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5. Functional Description

HID lamps have unique electrical characteristics, and require a careful control method.

Specifically, they require a high voltage for ignition, typically 3 kV to 4 kV, current

limitation during warm-up, and constant power control during running. It is important to

tightly regulate lamp power with respect to lamp voltage to minimize lamp-to-lamp color

and brightness variations. Also, HID lamps should be driven using an AC-voltage to

avoid mercury migration, and at a low frequency, typically less than 200 Hz, to prevent

lamp damage or explosion due to acoustic resonance. All of these requirements are

integrated in the IRS2573D.

Figure 5.1: HID lamp ignition, warm-up and running modes

The IRS2573D is a fully-integrated, fully-protected 600V HID control IC designed to drive

all types of HID lamps. Internal circuitry provides control for ignition, warm-up, running

and fault operating modes. The IRS2573D features include ignition timing control,

constant lamp power control, current limitation control, programmable full-bridge running

frequency, programmable over and under-voltage protection and programmable over-

current protection. Advanced protection features such as failure of a lamp to ignite,

open load, short-circuit and a programmable fault counter have also been included in the

design.