ICB1FL03G Datasheet, PDF (29/38 Pages) Infineon Technologies AG – Smart Ballast Control IC for Fluorescent Lamp Ballasts

ICB1FL03G
Application Examples
7 Application Examples
7.1 Operating Behaviour of a Ballast for a single Fluorescent Lamp
After turning on the mains switch the peak value of the rectified AC input voltage is available at C02 and smoothing
capacitor C10 (Fig. 17). Via R11 and R12 the supply voltage increases at bypass capacitors C12 and C13. At a
level of 10,5V a source current out of pin RES is sensing the existence of the low-side filament of the fluorescent
lamp. Fed from the BUS voltage a current is detected at pin LVS via R41, R42, R43, when the high-side filament
is connected. The current fed into pin LVS is used to charge C12 via internal clamping diode. The IC changes into
active mode when Vcc level achieves the turn-on threshold of 14V and both filaments are detected.
The active IC is sensing the BUS voltage level via R14, R15. Gate drives are disabled when open loop or
overvoltage are detected. If BUS voltage level is within the allowed range, the low-side Gate drive is starting with
the first pulse of the 125kHz softstart frequency. Only few cycles are required to charge the bootstrap capacitor
C14 via D6, R30 and Q3. Without R30 there is a risk of overcurrent shut down by exceeding the 1,6V threshold
at pin LSCS. The power supply is generated by a charge pump C16, D7 and D8. In normal operation C16 is
charged and discharged via C17 from the current forced by the resonance inductor L2 during the deadtime of the
inverter producing a zero voltage switching (ZVS) operation. Run frequency, preheating frequency and preheating
time are set by resistors R21, R22 and R23.
C5
L10
D1...4
C1 C4
90 ... 270 VAC
PE
C2
C3
L1
R34
R41
R42 R43
R35
L21 C21
R1 _Q1
R2
D5 ^R13
R14
R15
R16
R11 ^C10
PFCZCD
PFCGD
PFCVS
PFCCS
R26
HSGD
HSVCC
HSGND
C14
R27
LSGD
LSCS
Q2
C17
C15
Q3
C16
C18
K2 K1
L2
C20
R3 R12
D6
D7
K4 K3
R18 R19 C11R20
R61
D9
R21R22R23 R30
C12
C13
R24R25
D8
C61
SMD
K6 K5
D61
SMD-Z
L22 _C22 R36
C19
Figure 17 Application circuit of a Ballast for a single Fluorescent Lamp with voltage mode Preheating.
During run mode the lamp voltage is sensed via R41, R42, R43 in order to detect an abnormal increasing of lamp
voltage or an rectifier effect that can occur at end-of-life conditions of the lamp. At the pin RES there is also
detected a non-ZVS operation, classified into Capmode1 and Capmode2. This will be done by the capacitive
divider C18, C19, that transfers the divided AC-part of the inverter output voltage to pin RES. Dependent on the
shape of the signal two different time windows can be started at abnormal conditions in order to protect the ballast.
Zener diode D61 limits voltage transients at pin RES that can occur during removal of the lamp.
Voltage mode preheating is done by two separate windings on the resonant inductor L2. The bandpass filters L21,
C21 and L22, C22 are designed to pass preheating current at preheating frequency only and to block any current
during run mode. Ignition is provided by shifting the operating frequency towards the resonant frequency of L2
and C20. The voltage level during ignition is limited by the current sensed at Shunt resistors R24, R25 with a level
of 0,8V at pin LSCS. Overcurrents that exceed a voltage level of 1,6V for longer than 400ns will disable the IC at
any time and change into fault mode.
The PFC preconverter with L1, Q1 and D5 is starting with a fixed frequent operation and change over to a critical
conduction mode (CritCM) as soon as the level at pin PFCZCD is sufficient to trigger the operation. During light
load the operation mode changes into discontinuous conduction mode (DCM). Compensation of the voltage
Preliminary Datasheet Version 1.02
29
March 2009