ICB1FL02G Datasheet, PDF (29/37 Pages) Infineon Technologies AG – Smart Ballast Control IC for Fluorescent Lamp Ballasts

ICB1FL02G
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 LVS1 via R31...R35, when the high-side filament is
connected. The current fed into pin LVS1 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. If not required
the pin LVS2 can be disabled by connecting to GND.
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.
K01 ^F1 L0
180V..
270V ^C01
AC
K02
K03
PE
C05
D1...4
C04 C02
C03
D11
L1
D5
R13
R14
R15
R11 Q1
R16
C10
R12
PFCZCD
PFCGD
PFCVS
PFCCS
D9
R31 R32 R33
L21
Q2
R26
HSGD
HSVCC
N2
N1
R34 R35 N3
L2
C17
C21
K1
K2
HSGND
C14 Q3
LSGD ^R27
LSCS
D6
R29
C15 C16 C18
D7
L22
C20
K3
C22
K4
R36
R18 R19 C11 R20
C12
R30
D8
R21 R22 R23 C13 R24 R25
C19 D10
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 R31...R33 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 D10 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
control loop is completely integrated with a digital filter and error amplifier. PFC overcurrent is sensed by R18,
R19, Bus overvoltage and undervoltage at pin PFCVS. A bypass diode D11 between the DC side of the mains
rectifier and BUS capacitor is recommended in order to avoid an overload of the PFC MOSFET Q1.
Datasheet Version 1.2
29
February 2006