Apparatus and associated methods relate to powering a constant voltage DC load using a rectified output of a lighting ballast. In an illustrative example, the ballast may be configured to operate as a constant-current source. The DC load may, for example, comprise an array of LED strings connected in parallel. The number of LED strings may, for example, be selected to match a power output of the ballast. The number of LEDs in each string may, for example, be selected to match a rectified voltage output range of the ballast. A normally-open thermostat may, for example, be connected in parallel between the ballast and a rectifier and be configured to short-circuit the ballast if the circuit overheats. Various embodiments may advantageously utilize existing power processing functions of an electronic ballast to reduce complexity of a driver circuit for a constant voltage DC source.