An uninterruptible constant current regulator , comprising: a primary power input configured to receive a first voltage from a primary power source ; a secondary power input configured to receive a second voltage from a secondary power source ; 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 , that includes a lighting system, wherein the constant current regulating circuit comprises a controller , a DC/DC converter , a DC/AC inverter , and an output transformer coupled to an output of the DC/AC inverter , wherein the controller is configured to control an output voltage of the DC/DC converter provided to the DC/AC inverter ; and a switching device coupled to the primary power input , the secondary power input , and the constant current regulating circuit, wherein the switching device 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 is configured to receive a feedback signal from the load and a command current from a user-end input , wherein the controller 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 is configured to control a power provided to the load 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 ; a secondary power input configured to receive a second voltage from a secondary power source ; 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 , that includes a lighting system, wherein the constant current regulating circuit comprises a controller , a DC/DC converter , a DC/AC inverter , and an output transformer coupled to an output of the DC/AC inverter , wherein the controller is configured to control an output voltage of the DC/DC converter provided to the DC/AC inverter ; and a switching device coupled to the primary power input , the secondary power input , and the constant current regulating circuit, wherein the switching device 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 is configured to receive a feedback signal from the load and a command current from a user-end input , wherein the controller 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 is configured to control a power provided to the load 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. <EOS>