High-intensity discharge lamp ballast with live relamping feature

A dimming ballast (100) for a high-intensity discharge lamp (10) includes an ignitor (120), a control circuit (140), and a dimming interface (160) for connection to an external dimming controller (30). Following lamp replacement (10), external dimming controller (30) receives a user relamp command and, in response, sends a special relamp signal to dimming interface (160). In response to the special relamp signal, dimming interface (160) communicates with control circuit (140), which directs ignitor (120) to provide high voltage pulses for igniting the replaced lamp. In an alternative embodiment, an external control device such as a triac dimmer (40) receives a user relamp command following lamp replacement and, in response, sends a special relamp signal to a control circuit (240), which directs ignitor (220) to provide high voltage pulses for igniting the replaced lamp.