I have a circuit with 24V input that I need 5V at about 100mA. Using a standard linear regulator, I can get the volts and little current I need to run my mega48. But, I have a couple photo interrupters and turning on the LED causes big time heat buildup as expected due to the 19V drop.
I built a switching regulator that works great, but the cost of the inductor and low ESR caps make the regulator the most expensive part of the circuit. not to mention added real estate. I was thinking of using a dumb switcher to generate a rough 9 volts to get the Vin down to something reasonable.
Am I wacky? (wait... Don't answer that.)
Is this practical? Can a simple chopper be made to give an open loop cut of 60% or more of the input voltage? I was even thinking of using a timer output to generate the frequency.
You can use a cheaper inductor with a higher DCR and a general purpose filter cap on the front end to filter the input to a 25Â¢ LDO.
Or, should I just suck it up and pay the $$$ for the full switcher? Any suggestions on a low cost switcher solution? 24V in, 5V @120mA out.