An emergency lighting system (A), comprising: a battery supplying module , a DC transforming module , and a power controlling module ; the battery supplying module for supplying power to the DC transforming module when an emergency lighting condition is met; the DC transforming module for supplying power to a general lighting load ; the power controlling module for obtaining a rated voltage of the general lighting load , generating a control signal related to the obtained rated voltage using the obtained rated voltage and a predetermined power, and providing the generated control signal to the DC transforming module ; the DC transforming module for altering an output current provided by the battery supplying module using the control signal provided by the power controlling module and providing an altered output current to the general lighting load for operating the general lighting load at substantially the predetermined power; wherein the predetermined power is a constant value; characterised in that : the power controlling module comprises: a voltage sampling circuit, a first operational amplifier, and a second operational amplifier; the voltage sampling circuit for sampling the rated voltage of the general lighting load , the first operational amplifier for feeding the rated voltage sampled by the voltage sampling circuit to an inverting terminal of the second operational amplifier, and the second operational amplifier for generating the control signal using the rated voltage at the inverting terminal, wherein the larger the rated voltage fed to the inverting terminal, the smaller the altered output current provided by the DC transforming module to the general lighting load ; whereby, during an emergency lighting condition, the output current provided by the battery supplying module is altered by the DC transforming module to maintain operation of the general lighting load at a substantially constant predetermined power. a battery supplying module , a DC transforming module , and a power controlling module ; the battery supplying module for supplying power to the DC transforming module when an emergency lighting condition is met; the DC transforming module for supplying power to a general lighting load ; the power controlling module for obtaining a rated voltage of the general lighting load , generating a control signal related to the obtained rated voltage using the obtained rated voltage and a predetermined power, and providing the generated control signal to the DC transforming module ; the DC transforming module for altering an output current provided by the battery supplying module using the control signal provided by the power controlling module and providing an altered output current to the general lighting load for operating the general lighting load at substantially the predetermined power; wherein the predetermined power is a constant value; characterised in that : the power controlling module comprises: a voltage sampling circuit, a first operational amplifier, and a second operational amplifier; a voltage sampling circuit, a first operational amplifier, and a second operational amplifier; the voltage sampling circuit for sampling the rated voltage of the general lighting load , the first operational amplifier for feeding the rated voltage sampled by the voltage sampling circuit to an inverting terminal of the second operational amplifier, and the second operational amplifier for generating the control signal using the rated voltage at the inverting terminal, wherein the larger the rated voltage fed to the inverting terminal, the smaller the altered output current provided by the DC transforming module to the general lighting load ; whereby, during an emergency lighting condition, the output current provided by the battery supplying module is altered by the DC transforming module to maintain operation of the general lighting load at a substantially constant predetermined power. <EOS>