IRPLMB1E
International Rectifier
•
233 Kansas Street, El Segundo, CA 90245 USA
IRPLMB1E
- 25W 230VAC small size ballast using IR2520D
By
Cecilia Contenti
Topics Covered
Overview
Features
Electrical Characteristics
IR2520D Ballast Control IC
Circuit Description
Miniballast Circuit Diagram
Functional Description
Fault Conditions
Miniballast Layout
Design Tip: AUto-restart Option
Design Procedure to adapt the
design to different lamp types
1. Overview
Small sizes ballasts (often called Matchbox ballasts) are becoming very common in Europe to drive a wide
range of lamps with power between 18W and 26W like PLC 18W, PLT 18W, TC-L 18W, TC-L 24W, TC-F 18W,
TC-F 24W, TC-DEL/TEL 26W, T5 24W, T8 18W, T5C 22W and TR 22W. Limiting the maximum power to 25W
the design does not need to conform to THD and PF requirements and this allows saving the PFC stage
reducing the components count and maintaining a very small size.
The MINIBALLAST1 is an electronic ballast for driving 26W compact fluorescent lamps from 220VAC. The
circuit provides all of the necessary functions for preheat, ignition and on-state operation of the lamp and
also includes the EMI filter and the rectification stage. The ballast size is 36mmx55mm.
The circuit is built around the IR2520D Ballast Control IC. The IR2520D provides adjustable preheat time,
adjustable run frequency to set the lamp power, high starting frequency for soft start and to avoid lamp flash,
fault protection for open filament condition and failure to strike, low AC line protection and auto-restart after
line brownout conditions. The IR2520D is a low-cost solution with only 8 pins and allows the component
count for the complete solution to be reduced down to 19 components.
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IRPLMB1E
2. Features
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operating frequencies determined by bi-polar tran-
Programmable run frequency
Programmable preheat time
Open filaments and no-lamp protection
Failure to Strike and deactivated-lamp protection
Low AC line protection
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3. Electrical Characteristics
Input Power: 24W @ 220VAC
Input Current: 168mArms @ 220VAC
Starting Frequency: 100KHz
Average Run Frequency: 40KHz
Ballast turn-on voltage: 120VAC
Ballast turn-off voltage: 70VAC
Input
(VAC)
200
210
220
230
240
Pin
(W)
21
22
24
24.2
24.5
Iinrms
(mA)
160
160
168
168
168
Vbusav
(V)
280
290
300
310
320
Freq.
(KHz)
40.3
40.3
40.3
40.3
40.3
PF
0.63
0.625
0.62
0.62
0.61
THD
(%)
115
117
118
118
118
sistor storage time and toroid saturation (not easy to
design, very dependent on tolerances in production
and difficult to set the frequencies precisely),
unreliable “always hot” PTC thermistor used for
preheat that often fails in the field,
no protection against lamp non-strike or open
filaments conditions,
no smooth frequency ramping during ignition,
capacitive mode operations,
high crest factor in the lamp current.
4. IR2520D Ballast Control IC
The IR2520D is intended for driving CFL and TL
lamps in CFL or matchbox (small size ballasts)
applications. The IR2520D integrates all of the
necessary functions for preheat, ignition and on-state
operation of the lamp, plus, lamp fault protection and
low AC-line protection, together with a complete high
and low-side 600V half-bridge driver. The IR2520D
has only 8 pins and fits into a standard SOIC8 or
DIP8 package. The IR2520D has been designed to
overcome the disadvantage of discrete self-
oscillating solutions while maintaining low cost.
In the CFL market, the self-oscillating bipolar
transistor solution is still more popular than a
ballast control IC plus FETs solution due to lower
cost. This approach is very simple in nature but has
disadvantages including:
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DIAC or additional circuit required for starting,
additional free-wheeling diodes required
2
These can result in high susceptibility to components
and load tolerances and/or catastrophic failure of
ballast output stage components and a short lamp
life. The IR2520D includes adaptive zero-voltage
switching (ZV, adaptive run frequency for zero-volt-
age switching), internal crest factor and non-zero
voltage switching (ZVS) protection, as well as an in-
tegrated bootstrap diode. The heart of this IC is a
voltage controlled oscillator (VCO) with externally
programmable minimum frequency and a 0-5VDC
analog voltage input. One of the biggest advantages
of the IR2520 is that it uses the VS pin and the RDSon
of the low-side half-bridge MOSFET for over-current
protection and to detect non-ZVS conditions. An
internal 600V FET connects the VS pin to the VS sens-
ing circuitry and allows for the VS pin to be accu-
rately measured during the time when pin LO is
high, while withstanding the high DC bus voltage
during the other portion of the switching cycle when
the high-side FET is turned on and VS is at the DC
bus potential. This eliminates the need for a high-
precision current sensing resistor that is typically
used to detect over current. Please refer to the
IR2520D datasheet for further information on the
IR2520D including electrical parameters, state
diagram and complete functional description.
As a result of the IR2520 features, the MINIBALLAST1
circuit using the IR2520D is a complete matchbox
solution that offers better reliability and longer lamp
life than self oscillating solutions while reducing
component count and ballast size.
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IRPLMB1E
5. Circuit Description
The schematic for MINIBALLAST1 is shown in figure
5.1. The BOM with the components values is shown
in table 5.2.
The ballast incorporates a fuse, EMI filter, input recti-
fier, bus capacitor, half-bridge, control and output
stage. The output stage is the classical resonant
circuit consisting of an inductor, LRES, and a capaci-
tor, CRES. The circuit is built around the IR2520D
Ballast Control IC. The IR2520 provides adjustable
preheat time, adjustable run frequency to set the lamp
power, high starting frequency (about 2.5 times fmin)
to avoid lamp flash, capacitive mode protection for
open filament condition and current crest factor
protection for failure to strike or no lamp conditions.
The AC line input voltage is rectified to provide a bus
voltage of approximately 300 volts. The start up
resistor, Rsupply (in the reference design we have 2
resistors, Rsupply and Rsupply 2 in series), is sized
such that they can supply the micro-power current
during under-voltage lockout (UVLO). When VCC
exceeds the UVLO+ threshold, the IR2520 begins to
oscillate and the charge pump circuit (CSNUB, DCP1
and DCP2) supplies the current to VCC that causes
the internal 15.6V zener clamp to regulate.
The IR2520 Ballast Control IC controls the frequency
of the half-bridge programming the right parameters
on the lamp to provide lamp preheat, lamp ignition,
running mode, low AC line protection and lamp/
ballast fault protection.
RSUPPLY
DCP2
BR1
MHS
F1
LF
CVCC
CBUS
CF
RFMIN
CVCO
VCC
1
VB
8
LAMP
IR2520
COM
2
FMIN
3
VCO
4
HO
7
VS
6
LO
5
CBS
LRES
CSNUB
CRES
MLS
CDC
DCP1
Fig. 5.1) MINIBALLAST1 Circuit Diagram
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IRPLMB1E
Item #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Total
Qty
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
1
2
1
1
22
Manufacturer
International
Rectifier
Dale
Panasonic
Digikey
Epcos
Digikey
Wima
Panasonic
Panasonic
Panasonic
Panasonic
AVX
Wima
International
Rectifier
VOGT
International
Rectifier
Panasonic
Panasonic
Diodes
WAGO
WAGO
Part Number
DF10S
CW-1/2
ECQ-U2A104ML
P10730-ND
B82145-A1105-J
M5830-ND
MKS2 Series
EEU-EB2V100
ECJ-3VB1H104K
ECJ-3VF1E474Z
ECY-3YB1E105K
1812AA681J
MKP4 Series
IR2520D
5752602600
IRFU320
Description
Bridge Rectifier, 1A 1000V
Resistor, 0.5Ohm, 1/.2W
Capacitor, 0.1uF 275 VAC
EMI Inductor, 1mH 370mA
RF Chockes 1mH 200mA
Capacitor, 47nF 400V
Capacitor, 10uF 350VDC 105C
Capacitor, 0.1uF 50V 1206
Capacitor, 0.47uF 25V 1206
Capacitor, 1uF 25V 1206
Capacitor, 680pF 1KV SMT 1812
Capacitor, 4.7nF 1KV Polypropylene
IC, Ballast Driver
Inductor, 2.25mH, 5%, 1Apk
Transistor, MOSFET
Resistor, 1M, 1206, 100V
CDC
CBUS
CBS
CVCO
CVCC
CSNUB
CRES
BR1
F1
CF
LF
Reference
IC BALLAST
LRES
MHS, MLS
RSUPPLY1, RSUPPLY2
RFMIN
DCP1, DCP2
X1
X2
ERJ-8ENF6812V
LL4148DICT-ND
235-202
235-204
Resistor, 68.1K, 1%, 1206
Diode, 1N4148 SMT DL35
Connector, 2 terminal
Connector, 4 terminal
TABLE 5.2) MINIBALLAST1 Bill Of Materials.
Lamp type: Spiral CFL 26W, Line Input Voltage: 190-240 VAC. Note: Different lamp types may require BOM
changes.
4
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IRPLMB1E
6. Functional Description
Figure 6.1 shows the voltage across the lamp and
the current in the resonant inductor LRES during
Startup, Preheat, Ignition and Run Mode.
At startup, VCO is 0V and the frequency is very high
(about 2.5 times fmin). This minimizes voltage spikes
and lamp flash at startup. The frequency ramps down
towards the resonant frequency of the high-Q ballast
output stage, causing the lamp voltage and lamp
current to increase. During this time, the filaments of
the lamp are pre-heated to the emission tempera-
ture to guarantee a long lamp life. The frequency
keeps decreasing until the lamp ignites. If the lamp
ignites successfully, the IR2520D enters RUN Mode.
If the minimum frequency has been chosen below
or very close to the resonant frequency, the IC will
work near resonance and will adjust the frequency
continuously to maintain ZVS at the half-bridge and
to minimize the losses in the FETs. If the minimum
frequency has been chosen higher than the reso-
nant frequency the IR2520D will work at the mini-
mum frequency.
Figure 6.2 shows the current across the resonant
inductor and the voltage across the lamp filaments
at the startup.
Fig. 6.1:
Voltage across the lamp (yellow waveform) and current in
the resonant inductor (green waveform) during Startup,
Preheat, Ignition and Run Mode
When power is turned on, the IR2520D goes into
Under Voltage Lockout (UVLO) mode.
The UVLO mode is designed to maintain a very low
(<200uA) supply current and to guarantee that the IC
is fully functional before the high- and low-side out-
put drivers are activated. During UVLO, the high- and
low-side driver outputs (LO and HO) are both low
and pin VCO is pulled down to COM for resetting the
starting frequency to the maximum.
Once VCC reaches the startup threshold (UVLO+),
the IR2520D turns on and the half-bridge FETs start
to oscillate. The IC goes into Frequency Sweep Mode.
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Figure 6.2:
Voltage across the lamp filaments (yellow) and current
in the resonant inductor (green) at the startup.
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