An uninterruptible constant current regulator (100, 200), comprising: a primary power input configured to receive a first voltage from a primary power source (101, 202); a secondary power input configured to receive a second voltage from a secondary power source (103, 208); a constant current regulating circuit configured to regulate and provide power from either the primary power source or the secondary power source to a load (110, 208), that includes a lighting system, wherein the constant current regulating circuit comprises a controller (112, 224), a DC/DC converter, a DC/AC inverter, and an output transformer coupled to an output of the DC/AC inverter, wherein the controller (112, 224) is configured to control an output voltage of the DC/DC converter provided to the DC/AC inverter; and a switching device (106, 210) coupled to the primary power input, the secondary power input, and the constant current regulating circuit, wherein the switching device (106, 210) is configured to provide the first voltage to the constant current regulating circuit during a first operating mode, and to provide the second voltage to the constant current regulating circuit when the first voltage falls below a threshold value, wherein the controller (112, 224) is configured to receive a feedback signal from the load (110, 208) and a command current from a user-end input (114, 226), wherein the controller (112, 224) comprises a summing node and a loop compensating filter coupled to the summing node, wherein the summing node is configured to determine a difference between the feedback signal and the command current, wherein the loop compensating filter is configured to limit a gain and bandwidth of a feedback loop of the constant current regulating circuit, and wherein the controller (112, 224) is configured to control a power provided to the load (110, 208) at least based on an output of the loop compensating filter that is based on the difference between the feedback signal and the command current. a primary power input configured to receive a first voltage from a primary power source (101, 202); a secondary power input configured to receive a second voltage from a secondary power source (103, 208); a constant current regulating circuit configured to regulate and provide power from either the primary power source or the secondary power source to a load (110, 208), that includes a lighting system, wherein the constant current regulating circuit comprises a controller (112, 224), a DC/DC converter, a DC/AC inverter, and an output transformer coupled to an output of the DC/AC inverter, wherein the controller (112, 224) is configured to control an output voltage of the DC/DC converter provided to the DC/AC inverter; and a switching device (106, 210) coupled to the primary power input, the secondary power input, and the constant current regulating circuit, wherein the switching device (106, 210) is configured to provide the first voltage to the constant current regulating circuit during a first operating mode, and to provide the second voltage to the constant current regulating circuit when the first voltage falls below a threshold value, wherein the controller (112, 224) is configured to receive a feedback signal from the load (110, 208) and a command current from a user-end input (114, 226), wherein the controller (112, 224) comprises a summing node and a loop compensating filter coupled to the summing node, wherein the summing node is configured to determine a difference between the feedback signal and the command current, wherein the loop compensating filter is configured to limit a gain and bandwidth of a feedback loop of the constant current regulating circuit, and wherein the controller (112, 224) is configured to control a power provided to the load (110, 208) at least based on an output of the loop compensating filter that is based on the difference between the feedback signal and the command current.