Isolated LED power sources and DC-DC converters therefor are presented in which the DC-DC converter includes a self-oscillating inverter driving an output rectifier for operating an LED array of one or more LEDs, where the inverter uses a control transformer with core having a Curie temperature set to a maximum operating temperature of one or more power supply components to reduce inductances of secondary windings in the inverter oscillation circuitry to lower the power supplied to the load so as to prevent the inverter from overheating.