IRPLDIM2U rev.a
International Rectifier
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233 Kansas Street, El Segundo, CA 90245 USA
Digital Dimming DALI Ballast for 32W/T8 110V input
By
Cecilia Contenti and Tom Ribarich (International Rectifier)
and Ross Fosler (Microchip Technology, Inc.)
FEATURES
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Lamp Type: 1X 32W T8 Lamp
Line Input: 90-140VAC/60Hz
Interface DALI (2 wires)
High Power Factor/ Low THD
High Frequency Operation
Programmable Lamp Filament Preheating
Programmable Ignition
High precision Digital Dimming
Logarithmic Dimming
Diagnostic and fault control
Lamp Fault Protection
Brownout Protection
IR21592 HVIC Ballast Controller
PIC16F628 Microcontroller
Optically Isolated Communications
Low power standby mode
INTRODUCTION
This reference design is a high efficiency, high power factor, digital dimming electronic ballast designed to drive
rapid start fluorescent lamp types. The design contains an active power factor correction circuit for universal
voltage input as well as a ballast control circuit using the IR21592. The design also includes a PIC16F628
microcontroller and an isolation circuit for connecting to a Digitally Addressable Lighting Interface (DALI). Other
features include EMI filtering, transient protection and lamp fault protection.
IRPLDIM2U
Digitally Addressable Lighting Interface (DALI)
The Digital Addressable Lighting Interface (DALI), international standard prlEC929, is a communication protocol
and method to interface lighting units on a 2-wire network. The DALI protocol is 16 bits and supports addressing up
to 64 ballasts individually, 16 groups or broadcasting to the entire lighting network. Aside from the protocol, DALI
supports fading, logarithmic dimming, scenes and fault detection.
The DALI allows for a complete lighting environment to be controlled and managed efficiently. The DALI can control
(transmit and receive) up to 64 different ballasts with the same control system, transmitting instructions to single
ballasts or to a group of ballasts. The ballast provides eye sensitive dimming over a wide range (1-100%). Various
operating parameters can be changed and stored dynamically within the ballast memory. For example, scene
levels can be set for different groups of ballast. Also, maximum brightness, minimum brightness, fade-time and
several other features can be set as desired. Another feature is the ability to diagnose problems such as lamp failures.
Perfect Light Quality
By means of digital control, the light level can be adjusted very precisely according to individual lighting needs. The
DALI includes 256 levels of brightness and a logarithmic dimming curve (Figure 2). The use of this curve allows for
better control at lower light levels where the human eye is more sensitive.
Dim value
255
240
225
210
195
180
165
150
135
120
105
90
75
60
45
30
15
0
0
10
20
30
40
50
60
70
80
80
100
Relative lighting level %
Fig. 2 Dimming Characteristics
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IRPLDIM2U
FUNCTIONAL DESCRIPTION
The IRPLDIM2U Demo Board consists of an EMI filter, an active power factor correction front end, a ballast
control section, a digital control section and a resonant lamp output stage. A block diagram of the design is shown
in Figure 3.
The EMI filter blocks ballast generated noise. The power factor correction is used for sinusoidal input current and
a regulated DC bus. The ballast control section provides frequency modulation control of a traditional RLC lamp
resonant output circuit for preheating, igniting and ballasting the lamp. It is easily adaptable to a wide variety of
lamp types. The digital control section provides the Digitally Addressable Lighting Interface (DALI) and the neces-
sary circuitry and software to perform closed-loop dimming, lamp fault detection, shutdown and auto-restart.
L
N
E
EMI Filter
Rectifier
PFC
Output Stage
PC
DALI
input
Interface
OPTO
Interface
1
2
3
RA2
Micro
RA1
18
17
16
15
14
13
12
11
RS232/
DALI
converter
RA3
RA4
RA0
RA7
RA6
light level
Fade time
Fade rate
On/Off
Fault condition
actual level
light status
ballast
IR-IC
1
2
3
4
5
6
7
8
VDC
HO
16
15
14
13
12
11
10
9
Half Bridge
Driver
VCO
VS
4
RA5
5
VSS
6
RB0
7
RB1
NOTE: Ballast can also be
connected directly to a DALI
compliant system..
PC and RS232/DALI converter
are used for demo purposes.
8
RB2
9
RB3
IRPLDIM2 Reference Design
Fig. 3 IRPLDIM2 Block diagram
You can connect the board directly to the DALI input (2 connections) or you can use the RS232/DALI converter
board (for demo purposes with the IRPLDIM2U board) to connect it to the PC.
The ballast control circuit uses the IR21592 Dimming Ballast Control IC programmed by the PIC16F628
microcontroller. The IR21592 controls the ballast according to the signals received from the microcontroller. The
microcontroller is connected to the ballast and the IC to receive diagnostic signals.
The communication between the ballast and the external world is done with two signals: TX (digital serial signal
transmitted from the network to the microcontroller) and RX (digital serial signal from the microcontroller to the
network). This system allows the ballast to communicate bi-directionally with the network (a PC or generally a
DALI system). A digital interface assures high voltage isolation between DALI inputs and the resonant lamp output
stage. The microcontroller manages the communication between interface and ballast IC.
The complete circuit is shown in Appendix A. In the circuit thick races represent high frequency and high current
paths. Lead lengths should be minimized to avoid high-frequency noise problems. Appendix B shows the Bill of
Materials.
PIC16F628
Lamp
Dimming Feedback
Preheat Feedback
CPH
VB
IR21592
DIM
VCC
CO
M
LO
VDD
RB7
RB6
RB5
RB4
MAX
MIN
FMI
N
IPH
CS
SD
10
Lamp Fault
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IRPLDIM2U
Power Factor Control
The power factor correction section consists of a Power Factor Controller IC (IC1), MOSFET (M1), inductor (L2),
diode (D2), capacitor (C6) and additional biasing, sensing and compensation components (see Appendix A: sche-
matics). The power factor correction circuit is a boost converter type running in critical conduction mode. This
means that the inductor current discharges to zero each cycle before the boost MOSFET is turned on. The ST
L6561D PFC IC is used which shapes the input current to the input voltage while regulating the DC bus voltage at
400 VDC. The IC is chosen for its minimal component count, low start-up supply current and robust error amplifier.
Ballast Control
The ballast control section is built around the IR21592 Dimming Ballast Control IC (IC2). The IR21592 is used for
preheating and igniting the lamp, controlling the lamp power and detecting fault condition (over temperature, over
current, VCC fault and DC Bus/ AC line fault). The IR21592 contains a voltage-controlled oscillator (VCO) control-
ling the half-bridge frequency while maintaining a 50% duty cycle, a high voltage half-bridge driver, an amplitude
control, fault circuit and an analog dimming interface.
To preheat the lamp, the amplitude control feature of the IR21592 is used, which regulates the resonant tank
current during the Preheat period. The VCO starts at maximum frequency and then decreases the frequency until the
voltage at the CS pin is equal to the programmed voltage at the IPH pin. The VCO is then adjusted internally (and
therefore the frequency) such that the inductor current remains constant until the external capacitor on pin CPH
charges above 5.1V. The preheat current (voltage) can be adjusted by increasing or decreasing the resistor on the
IPH pin (RIPH) and the preheat time can be adjusted by increasing or decreasing the capacitor on pin CPH (CCPH).
When pin CPH exceeds 5.1V, the IR21592 enables the over-current protection and the next cycle where the CS
pin exceeds the internal threshold of 1.6V the half-bridge is disabled. The VCO voltage decreases to a minimum
value and the IR21592 starts to decreases the frequency to a minimum frequency which is set by the external
resistor on pin FMIN (RFMIN) and the current sensing resistor RCS. In this way it generates a high voltage for
igniting the lamp. This voltage can be adjusted by adjusting RCS.
When the lamp is successfully ignited, The IR21592 regulates the phase angle of the inductor current with respect
to the half bridge voltage to regulate the lamp power. This is done by measuring the zero crossing of the current
and regulating it against the reference angle from the dimming interface. The IR21592 provides a 0-to-5 VDC
dimming interface which converts the analog input voltage to an internal phase angle reference for controlling the
lamp power. The DIM pin is a high impedance analog control input and the RMAX and RMIN pins set the maximum
and minimum angles boundaries. The RMIN resistor sets the minimum lamp power at 1% when VDIM=0V and the
RMAX resistor sets the maximum lamp power at 100% when VDIM=5V.
Digital Control
The digital control section is built around the PIC16F628 Microchip microcontroller. This microcontroller acts as an
interface between the IR21592 ballast controller and the Digitally Addressable Lighting Interface (DALI). Data is
transmitted to the unit and the PIC16F628 collects the data through an isolation circuit. It then interprets the data
and sends the appropriate signals to the ballast controller IR21592 if necessary or sends information back to the
DALI. The PIC16F628 also performs fault detection and disables the IR21592 if a fault is present.
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IRPLDIM2U
BALLAST DESIGN
The ballast design incorporates two parts, hardware and software. The ballast controller design portion incorpo-
rates most of the hardware design. The digital design control portion incorporates most of the software design.
Appendix A shows the complete schematic and Appendix B the Bill of Materials.
The Ballast Controller Design
The design of the Ballast control portion of the circuit has been accomplished in International Rectifier’s Reference
Design IRPLDIM1. Refer to this for waveforms and specific calculations regarding the ballast controller portion of
this design.
Signals of the IR2159
The communication between the microcontroller and the IR21592 is done with four signals, as shown in Fig. 4.
These signals are used for digital dimming (RB3), turning the ballast on or off (RB4), and fault detection (RB5 &
RB6). The microcontroller controls the IR21592 by the following 3 pins: pin SD for shutdown of the IC (active high),
pin FMIN used for fault detection (0 if the IC is
Lamp
in fault mode) and pin DIM to control the bright-
VDD
Out
ness. The microcontroller receives lamp infor-
R17
mation by the signal Lamp-out, connected to
the lamp.
1
16
VDC
HO
If 0 Lamp OK
If 1 Lamp Fault
R16
2
C11
VCO
VS
15
14
13
3
RDIM
CPH
VB
1
2
3
TR data signal
from the network
to the micro
4
5
6
7
RA2
RA1
18
17
16
15
14
13
12
11
10
IR21592
4
RA3
RA0
DIM
VCC
PIC16F628
RA4
RA7
5
6
7
8
MAX
COM
12
RA5
RA6
MIN
LO
VSS
VDD
If 0 IC OFF
If 1 IC OK
11
10
9
FMIN
CS
RB0
RB7
RB1
RB6
IPH
SD
Interfac
e
with
Optos
8
RX data signal
from the micro
to the network
9
RB2
RB5
TURN ON IC
TURN OFF IC
RB3
RB4
R25
C17
1.25V
2.5V
Digital Signal CMOS
DALI Signal
VSS
3.75V
Fig. 4 Micro/IR21592 Communication
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