im designing a boost converter to step up supercap voltage to 24V constant.. the problem is the voltage from supercap is decreasing by time.. what is a program that can control the duty cycle to ensure the voltage is constant 24??
There are chips that do that - an inductor is used with a chopper circuit to boost the output.
Look as some of the circuits here.
Your super cap needs to have very low ESR so it can output enough current to support the output voltage.
Linear Technology also makes chips, I've only used one with a single smaller supercap to hold up 5V long enough to store some data to EEPROM during a power loss.