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Non-magnetic shielding

IP.com Disclosure Number: IPCOM000030867D
Publication Date: 2004-Aug-31
Document File: 1 page(s) / 14K

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The IP.com Prior Art Database



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Non-magnetic Shielding

A typical set-up for driving HID (High Intensity Discharge) automotive headlamps consists of a driver, an igniter and the HID lamp. The three components are typically arranged as described in figure 1:

Figure 1: System set-up driving an HID lamp

Improved systems integrate the igniter into the base of the HID lamp. The integrated igniter is connected to the driver by use of a three wired coaxial shielded cable, called harness. The coaxial shielding of the harness allows a continuous shielding of the system, because the driver and the igniter are also capsulated by an electric conductive shielding. The shielding of the igniter is typically isolated to the electronic inside the igniter.

One possible concept for the igniter is to use a serial high voltage (HV-) generator. The HV- generator might be realized by an HV-transformer. In case of a rod core transformer the magnetic field might be coupled into the shielding of the igniter. If the shielding material is magnetic the magnetic field of the transformer is guided by the shielding.

Typically the driver drives the HID lamp with an AC-signal. Consequently the magnetic field guided by the shielding is also alternating. The alternating magnetic field causes eddy currents in the shielding. These eddy currents result in electrical losses. These losses decrease the commutation performance of the complete system, by reducing the amplitude of the transient (over-) voltage generated by a transient osci...