IRPLCFL4 International Rectifier, IRPLCFL4 Datasheet - Page 8

• 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
The resistor R13 can be added if necessary to remove striations (dark rings) in the lamp that may
occur at low dimming levels.
R1 and R2 are fusible resistors that are optional and L1, L2, C1 and C2 are recommended for EMI
filtering but have no bearing on the functional operation of the ballast.
Protection Circuits (if included)
The SD pin of the IR2156 is used as lamp removal protection. If there is no lamp present the voltage
at SD pin will be pulled above the 5.1V threshold via R9 and R21 charging C19. When a lamp is in
circuit the voltage at the junction of R21 and R22 will be held low via D5 and R14.
The current sense resistor R20 has been selected so that if the lamp fails to strike as the frequency
approaches resonance in ignition mode, IC2 will shut down thus protecting the Q1 and Q2.
The VDC pin of IC2 is also used connected to the DC bus through R15 with C20 to COM to remove
noise. This provides brown out protection for the ballast which works by increasing the frequency
when the DC bus drops thus always keeping it above resonance so that hard switching will never
occur. Without this protection, if the CS pin is implemented, then the ballast will shut down in the event
of any hard switching provided the value of C11 is sufficiently low as not to filter out fast transients. If
a brown out occurs and the DC bus briefly falls and hard switching occurs the ballast will shut down
and remain off until the line is switched off and then back on again. This is undesirable and with the
implementation of the VDC pin of the IR2156 can easily be avoided.
Layout Issues
Care should be taken when laying out this circuit as with any closed loop control system. There
should be a star point for all of the 0V returns, particularly IC1 pin 4, IC2 pin 8, R20, C12, R14, D6,
C9, C10, C11 and C6, which is then returned to the negative side of C4 via a single track which is as
short as possible. This point should as close to IC2 COM pin 8 as possible and C21 should be located
as close to IC2 as possible with short tracks. This will avoid potential ground loop problems.
The connecting track from C5 to the MOSFET half-bridge should also be kept short and as far away
from the error amplifier as possible. C14 should be close to IC1 and IC2 with short tracks to the
positive supply pins to provide maximum decoupling. All tracks carrying HF currents in the output
section should be kept away from IC1 and IC2 and associated components.
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