AN10958
Fluorescent lamp driver with PFC using the UBA2015/16
family
Rev. 2 — 9 August 2012
Application note
Document information
Info
Keywords
Abstract
Content
UBA2015, UBA2015A, UBA2016A fluorescent lamp driver, PFC
This application note describes designs using IC family UBA2015,
UBA2015A and UBA2016A for common ballast topologies.
The IC is a controller used in electronic ballast for fluorescent lamps
incorporating controllers and NMOST drivers for Power Factor Correction
(PFC) and the half-bridge circuit.
The high-voltage fluorescent lamp ballast controller drives a zero-voltage
switching resonant topology. The lamp controller module includes a
high-voltage level shift circuit and several protection features. The
protection features include hard switching/capacitive mode protection,
half-bridge overcurrent (coil saturation) protection, lamp overvoltage (lamp
removal) protection and temperature protection.
In addition to the lamp controller, the IC also contains a PFC controller.
The quasi-resonant operation guarantees efficient operation of the PFC
circuit. Overcurrent protection, overvoltage protection and
demagnetization sensing ensure safe operation under all conditions. The
brownout protection of the PFC controller reduces the half-bridge
frequency to prevent excessive currents.
The proprietary high-voltage BCD power logic process enables efficient,
direct start-up from the rectified universal mains voltage. The IC can drive
half-bridge circuits with a supply voltage up to 600 V (AC).
The PFC and lamp controller combination makes the IC suitable for
dimmable or fixed current output fluorescent ballasts with a PFC for AC
mains voltages up to 390 V.
NXP Semiconductors
AN10958
Fluorescent lamp driver with PFC using the UBA2015/16 family
Revision history
Rev
v.2
v.1
Date
20120809
20110620
Description
second version
first version
Contact information
For more information, please visit:
http://www.nxp.com
For sales office addresses, please send an email to:
salesaddresses@nxp.com
AN10958
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Application note
Rev. 2 — 9 August 2012
2 of 56
NXP Semiconductors
AN10958
Fluorescent lamp driver with PFC using the UBA2015/16 family
1. Introduction
1.1 General IC description
Today’s market demands high-quality, reliable, lightweight, small and efficient electronic
High Frequency (HF) ballast with lamp end-of-life detection. The high-end market
segment also requires dimming functionality.
Electronic ballasts provide high efficiency performance because the lamp is operated at
high frequencies above 10 kHz. At this frequency, the lamp is more efficient when
compared to a magnetic ballast operating at 50 Hz to 60 Hz. High frequency operation
enables smaller magnetic components in the electronic ballast to be smaller. This
reduction makes electronic ballasts are approximately one fifth the weight of magnetic
ballasts.
The UBA2015, UBA2015A and UBA2016A combines Power Factor Correction (PFC) and
half-bridge controller in one IC which reduces the component cost significantly and
increases reliability. It has several protection mechanisms such as overvoltage/no ignition,
coil saturation, overtemperature and on some pins, open/short protection to guarantee
reliable and safe operation.
The integrated dimming option allows control of the lamp current down to 1 % of the
nominal lamp current. The integrated double-sided rectification of the lamp current
feedback signal and a control loop compensation network pin allows stable lamp
operation and achieves good dimming performance.
The IC is intended for fluorescent lamp ballast with fixed or dimmable light output, with
PFC for AC mains voltages up to 390 V.
A feature list, block diagram and flow chart for the IC are provided in the IC data sheet.
1.2 Basic electronic ballast circuit
Cs
V
AC
EMI
Lpfc
Ls
Lr
PFC AND HALF-BRIDGE
CONTROLLER/DRIVER
Cr
Ls
Cs
Cdc
019aaa610
The feedback signals are not shown.
Fig 1.
Basic electronic ballast circuit for inductive heating topology
AN10958
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© NXP B.V. 2012. All rights reserved.
Application note
Rev. 2 — 9 August 2012
3 of 56
NXP Semiconductors
AN10958
Fluorescent lamp driver with PFC using the UBA2015/16 family
1.2.1 Power factor correction
Lighting applications above 25 W need a PFC circuit to fulfill the Total Harmonic Distortion
(THD) and Power Factor (PF) requirements. The PFC circuit is actually a boost or step-up
converter, therefore the output voltage must be higher than the peak AC mains voltage.
The PFC provides a fixed DC output voltage which helps to create a better defined
half-bridge circuit and therefore longer lamp life. A high DC voltage also results in more
efficient ballasts for lamps operating at higher voltages.
The PFC operates at a fixed on-time over one mains cycle. The PFC circuit inductor peak
current follows the sinusoidal mains waveform. EMI filtering averages the PFC switching
current and blocks common mode currents (see
Figure 2).
The frequency limit also reduces switching losses using valley skipping are reduced which
is very effective at low AC mains input voltage and medium to low output load conditions.
I
(1)
(2)
(3)
I
(1)
(2)
t
0.5
×
T
ac
019aaa608
on-time
T
PFC
t
zero current switching
019aaa609
a. Half AC mains cycle
(1) I
LPFC(peak)
.
(2) I
LPFC
.
(3) I
ac(avg)
.
b. PFC switching cycle
(1) I
QPFC
.
(2) I
DPFC
.
Fig 2.
PFC circuit currents
A fixed output voltage has the advantage that the half-bridge circuit can be designed for a
high input voltage. The fixed bus voltage makes the half-bridge design more efficient for
lamps with a high operating voltage such as T5 lamps.
1.2.2 Inductive heating half-bridge and ballast
Refer to
Figure 1.
The capacitor (C
r
) across the lamp is the resonant capacitor and
inductor (L
r
) is the resonant inductor. The capacitor in series with the lamp is the DC
blocking capacitor (C
DC
). Before ignition, the electrodes are preheated at a predefined
half-bridge current (UBA2016A) or frequency (UBA2015).
After preheat, the lamp voltage increases while sweeping the half-bridge operating
frequency down to the resonant frequency. Finally, the lamp ignites when the lamp ignition
voltage is reached. When the lamp does not ignite, the switching frequency ramp down is
stopped to avoid damage to components. Then a new ignition attempt is started. After a
maximum of two ignition attempts, the IC enters a standby mode.
Once the lamp is ignited, the resonant tank and switching frequency limit the amount of
current through the lamp. The half-bridge operating frequency controls the lamp current.
AN10958
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Application note
Rev. 2 — 9 August 2012
4 of 56
NXP Semiconductors
AN10958
Fluorescent lamp driver with PFC using the UBA2015/16 family
1.2.3 IC family overview
This family of half-bridge controller ICs comprises three functionally different versions. All
versions are available in both SO20 and DIP20 packages. The functional differences are
explained in
Table 1.
Table 1.
Function
PFC controller
Preheat operation
Boost function
Dim function
IC family overview
UBA2015
yes
current controlled and
fixed frequency
no
no
UBA2015A
yes
current controlled and
fixed frequency
no
yes
UBA2016A
yes
current controlled
yes
yes
1.2.3.1
Preheat operation
The current controlled preheat operation is intended for a series-resonant topology where
the half-bridge current is equal to the filament currents. The accuracy is independent of
the LC tank tolerances. Therefore, the preheat frequency is closer to the maximum
preheat voltage allowed. As a result, the preheat current is higher than with fixed
frequency preheat.
The fixed frequency preheat operation is intended for multi-lamp ballasts where the total
half-bridge current is not equal to the filament current. For example: the half-bridge
current is reduced by a factor of two when a lamp is removed in a two-lamp ballast with
conventional series-resonant topology.
1.2.3.2
Boost function
The boost function is used for amalgam lamps or outdoor applications to provide a rapid
light output run-up time. The run-up time is the time a discharged lamp takes to reach
80 % of the nominal light output. The boost function allows the lamp to be operated at 1.5
to 2.0 times its nominal current. As a result, the lamp reaches the optimum operating
temperature sooner. The boost is applied at ballast power-on. A capacitor in the
application determines the boost time.
1.2.3.3
Dim function
The dim function is intended for energy harvesting or light reduction.
2. Basic circuit description
This section describes the deep dimming ballast in the inductive series-resonant topology
shown in
Figure 1.
The inductors L
s
and L
r
are coupled, therefore the current through the
filaments is inductively coupled to the current through L
r
in the LC tank.
A complete electronic schematic of a ballast with dimming and boosting using the
UBA2016A is shown in
Figure 3.
This application note uses this schematic as a guide.
AN10958
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Application note
Rev. 2 — 9 August 2012
5 of 56
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