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Improved electrode tip formation and EMI prevention in automotive HID lamp

IP.com Disclosure Number: IPCOM000166550D
Publication Date: 2008-Jan-16
Document File: 2 page(s) / 39K

Publishing Venue

The IP.com Prior Art Database

Abstract

ID678767

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Improved electrode tip formation and EMI prevention in automotive HID lamp

Abstract

The invention relates to automotive HID lamps. The electrodes of these lamps are known to partly melt and solidify in each run-up. The electrode morphology after solidification influences the lamp performance strongly. Presently this process is not well controlled. A desired run-up should end with an electrode with a conical tip on top. This invention describes settings in order to get a more robust tip formation during run-up. Such a shape will a) shorten the time for electrode-discharge attachment to go from diffuse to spot mode, b) lower the risk for Electro Magnetic Interference (EMI), and c) define and stabilize the arc attachment.

Background of the invention

The invention relates to automotive HID lamps, in particular to the xenon types. The electrodes of these lamps are known to partly melt and solidify in each run-up. The electrode morphology after solidification influences the lamp performance highly. Presently this process not well controlled. A desired run-up should end in an electrode with a conical tip on top. Such a shape will help:

Shortening time for the electrode-discharge attachment to go from diffuse into spot mode Lowering the risk for Electro Magnetic Interference (EMI)

Defines and stabilizes the arc attachment

A short time from diffuse to spot mode is desired to lower the temperature and electrical losses of the electrode. This way the system will be less energy consuming and lamp life will be prolonged. EMI is a problem because it can disturb for example the tv-antenna in car applications. There are 2 varieties of EMI: Commutation EMI and EMI during a half-wave. The latter is seen as the most severe. A defined and stable arc is of importance in optical applications. Non-stable arcs will cause flicker, which is mostly unwanted.

EMI and tip-formation have been examined in the past. During run-up conical tips are formed on the electrode. It is believed that these tips have a positive influence on among previous mentioned things, reducing EMI. However it is not known how these conical tips are formed exactly. The influence of the operating frequency has not been taken under investigation before. The operating frequency appears to have a major influence on the tip formation.

Problems or disadvantages overcome by the invention

During analyses of the run-up scheme there was the impressio...