Instead of controlling the power supply voltage, the diode voltage drop could be adjusted to share the load between the two supplies. With these special adjustable diodes, the drop on the higher voltage supply would be dialed up to offset the mismatch in the supply voltages. As shown on this slide, the diode on the 5.1V supply drops 100mV more than that on the 5V supply. Again, the accuracy is good. No access to the supply is required, loop compensation is simpler, and the supply-agnostic design makes it usable with different kinds of supplies. One thing to watch-out for with this method is that the diode on the higher voltage supply gets hot as its voltage drop increases to offset the supply difference. The solution is to have accurate supplies with tight tolerances, so that the diode power dissipation stays within manageable limits.