Electronic power supplies for high-density discharge (HID) lamps

The principal methods of electronically controlling the power to high-intensity discharge lamps is summarised. These include phase shift control, resonant inverters and variable pulse width control, using half- or full-bridge configurations depending on the power capability of the switching elements. Control of power is possible by varying the pulse width, varying the frequency or both. Varying the frequency is less demanding on the switching characteristics of the devices. Both IGBTs and MOSFETs can be used, however the power loss using IGBTs is generally lower for a given power at lower frequencies. Powers above 10 kW are readily achievable by these means.