Datasheet

UBA20260 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2011. All rights reserved.
Product data sheet Rev. 2 — 10 October 2011 7 of 30
NXP Semiconductors
UBA20260
600 V driver IC for step dimmable CFLs
New preheat cycles start after the CP pin level slowly discharges until V
CP
<V
th(rel)CP
and
recharges above V
th(CP)max
provided V
DD
> V
DD(start)
(see Figure 5).
7.2.4 Ignition state
After the preheat state has been completed, the ignition state is entered. In the ignition
state, the frequency sweeps down on the CI pin due to capacitor C
CI
charging at a fixed
current as shown in Figure 4
. During this continuous decrease in frequency, the circuit
approaches the resonant frequency of the resonant tank (L2, C5). This action causes a
high voltage across the lamp to ignite the lamp. The ignition current sensor circuit which
monitors the voltage over resistor R
CSI
(see Figure 12) detects lamp ignition.
If the voltage on pin CSI is above the typical ignition detection threshold voltage level of
0.6 V, lamp ignition is detected. The system changes from ignition state to either the boost
or burn state.
If ignition not is detected, the frequency drops further to the minimum half-bridge
frequency f
bridge(min)
frequency. To avoid repeated ignition attempts and overheating of the
application due to lamp damage, the IC only tries to ignite the lamp twice after power-up.
The ignition attempt counter increments at the end of the ignition enabling time when the
lamp ignition threshold voltage on the CSI pin is not exceeded. The ignition enabling time
is typically
1
⁄
4
of the preheat time t
ph
. If a second ignition attempt also exceeds the ignition
time-out period, the IC enters the power-down state (see Figure 5
).
Fig 4. CFL frequency from start to burn state
boostignition burntransitionpreheat
100
f
(kHz)
start frequency
preheat frequency
CFL ignition
time (s)
100 %
001aam764
boost bottom ~22 kHz
A CB