Boost converter are voltage converter with higher output voltage than the actual input voltage . I wrote about how to build a buck converter with 555 timer IC9l0l0l. Here I wanted to take a note on how to build a boost converter using 555 timer.
So how is it possible to convert a low voltage to higher voltage?
When there is input voltage like 3.7V, the13 inductor(with typical value between 100uH to 300uH) which is in series with the input voltage and the control pulse is high turning on the mosfet channel gets grounded. And therefore the inductor develops voltage equal to the input voltage. As soon as the pulse magnitude changes to low, the mosfet switch gets tuned off and the energy stored in the inductor passes through the schotty diode and into the output capacitor. The capacitor charges until the mosfet switch is turned on because now the current starts to flow into the ground instead into the capacitor. During this period the capacitor release energy into the load. The diode stops the flow of energy back into the input voltage side.
So to build a boost converter we need active switch, a mosfet or bjt transistor, and a device that can generate high low signal at certain frequency, between 50khz and 100khz typically, that turns on/off the mosfet switch. For the active switch mosfet such as the IRFZ44N can be used and for the pulse generator we can use 555 timer IC. That means the output of the 555 timer is connected to the gate of IRFZ44N. The regular pulses generated the 555 timer IC must have amplitude greater than the gate turn voltage of the MOSFET.