UM10412
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2010. All rights reserved.
User manual
Rev. 1 — 2 November 2010
12 of 26
NXP Semiconductors
UM10412
UBA2021 evaluation board
5.5 Transformer
T1
In the default setup, transformer T1 will be used and is connected with jumpers to lamp
connector 4 (X 8). The transformer specifications are listed in
5.6 FET
Two NMOST FETs should be placed in X2 and X14. The supplied NMOST's are Toshiba
2SK3569 (V
DS
= 600 V; I
D
= 10 A; R
DSon
= 0.54
Ω
). When using different NMOS types, the
values of gate resistors R1 and R3 (default 33
Ω
) maybe changed.
5.7 Current
sense
selection
A feed forward mechanism in the UBA2021 ensures that the lamp power will not increase
above the maximum allowed value due to an increased mains voltage. This means that
the operating frequency is controlled by the bus voltage rather than by the lamp current or
the half-bridge current.
5.7.1 Half-bridge current sensing
The half-bridge current is sensed for controlling the preheat current. Different values of
the sense resistor can be selected using jumpers X32 and X34. To connect the lamp to
ground, X39 should be shorted between pin 2 and pin 3.
5.7.2 Lamp current sensing
The UBA2021 does not sense the lamp current, so X39 should be shorted between pin 2
and pin 3 in order to connect the lamp to ground.
Table 8.
Default connection transformer T1
Header
Comment
X110
Insert to connect T1 to filament 1, lamp 4
X111
Insert to connect T1 to filament 1, lamp 4
X112
Insert to connect T1 to filament 2, lamp 4
X113
Insert to connect T1 to filament 2, lamp 4
X114
Insert to connect SH to transformer T1
X115
Insert to connect T1 to resonant capacitor C6 (4.7 nF, 2000 V)
Table 9.
Current sensing selection
X33
pins 1 and 2
pins 2 and 3
half-bridge
open
open
lamp current
open
open
Table 10.
Current sensing selection
X32
X34
Resistance
short
short
0.5
Ω
short
open
1.0
Ω
open
short
1.5
Ω
open
open
2.0
Ω
