Hi Melanie,

I get it. The diode keeps the input capacitor from discharging through the voltage divider network or the input terminals and only allows it to discharge through the regulator and the load.

That's perfect and simple! Now why didn't I think of that?

I like solutions that are simple, they are almost always the best.

This reminds me of my first engineering job. A co-worker and I were given the task of autoconfiguring a power supply to supply 13.5 volts when one type of device was connected and to supply 15 volts when another type of device was connected. It had to be "pokey-okey" (idiot proof) and we couldn't use any jumpers or switches that the user could screw up. Well we had all kinds of semiconductors on this thing and we had run the cost up by about 6 dollars. Then, my supervisor took a look at it for a moment and suggested that we add another pin to the power supply's output connector and branch the power supply's output to 2 separate pins on that connector. One pin would get the straight 15 volts and the other would have two diodes inserted between the power supply output and the other connector pin. Now, the devices we connected to the power supply output connector had different connector types. So, we simply wired up one cable assembly to tap the 15 volt pin and the other cable assembly to tap the 13.6 volt pin. How simple is that?
The cable assemblies could only be connected to the device that they were intended for. Perfect!

To make a long story short, the project was on time and on budget (the first time in the company's history).

I learned my lesson early. Don't over-design!!! Bells and whistles are not worth compromising reliability and feature creep is the enemy!