IRPLCFL4 International Rectifier, IRPLCFL4 Datasheet - Page 9

• Manufacturer Part Number: IRPLCFL4
• Description: IC BALLAST DIMMING CFL 3-WAY
• Manufacturer: International Rectifier

Specifications of IRPLCFL4

• Main Purpose: Lighting, Ballast Control
• Utilized Ic / Part: IR2156
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Secondary Attributes: -
• Embedded: -
• Primary Attributes: -
• Other names: *IRPLCFL4

IRPLCFL4
Component Selection
The output inductor and capacitor values should be chosen for the ballast to allow it to run at maxi-
mum brightness around 40-45kHz. This will minimize losses in the inductor. For this example the IR
Ballast Designer software * has been used to select the required preheat, ignition and run frequen-
cies for a 25W spiral CFL lamp giving an L3 of 2.2mH and C of 4.7nF.
The values of R16, R17 and C9 have been calculated to give a preheat frequency of 65kHz and a run
frequency of 40kHz. The ignition frequency will be around 58kHz.
Output Inductor Design
The output inductor L3 should be designed to allow a high peak ignition current without saturating.
This is important as the IR2156 shutdown will be triggered if the inductor saturates. The ignition
current depends on the type of lamp being used and must be kept to a minimum by ensuring the
preheat is correct. To minimize losses in the inductor multi-stranded wire should be used in combina-
tion with Ferrite cores of sufficiently good quality. The best approach to design is to wind as many
turns as possible of multi-stranded wire and have the largest gap possible to achieve the correct
inductance. This will produce the highest available peak current before saturating the inductor. It is
important to bear in mind that when the cores are hot the saturation point and hence the peak current
for the inductor will be lower therefore a poorly designed inductor may result in the ballast shutting
down during an attempted hot re-strike.
The inductor design process can be greatly simplified by using the Ballast Designer software pro-
duced by I.R. For this application it is recommended to fix the core size to EF20.
Lamp Preheating
The lamp must be sufficiently preheated before ignition. The correct preheat current can be deter-
mined from published data or from International Rectifiers Ballast Designer software.
The preheat time can be set by adjusting the value of C10. As a general rule the lamp filament should
glow red before ignition. If preheat is insufficient the ballast is likely to shutdown during ignition
because the output inductor will be unable to operate at the high current required. The number of
turns in the auxiliary cathode windings of the output inductor L2 should be chosen to provide suffi-
cient preheat. In designs for ballasts with integral lamps the shutdown pin can be grounded so that the
inductor may saturate without shutting down the circuit.
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