A method and apparatus for providing current pulses to the illumination source in an imaging scanner. The method includes: (1) sensing a current supplied from a current port to obtain a current-monitoring signal; (2) controlling a charge current provided to a storage capacitor based on the current-monitoring signal; (3) measuring a parameter related to a voltage across the storage capacitor; and (4) generating a driving current for the illumination source by the illumination driver circuit, if the parameter is above a predetermined threshold value, to provide a driving current for a illumination source in an imaging scanner.