I know you are favorable to DC lighting ..Put those circuits on a UPS ?
The problem you have with multiple DC power supplies is that they are switching power supplies.T hey regulate in either constant voltage or constant current mode. They are really turning on and off rapidly to regulate either current or voltage and have a sense circuit to determine regulation.
I said all of that so you will understand there are two things you require in your scenario current and voltage regulation - You will need to make sure you have the right power supplies to do this - although I will say the DC power supplies probably use AC - although you can find DC to DC supplies.
"Two or more power supplies being capable of CV/CC automatic cross over operation can be connected in parallel to obtain a total output current greater than that available from one power supply. The total output current is the sum of the output currents of the individual power supplies. The output of each power supply can be set separately. The output voltage controls of one power supply should be set to the desired output voltage (CV); the other power supplies should be set for a slightly higher output voltage. The supplies with the higher output voltage setting will provide constant current output, and will drop their output voltage until it equals the output of the CV supply. " copied from the link below: