Gas discharge lamp power supply
An apparatus for providing power to a gas discharge lamp comprises a storage capacitor and an ignition switch coupled through a primarily parasitic first inductor to a parallel combination of a diode assembly and a second inductor in series with a gas discharge lamp. The second inductor is selected to optimize the energy transfer from the capacitor to the gas discharge lamp. During a first interval determined by the time constant of the series combination of a storage capacitor, a first inductor, and a second inductor, the diode assembly is not conducting and a forward sense current builds in the first and second inductors. During a second interval determined by the interaction of the two parallel circuits driving the gas discharge lamp, during which the diode array is conducting, the smaller reversed sense current flowing in the first inductor and a larger forward sense current flowing in the second inductor add, thereby generating a unipolar, forward sense, single pulse current output for the generation of optical energy by a gas discharge lamp.
1. A power supply having:
a first series circuit comprising a capacitor charged to an initial voltage and a switch;
a first inductor coupled between said first series circuit and an output circuit;
said output circuit comprising a diode assembly in parallel with a series combination of a gas discharge lamp having a lamp resistance and a second inductor;
where said diode assembly is not substantially conducting during a first interval from said switch operation to a first time determined by a time constant of said capacitor and the series combination of said first inductor and said second inductor;
and said diode assembly is substantially conducting during a second interval following said first interval and having a time duration determined primarily by a time constant of said capacitor and said second inductor.
2. The power supply of claim 1 where said controllable switch is an ignition.
3. The power supply of claim 1 where said capacitor, said first inductor, and said second inductor are related according to:
I
mFL
·
exp
(
-
(
T
0
4
+
T
1
2
)
·
(
R
d
+
R
fl
)
L
2
)
>
I
mC
·
R
d
(
R
d
+
R
fl
)
2
+
L
2
2
(
L
1
+
L
2
)
·
C
0
where:
L 1 and L 2 are the inductances of said first inductor and said second inductor;
C 0 is the capacitance of said capacitor;
T 0 =2·π·(( L 1 +L 2 )· C 0 ) 0.5 ;
T 1 =2·π·[( L 1 )· C 0 ] 0.5 ,
I mFL is peak current through said gas discharge lamp,
I mC is peak current of said capacitor,
R d is the resistance of said diode;
R fl is the resistance of said gas discharge lamp.
4. The power supply of claim 3 where said peak capacitor current is determined during the time period t where
0< t<T 0 /4.
5. The power supply of claim 3 where said diode resistance is the average resistance during the time period t where T 0 /4<t<T 0 /4+3T 1 /4.
6. The power supply of claim 3 where said gas discharge lamp resistance is the average resistance during the time t where 0<t<T 0 /4+3T 1 /4.
7. The power supply of claim 3 where
R fl <<2·( C 0 /( L 0 +L 1 )) 0.5 .
8. The gas discharge lamp of claim 1 where said diode comprises a plurality of individual series diodes.
9. The gas discharge lamp of claim 8 where each said individual series diode has substantially the same reverse voltage applied at a particular instant in time.
10. The gas discharge lamp of claim 8 where each said individual series diode includes a plurality of parallel individual diodes.
11. The gas discharge lamp of claim 10 where each said parallel individual diode carries substantially the same current at a particular instant in time.
12. A power supply having:
a reference node;
a source of charge comprising a capacitor in series with a switch, said source of charge having one end connected to said reference node and the other end being a charge output;
a clamping diode connected between said reference node and said charge output;
a load comprising a gas discharge lamp connected in series with a storage inductor, said load connected between said reference node and said charge output.
13. The power supply of claim 12 where said switch comprises an ignition.
14. The power supply of claim 12 where said clamping diode includes a series inductance and a series resistance.
15. The power supply of claim 12 where said capacitor, said first inductor, and said second inductor are related according to:
I
mFL
·
exp
(
-
(
T
0
4
+
T
1
2
)
·
(
R
d
+
R
fl
)
L
2
)
>
I
mC
·
R
d
(
R
d
+
R
fl
)
2
+
L
2
2
(
L
1
+
L
2
)
·
C
0
L 1 and L 2 are the inductances of said first inductor and said second inductor;
C 0 is the capacitance of said capacitor;
T 0 =2·π·(( L 1 +L 2 )· C 0 ) 0.5 ;
T 1 =2·π·[( L 1 )· C 0 ] 0.5 ,
I mFL is peak current through said gas discharge lamp,
I mC is peak current of said capacitor,
R d is the resistance of said diode;
R fl is the resistance of said gas discharge lamp.
16. The power supply of claim 12 where
R fl <<2·( C 0 /( L 0 +L 1 )) 0.5 .
17. The power supply of claim 15 where said peak capacitor current is determined during the time period t where
0< t<T 0 /4.
18. The power supply of claim 15 where said diode resistance is the average resistance during the time period t where T 0 /4<t<T 0 /4+3T 1 /4.
19. The power supply of claim 15 where said gas discharge lamp resistance is the average resistance during the time t where 0<t<T 0 /4+3T 1 /4.
20. The power supply of claim 15 where
R fl <<2·( C 0 /( L 0 +L 1 )) 0.5 .
21. The gas discharge lamp of claim 12 where said diode comprises a plurality of individual series diodes.
22. The gas discharge lamp of claim 21 where each said individual series diode has substantially the same reverse voltage applied at a particular instant in time.
23. The gas discharge lamp of claim 21 where each said individual series diode includes a plurality of parallel individual diodes.
24. The gas discharge lamp of claim 23 where each said parallel individual diode carries substantially the same current at a particular instant in time.