uba20270 NXP Semiconductors, uba20270 Datasheet - Page 7

• Manufacturer Part Number: uba20270
• Description: 600 V Driver Ic For Dimmable Compact Fluorescent Lamps
• Manufacturer: NXP Semiconductors

NXP Semiconductors
UBA20270
Product data sheet
7.1.4 Ignition state
The preheat time consists of eight saw-toothed pulses at the CP pin. Preheat begins as
soon as the capacitor on the CP pin is charged to a voltage higher than V
the preheat time, the current feedback sensor circuit (input CSI pin) is disabled. To
increase noise immunity, an internal filter of 30 ns is included at the SLS pin.
If during preheat, the level on the DCI pin drops lower than V
= 0.24 V or the V
stopped. The circuit enters the hold state delaying a new preheat cycle. A fixed voltage
drop on the preheat capacitor C
delay time.
A new preheat cycle starts after the CP pin level slowly discharges. This condition
continues until V
V
Directly after the preheat state has been completed, the ignition state is entered. In the
ignition state, the frequency sweeps down due to charging of the capacitor C
pin with an internally fixed current. See
frequency, the circuit approaches the resonant frequency of the resonant tank L2, C5.
This results in a high voltage across the lamp to ignite the lamp. The current sensor circuit
which monitors the voltage over resistor R
If the voltage on the CSI pin is above the typical ignition detection threshold voltage level
of 0.6 V, lamp ignition is detected. The system then changes from ignition state to the
boost or burn state. If no ignition is detected, the frequency decreases further to the
minimum half-bridge frequency f
over-heating of the application due to lamp damage, the UBA20270 only attempts to ignite
the lamp twice after power-up. The ignition attempt counter is incremented when the lamp
ignition threshold voltage on the CSI pin is not exceeded at the end of the ignition
enabling time. If a second ignition attempt also exceeds the ignition time-out period, the IC
enters the power-down state. See
Fig 4.
DD
(kHz)
100
> V
f
DD(start)
CFL frequency from start to burn state
preheat frequency
preheat
start frequency
AND V
All information provided in this document is subject to legal disclaimers.
CP
DD
< V
pin drops lower than V
Rev. 2 — 8 September 2011
i(DCI)
th(rel)CP
ignition
CFL ignition
> V
boost bottom ~22 kHz
600 V Driver IC for dimmable compact fluorescent lamps
and recharges higher than V
th(start)DCI
CP
bridge(min)
Figure
and a fixed discharge current on the CP pin sets the
A
. See
Figure
. To prevent continuous ignition attempts and
5.
CSI
DD(stop),
B
Figure
detects lamp ignition. See
boost
4. During this continuous decrease in
the preheat state is immediately
C
5.
th(CP)max
th(start)DCI
transition
UBA20270
provided
 V
© NXP B.V. 2011. All rights reserved.
Figure
th(CP)max
th(hys)DCI
burn
CI
001aam764
on the CI
11.
. During
100 %
time (s)
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