EVAL6569 Datasheet, PDF (10/14 Pages) Panasonic Semiconductor – THE L6569 A NEW HIGH VOLTAGE IC DRIVER FOR ELECTRONIC LAMP BALLAST

AN880 APPLICATION NOTE
Figure 22: Open load detection example.
L6569
3_CF
4_GND
18V
LAMP
10.R
11.R
100.R
10.R
Several ways can achieve the protection task.
First it can be done by sensing the resonant cur-
rent through a MOSFET source resistor or a sec-
ondary winding on the choke. The switching is
stopped when a large current reduction is de-
tected by analog means.
A logic circuit can also detect the presence of the
lamp filaments. One end of a filament is always
connected to a fixed voltage. If the other end of
the filament is connected through a high imped-
ance resistor to another voltage, the absence of
the filament can be easily detected by monitoring
the resistor voltage change as shown on figure
22.
CONCLUSION
The foregoing note shows how high voltage driv-
ers, like the L6569, simplify the design of the
lamp ballast. These devices includes all the cir-
cuitry to drive MOSFETs in half bridge inverter.
Since the optimized switching frequency in-
creases above 50 kHz with a low tolerance, the
size of the passive resonant components is re-
duced, and the ballast becomes cheaper.With its
supply and its oscillator the L6569 is versatile,
and its flexibility permits to design any improved
power control.
BIBLIOGRAPHY
[1]: AN 527 "Electronic fluorescent lamp ballast"
A.Vitanza, R.Scollo, SGS-THOMSON
[2]: Smart Power ICs, Chapter 8, High voltage in-
tegrated circuits for off-line power applications.
C.Diazzi, SGS-THOMSON
[3]: AN 512 "Characteristics of power semicon-
ductors" JM Peter, SGS-THOMSON
[4] : "The L6569 half bridge driver: the shutdown
function"
[5] : "Compatibility test of dimming electronic bal-
lasts used in daylighting and environment con-
trols", A.Buddenberg, Rensselaer Polytechnic In-
stitute
[6]: "PSpice High Frequency Dynamic Fluores-
cent Lamp Model", Bryce Hesterman, APEC’96,
p.641
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