A multi-mode control scheme for an LED lamp system uses the detected firing angle of an AC input voltage waveform to select from multiple regulation modes. In operation, a current controller compares the detected firing angle to one or more specified thresholds and selects the appropriate regulation scheme based on the comparison result. When the detected firing angle is less than a first firing angle threshold, the controller employs a current shaping regulation mode. When the detected firing angle is greater than a second firing angle threshold, the controller employs a switching cycle-I Peak modulation regulation mode. And when the detected firing angle is greater than the first firing angle threshold and less than the second firing angle threshold, the controller employs a hybrid regulation mode.