International Rectifier
•
233 Kansas Street, El Segundo, CA 90245 USA
IRPLCFL
2
a
IRPLCFL2 42 Watt Compact Fluorescent Ballast
Reference Design
Overview
The CFL-2 is an electronic ballast design for driv-
ing a 42 watt compact fluorescent lamp from a
120 or 230 volt AC line. The circuit was designed
using the IR2156 Ballast Driver IC. The main
features of the circuit are programmable fre-
quency, preheat time, over-current threshold and
dead time. A circuit board was designed and
tested to verify reliable functionality under actual
operating conditions.
LAMP TYPE: GE BIAX Q/E 42W (F42QBX)
Features
*
*
*
*
*
Programmable preheat frequency
Programmable preheat time
Programmable over-current threshold
Programmable run frequency
Programmable dead time
Electrical Characteristics
Parameter
Input Power
Input Current (120V)
Preheat Frequency
Run Frequency
Value
42W
530mA
75kHz
45kHz
Circuit Description
The schematic for CFL-2 is shown in Figure 1. With a 120 volt AC line input (AC1-N), the voltage is
rectified and doubled to provide a bus voltage of approximately 300 volts. With a 220 volt AC line
input (AC1-AC2), the voltage is rectified but not doubled and again provides a bus voltage of approxi-
mately 300 volts. The start up resistor, R
SUPPLY
, is sized such that it can supply the micro-power
current during under-voltage lockout (UVLO). When V
CC
exceeds the UVLO+ threshold, the IR2156
begins to oscillate and the charge pump circuit (CCP, DCP1, and DCP2) supplies the current to VCC
which causes the internal 15.6V shunt clamp to regulate.
www.irf.com
1
IRPLCFL2
AC1
R
VDC
D
BOOT
R
SUPPLY
F1
NC
1
VCC
14
13
VB
D
CP2
M1
C
ELCAP1
2
3
RT
HO
IR2156
C8 + C
VCC1
VDC
L
RES
12
11
VS
LO
N
C
BOOT
M2
C
CP
R
1
C
CS
C
RES
4
RPH
R
T
R
PH
CT
CS
5
6
CPH
10
SD
C
ELCAP1
D
CP1
9
COM
7
C
T
C
VDC
C
CPH
8
R
CS
AC2
BR1
Figure. 1, IRPLCFL2 Schematic Diagram
2
www.irf.com
IRPLCFL2
At initial startup, the output frequency is determined by timing capacitor CT and the parallel combina-
tion of RT, RPH and an internal resistor, RSOFTSTART. CT is selected depending on the desired
deadtime and is given as:
t
DT
=
C
T
⋅
1475
[Seconds]
(1)
After a few hundred micro-seconds, RSOFTSTART is slowly switched away (See Figure 4).
This provides a soft-start of the resonant output stage which eliminates large voltage transients
which can cause a small start-up flash across the lamp. Once RSOFTSTART is disconnected, the
parallel combination of RT and RPH determine the output frequency during preheat and is given as:
f
PH
=
1
0.51
⋅
R
T
⋅
R
PH
2
⋅
C
T
⋅
+
1475
R
+
R
T
PH
(2)
The IC remains in preheat mode until the voltage on CPH exceeds VCC-2V. The preheat
time is determined by an internal current source charging external capacitor CPH and is given as:
t
PH
=
C
PH
⋅
2.6
e
6
(3)
When CPH exceeds VCC-2V, RPH is slowly disconnected from RT, which causes the fre-
quency to ramp smoothly from the preheat frequency, through the ignition frequency to the final run
frequency.
The voltage across the lamp at ignition should be sufficient to ignite the lamp under all
operating conditions. The ignition current should never saturate the inductor, and is given as:
I
IGN
=
1.3
R
CS
[Amps Peak]
(4)
www.irf.com
3
IRPLCFL2
The run frequency is programmed using only external components RT and CT and is given as:
f
R UN
=
1
2
⋅
C
T
(
0.51
⋅
R
T
+
1475
)
[Hertz]
(5)
If VCS exceeds the over-current threshold of 1.3V, the IC will enter fault mode, and the half-
bridge is disabled (See Figure 6). At this point, VCC requires only micro-power current and remains
at the shunt clamp voltage. The IC can only be reset with a re-cycling of VCC below and back above
the UVLO thresholds, or, pin SD, (shown grounded in the schematic) can be recycled above and
back below the internal 5.1V threshold.
If the lamp is removed during normal operation, or either of the lamp filaments fail, the
resonant tank is interrupted and the charge pump becomes disconnected. The charge pump can no
longer supply current to VCC and VCC drops below UVLO-. RSUPPLY charges VCC up to UVLO+
and the half-bridge begins to oscillate again, but only temporarily. Since RSUPPLY cannot supply
enough current to VCC to sustain oscillations, VCC once again drops below UVLO- and oscillations
stop. This burst mode continues (See Figure 5) until a lamp is re-inserted, and the IR2156 starts
again in the preheat mode. For a more detailed description of the IR2156, including a STATE dia-
gram, TIMING diagram, and a complete functional description and electrical characteristics, please
refer to the ”IR2156 Ballast Control IC” data sheet.
Fig. 2: VS & VLAMP during Preheat Mode
Fig 3: VS & VLAMP during Run Mode
4
www.irf.com
IRPLCFL2
Fig 4: VLAMP during Softstart Mode
Fig 5: VS & VCC during lamp out or filament failure
Fig 6: DCBUS & VLAMP during a
non-strike lamp fault condition
Fig 7:V LAMP during Preheat, Ignition
and Run Modes
www.irf.com
5
模拟电子
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
