Electric lamp and discharge devices: systems – Periodic switch in the supply circuit – Impedance or current regulator in the supply circuit
Reexamination Certificate
2002-11-01
2004-01-20
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Periodic switch in the supply circuit
Impedance or current regulator in the supply circuit
C315S291000, C315S307000
Reexamination Certificate
active
06680584
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an electric-discharge lamp lighting apparatus in which voltage applied to an electric-discharge lamp is generated by using a transformer.
BACKGROUND ART
FIG. 1
is a circuit view showing a conventional electric-discharge lamp lighting apparatus disclosed in the Published Unexamined Japanese Patent Application No. 2000-12273. In
FIG. 1
,
1
indicates a direct-current power source (12 V).
2
indicates an LC filter.
3
a
indicates a primary winding connected with the direct-current power source
1
.
4
a
indicates a primary winding connected with the direct-current power source
1
.
3
b
indicates a secondary winding for rising a level of voltage generated in the primary winding
3
a.
4
b
indicates a secondary winding for rising a level of voltage generated in the primary winding
4
a.
3
indicates a transformer.
4
indicates a transformer.
5
indicates a smoothing circuit for smoothing a level of voltage generated in the secondary winding
3
b
and a level of voltage generated in the secondary winding
4
b.
6
indicates an H-bridge circuit for inverting a polarity of a current supplied to an electric-discharge lamp
8
.
7
indicates a high-voltage generating circuit for generating a high voltage (about 20 kV) required to light the electric-discharge lamp
8
.
8
indicates the electric-discharge lamp (HID) boarded on a vehicle. For example, a halogen lamp generally used as an electric-discharge lamp has a luminance ranging from 1000 to 1500 lm. In contrast, the electric-discharge lamp
8
has a luminance of 3200 lm, so that the electric-discharge lamp
8
is a very bright lamp.
9
indicates a transistor for performing an on-off control to apply a voltage or no voltage to the primary winding
3
a.
10
indicates a transistor for performing an on-off control to apply a voltage or no voltage to the primary winding
4
a.
11
indicates an inverter for inverting a chopping wave.
12
indicates a feed-back circuit for generating a feed-back voltage.
13
indicates a comparing circuit for comparing a voltage level of the chopping wave and a level of the feed-back voltage generated by the feed-back circuit
12
and outputting a control signal to the transistor
9
.
14
indicates a comparing circuit for comparing a voltage level of the chopping wave inverted by the inverter
11
and a level of the feed-back voltage generated by the feed-back circuit
12
and outputting a control signal to the transistor
9
.
Next, an operation will be described below.
A power source voltage of the direct-current power source
1
is applied to the primary windings
3
a
and
4
a
of the transformers
3
and
4
. When an on-off control (or a chopping control) for the power source voltage is performed by the transistors
9
and
10
, a risen-up voltage higher than the power source voltage is generated in the secondary windings
3
b
and
4
b
of the transformers
3
and
4
. A current of the risen-up voltage higher than the power source voltage generated in the secondary windings
3
b
and
4
b
of the transformers
3
and
4
is smoothed in the smoothing circuit
5
, and the risen-up voltage is applied to the electric-discharge lamp
8
while inverting the polarity of the current of the risen-up voltage in the H-bridge circuit
6
. Also, because a high voltage of about 20 kV is required to light the electric-discharge lamp
8
, the risen-up voltage is applied to the electric-discharge lamp
8
through the high-voltage generating circuit
7
.
Here, control signals for the transistors
9
and
10
are produced as follows.
A chopping wave used as a reference wave is inverted in the inverter
11
and is supplied to the comparing circuit
14
. In the comparing circuit
13
, a voltage level of the chopping wave not inverted is compared with a level of the feed-back voltage generated by the feed-back circuit
12
, and a control signal is output to the transistor
9
. Also, in the comparing circuit
14
, a voltage level of the chopping wave inverted in the inverter
11
is compared with a level of the feed-back voltage generated by the feed-back circuit
12
, and a control signal is output to the transistor
10
.
Therefore, the control signals have phases shifted from each other by 180 degrees and are supplied to the transistors
9
and
10
.
Because the conventional electric-discharge lamp lighting apparatus has the above-described configuration, the chopping wave used as a reference wave is inverted in the inverter
11
to generate the control signals having phases shifted from each other by 180 degrees and to supply the control signals to the transistors
9
and
10
. However, the chopping wave cannot be preferably inverted in the inverter
11
.
Also, there is another configuration in which an operation amplifier (or an inverting amplifier) is used in place of the inverter
11
to invert the chopping wave used as a reference wave in the operation amplifier. However, to obtain an inverted chopping wave symmetric to the chopping wave used as a reference wave, it is required to perform an inversion operation within a time-period in which the operation amplifier can follow to the chopping wave. Therefore, when a chopping wave having a high frequency is input to the operation amplifier, the operation amplifier cannot follow a leading edge or a trailing edge of the chopping wave, the amplified chopping wave having a level gradually changed is output from the operation amplifier, a wave height value of the inverted chopping wave is lowered, and the symmetry between the inverted chopping wave and the chopping wave used as a reference wave is undesirably lost.
In general, in a widely-used operation amplifier manufactured at low cost, to obtain an inverted chopping wave symmetric to the chopping wave used as a reference wave, the maximum of a frequency of the chopping wave is limited to tens kHz. In contrast, to operate the conventional electric-discharge lamp lighting apparatus shown in
FIG. 1
, it is required to operate the conventional electric-discharge lamp lighting apparatus at a high speed corresponding to a frequency higher than tens kHz. Therefore, to follow to each input pulse of a chopping wave having a high frequency, it is undesirably required to use an expensive operation amplifier operative at high frequency.
Also, in case of the operation of an electric-discharge lamp lighting apparatus having the transformers
3
and
4
and the transistors
9
and
10
shown in
FIG. 1
, when a duty ratio of the control signal used for the on-off control of the transistor
9
considerably differs from a duty ratio of the control signal used for the on-off control of the transistor
10
, an electric power and loss loaded on the transformer
3
is unbalance with that on the transformer
4
. Therefore, it is undesirably required to use the transformers
3
and
4
and the transistors
9
and
10
respectively having a surplus size for the operation of the electric-discharge lamp lighting apparatus, and a problem has arisen that an electric-discharge lamp lighting apparatus having a small size cannot be manufactured at low cost.
As another technical literature relating to the prior art, the Published Unexamined Japanese Patent Application No. H10-25775 (1998) is known.
The present invention is provided to solve the above-described problem, and the object of the present invention is to provide an electric-discharge lamp lighting apparatus which is manufactured at low cost and is operated at high speed operation without using a circuit for inverting a chopping wave used as a reference wave.
DISCLOSURE OF THE INVENTION
An electric-discharge lamp lighting apparatus according to the present invention written in claim
1
of “WHAT IS CLAIMED IS” includes a referential rectangular wave generating circuit for generating a referential rectangular wave, an inverting circuit for inverting the referential rectangular wave generated in the referential rectangular wave generating circuit, a first integrating circuit and a second integrating circuit for integrating a level of
Mitsubishi Denki & Kabushiki Kaisha
Tran Thuy Vinh
Wong Don
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