1 12V to 9V buck converter using 555 timer IC

converter schematic

This  buck converter is driven by 555 timer IC and converts 12V dc from a battery to 9V dc. The 555 IC  (operated in astable mode ) generates pulses of voltages of 75% duty cycle. This pulses turns the transistor on and off and drives the inductor L (buck converter circuit), and as a result generates 9V dc output. For this configuration,
Ra =27K
Rb =10K
C =10nF
L = 20 turns of #22AWG in antenna bar
Q = TIP41C or any of the same specs
Cout = 2200uF (higher the better)
You can add 1N4739A zener diode at the output side for better regulation.


  1. sir for L what type of choke core can be preferred instead of antenna bar?
    and what diode is placed at D ?