VS - Lighting Systems - Lighting - 998542

11.2. Xenon system operation HID headlamp bulbs cannot operate on a low- voltage direct current, so they require a ballast system with an ignitor. The ignitor may be either internal or external to the lamp. The ignitor is integrated into the bulb in D1 and D3 systems, and is a separate unit or part of the ballast in D2 and D4 systems. The ballast controls the ignition voltage and current to the bulb.

lamp

Igniter

DC/DC converter

DC/AC converter

V

Battery

lamp

I

lamp

Inverter signal

PWM signal

Digital signal controller

The start-up process of automotive HID lamps is quite complex. The diagram below shows the voltage and current of a HID lamp from power-on to steady state.

Warm-up

Run-up

Steady-state

Turn-on

Ignition Takeover

30 ms

50 ms

6 s - 8 s

65 V - 105 V

V

lamp

20 V - 40 V

-400 V

25 kV

I

2.5 A (max.)

lamp

0.41 A (@85 V, 35 W)

0 A

-12 A (max.)

-2.5 A (max.)

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