Adaptive control for half-bridge universal lamp drivers

Details Adaptive control for half-bridge universal lamp drivers Adaptive control for half-bridge universal lamp drivers

2001-09-04

2003-06-10

Philogene, Haissa (Department: 2821)

Electric lamp and discharge devices: systems

Current and/or voltage regulation

C315S307000, C315S224000, C315S2090SC, C315S126000, C315S360000, C315SDIG004

Reexamination Certificate

active

06577076

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to controlling a dimming of various types of lamps. The present invention specifically relates to hindering discontinuities and oscillations within a lamp due to the ionization and recombination time delay of the lamp during steady state operation.
2. Description of the Related Art
FIGS. 1 and 4
illustrates a known structural arrangement of a universal lamp driver
20
including a N-depletion metal oxide semiconductor field-effect transistor (“MOSFET
1
”), a N-depletion metal oxide semiconductor field-effect transistor (“MOSFET
2
”), a capacitor C
1
, an inductor L
1
, and a capacitor C
2
for providing a lamp voltage V
L
and a lamp current I
L
to lamp
10
in response to a source supply voltage V
SS
and a source supply current I
SS
.
FIG. 1
further illustrates a conventional multiplier
30
and a known structural arrangement of a feedback compensation circuit
40
having a conventional gate driver
41
, a conventional pulse width modulator
42
, a comparator in the form of an operational amplifier (“OP AMP
1
”), a capacitor C
3
, and a resistor R
2
. Multiplier
30
computes and provides a lamp power signal LP
S
to feedback compensation circuit
40
that is indicative of lamp voltage V
L
and lamp current I
L
. In response to lamp power signal LP
s
and a reference voltage V
REF
, feedback compensation circuit
40
controls an active mode of operation of MOSFET
1
and an active mode of operation of MOSFET
2
whereby lamp current I
L
can be adjusted to thereby adjust a dimming level of lamp
10
.
An advantage of universal lamp driver
20
is the ability to drive various forms of lamp
10
(e.g., any type of gas discharge lamp). A disadvantage of feedback compensation circuit
40
is the inability to control an adjustment of lamp current I
L
for all types of various forms of lamp
10
.
FIG. 2
illustrates the inability of feedback compensation circuit
40
to control an adjustment of lamp current I
L
within an inaccessible area. The result is a discontinuity in lamp current I
L
as illustrated in FIG.
3
A.
FIG. 4
illustrates a rectifier
50
and a known structural arrangement of a feedback compensation circuit
60
having a conventional gate driver
61
, a conventional voltage controlled oscillator
62
, a comparator in the form of an operational amplifier (“OP AMP
2
”), a capacitor C
4
, a capacitor C
5
, a resistor R
3
, and a resistor R
4
. Rectifier
50
computes and provides lamp power signal LC
S
to feedback compensation circuit
60
that is indicative of lamp current I
L
. In response to lamp current signal LC
S
and reference voltage V
REF
, feedback compensation circuit
60
controls an active mode of operation of MOSFET
1
and an active mode of operation of MOSFET
2
whereby lamp current I
L
can be adjusted while experiencing a continuity as illustrated in FIG.
3
B.
However, a disadvantage of feedback compensation circuit
60
is the inability to provide a compensation to half-bridge universal lamp driver
20
that is adapted to a particular type of lamp
10
. The result is an instability problem of lamp driver
20
for some types of lamp
10
. For example, feedback compensation circuit
60
can be designed to provide a 2 pole-1 zero compensation with a zero at 200 rad/sec and a pole at 10 rad/sec. Consequently, lamp current I
L
can be unstable as illustrated in
FIG. 5A
when lamp
10
is a type of lamp having a time constant of 50 &mgr;s during steady state operation, and lamp current I
L
can be stable as illustrated in
FIG. 5B
when lamp
10
is a type of lamp having a time constant of 500 &mgr;s during steady state operation.
The present invention addresses the shortcomings of the prior art.
SUMMARY OF THE INVENTION
The present invention relates to an adaptive control of universal lamp drivers. Various aspects of the present invention are novel, non-obvious, and provide various advantages. While the actual nature of the present invention covered herein can only be determined with reference to the claims appended hereto, certain features, which are characteristic of the embodiments disclosed herein, are described briefly as follows.
One form of the present invention is a method of adaptively controlling a lamp driver coupled to a lamp. First, a time constant corresponding to the lamp is determined. Second, the lamp driver is operated to provide a lamp current to the lamp as a function of the time constant of the lamp.
A second form of the present invention is a device comprising a lamp driver and an adaptive compensation circuit. The lamp driver is operable to provide a lamp current to a lamp. The adaptive compensation circuit is operable to control the lamp current as a function of a time constant of the lamp.
The foregoing forms and other forms, features and advantages of the present invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the present invention rather than limiting, the scope of the present invention being defined by the appended claims and equivalents thereof.


REFERENCES:
patent: 4791338 (1988-12-01), Dean et al.
patent: 5677602 (1997-10-01), Paul et al.
patent: 5910712 (1999-06-01), Toyama
patent: 5925990 (1999-07-01), Crouse et al.
patent: 6160361 (2000-12-01), Giannopoulos et al.
patent: 6188183 (2001-02-01), Greenwood et al.
patent: 6351081 (2002-02-01), Hwang
patent: 0702508 (1996-03-01), None
patent: 1041862 (2000-10-01), None
patent: WO0072640 (2000-11-01), None

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