Claims
- 1. A circuit arrangement for operating a lamp having a known assumed correspondence between various possible values of luminous flux produced by the lamp and the combinations of lamp voltage and lamp current that produce the various possible values of luminous flux comprising:
- a ballast for applying an actual lamp voltage across the lamp and causing an actual lamp current to flow through the lamp, the ballast being controllable;
- a memory in which various possible values of luminous flux produced by the lamp are stored in correspondence with the combinations of lamp voltage and lamp current that produce the various possible values of luminous flux;
- means I for generating a signal S1 which is a measure of the actual voltage applied across the lamp;
- means II for generating a signal S2 which is a measure of the actual current flowing through the lamp;
- means III for generating a signal S3 which is a measure of a desired value of luminous flux of the lamp;
- means IV for determining the actual luminous flux of the lamp from the memory by retrieving a stored value of luminous flux corresponding to signals S1 and S2; and
- means V for controlling the ballast in dependence on the luminous flux of the lamp determined by means IV and on signal S3.
- 2. A circuit arrangement as claimed in claim 1 wherein the memory stores various possible values of luminous flux produced by the lamp in correspondence with the combinations of lamp voltage and lamp current that produce the various possible values of luminous flux in the form of a table.
- 3. A circuit arrangement as claimed in claim 1 wherein at least one combination of lamp voltage and lamp current stored in the memory corresponds to more than one stored value of possible luminous flux and means IV includes means for temporarily changing the value of current flowing through the lamp in the event S1 and S2 correspond to one of said at least one combination and for detecting a change in voltage across the lamp resulting therefrom as a basis for determining which of the more than one stored value of possible luminous flux corresponds to the actual luminous flux.
- 4. A circuit arrangement as claimed in claim 1 wherein means V includes a comparator for determining a difference between signal S3 and the luminous flux of the lamp determined by means IV and wherein the ballast is controlled so as to reduce this difference.
- 5. A circuit arrangement for operating a lamp having a known assumed relationship between the luminous flux output from the lamp and the lamp voltage and lamp current, comprising:
- a ballast for applying an actual lamp voltage across the lamp and causing an actual lamp current to flow through the lamp, the ballast being controllable;
- a memory in which a relationship is stored between output luminous flux of the lamp and corresponding lamp voltage and lamp current;
- means I for generating a signal S1 which is a measure of the actual voltage applied across the lamp;
- means II for generating a signal S2 which is a measure of the actual current flowing through the lamp;
- means III for generating a signal S3 which is a measure of a desired value of luminous flux of the lamp;
- means IV for determining the actual luminous flux of the lamp from the relationship stored in the memory and the signals S1 and S2; and
- means V for controlling the ballast in dependence on the luminous flux of the lamp determined by means IV and on signal S3.
Priority Claims (1)
Number |
Date |
Country |
Kind |
94202542 |
Sep 1994 |
EPX |
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Parent Case Info
This is a continuation of application Ser. No. 08/523,063, filed Sep. 1, 1995, now abandoned.
US Referenced Citations (1)
Number |
Name |
Date |
Kind |
5039921 |
Kakitani |
Aug 1991 |
|
Foreign Referenced Citations (1)
Number |
Date |
Country |
0391383 |
Oct 1990 |
EPX |
Continuations (1)
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Number |
Date |
Country |
Parent |
523063 |
Sep 1995 |
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