UM10525
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1 — 19 April 2012
7 of 21
NXP Semiconductors
UM10525
120 V 20 W CFL demo board using the UBA2212
In preheat, current I
SW
charges capacitor C
SW
generate the preheat timing (t
ph
).
Capacitor C
CB
connected to pin CB is connected to the boost timer input to control the
boost time. After preheat, the C
CB
voltage sweeps up and down at the boost timing (t
bst
).
The boost ends after 25 C
CB
sweeping cycles.
The transition from the boost state to the burn state is triggered when the boost timer
indicates the end of the boost state. During the boost to burn transition, the boost
transition timer is active. The timer defines transition time which is also realized using
capacitor C
CB
on CB pin.
When the RMS current control circuit leaves the system operating at the normal lamp
current, it enters the burn state. In this state, a feedback loop controls the V
SW
voltage on
pin SW. This feature makes the lamp current independent mains or lamp voltage
variations.
Fig 4.
Timing sequence of the system
001aan302
preheat
V
CB
V
SW
VCO input
burn
time (s)
ignition and boost
transition
V
lamp
f
osc(nom)
... ...
