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RD0802
IRPLDIM5E
4 Level Switch Dim Fluorescent Ballast using the
IRS2530D DIM8
TM
Table of Contents
Page
1. Features...........................................................................................2
2. Overview ..........................................................................................2
3. Circuit Schematics ...........................................................................3
4. Functional Description......................................................................4
5. Fault Conditions .............................................................................10
6. Bill of Materials...............................................................................14
7. IRPLDIM5E PCB Layout ................................................................15
8. Inductor Specifications ...................................................................17
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1. Features
Drives 25W CFL Lamp
Input Voltage: 220VAC
High Frequency Operation
Lamp Filament Preheating
Lamp Fault Protection with Auto-Restart
Low AC Line/Brownout Protection
Microcontroller driven 4 level power pulse dimming
IRS2530D DIM8
TM
HVIC Ballast Controller
2. Overview
The IRPLDIM5E reference design kit consists of a dimming fluorescent ballast, with a
microcontroller driven dimming control system providing four fixed levels and actuated
by power re-cycle pulses of less than one second, driving a single 25W CFL lamp. The
design contains an EMI filter and a dimming ballast control circuit using the IRS2530D.
This demo board is intended to help with the evaluation of the IRS2530D (DIM8
TM
)
dimming ballast control IC, demonstrate PCB layout techniques and serve as an aid in
the development of production ballasts using the IRS2530D.
EMI Filter Half-Bridge Driver
Rectifier
Lamp Fault
Line
Microcontroller
Dimming Feedback
Pulse Detect
DIM8 Ballast Control
Output Stage
Lamp
Figure 2.1: IRPLDIM5E Block Diagram
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3. Circuit Schematic
PIC12F629
IRS2530D
Figure 3.1: IRPLDIM5E Circuit Schematic
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4. Functional Description
The IRPLDIM5E reference design is built on the IRS2530D (DIM8
TM
) dimming platform.
The lamp arc current is detected through RCS after ignition and added to a DC control
voltage to provide an AC signal with a positive offset at the DIM pin of IC1. During DIM
mode the IRS2530D adjusts the oscillator frequency in order to maintain the amplitude of
this feedback signal such that the negative going peak is regulated at the 0V reference. In
this way the peak to peak AC feedback signal amplitude is regulated to twice the DC
control voltage level.
The IRS2530D incorporates a voltage controlled oscillator, whereby the voltage at the
VCO pin determines the frequency. This is also used to realize the preheat and ignition
ramp required to start the lamp. At switch on the voltage at the VCO pin will steadily rise
from 0V. At 0V the frequency will be at its maximum level, which is considerably above the
open circuit resonant point. As the voltage increases, the frequency gradually falls and the
voltage at the lamp increases as well as the current in the cathodes. This configuration
utilizes voltage mode heating, which is provided by means of two auxiliary windings on the
resonant output inductor of the ballast circuit. This method is the simplest and cheapest,
however current mode heating could be used if an additional transformer were to be
added to sense the arc current.
As the frequency continues to fall, the voltage at the ballast output to the lamp increases
until it reaches a point where it is sufficient to ignite the lamp. At this point arc current
begins to flow in the lamp and a feedback signal is produced at the current sense resistor
RCS. If ignition fails then the IRS2530D will shut down, going into a low VCC current fault
mode.
The dimming control reference voltage is provided at the DIM pin of IC1 and generated by
the micro controller IC2 at output GP2. GP pins refer to general purpose I/O pins of the
micro controller, which can be configured by software as high impedance inputs or CMOS
outputs. The DC dimming control voltage is produced by means of an RC integrating filter
supplied by a square wave signal. The square wave signal is generated by the micro
controller, which generates a fixed frequency signal with four separate duty cycle modes.
The higher the duty cycle, the higher the resulting filtered DC dimming control voltage
(Figure 4.1).
The GP1 input of the micro controller IC2 is also connected to the AC line input voltage
through a filter circuit with a very short delay. This allows IC2 to detect very rapidly when
AC power has been removed and restored. The 5V VDD supply storage capacitor C1 is
sufficiently large to allow IC2 to continue to run for more than one second after AC power
has been removed from the ballast. When the AC line is switched off, IC2 detects this
rapidly and starts a timer from this point. If power is restored within one second, the
dimming level is reduced by one level, thus reducing the output square wave duty cycle
and reducing the dimming level by one step. If the dimming level was already at minimum
then it will cycle back to maximum. In the case of AC power being removed for more than
one second the dimming level will not be changed. After C1 has discharged below the
minimum VDD operating voltage of IC2 the micro controller will shut off.
The micro controller that has been used here is a PIC12F629, which contains some
EEPROM non-volatile memory. The EEPROM allows the micro to store the last dim level
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setting before shutting down when power is switched off, therefore allowing the ballast
start up at that same setting when power is restored, no matter how long the ballast has
been off. For the micro controller code, please refer to the CD that comes with the
reference design kit. There are of course several alternative low cost micro controllers that
could be used equally well to realize this kind of ballast and that contain the same
functionality.
Figure 4.1 shows the microcontroller PWM outputs for all 4 dimming level.
Maximum Dim Level Intermediate Dim Level 1
Intermediate Dim Level 2 Minimum Dim Level
Figure 4.1: Microcontroller PWM Outputs
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Figure 4.2 shows the voltage at the DIM pin for all 4 dimming level.
Maximum Dim Level Intermediate Dim Level 1
Intermediate Dim Level 2 Minimum Dim Level
Figure 4.2: IRS2530D DIM pin voltages
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Figure 4.3 shows the voltage at the VCO pin, and the VS (half-bridge) voltage for all 4
dimming level.
Maximum Dim Level Intermediate Dim Level 1
Intermediate Dim Level 2 Minimum Dim Level
Figure 4.3: IRS2530D VCO (red) and VS (yellow) pin voltages
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Figure 4.4 shows the voltage across the lamp, and the current through the lamp for all 4
dimming level.
Maximum Dim Level Intermediate Dim Level 1
Intermediate Dim Level 2 Minimum Dim Level
Figure 4.4: Lamp Voltage and Arc Current
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Figure 4.5: Lamp Voltage and Arc Current during preheat and ignition
It should be noted in this example that the VCO voltage and consequently the ballast
frequency varies only by quite a small amount between the four different dimming levels,
although the lamp arc current varies considerably. This is because the system is operating
above the point in the dimming response curve known as the "knee", this is illustrated
below.
Lamp
Current
Ballast Running
Frequency
Ballast / Lamp Operating Characteristic
Figure 4.6: Lamp current against ballast frequency
R6 is also required in order to ensure that the DIM pin of IC1 will be biased above 0V
before the voltage at VCC exceeds the UV+ threshold at startup. This prevents the
IRS2530D from shutting down during the first few cycles of hard switching that occur
when the half bridge starts to oscillate at maximum frequency.
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5. Fault Conditions
In case of fault conditions such as open filaments, failure to strike, or lamp removal, the
IRS2530D will go into Fault Mode. In this mode, the internal fault latch is set, HO is off, LO
is open circuit, and the IRS2530D consumes an ultra-low micro-power current. The
IRS2530D can be reset with a lamp exchange (as detected by the LO pin) or a recycling
of VCC below and back above the UVLO thresholds.
Failure to Strike
At initial turn-on of the ballast, the frequency will ramp down from f
MAX
toward the
resonance frequency. When the lamp fails to strike, the VCO voltage continues to
increase and the frequency continues to decrease until the VCO voltage exceeds
VVCOFLT+ (4.0V, typical), and the IRS2530D enters Fault Mode and shuts down
(Figure 5.1). It should be noted that in case of failure to strike, the system will operate in
capacitive side of resonance, but only for short period of time.
Figure 5.1: Lamp non-strike: CH1 is the VCO voltage, CH4 is the voltage across lamp
AC Mains Interrupt / Brown-Out Conditions
This protection relies on the non-ZVS circuit of IRS2530D, enabled in the Dim Mode.
During an AC mains interrupt or brown-out condition, the DC bus can decrease and
cause the system to operate too close to, or, on [the] capacitive side of resonance. The
result is non-ZVS switching that causes high peak currents to flow in the half-bridge
MOSFETs that can damage or destroy them.
To protect against this, the IRS2530D will detect non-ZVS by measuring the VS voltage
at each rising edge of LO. If the voltage is greater than VZVSTH (4.5V, typical), the IC
will reduce the voltage at VCO pin, and thus increase the frequency until ZVS is
reached again (Figure 5.2).
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In case the DC bus decreases too far and the lamp extinguishes, the VCC voltage will
go below VCCUV- and the ignition/preheat ramp will be reset to re-ignite the lamp
reliably.
Figure 5.2: Brown-out conditions: CH1 is the VCO voltage, CH2 is the VS voltage
Lamp Removal
When the lamp is removed, the IRS2530D uses the Crest Factor Over-current
Protection to enter the Fault mode and shut down. During lamp removal, the output
stage will transition to a series-LC configuration, and the frequency will move towards
resonance until the inductor saturates. The IRS2530D uses the VS-sensing circuitry
and the RDSon of the low-side half-bridge MOSFET to measure the MOSFET current
for detecting an over-current fault. Should the peak current exceed the average current
by a factor of 5.5 (CF>5.5) during the on-time of LO, the IRS2530D will enter Fault
Mode, where the half-bridge is off. Performing crest factor measurement provides a
relative current measurement that cancels temperature and/or tolerance variations of
the RDSon of the low-side half-bridge MOSFET.
Figure 5.3 shows the voltage across the lamp and the VS voltage when the lower
filament of the lamp is removed. Figure 5.4 shows these voltages when the upper
filament of the lamp is removed. In both cases, the IRS2530D will enter the Fault Mode
and shut down after detecting that the crest factor exceeds 5 during the on-time of LO.
Figure 5.5 shows the VS pin, inductor current, and voltage across lamp when the
inductor saturates and the ballast shuts down.
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Figure 5.3: Lower filament removed: CH2 is the VS voltage, CH4 is the voltage across the lamp
Figure 5.4: Upper filament removed: CH2 is the VS voltage, CH4 is the voltage across the lamp
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RD0802
Figure 5.5: Inductor saturation: CH1 is the LO voltage, CH2 is the VS voltage, CH3 is the current
through the resonant inductor, and CH4 is the voltage across the lamp
Figure 5.6 shows the VS voltage and the voltage across the lamp when the IC undergoes
reset with a lamp exchange. When the lamp is removed, crest factor protection is
triggered, and the IC enters the Fault mode and shuts down. Since the lamp is removed,
LO pins is pulled above VLOSD+, and the IC goes to UVLO mode. When the lamp is re-
inserted, the IC goes back to the Preheat / Ignition mode, and the half-bridge starts to
oscillate again.
Figure 5.6: Lamp exchange: CH1 is the LO voltage, CH2 is the VS voltage, and CH4 is the
voltage across the lamp
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6. Bill of Materials
Item # Qty Manufacturer Part Number Description Reference
1 1 IR IRS2530D Dimming Ballast Control IC IC1
2 1 Microchip PIC12F629 8 pin DIP µController IC2
3 2 IR IRFU320 Transistor, MOSFET, 400V MHS, MLS
4 1 Digi-key RH06DICT-ND Bridge Rectifier, 0.5A 600V, miniDIP BR1
5 1 Diodes Inc ZMM5247B-7 Diode, Zener 17V, 500mW, MiniMelf DCP1
6 1 Diodes Inc LL4148DICT-ND Diode, 75V, 100mA DL35 DCP2
7 2 Diodes Inc ZMM5231B-7 Diode, Zener 5.1V, 500mW MiniMelf D1 D2
8 1 Diodes Inc MURS160-13 Diode, 600V, 1A, SMB DIN
9 1 Digi-key M8301-ND Inductor, 1mH, 200mA LF
10 1 Vogt IL 070 503 11 02 Inductor, 2.3mH, EF20 LRES
11 1 Panasonic ECA-0JHG331 Capacitor, 330µF, 6.3V, 105C, Radial C1
12 1 Panasonic ECJ-3YB1E225K Capacitor, 2.2µF, 25V, 1206 C6
13 1 Wima MKS2 Series Capacitor, 47nF, 400V CDC
14 1 Digi-key P10730-ND Capacitor 0.1µF, 275VAC CF
15 1 Panasonic EEU-EB2V100 Capacitor, 10µF, 350V, 105C, Radial CBUS
16 6 Panasonic ECJ-3VB1H104K Capacitor, 0.1µF, 50V, 1206 CBS, CFB, CH1,
CH2,C2,C7
17 1 Panasonic ECU-V1H222KBM Capacitor, 2.2nF, 50V, 1206 CVCO
18 1 Panasonic ECJ-3YB1E684K Capacitor, 0.68µF, 25V, 1206 CPH
19 1 Panasonic ECJ-3YB1E105K Capacitor, 1µF, 25V, 1206 CVCC
20 2 Panasonic CC1206KRX7R9B
B103 Capacitor, 10nF, 50V, 1206 C3,CDIM
21 1 Panasonic ECK-D3A102KBP Capacitor, 1nF, 1KV, Ceramic disk CVS
22 1 Wima
TAW
MKP10 Series
MKP472K1K6
Capacitor, 4.7nF, 1600V
Polypropylene CRES
23 0 NOT FITTED CLO
24 1 Panasonic ERJ-8GEYJ106V Resistor, 10M, 0.25W, 1206 R6
25 2 Panasonic ERJ-8GEYJ154V Resistor, 150K, 0.25W, 1206 R1, R2
26 1 Panasonic ERJ-8GEYJ124V Resistor, 120K, 0.25W, 1206 R3
27 1 Panasonic ERO-S2PHF1203 Resistor 120K, 0.25W, Axial R4
28 1 Panasonic ERJ-8GEYJ243V Resistor, 24K, 0.25W, 1206 R5
29 2 Panasonic ERJ-8GEYJ364V Resistor, 360K, 0.25W, 1206 RVCC1, RVCC2
30 1 Panasonic ERD-S2TJ7R5V Resistor, 7.5 Ohm, 5%, 0.5W, Axial RCS
31 1 Panasonic ERJ-8GEYJ474V Resistor, 470K, 0.25W, 1206 RLMP1
32 1 Panasonic ERJ-8GEYJ105V Resistor, 1M, 0.25W, 1206 RLMP2
33 3 Panasonic ERJ-8GEYJ104V Resistor, 100K, 0.25W, 1206 R7, R9, R10
34 1 Panasonic ERJ-8GEYJ563V Resistor, 56K, 0.25W, 1206 R8
35 1 Panasonic ERJ-8GEYJ102V Resistor, 1K, 0.25W, 1206 RFB
36 1 Panasonic ERJ-8GEYJ152V Resistor, 1.5K, 0.25W, 1206 RVCO
37 2 Panasonic ERJ-8GEYJ100V Resistor, 10 Ohm, 0.25W, 1206 RHO, RLO
38 1 Vishay/BC NFR25H0004707J
R500 Resistor, 0.47R, 1/2W F1
39 1 Wire Jumper J1
40 1 Wago 235-202 Connector, 2 terminal X1
41 1 Wago 235-204 Connector, 4 terminal X2
42 6 Digi-key 5000K-ND Test Point
VCC, COM, LO,
VCO, DIM,
VLAMP, VS
43 1 IRPLDIM5E_Rev2 PCB, Single Layer
TABLE 6.1: IRPLDIM5E Bill of Materials.
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7. IRPLDIM5E PCB Layout
Top Assembly
Top Copper
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Bottom Assembly
Bottom Copper
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8. Inductor Specifications
Vogt # IL 070 503 11 02
BI Technologies # HM00-07544
INDUCTOR SPECIFICATION
CORE SIZE
CORE MATERIAL
GAP LENGTH
E20/10/ 6 (EF20)
Philips 3C85 , Siemens N27 or equivalent
WINDING START PIN FINISH PIN TURNS WIRE DIAMETER (mm)
MAIN
CATHODE
CATHODE
PHYSICAL LAYOUT
TEST
MAIN WINDING INDUCTANCE MAX 2.4
mm
mH
mH
1.0
16
( Vertical 6- Pin Bobbin)
10/ 38 Multistranded
2 5
3 4
5.5
5.5
240*
MIN 2.1
* Adjust turns for specified Inductance
26 awg insulated
26 awg insulated
0.4"
0.4"
Pin View
1
2
34
5
6
NOMINAL INDUCTANCE
TEST TEMPERATURE C
100
2.3 mH
TEST TEMPERATURE C
100
