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University of Portland
School of Engineering
5000 N. Willamette Blvd.
Portland, OR 97203-5798
Phone 503 943 7314
Fax 503 943 7316
Final Report
Project Surf Scoter: Electronic Ballast
Contributors:
Lance McGuire
Sam Nelson
Sam Ortiz
Jordan Stone
Approvals
Name
Dr. Hoffbeck
Date
Name
Date
Dr. Ward
Insert checkmark (√) next to name when approved.
UNIVERSITY OF PORTLAND
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CONTACT: A. NAME
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Revision History
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Rev.
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0.1
4/11/08 .
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Author
J. Stone
Reason for Changes
Initial draft
Note on TR Numbers
Your instructor will assign each team a Technical Report (TR) number. You will place this
number in your header so that your document may be referenced and potentially retrieved
by others. In addition, it provides you a publication to place in your resume.
Below are a couple of example numbers that illustrate the format.
UP-CS-TR-08-01
UP-EE-TR-08-01
UNIVERSITY OF PORTLAND
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Acknowledgments
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Dr. Joseph Hoffbeck was our advisor and assisted with any problem we had, whether technical
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or involving.our documentation.
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Mr Jonathan Fant ensured our documentation was up to quality standards. He also helped us
with a good amount of technical specifications. He helped us acquire a luminaire and ballast.
Dr. Wayne Lu was extraordinarily helpful with getting us a transformer that matched our ideal
specifications.
Dr. Robert Albright helped us with technical consultation.
Dean Yamayee helped us with technical consultation.
Sandy Ressel was a great help with soldering advice and other general electronics knowledge.
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Table of Contents
Summary....................................................................................................................... 1
Introduction .................................................................................................................. 2
Background .................................................................................................................. 3
Methodology ................................................................................................................ 4
Design Process .......................................................................................................................................4
Pre-Approval.....................................................................................................................................4
Functional Specification ...................................................................................................................4
Project Plan ......................................................................................................................................5
Design Review .................................................................................................................................5
TOP Approval ...................................................................................................................................5
Construction .....................................................................................................................................5
Testing and Debugging....................................................................................................................6
Results .......................................................................................................................... 7
Technical..................................................................................................................................................7
Fuse and Safety Switch ...................................................................................................................7
EMI Filter...........................................................................................................................................7
Transformer ......................................................................................................................................7
PFC / Rectifier ..................................................................................................................................8
Ballast Controller ..............................................................................................................................9
Operating Modes........................................................................................................................... 11
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Under-Voltage Lockout Mode ............................................................................................... 11
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Pre-Heat Mode ....................................................................................................................... 11
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Ignition Mode........................................................................................................................... 13
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Run Mode ............................................................................................................................... 14
Fault Mode.............................................................................................................................. 15
Conclusion .............................................................................................................................. 15
Process ................................................................................................................................................. 16
Assumptions .................................................................................................................................. 16
Milestone Review .......................................................................................................................... 17
Risks .............................................................................................................................................. 17
Resources ..................................................................................................................................... 17
Conclusions ...............................................................................................................18
Appendices.................................................................................................................19
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List of Figures.
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Figure 1. Block Diagram of.Surf Scoter Product...........................................................................................7
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Figure 2. Voltage and Lagging
. Current .........................................................................................................9
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Figure 3. Synched Voltage and Current........................................................................................................9
Figure 4. Pre-Heat Mode Switching ........................................................................................................... 12
Figure 5. Pre-Heat Mode Switching Detail ................................................................................................. 13
Figure 6. Ignition Mode Switching .............................................................................................................. 13
Figure 7. Ignition Mode Switching Detail .................................................................................................... 14
Figure 8. Run Mode Switching ................................................................................................................... 14
Figure 9. Run Mode Switching Detail ......................................................................................................... 15
Figure 10. Input Stage Schematic .............................................................................................................. 19
Figure 11. Front End of Circuit Design for Simulation ............................................................................... 20
Figure 12. PSPICE Detail of Ballast Controller and Lamp RLC Circuit .................................................... 21
Figure 13. Flow Chart of Ballast Controller Modes .................................................................................... 22
Figure 14. PSPICE Output Simulation Circuit............................................................................................ 23
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List of Tables .
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Table 1. Transformer Table
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Table 2. Initial Values ..................................................................................................................................
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Table 3. Calculated Values ......................................................................................................................... 11
Table 4. Transformer Results ..................................................................................................................... 15
Table 5. Parts List and Ratings................................................................................................................... 24
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Summary
The goal of Surf Scoter was to design and build an electronic ballast for a fluorescent tube
light. Fluorescent lights are much more efficient than traditional incandescent lights, as
they consume about ten times less power. Incandescent lights waste energy by
converting more of their consumed power into heat, while fluorescents achieve higher
efficiency by converting a greater percentage of consumed power into light. The
remainder of this document describes the design process, project results and it ends with
a conclusion.
The challenge concerning fluorescent tube lamps is the higher voltage and frequency
required to achieve high efficiency. While incandescent lamps operate at a standard
residential voltage and frequency of 120V and 60Hz, respectively, fluorescent lights
operating at maximum efficiency require voltages between 200 and 300V and frequencies
ranging in the tens of kHz. An electronic ballast must be used to regulate the electricity
delivered to the lamp because of these constraints.
A ballast is a device that controls the voltage, current and sometimes frequency of the
signal driving a lamp. An electronic ballast uses solid-state electronic circuitry to achieve
the necessary conditions.
This document is the final report for Project Surf Scoter.
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Introduction
The purpose of this document is to describe the results of the project and how they were
achieved. This is the result of two semesters’ worth of research, design, implementation
and debugging to create an electronic ballast.
This document is intended for the faculty and senior Electrical Engineering students of the
School of Engineering at the University of Portland, as well as the industry representative
overseeing this project. A general introduction to fluorescent lamps and electronic ballasts
is first presented in this document, followed by a detailed description of the functionality of
the electronic ballast which was designed and built. The basic blocks of circuitry that were
implemented are also discussed.
The next section of this document describes the process and planning behind the final
product. It starts by explaining the research required to understand fluorescent lighting
technology. This section also explains how the project was broken down into individual
pieces, how each section was tested, and then finally integrated together.
The final section of this document includes the results. The full system block diagram is
discussed and then each section of this project is described in greater detail. This section
ends by describing the results of the final prototype which includes discussion about the
shortcomings of Project Surf Scoter.
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Background
An electronic ballast is an apparatus that controls the current flow into a circuit. In this
case, the circuit is a fluorescent lamp. There are various types of ballasts, but the
electronic ballast increases the input frequency (typically 60 Hz in the United States) to a
much higher frequency in the range of 10 to 40 kHz. Not only does this eliminate the
flickering that is typical of fluorescent lighting but also increases the efficiency of the lamp.
An electronic ballast can be as simple as a resistor and inductor, but the ballast that will be
used here will be made of more complicated solid-state devices.
The type of electronic ballast that was designed works by increasing the frequency and
amplitude of the input voltage for the initial ionization of the gas within the lamp. Once the
arc inside the lamp is started, the amplitude of the input voltage is decreased to a nonzero constant value to maintain the arc.
The electronic circuitry that was used can be broken up into several functional blocks, as
shown in Figure 1. First, the standard 120V, 60Hz line power entered an electromagnetic
interference filter. A rectifier then converted the AC signal into DC and a Power Factor
Correction (PFC) element was used to eliminate any reactive power consumption
introduced by the circuit or lamp. Next, an inverter converted the DC power into AC power
of the desired voltage, current and frequency to operate the lamp. This inverter was be
controlled by a microcontroller to achieve the desired output power.
The circuitry in this product was contained in a Plexiglas case which incorporated a safetyswitch so that the input voltage could not be applied unless the case was closed, making
the circuitry inaccessible to any humans. The fluorescent lamp itself was also encased so
that particles or chemicals would not cause harm should the circuit or tube malfunction
during testing.
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Methodology
This section details the path to developing the project and the order in which steps were
taken to complete Project Surf Scoter.
Design Process
Success of this project depended on coordination between design and documentation
activities. Specifically, Pre-Approval and Functional Specifications required approval
before continuing. Once those had been approved the project moved into the design
phase. Meanwhile the Project Plan and Design Release were authored while some
preliminary design took place.
The design process was started at the output stage with the inverter and the
microcontroller that controls it. From there each block was designed or purchased and
then tested to see whether or not the block fulfilled the goal parameters. The EMI, Rectifier
and PFC blocks were developed around the same time. The parts were integrated into
one circuit once all of the individual blocks were developed. The final process involved
testing the circuit, recording performance, and observing if the lamp was operable from the
designed ballast.
Throughout the project, priority was given to the completion and approval of the
documents described in this section. It was the view of the team that since these
documents required sufficient design progress for approval the project would stay on track
as long as the documents were submitted and approved on schedule.
Pre-Approval
The first document to be submitted for approval was the Pre-Approval project request. For
this document, electronic ballast operation was concisely summarized as were the
advantages of fluorescent lighting. Also given in this document were the technologies that
were used in electronic ballasts like the one to be designed. The functional blocks as
identified at this stage were reported as were the components usually used in each block
and the team’s familiarity with these various technologies therein. This document also
outlined the basic functionality of the proposed product and potential parameters that
could be measured and evaluated in the finished prototype.
The Pre-Approval document was approved with the condition that safety precautions be
explicitly designed and implemented as to the high voltage nature of the project.
Functional Specification
Upon receiving approval for the project, the group was then required to define the basic
functionality of the electronic ballast with the Functional Specification document. The
purpose of this was to provide numerical goals for parameters of the project and a basic
outline of the components of which the ballast circuit will consist. The goal of this
document was to specify the physical properties of the ballast such as design structure,
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weight, wiring details, and the overall dimensions of the proposed product. It also defined
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environmental details in regard to the typical environment (temperature, humidity, altitude)
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in which the ballast would be required to operate. Finally, the document outlined the
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hardware components
required to complete the project. This included power
. andthatthenwere
supply, peripherals,
detailed the board hardware. The board hardware section
. part of the functional block diagram which summarized the operation of
discussed each
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Project Surf Scoter. This did not define the specific parts that the group would be using, it
simply discussed the functionality of each block and how they would be implemented.
Project Plan
In order for the project to be completed in an organized and timely fashion, the group
devised a Project Plan. The Project Plan outlined all tasks that the group needed to
complete in order to construct the ballast. A timeline was developed based on how long
the group members felt each stage of construction would take. This took into account time
needed to learn new or unfamiliar technology, actual implementation, and debugging.
This information was entered into Microsoft Office Project 2003 in order to keep track of
the schedule and make changes whenever necessary.
Design Review
In order to continue with the Project Surf Scoter, the group was required to pass the
Design Review. This required the group to gather documents and run PSPICE
simulations in order to convince the faculty advisor and industry representative that the
design would be able to produce an operational ballast. The PSPICE simulations were
necessary to show that each functional block met the design parameters and could be
implemented with the other blocks. Once the PSPICE simulations were complete, the
group was able to create a list of parts to be used in the ballast. The parts list included
part numbers, electrical tolerances, and was accompanied by a datasheet.
TOP Approval
In order to obtain a final approval for the project the group submitted a Theory of
Operations (TOP) document. This document discussed the overall functionality of each
component of the circuit and how each component would be implemented in order to
create the electronic ballast. These descriptions included the operating values of many
components and some simulated circuit values. It also included a top-down description of
how the circuit architecture would be implemented. The TOP included circuit schematics
which detailed of the circuitry and the connections to be made between the components.
Construction
Following approval on the TOP document, the group ordered all the parts necessary to
construct the ballast. The group encountered a significant complication at this point as
Digi-Key was out of stock of the transformer which the design of Project Surf Scoter was
based. The group realized that without a transformer the project could not be completed.
In an act of great generosity, Dr. Lu provided the group with some used transformers to try
and implement.
Before the group could begin constructing the circuit, the safety precaution needed to be
implemented. The group constructed the safety box which was made with Plexiglas and
implemented a switch which would only allow power to reach the circuit when the box was
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in place. The group then labeled all components and began soldering them to the
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breadboard. This process was simplified by labeling each component and organizing the
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circuit according to PSPICE schematics.
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. input section of the design was built first before the output section. Parts
In general, the
were placed .
on the circuit board and then leads were soldered together on the opposite
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side.
Testing and Debugging
In order to simplify the testing and debugging process the group constructed the circuit by
building individual blocks from the block diagram and testing each as they were
completed. This practice led to the early detection of transformer problems and allowed
them to be addressed as the rest of the circuit was being built. The rectification and power
factor correction elements were also tested as they were being constructed. The output
section of the design was only connected after the input section was constructed, tested
and found to be giving DC output voltage with little or no ripple voltage.
The output section of the circuit could not be tested as it was being built due to the
complex operating nature of the ballast controller IC. The parts were simply arranged in
the regular setup as specified by the ballast controller datasheet and then soldered
accordingly.
After the input portions of the circuit were tested and both sections were soldered into
place the entire circuit was connected in its final configuration and the entire circuit was
turned on. After initial failure of the lamp to ignite a process of debugging was determined.
DMM leads were connected to monitor DC voltage coming from the rectifier and PFC and
also pin voltages of the ballast controller. In particular, the VCC, VDC and SD pins of the
controller were monitored as voltages at these pins were required to be within certain
ranges for the chip to enter Pre-Heat mode.
To adjust the voltages of the ballast controller pins to their necessary values, the resistor
values of the output section of the circuit were changed gradually to ensure against
overloading any part of the circuit. For each replacement this involved discharging all high
voltage capacitors, disconnecting the power cord, removing the Plexiglas box, unsoldering
a resistor and then soldering into place a new resistor.
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Results
This section describes to the reader the design created through project Surf Scoter in the
technical section. The process section describes how the implementation of the design
played out through the last semester.
Technical
Figure 1. Block Diagram of Surf Scoter Product
Fuse and Safety Switch
A safety switch is normally closed and opens when the Plexiglas box is raised, exposing
the circuit board. The fuse used in the circuit is a 10A fuse and will be connected in series
with the circuit immediately after the switch inside the box. It is a double-blade fuse similar
to the fuses used in cars and is encased in a holder with 12 gauge leads attached. Butt
splices or soldering will be used to connect the leads of the switch to the rest of the circuit.
EMI Filter
The purpose of the EMI filter is to prevent the ballast circuit from generating interfering
frequencies back onto the power supply line. Such interfering frequencies can negatively
affect the performance of other devices on the same supply line. The filter also protects
the ballast circuit from any interference already present on the supply line. The
MAW120322 EMI Filter is rated for 3A at 250V maximum.
Transformer
The transformer steps up the voltage from the AC input and has a turns ratio of 1:3. The
voltage steps up from 94.26V AC (133.33 VPEAK) to 282.8V AC (400 VPEAK). With this
transformation current is decreased in proportion to the increase of voltage as power flows
from the primary side to the secondary. To achieve the desired voltage across the primary
side of the transformer, a resistor RTRANS with a resistance 0.214 times the resistance of
the primary side of the transformer will be used. This will lower the voltage across the
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primary side of the transformer to 133.33 V
from 170 V
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voltage of 400 V
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Table 1. Transformer Table
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Voltage
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to achieve the secondary
PEAK
Current
Primary side
94.26V (133.33 VPEAK)
1.035 ARMS (Run Mode)
Secondary side
282.8V (400 VPEAK)
345 mARMS (Run Mode)
PFC / Rectifier
The Power Factor Correction (PFC) is included in the project because it keeps the supply
line clean by synchronizing the incoming AC current and voltage while providing a 400
VDC to the bus line. The capacitors in the PFC are put together so that they are charged
in series and then discharged in parallel. This design allows for the spikes in current and
voltage to be synchronized, thus reducing the reactive power used by the circuit. The
rectification that is performed converts the AC input to a DC voltage on the bus line. The
DF06 full-bridge rectifier is rated for 1.5A and 400VRMS maximum.
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Figure 2. Voltage and Lagging Current
Figure 3. Synched Voltage and Current
Ballast Controller
The final part of the ballast design is composed of the ballast controller, the fluorescent
lamp and the passive RLC circuitry connecting them. This section receives the 400V DC
bus voltage from the first section and uses it to operate the fluorescent lamp. The
IR21571 ballast microcontroller IC performs all the necessary voltage, current and
frequency modifications to drive the lamp. The IR21571 is customizable in that the
component values of the resistors, inductors and capacitors can be changed to affect
the behavior of the IC. In supplementary documents for the IR2157, equations are
provided that allow for the calculation of component values based on desired
operational parameters such as voltage and current. This method requires that the
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ballast controller be in its standard circuit setup (see Appendix C). The run mode
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power was chosen to be 32 Watts because the lamp being used in the project is
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rated at 32 Watts. To aid in the selection of component values, the target efficiency η
was chosen .to be 0.95. All other parameters given in Table 2 were chosen through
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research of standard
T8 lamp operation and from the datasheet and supplementary
. the IR2157
documents of
ballast controller. Refer to Appendix D for a list of
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components.
Table 2. Initial Values
Name
VPH
IPH
VIG
VRUN
PRUN
fRUN
η
VIN
CT
tDEADTIME
tPH
tIGN
ROC
Initial Values
Function
Pre-Heat Mode Voltage
Pre-Heat Mode Current
Ignition Mode Voltage
Run Mode Voltage
Run Mode Power
Run Mode Frequency
Run Mode Efficiency
Input Switching Voltage
Oscillation Timing
Capacitor
Switching Deadtime
Pre-Heat Time
Ignition Time
Open Circuit Detection
Resistor
Value
330
1
500
140
32
36
0.95
200
1E-09
1.2E-06
2
0.05
30000
Unit
V
A
V
V
W
kHz
V
F
s
s
s
Ohms
By using the equations and information provided by the IR21571 Data Sheet, values
for secondary parameters and components values are calculated as shown in Table
3.
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Table 3. Calculated Values
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Calculated Values
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Function
Calculated
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DC.Bus Voltage
400
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Name
Unit Rounded
VBUS
V
400
L
Inductor
0.0023633 H
0.0025
fPH
Pre-Heat Mode Frequency
48228.771 Hz
48000
fIG
Ignition Mode Frequency
39105.452 Hz
39000
fRUN
Run Mode Frequency
35195.861 Hz
35000
C
Capacitor
1E-08 F
1E-08
RLAMP Lamp Resistance*
306.25 Ω
300
VPH
Pre-Heat Mode Voltage
515.95359 V
IIGN
Ignition Mode Current
1.2252211 A
RT
Timing Resistor
15561.682 Ω
15000
RDT
Deadtime Resistor
2148 Ω
2000
RRUN
Run Resistor
82244.902 Ω
68000
CPH
Pre-Heat Capacitor
3.883E-07 F
4.00E-07
RPH
Pre-Heat Resistor
68297.859 Ω
115000
CIGN
Ignition Capacitor
1.449E-07 F
1.50E-07
RCS
Grounding Resistor
1224.2688 Ω
1100
*The lamp can be modeled as a resistor when the ballast is in Run Mode.
Operating Modes
The IR21571 ballast microcontroller IC will run through five operating modes: UnderVoltage Lockout Mode, Pre-Heat Mode, Ignition Mode, Run Mode and Fault Mode. These
modes are described below and a flow chart is shown in Appendix E.
Under-Voltage Lockout Mode
When power is first supplied to the IC, it enters Under-Voltage Lockout Mode. This is the
default operating mode of the IC and it will return to this mode if there is an error detected
during any point of operation. If the bus voltage is high enough, then VCC is greater than
11.4V and VDC is greater than 5.1V, allowing the IC to enter Pre-Heat Mode. Additional
requirements to enter Pre-Heat Mode are that the shut down input VSD is less than 1.7V,
ensuring the lamp has not failed, and the junction temperature TJ is less than 160°C. If
these conditions are met, the IC will enter Pre-Heat Mode. Otherwise, the IC will stay in
Under-Voltage Lockout Mode.
Pre-Heat Mode
During Pre-Heat Mode, the IC provides a switching frequency of fPH to the MOSFETs to
create a voltage VPH across the lamp (before igniting, the lamp functions as an open
circuit). This voltage is high enough to heat the cathodes of the lamp, while the frequency
is high enough to prevent the lamp from igniting. Pre-heating in this fashion allows for a
less stressful ignition and overall longer life for the lamp. Also during Pre-Heat Mode, a
current is provided to the capacitor CPH from pin CPH at 1uA, which will charge the 0.4uF
capacitor to 4 V in 2 seconds. When CPH has charged to 4V, the IC switches to Ignition
Mode. If, during Pre-Heat Mode or any mode other than Under Voltage Lockout Mode,
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the V should fall below 9.5 V or V below 3.0V (indicating power off or a bus line failure)
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or SD should rise above 2.0V (indicating lamp removal) the IC will return to Under Voltage
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Lockout Mode. Similarly, if the junction temperature Tj should rise above 160ºC during
. or Run Mode, the IC will enter Fault Mode.
Pre-Heat, Ignition
.
. the MOSFETs are modeled as ideal switches and the lamp as a large
For the simulation,
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DC
resistor to represent an open circuit. The switching frequency across the lamp is 47.49
kHz (see Figures 5 and 6). This frequency is high enough to prevent the lamp from
igniting while the cathodes are heated, and is not significantly less than the desired fPH of
48 kHz. As simulated, the Pre-Heat voltage is 411V peak (290VRMS), and the current
1.1A. This Pre-Heat voltage level is higher than specified due to power MOSFETs being
modeled as ideal switches in the PSPICE simulations. A higher voltage will not negatively
impact the operation of the circuit either, as a high voltage is desired to heat the lamp
cathodes. The simulation circuit is shown in Appendix F.
Figure 4. Pre-Heat Mode Switching
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Figure 5. Pre-Heat Mode Switching Detail
Ignition Mode
In Ignition Mode, the switching frequency ramps down to fig, while pin CPH continues to
charge with a current of 1uA. This lower frequency causes the lamp to ignite. When the
capacitor CPH reaches 5.1V, the IC enters Run Mode.
In the simulation, when the switching frequency is fig and the lamp is again modeled as an
open (non-ignited) circuit, the switching frequency across the lamp is 38.46 kHz, the
voltage is 531V peak (375VRMS) and the current is 1.43A (see Figures 7 and 8). These
values are slightly higher than the expected values, but again they don’t take into account
losses inherent in the circuit components.
Figure 6. Ignition Mode Switching
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Figure 7. Ignition Mode Switching Detail
Run Mode
In Run Mode, the switching frequency ramps down further to frun. The IC will continue to
operate in run mode until a failure is detected, such as low input voltage (turning the power
off) or lamp removal/failure.
As the lamp is rated at 32W and the Run Mode voltage is 140V peak (99VRMS), the
resistor is modeled as 300Ω for simulation (using the equation R=V2/(2P). In simulation,
the switching frequency across the lamp is 35.7 kHz, the voltage 137.6V and the current
488mA (see Figures 9 and 10).
Figure 8. Run Mode Switching
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Figure 9. Run Mode Switching Detail
Fault Mode
In Fault Mode, the IC no longer provides the switching signal to the MOSFETs, disabling
the flow of current to the lamp. Once in Fault Mode, the IC waits until VCC falls below 9.5
V (power off) or SD rises above 2.0V (lamp removal), at which time the IC switches to
Under Voltage Lockout Mode.
Fault Mode is entered any time the junction temperature exceeds 160ºC during Pre-Heat,
Ignition or Run Mode. The IC will also switch to Fault Mode when there is excess current
through the lamp, failure of the lamp to ignite within the ignition time, or other problems
with the lamp.
Conclusion
At this time our project does not work to our original specifications due to a large amount
of our time being expended towards locating an ideal transformer. Our ballast controller is
not currently getting the right voltages and therefore it cannot operate under its ideal
circumstances. We ruined two chips because of high voltages going into the chips. As
you can see above we spent a great deal of time calculating the component values based
on our bus voltage.
As you can see in table 1 below our voltages out of the transformer did not match our
original design. So we recalculated the component values so that correct voltages and
currents go into the ballast controller.
Table 4. Transformer Results
Voltage
UNIVERSITY OF PORTLAND
Primary side
120V (170 VPEAK)
Secondary side
235V (333 VPEAK)
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We were able to get the controller into preheat mode, but the voltages applied to the
. were not being controlled properly by the IR21571. When we checked the
switching gates
. to crucial pins (VCC, VDC, SD) the voltages were usually around their
voltages applied
. VCC > 11.4V (UV+) and VDC > 5.1V (Bus OK) and SD < 1.7V (Lamp
desired values:
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OK). However the lamp would still go into under voltage lockout mode. Had we had
more time, we would have been able to focus on this problem and come up with a
solution, whether it be switching out components or leaving some out altogether.
Process
Assumptions
From the start of the project we felt that locating data for the ignition and operation of T8
lamps would not be a difficult process. We eventually tracked down some ANSI
specifications that gave us worthwhile information, but what we really wanted was the type
of waveforms that are finally put through the lamp for operation. This required us to
consult various application notes and other ballast technologies in order for us to get a
good idea. We finally were able to find that we could convert a High DC voltage into a
square wave, which could then be smoothed out by a circuit with an inductor a capacitor
and the lamp modeled as a resistor.
The biggest assumption that was pretty crucial to our project was the fact that we thought
a voltage step up would be simple to implement. This was enforced by consulting Dr.
Albright and finding that our ideal parameters from 120 V mains to about a 400 V voltage
would not require overly complicated equipment. We went through four transformers on
this project after we found that the one we submitted through design review was no longer
available. This led to a lot of expended time that could have been used towards
debugging the ballast controller and MOSFETs. All in all this wasn’t a bad assumption.
We found a transformer that gave us a pretty good step up (to 333Vrms) and it only cost
us twenty dollars at a local surplus electronics store.
We had a lot of confidence in our design, but we underestimated the difficulty of the
analog components. Timing was very crucial to the operation of the ballast controller and
therefore the operation of the lamp. The team felt that the biggest problem would be
converting the AC mains line to our ideal high voltage DC bus line. The fact hat we got a
longer voltage than our ideal wasn’t that great of a factor since we could just recalculate
the resistors for a proper voltage divider. The chip posed a lot of unforeseen problems to
us.
Overall, we were able to acquire a strong DC bus voltage and we were able to get the chip
wired up to perform preheat mode in a test circuit. Because of this I feel that our
assumptions weren’t as flawed as they might look. Bad luck and a time crunch are what
mainly caused the project to not meet full specification.
UNIVERSITY OF PORTLAND
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Milestone Review .
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There were not
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We should have definitely ordered the parts before winter break, but looking back we
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ordered them right after and received them promptly. Conclusively, this didn’t cost us as
much time thanks to fast shipment.
The completion of the transformation functional block was the only crucial milestone
missed. This cost us a lot of time. We required a high voltage DC bus line to really test
the ballast controller, MOSFETs and lamp fully. The more time spent on the transformer
meant the more those other stages of the project got delayed. This domino effect left us
very little time to complete other crucial debugging of the circuit.
Risks
The biggest risk in our project was our vulnerability of working with dangerous high
voltage. By implementing a number of safety factors into our project we were able to
avoid any injuries to project members. By making a Plexiglas safety box we were able to
isolate ourselves from the circuit when running at high voltage. The box would put
pressure down on a switch that would only allow current to flow in once the switch was
pressed down. The switch pressed down means that the box is in the proper position.
We also used a fuse to limit the amount of current that would be allowed to go into the
circuit.
Our use of analog components in the circuit worried us. We knew it would be a risk and
several professors told us that analog circuits have a higher risk of failure. This risk came
into play, but it was only a part of the problems that plagued us. This just really meant that
we would need to dedicate more time to the projects. Loss of time combined with the
analog components made this risk a valid problem.
Another unforeseen risk that we did not consider coming into the project was our limited
knowledge of the use of transformers. Difficulty of resources and faulty test equipment
made this a problem with our project. Even though we eventually got a satisfactory step
up it still took a lot of crucial time off the clock that could have been put towards other
crucial parts of the project.
Resources
The resources we had were adequate for project completion. We found the oscilloscopes
to be very useful. The yellow digital millimeters (DMM) us off for a good two hour project
session one day because the yellow ones were telling us that was a huge AC ripple (760
Vp-p) output from our power factor correction 220 uF capacitor. When using an alternate
DMM we found that there was limited ripple (1-2 Vp-p) which matched our specifications.
Other than that the lab and test equipment fulfilled our needs.
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Conclusions
After extensive effort put into the design and building of the ballast, we were unable to get
the lamp to light. Reasons for this include the difficulty involved with analog circuits, time
lost finding a usable transformer, the inability to work ahead on other parts of the project
while we were searching for a transformer, and high voltage testing.
We each, however, gained extensive knowledge of lighting, specifically fluorescent
lighting, throughout this project. We also gained invaluable hands-on skills and
understanding of working with electrical components, especially high voltage. As most of
the first semester was design and documentation while working as a team, much
teamwork was needed to accomplish this project.
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Appendices
Figure 10. Input Stage Schematic
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Figure 11. Front End of Circuit Design for Simulation
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Figure 12. PSPICE Detail of Ballast Controller and Lamp RLC Circuit
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Under-Voltage
Lockout Mode
SD > 2.0V
(Lamp Removal)
or
VCC < 9.5V
(Power Turned Off)
VCC > 11.4V
(UV+)
VDC > 5.1V
(Bus OK)
SD < 1.7V
(Lamp OK)
TJ < 160C
(Tjmax)
VCC < 9.5V
(VCC Fault or Power Down)
or
VDC < 3.0V
(dc Bus/ac Line Fault or Power
Down)
or
SD > 2.0V
(Lamp Fault or Lamp Removal)
Pre-Heat Mode
Fault Mode
Over Temperature
Tj >160
CPH > 4.0V
(End of Pre-Heat Mode)
CS > CS+ Threshold
(Over-Current or Hard
Switching)
or
CS < 0.2V
(No-Load or Below Resonance)
or
TJ > 160C
(Over-Temperature)
Ignition Mode
CPH > 5.1V
(End of Ignition Ramp)
Run Mode
Figure 13. Flow Chart of Ballast Controller Modes
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Figure 14. PSPICE Output Simulation Circuit
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Table 5. Parts List and Ratings
Parts List and Ratings
Manufacturer
Part #
Description
Reference
4
TDK
FK26X7R2E104K
Capacitor, 0.1uF, 250V
C1, CBS, CVCC
3
Vishay
128 SAL-RPM
Capacitor, 0.47uF
C2
2
Vishay
128 SAL-RPM
Capacitor, 47uF, 450V
C3, C4
1
Vishay
MMKP 383
Capacitor, 0.1uF 1600 VDC
CBLOCK
1
Murata
RDER72J222K2K1C11B
Capacitor, 2.2nF 630V
CGND
1
Vishay
MKT 371
Capacitor, 0.39uF 67V
CPH
3
Vishay
MMKP 383
Capacitor, 0.01uF 600VAC
CRAMP, CSTART
1
Nichicon
493-2611-ND
Capacitor, 220uF, 450V
CRECT
1
Murata
DEBF33D103ZA3B
Capacitor, 10nF 2.0kV
CRES
1
Kemet
C322C102KFR5TA
Capacitor, 1nF 1.5kV
CSNUBBER
1
Murata
DEA1X3A471JA2B
Capacitor, 470pF 1kV
CT
1
AVX
SR211C105KAR
Capacitor, 1uF 100V
7
Diode Inc.
Um9601
High Power Diode
CVCC2
D1, D2, D3, D4, D5, D6,
DBOOT
1
Lambda
MAW120322
EMI filter
EMI Filter
1
International Rectifier
IR21571
Ballast Controller IC
IR21571
1
N/A
N/A
48 inch, 32W, T8 Lamp
LAMP
1
Vishay
TJ-6
Inductor, 2.5mH, 2A
LRES
2
Vishay
497-2451-1-ND
Power MOSFET
M1, M2
1
Vishay
PPCQF130KCT-ND
Resistor, 130K ohm
R1
2
Vishay
PPC2.20MZCT-ND
Resistor, 2.2M ohm ¼ watt (x2)
R2
1
Yageo
910KH-ND
Resistor, 901k ohm ½ watt
R2
1
Vishay
CMF1.00KQFCT-ND
Resistor, 1K ohm
R3
1
Vishay
PPCQJ680KCT-ND
Resistor, 680K ohm
R4
1
Vishay
PPC2.20MZCT-ND
Resistor, 2.2M ohm
R5
1
Vishay
CMF49.9QFCT-ND
Resistor, 50 ohm
R6
1
Vishay
PPC1.2W-1CT-ND
Resistor, 1.2 ohm ½ watt
RCS
1
Vishay
CMF2.00KQFCT-ND
Resistor, 2K ohm
RDT
1
Fairchild Semiconductor
DF06M-ND
Full Bridge Rectifier
Rectifier
3
Vishay
PPC22W-1CT-ND
Resistor, 22 ohm
RGHS, RGLS
1
Vishay
PPC30KW-1CT-ND
Resistor, 30K ohm
ROC
1
Vishay
PPC68KW-1CT-ND
Resistor, 68K ohm
RPH
1
Vishay
PPC82KW-1CT-ND
Resistor, 82K ohm
RRUN
2
Vishay
PPC22KW-2CT-ND
Resistor, 22K ohm
RSTART
1
Ohmite
OY394K-ND
Resistor, 390K ohm 2 watt (x2)
RSUPPLY
1
Ohmite
OY154K-ND
Resistor, 150k ohm 2 watt
RSUPPLY
1
Vishay
CMF15.0KQFCT-ND
Resistor, 15K ohm
RT
1
SAE
#16231 PRC
1:3 turns ratio
Transformer
Appendix D – Parts List and Ratings
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