So I have this 9V 2.5A power supply and a flash unit which needs 6V. I use LM7806 to drop voltage, but when the flash is charging up it overload regulator, thus further dropping voltage to megger 2.5V. I think I need to somehow limit max current draw to 1.5A. Surprisingly I couldn't find a solution in google, so maybe you guys can help me out?
edit** Reason? LDO will drop 2.5V at 1.5A at 85'C , which means you need 8.5 min anyway but chances are your load demands more than 1.5 and that's causing shutdown on starting.
Power dissipation (9-6V)*1.5A= 4.5W is a big problem
A heatsink will improve overtemp condition, but not enough. if overloaded. thus use a 1.5A PTC in front is a bandaid fix.
A better solution is use a better adjustable LDO with 0.5 Dropout and lose 2.5V*1.5A=3.75W in a power resistor or 3 power diodes.
The best solution is a 99% efficient Buck regulator which can output >3.5A @6V = 21W from 9V*3,5A = 22.5W
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It may be possible to bypass LDO with a Pch FET with a heatsink
Using LDO drain current to bias Vgs=-1V (8V)