UBA20271 データシートの表示（PDF） - NXP Semiconductors.
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UBA20271 Datasheet PDF : 33 Pages
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NXP Semiconductors
UBA20271/2
350 V and 600 V Power ICs for dimmable compact fluorescent lamps
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 Vth(CP)max. During
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 Vth(start)DCI Vth(hys)DCI
= 0.24 V or the VDD pin drops lower than VDD(stop), the preheat state is immediately
stopped. The circuit then enters the hold state delaying a new preheat cycle. A fixed
voltage drop on the preheat capacitor CCP and a fixed discharge current on the CP pin
sets the delay time.
A new preheat cycle starts after the CP pin level slowly discharges. This condition
continues until VCP < Vth(rel)CP and recharges higher than Vth(CP)max provided
VDD > VDD(start) AND Vi(DCI) > Vth(start)DCI. See Figure 5.
f
(kHz)
100
start frequency
CFL ignition
A
B
C
preheat frequency
100 %
boost bottom ~22 kHz
time (s)
preheat
ignition
boost
Fig 4. CFL frequency from start to burn state
transition
burn
001aam764
7.1.4 Ignition state
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 CCI on the CI
pin with an internally fixed current. See Figure 4. During this continuous decrease in
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 RCSI detects lamp ignition. See Figure 11.
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 fbridge(min). To prevent continuous ignition attempts and
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 Figure 5.
UBA20271_UBA20272
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 2.1 — 12 October 2011
© NXP B.V. 2011. All rights reserved.
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