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I am trying to control an OSRAM XENARC 66140 35W HID (High-intensity discharge) Lamp with a circuit which contains Texas Instruments UCC2305. I have obtained 4 original lamps from OSRAM and tried on my controller circuit, 3 of 4 are worked correctly and gave light, however one lamp did not emit any light.

Then I have checked this not working lamp with a test setup implemented for 66140 and it worked. So the lamp is not actually damaged.

I have considered that there are little differences that can not be easily observed between working and not working lamps and my controller circuit is not be able to tolerate this differences. I can not say that the electronic design of my circuit is totally wrong because 3 of 4 66140 lamps are working troubleless. But I did not understand why one of that lamp's behavior -which I tried and saw on test setup and working.

If you share your comments it may be solve my problem.

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    \$\begingroup\$ Show oscillograms. At what point does it fail? \$\endgroup\$ – winny Aug 1 '18 at 7:24
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There will be a tolerance on the breakdown threshold of the lamp and the ballast must meet or exceed the requirements of all bulbs.

The typical xenon headlamp operational values may not match this bulb exactly;

1) Turn-on stage (T1 ≈ 30 ms) V>=360 V
2) Ignition stage (T2 ≈ 100 ns) 23~30 kV
3) Take-over stage (T3 ≈ 300 μs) 10~30 ohms with 12 A peak decaying in xxx μs
4) Warm-up stage (T4 ≈ 20 ms) voltage is temperature dependent 2.6 A
5) Run-up stage (T5 ≈ 6~10 s) cold lamp comes up from 20~30 V to nominal 85 V
6) Steady state (T6) 85 ±17V, 35W max., 250~400 Hz
Ref enter image description here Failure at any stage is due to the electronic ballast tolerances meeting the bulb specifications.

The obvious question is which stage # fails? 2, 3, 4 or 5?
Show the output Voutsense, Isensein, Iloadsense during start-up.
Compare lamps.

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