Discharge lamp unit with noise shields and noise control...

Details Discharge lamp unit with noise shields and noise control... Discharge lamp unit with noise shields and noise control...

2002-02-14

2003-12-30

Wong, Don (Department: 2821)

Electric lamp and discharge devices: systems

Combined load device or load device temperature modifying...

Discharge device load

C313S479000

Reexamination Certificate

active

06670764

ABSTRACT:

CROSS REFERENCE TO RELATED APPLICATION
This application is based on and incorporates herein by reference Japanese Patent Application No. 2001-53648 filed on Feb. 28, 2001.
BACKGROUND OF THE INVENTION
The present invention relates to a discharge lamp unit with noise shields and a noise control method for a discharge lamp unit.
One proposed arrangement for noise control in a discharge lamp unit is shown in
FIG. 7. A
discharge lamp
200
includes a discharge lamp body
201
and a connector
202
. The connector
202
is electrically connected with a discharge lamp control circuit
210
which regulates a voltage applied to the discharge lamp
200
. A filter circuit
211
is connected between the control circuit
210
and a power supply
230
to reduce noise radiation and conduction from the discharge lamp
200
or the control circuit
210
to the power supply
230
.
In this arrangement, noise produced during an operation of driving the discharge lamp
200
with a rectangular wave is conducted to the control circuit
210
. When a DC/DC converter in the control circuit
210
is switched to step up a voltage to the level required for a start or steady lighting of the discharge lamp
200
, switching noise is produced. In the case of the discharge lamp
200
being used for a headlight of a vehicle, noise in power supply lines may result in radio noise. To avoid this, a filter circuit
211
is connected between the control circuit
210
and the power supply
230
. Moreover, the control circuit
210
is shielded with a shield case
220
to reduce noise radiation therefrom.
Although the noise from the control circuit
210
can be reduced by the shield case
220
, it may still be radiated outside the shield case
220
via wires
240
. To counter this problem, another arrangement, as shown in
FIG. 8
, is proposed. In this proposed arrangement, the control circuit
210
, the filter circuit
211
, and the wires
240
are shielded by a shield case
221
. However, this does not provide sufficient shielding since the noise may be conducted to the power supply
230
or radiated via wires
241
.
SUMMARY OF THE INVENTION
The present invention therefore has an objective to provide a discharge lamp unit with noise shields which enable superior control of noise radiation and noise conduction from a discharge lamp or a discharge lamp control circuit to a filter circuit and a power supply.
Another objective of the present invention is to provide a superior noise control method for a discharge lamp control unit.
According to the present invention, the second shield case is installed to exclusively shield the control circuit in addition to the first shield case shielding the discharge lamp control circuit and the filter circuit. One of the wires connecting the filter circuit to the power supply, referred to as a ground wire and the first shield case are electrically connected near the shield case opening through which the ground wire passes. As a result, noise is reduced even if noise produced by the discharge lamp or the control circuit is conducted outside the first shield case via the wires.


REFERENCES:
patent: 4864194 (1989-09-01), Kobayashi et al.
patent: 5188444 (1993-02-01), Makita et al.
patent: 5343370 (1994-08-01), Ohashi et al.
patent: 5838109 (1998-11-01), Kobayashi et al.
patent: A-6-5375 (1994-01-01), None
patent: A-9-251895 (1997-09-01), None

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