Electric lamp and discharge devices: systems – Special application – Vehicle
Reexamination Certificate
2000-08-30
2002-04-09
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Special application
Vehicle
C315S224000, C315S077000, C307S010800
Reexamination Certificate
active
06369513
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a vehicle lamp lighting-driving apparatus, and more particularly to a vehicle lamp lighting-driving apparatus wherein a lamp is lighted by the use of a battery power source having a voltage higher than a required voltage of the lamp.
2. Description of the Related Art
A battery having a voltage of 12 volts (hereinafter “V”) is generally used as a vehicle carried battery power source. However, because there are a lot of vehicle applied devices which require a voltage higher than 12V for effective operation, and also the higher voltage enables a power feeder to be thinner, a high-voltagization of a power source has begun to be studied recently.
There exist, however, loads which are difficult to be operated with a higher voltage. As one of the above loads, there exists a lamp. In case of a lamp, when a battery power source of a higher voltage is used, a power consumption thereof increases due to its current increase. Besides, deterioration or a melt-breaking of a filament of the lamp, caused by generation of heat, would arise.
For example, in case that the voltage of a battery power source for a lamp is raised to
3
times and the resistance value of the lamp is below 9 times, the power consumption increases. A filament shall be lengthened in order to make the resistance value 9 times, which requires a shape of the filament and therefore a shape of a reflector to be changed. Like this, it would not be easy to obtain a lamp suitable to a higher voltage.
Therefore, carrying a plurality of battery power sources including a generally used 12V battery power source has also begun to be studied so as to apply a generally used 12V lamp. In such a case, however, a voltage raising means or a voltage lowering means for an alternate voltage generated by an alternator is also required. Therefore, to lighting-drive a generally used 12V lamp by the use of the battery power source having the higher voltage is being studied.
Japanese Patent Application Laid-open No.5-168164 discloses a lamp lighting-driving apparatus (FIG.
5
), wherein a battery power source of an effective voltage of 42V is applied to a lamp having a required voltage of 12V.
As shown in
FIG. 5
, a battery power source (not illustrated) of the effective voltage 42V is applied to the lamp
27
through a FET (i.e. field-effect transistor)
28
. On/off-driving of the FET
28
is carry out through a resistance R
2
, a transistor
29
-
1
, and a resistance R
3
, based on a pulse driving signal generated by a driving signal generation portion
25
(
a
). The period of the pulse forming the pulse driving signal is set to a time period not allowing recognition of on-and-off of the lamp
27
.
The driving signal generating portion
25
(
a
) watches a state of a switch
26
connected to an input terminal
21
for lighting the lamp installed on a vehicle operating panel, and generates and outputs the pulse driving signal from an output terminal
22
(
a
) while the switch
26
is closed.
The above pulse driving signal is outputted so that a duty factor thereof is the same as that of the case wherein the lamp
27
is lighted with the usual 12V. Because the battery power source of the effective voltage of 42V applies a voltage of 36V to the lamp
27
. That is, a voltage of 3 times the usual 12V is applied to the lamp.
In such a case, the power consumption of the lamp
27
becomes 9 times. Then, as shown in
FIG. 6
, a duty factor t
1
/t
2
is set to 1/9 to shorten duration of a current to the lamp
27
and to equalize a power consumption to the case of driving the lamp
27
with 12V.
At a timing of the output from the output terminal
22
(
a
) being High, a current flows to the resistance R
4
and a voltage is generated between base-collector of the transistor
29
-
1
. Accordingly, the transistor
29
-
1
becomes an ON state because a resistance value between base-emitter of the transistor
29
-
1
becomes smaller in comparison with a resistance value at a timing of the output from the output terminal
22
(
a
) being Low. At this time, the FET
28
is on-driven because a voltage is generated between source-gate of the FET
28
by means of a voltage drop due to a current flowing through the resistance R
1
. And, a current flows to the lamp
27
connected to the drain of the FET
28
.
At a timing of the output from the output terminal
22
(
a
) being Low, the transistor
29
-
1
becomes an OFF state because a resistance value between base-emitter of the transistor
29
-
1
becomes large in a degree capable of ignoring the resistance R
1
. At this time, because a current does not flow to the resistance R
1
, a voltage drop is not generated. Accordingly, the FET
28
becomes an OFF state because the voltage is not generated between source-gate of the FET
28
, and a current does not flow through the lamp
27
.
With the above apparatus, because the lamp
27
consumes electric power while the FET
28
is on-driven, the power consumption of the lamp
27
is the same as that of the case of the 12V battery power source. And, an effective value of the current flowing through the cable for applying the voltage to the FET
28
can be decreased.
With respect to the structure shown in
FIG. 5
, however, a current exceeding the rated current of the lamp
27
suddenly flows thereto just after the voltage is applied to the lamp
27
, which causes to shorten lifetime of the lamp
27
. The current exceeding the rated current is called a rush current.
A resistance value of the lamp
27
is extremely small while the temperature is low, and therefore the rush current flows just after the voltage has been applied to the lamp
27
. Upon generation of heat by the lamp
27
, the resistance value of the lamp
27
increases, which lowers a current flowing to the lamp
27
.
Upon cutting the current to the lamp
27
, the lamp
27
stops generating heat, and the temperature goes down, which lowers the resistance value of the lamp
27
. When the voltage is applied again to the lamp
27
subsequently the above, the rush current also flows to the lamp
27
. However, because the temperature of the lamp
27
itself rises, the level of the rush current is lowered.
FIG. 6
is a timing chart showing the details of operation of the prior art vehicle lamp lighting-driving apparatus. On closing the switch
26
, the driving signal generating portion
25
(
a
) detects voltage at the input terminal
21
and outputs the pulse driving signal from the output terminal
22
(
a
). The pulse driving signal continues to be outputted until the voltage at the input terminal
21
is not detected.
When a current begins to flow to the lamp
27
, the rush current
31
flows as shown in FIG.
6
. The rush current
31
repeatedly flows into the lamp
27
at a timing of High-level of the pulse driving signal outputted from the driving signal generating portion
25
(
a
) until the temperature of the filament of the lamp
27
rises enough.
Because the rush current
31
is in proportion to the voltage applied to the lamp
27
, the higher the voltage of the battery power source is, the larger the rush current is. The lifetime of the lamp
27
is shortened by the repeated large rush current
31
.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of the present invention is to provide a vehicle lamp lighting-driving apparatus, wherein a lamp, which is lighted by the use of a battery power source having a voltage higher than a rated voltage of the lamp, is driven with a pulse having a duty factor to make a power consumption of the lamp be a rated value and deterioration of the lamp is prevented by controlling an occurrence of a rush current to the lamp.
In order to achieve the above-described object, as a first aspect of the present invention, a vehicle lamp lighting-driving apparatus as shown in
FIG. 1
comprises: a lighting driving means
3
to lighting-drive a lamp
27
; a driving signal generating means
5
to generate a pulse driving signal having a pulse with a duty factor to make a power consumpti
Armstrong Westerman & Hattori, LLP
Vu Jimmy T.
Wong Don
Yazaki -Corporation
LandOfFree
Vehicle lamp lighting-driving apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Vehicle lamp lighting-driving apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vehicle lamp lighting-driving apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2900123