AN11199
UBA2015 TL Ballast for multiple lamps with independent lamp
operation
Rev. 1 — 24 December 2012
Application note
Document information
Info
Keywords
Abstract
Content
UBA2015, tube lamp (TL), Independent lamp operation (ILO)
This application note describes how to drive multiple lamps with a
UBA2015 so that when one lamp fails the other lamps keep burning.
NXP Semiconductors
AN11199
UBA2015 TL Ballast for multiple lamps with independent operation
Revision history
Rev
v.1
Date
20121224
Description
first issue
Contact information
For more information, please visit:
http://www.nxp.com
For sales office addresses, please send an email to:
salesaddresses@nxp.com
AN11199
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Application note
Rev. 1 — 24 December 2012
2 of 38
NXP Semiconductors
AN11199
UBA2015 TL Ballast for multiple lamps with independent operation
1. Introduction
There are several topologies possible for multiple lamps. The topology chosen depends
on the Bill Of Materials (BOM) and the requirements.
Table 1
shows the topologies for
independent Tube Lamp (TL) operation described in this document.
Table 1.
Topology
Topologies for independent TL operation
Pros
Cons
Ballast
Efficacy
Factor
(
BEF)
0
+
++
Independent
lamp
operation
(ILO)
full
half
full
One resonant tank per lamp
simple architecture
one inductor per lamp
needed
if one lamp fails, then two
lamps are off
more complicated control
circuit
no preheat
One resonant tank per two lamps less magnetic and
(two by two lamps in series)
half-bridge current
All lamps on one resonant tank
separate heating
transformer delivers short
preheat and high BEF
instant activation
All lamps on one resonant tank
with transformer
++
full
Remark:
All topologies are free of patents.
AN11199
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Application note
Rev. 1 — 24 December 2012
3 of 38
NXP Semiconductors
AN11199
UBA2015 TL Ballast for multiple lamps with independent operation
2. Overview of Commonly Used Topologies
This application note uses four 18 W T8 lamps as an example. Some of the topologies
also apply to T5 lamps.
2.1 Topology 1: four lamps in parallel with four resonant tanks
Figure 1
shows a topology of four lamps in parallel, each with a resonant tank. Only the
resonant tank part is shown. The PFC section design generating the bus voltage does not
depend on the ballast topology and is therefore not shown.
The advantage of this topology is that it is true ILO, that is, the ballast works with one, two,
three or four lamps inserted. The main disadvantage is that four rather expensive
inductors are needed. This topology has the capacitor through the filaments, so it is not
suitable for the T5 Hawaiian Electric Industries series of lamps.
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Fig 1.
Four lamps in parallel with four resonant tanks
AN11199
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Application note
Rev. 1 — 24 December 2012
4 of 38
NXP Semiconductors
AN11199
UBA2015 TL Ballast for multiple lamps with independent operation
2.2 Topology 2: two
two
lamps in parallel with two resonant tanks
Figure 2
shows a topology that only requires two inductors. It is therefore, cheaper and
has fewer losses than topology 1.
The current through the MOSFETs is also lower, reducing the losses/BOM cost even
further. The only disadvantage of this topology is that if one lamp is missing or broken, two
out of four lamps do not burn.
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Fig 2.
Two
two
lamps in parallel with two resonant tanks
2.3 Topology 3: four lamps in parallel with one resonant tank
The topology shown in
Figure 3
allows full ILO (one, two, three or four lamps) but has a
larger BOM and is more complex.
The resonant capacitors cannot now be placed over the lamp so some form of inductive
heating must be used if preheat is required. This heating allows this topology to be used
for T8 and T5 lamps. The inductive heating can be switched off after preheat with an extra
MOSFET.
To enable optimal operation, a feedback control loop is required. This loop keeps the lamp
discharge current constant regardless of the number of working lamps in the ballast.
If relamp is required, place a DC blocking capacitor in series with the inductive filament
heating windings. A simple, one transistor circuit can generate a reset pulse if a lamp is
inserted.
Inductor L1 carries the current of the lamps in parallel, plus the resonant tank current. This
voltage is large due to the 200 V to 300 V voltage on the resonant tank capacitor during
lamp operation. Inductor L1 is therefore bulky/expensive, partially undoing the benefit of
having only one resonant tank inductor instead of four.
AN11199
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Application note
Rev. 1 — 24 December 2012
5 of 38
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