AT89RFD-10 / EVLB002
Non-Dimmable Fluorescent Ballast
..........................................................................................................................................................
User Guide Ballast Demonstrator User Guide
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7629AAVR04/06
Section 1
Introduction ........................................................................................... 1-1
1.1
General Description .................................................................................1-2
1.2
Ballast Demonstrator Features ................................................................1-2
Section 2
Ballast Demonstrator Device Features ................................................ 2-5
2.1
Atmel Supported Products .......................................................................2-5
2.2
IXYS Supported Products ........................................................................2-5
Section 3
Ballast Description ............................................................................... 3-7
3.1
Circuit Topology .......................................................................................3-7
3.1.1
Line Conditioning ...............................................................................3-7
3.1.2
Low Voltage Supply ...........................................................................3-7
3.1.3
PFC Boost Regulator .........................................................................3-8
3.1.4
PFC Magnetics ..................................................................................3-8
3.1.5
Lamp Drive ........................................................................................3-8
3.1.6
Control ...............................................................................................3-8
3.1.7
IXYS IXI859 Charge Pump Regulator ...............................................3-9
3.1.8
IXYS IXTP02N50D Depletion Mode MOSFET used ..........................3-9
3.1.9
IXYS IXD611 Half bridge MOSFET driver .......................................3-10
3.1.10 IXYS IXTP3N50P PolarHV N-Channel Power MOSFET .................3-10
Section 4
Circuit Operation................................................................................. 4-11
4.1
PFC ........................................................................................................4-11
4.1.1
PFC Sequence ................................................................................4-12
4.2
Lamp Circuit ...........................................................................................4-12
4.2.1
General ............................................................................................4-12
Section 5
AT8xEB5114 Non-dimmable Software ............................................... 5-15
5.1
Main_AT8xEB5114_fluo_demo.c ..........................................................5-17
5.1.1
ADC STATE MACHINE ...................................................................5-17
5.2
Pfc_ctrl.c ................................................................................................5-19
5.2.1
PFC STATE MACHINE ...................................................................5-19
5.3.1
Lamp State Machine ........................................................................5-21
Section 6
Conclusion ......................................................................................... 6-23 -2
Ballast Demonstrator User Guide
7629AAVR04/06
6.1
Appendix 1: Capacitor Coupled Low Voltage Supply .............................6-23
6.2
Appendix 2: PFC Basics .........................................................................6-24
6.3
Appendix 3: Bill of Materials....................................................................6-25
6.4
Appendix 4: Schematic ...........................................................................6-28 Ballast Demonstrator User Guide
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7629AAVR04/06
Section 1
Introduction
Efficient fluorescent lamps and magnetic ballasts have been the standard lighting fixture
in commercial and industrial lighting for many years. Several lamp types, rapid start,
high output, and others are available for cost effective and special applications. This
user guide covers operation and development details of the non-dimmable version of
our fluorescent ballast for operating a variety of lamps that are available today. This
guide also covers power electronic circuits that find wide utilization in other applications
beyond lighting alone, which include Power Factor Correction, Half-Bridge Inverter
Drives, and Charge Pump Regulators all employing a variety of IXYS / Atmel parts.
Typical rapid start fluorescent lamps have two pins at each end with a filament across
the pins. The lamp has argon gas under low pressure and a small amount of mercury in
the phosphor coated glass tube. As an AC voltage is applied at each end and the fila-
ments are heated, electrons are driven off the filaments that collide with mercury atoms
in the gas mixture. A mercury electron reaches a higher energy level then falls back to a
normal state releasing a photon of ultraviolet (UV) wavelength. This photon collides with
both argon assisting ionization and the phosphor coated glass tube. High voltage and
UV photons ionize the argon, increasing gas conduction and releasing more UV pho-
tons. UV photons collide with the phosphor atoms increasing their electron energy state
and releasing heat. Phosphor electron state decreases and releases a visible light pho-
ton. Different phosphor and gas materials can modify some of the lamp characteristics.
Figure 1-1. Fluorescent Tube Composition -2
Ballast Demonstrator User Guide
7629AAVR04/06
Since the argon conductivity increases and resistance across the lamp ends decreases
as the gas becomes excited, an inductance (ballast) must be used to limit and control
the gas current. In the past, an inductor could be designed to limit the current for a nar-
row range of mains voltage and frequency. A better method to control gas current is to
vary an inductor's volt-seconds to achieve the desired lamp current and intensity. A vari-
able frequency inverter operating from a DC bus can do this. If the inductor is part of an
R-L-C circuit, rapid start ignition and operating currents are easily controlled depending
on the driving frequency versus resonant frequency.
Utility is enhanced by designing a power factor correcting boost converter (PFC) to
achieve the inverter DC bus over a wide mains voltage range of 90 - 265VAC, 50/60 Hz.
Since a PFC circuit keeps the mains current and voltage in phase with very low distor-
tion, mains power integrity is maintained. Additional utility is achieved by designing a
microcontroller for the electronic ballast application that can precisely and efficiently
control power levels in the fluorescent lamp. An application specific microcontroller
offers the designer unlimited opportunity to enhance marketability of lighting products.
The final design topology is shown in the block diagram of Figure 1-3.
1.1
General
Description
Fluorescent ballast topology usually includes line conditioning for CE compliance, a
power factor correction block including a boost converter to 380 V for universal input
applications and a half bridge inverter. Varying the frequency of the inverter permits time
for filament preheat and ignition for rapid starting, including precise power control. As
shown in the block diagram, figure 3, all of these functions can be timed, regulated, and
diagnosed with the Atmel AT89EB5114 microcontroller.
1.2
Ballast
Demonstrator
Features
Automatic microcontroller non-dimmable ballast
Universal input _ 90 to 265 VAC 50/60 Hz, 90 to 370 VDC
Power Factor Corrected (PFC) boost regulator
Power feedback for stable operation over line voltage range
Variable frequency half bridge inverter
18W, up to 2 type T8 lamps
Automatic single lamp operation Ballast Demonstrator User Guide
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7629AAVR04/06
Figure 1-2.
Ballast demonstrator assembled board
Figure 1-3.
Non-Dimmable Ballast block diagram
UVLO
15V
3.3V
Regulator
PFC Driver
IX859
PFC BOOST REGULATOR
Driver
Driver
15V
INVERTER
DECOUPLING CAP
A
CIT
OR
RESONATING
INDUCTOR
AND
FILAMENT
TRANSFORMER
2
11
3
10
5
8
6
7
T4
IXD611
R28
IXTP3N50P
Q5
Q4
B
ULK CAP
A
CIT
OR
C9
C14
D4
Q3
R2
Q1
D2
D3
R9
&
R13
R35
T1
IXTP02N50D
R10
&
R14
R39
11
2
10
3
5
6
7
C11
RESONA
TING CAP
A
CIT
OR
T3
BALANCE
TRANSFORMER
AND
LAMPS
POWER
VOLTAGE
R42
PFC Output
Inverter High
Inverter Low
V_HAVERSINE
V_BUS
V_LAMP
I_LAMP
P3.5/W0M1
P3.5W1M0
P3.6/W1M1
P4.0/AIN0
P3.3/AIN4
P4.1/AIN1
P4.3/AIN3
PFC_ZCD
P3.2/INT0
AT89EB5114
8
12
1
PFC Inductor Ballast Demonstrator User Guide
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Section 2
Ballast Demonstrator Device Features
2.1
Atmel Supported
Products
AT89EB5114 Microcontroller
High speed configurable PWM outputs for PFC and ½ bridge inverter
6 Analog inputs for A/D conversion, 2.4V internal reference level
3 High speed PWM outputs used for the PFC and ½ bridge driver
A/D with programmable gain used for efficient current sensing
SOIC 20 pin package
2.2
IXYS Supported
Products
IXI859 Charge pump with voltage regulator and MOSFET driver
3.3V regulator with undervoltage lockout
Converts PFC energy to regulated 15VDC
Low propagation delay driver with 15V out and 3V input for PFC FET gate
IXTP3N50P MOSFET
500V, low R
DS
(ON) power MOSFET, 3 used in design
IXD611S MOSFET driver
Up to 600mA drive current
½ bridge, high and low side driver in a single surface mount IC
Undervoltage lockout Ballast Demonstrator User G