uba20271 NXP Semiconductors, uba20271 Datasheet - Page 7

• Manufacturer Part Number: uba20271
• Description: 350 V And 600 V Power Ics For Dimmable Compact Fluorescent Lamps
• Manufacturer: NXP Semiconductors

NXP Semiconductors
UBA20271_UBA20272
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 then enters the hold state delaying a new preheat cycle. A fixed
voltage drop on the preheat capacitor C
sets the 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 UBA20271/2 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.
350 V and 600 V Power ICs for dimmable compact fluorescent lamps
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
and recharges higher than V
th(start)DCI
bridge(min)
Figure
A
. See
Figure
CP
. To prevent continuous ignition attempts and
5.
CSI
DD(stop)
and a fixed discharge current on the CP pin
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
UBA20271/2
transition
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)
7 of 33