DN06006/D
Design Note – DN06006/D
1 A, 12 W Constant Current
Off-Line LED Driver
Device
Application
Input Voltage
Output Power
Topology
I/O Isolation
NCP1027
Off-line Constant
Current LED Driver
90 to 265 Vac
12 W max
Flyback
No line isolation
Other Specifications
Output Voltage
Ripple
Nominal Current
Max Current
Output 1
Output 2
Output 3
Output 4
15 V max
< 250 mV
1A
1.1 A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
PFC (Yes/No)
No
Minimum Efficiency
Cooling Method/Supply
Orientation
70%
Convection
Circuit Description
Key Features
The LED driver circuit uses an NCP1027 monolithic
controller in a 1 amp, 12 watt constant current output
flyback converter. Both current and peak voltage control
are achieved by the use of transistor Q1, zener D7, and
current sense resistor R3. The circuit provides a
regulated current output down to about 7 volts dc and
clamps the output to about 15 volts under no load
conditions. The level of Vcc control bias on U1 is set by
R9 and will depend on the characteristic Vf of the total
LED load that reflects to the output. The circuit includes
and optional EMI filter (C1, L1, and C10), and brownout
protection whose level is set by R7 and R8.
y Constant current output with voltage clamp
y Simple flyback circuit using NCP1027
y Conducted EMI filter
y Universal AC input (90 to 265 Vac)
y Non-isolated output for simplicity
July 2006, Rev. 0
www.onsemi.com
1
DN06006/D
Schematic
R1
15, 2W
AC
input
D1, 2, 3, 4
1N4007 x 4
L1, 1 mH
C1
1
4.7nf
"x"
C2
4.7uf,
400Vdc
x2
7,8
C4
1.5 nf
1 kV
C3
T1
R2
47K,
1W
D6
MBR350
C5
470uf
25V
D5
MUR160
5,6
D8
C6
10 nf
R3
+
Output
12V@1A max
_
0.68
2W
4
3
1N4148A
2
R8
3M, 0.5W
R9
1K
C10 ("Y" cap)
R4
100
U1
2
4
7
1
Q1
C10
1nF
R6
390K
Vmax
1N5245B
(15V)
5
3
R7
18K
D7
2.2 nF
NCP1027
(100 kHz)
8
+ C9
10uf
25V
R5
C8
C7
1 nF
2N2222A
10nF
2K
R6
220
NOTES:
1. L1 is Coilcraft part RFB0807-102 (1 mH @ 250 mA) for EMI compliance.
2. See Magnetics Data Sheet for T1 construction details (EF-16 core & horizontal bobbin.)
3. D7 zener sets Vout max: Vout = Vz + 0.65V.
4. R3 sets max current: Imax = 0.7/(Rtotal).
5. Fuse resistor recommended for R1.
6. Crossed schematic lines are not connected.
7. R7, R8 sets brownout voltage shutdown level.
8. R9 value may vary depending on output voltage level dependence on LED Vf total.
July 2006, Rev. 0
www.onsemi.com
Constant Current LED Supply
with Peak Voltage Limit
and Universal AC Input
2
DN06006/D
1
MAGNETICS DESIGN DATA SHEET
Project / Customer: ON Semiconductor - NCP1027 Off-line LED Supply
Part Description: 13 watt flyback transformer, 100 kHz, 12V / 1.0 A
Schematic ID: T1
Core Type: EF16 (E16/8/5); 3C90 material or similar
Core Gap: Gap for 1.1 mH
Inductance: 1.1 mH +/-5%
Bobbin Type: 8 pin horizontal mount for EF16
Windings (in order):
Winding # / type
Turns / Material / Gauge / Insulation Data
Vcc/Boost (2 - 3)
12 turns of #32HN spiral wound over 1 layer. Insulate
with 1 layer of tape (500V insulation to next winding)
Primary (1 - 4)
105 turns of #32HN over 3 layers, 35 TPL. Insulate
for 3 kV to next winding.
12V Secondary (5, 6 - 7, 8)
10 turns of 2 strands of #26HN flat wound over 1 layer
Insulate with tape.
Vacuum varnish assembly.
Note: Transformer available from Mesa Power Systems, Escondido, CA; 1-800-515-8514
Part number 13-12-1000
Hipot: 3 kV from boost/primary to secondary for 1 minute.
Lead Breakout / Pinout
Schematic
(Bottom View - facing pins)
1
8
7
4
4
6
5
3
2
1
5
6
7
8
3
2
1
© 2006 ON Semiconductor.
Disclaimer: ON Semiconductor is providing this design note “AS IS” and does not assume any liability arising from its use; nor
does ON Semiconductor convey any license to its or any third party’s intellectual property rights. This document is provided only to
assist customers in evaluation of the referenced circuit implementation and the recipient assumes all liability and risk associated
with its use, including, but not limited to, compliance with all regulatory standards. ON Semiconductor may change any of its
products at any time, without notice.
Design note created by Frank Cathell, e-mail: [email protected]
July 2006, Rev. 0
www.onsemi.com
3