VK05CFL STMicroelectronics, VK05CFL Datasheet - Page 6

• Manufacturer Part Number: VK05CFL
• Description: Electronic Driver For Cfl Application
• Manufacturer: STMicroelectronics

VK05CFL
Figure 3: Start-up phase
diac
midpoint
From figure 4 it can be observed that the value of secondary voltage decreases when the lamp current
increases. This happens because increasing the value of the current flowing through the tube, increase
the drop on it, consequently decreasing the voltage on the ballast inductor Lp and thereby decreasing also
the secondary voltage.
By inserting the filters (R4-C10; R5-C11) between the two secondary windings and the devices, it is
possible to guarantee a higher voltage on the input pin of the devices for longer time compared to the
secondary signal. In this way it is possible to extend the use of the VK05CFL to all the power range eg.5W
– 23W.
Figure 4: Steady state waveforms
V
midpoint
V
L2s
V
sec
I
lamp
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