and ensures better efficiency, since the load is able to operate during the OFF time of the BJT, which in turn prevents the BJT from overloading.
While experimenting I found that adding C1 drastically improved the performance of the circuit, without this capacitor the output current did not look too impressive.
3.7V to 24V Converter
A simple boost converter circuit can be also built using an IC 555 circuit for boosting USB 5V to 24V, or any other desired level. The same design can be used for boosting a 3.7V to 24V from a Li-Ion cell.
The above circuit can be regulated with a feedback as shown below:
The idea looks quite straightforward. IC 555 is configured as an astable multivibrator whose frequency is decided by the values of resistors and capacitor at pin#7 and pin#6/2.
This frequency is applied to the base of a driver transistor TIP31 (incorrectly shown as BD31). The transistor oscillates at the same frequency and forces supply current to oscillate within the connected inductor with the same frequency. The selected frequency saturates the coil and boosts the voltage across it to a greater amplitude which is measured to be around 24V. This value can be tweaked to even higher levels by modifying the turns of the inductor and the frequency of the IC .
Video Links for the above boost converter circuits are provided below: