DN06012/D
Design Note – DN06012/D
10 W, 24 V / 5 V Off-Line Power Supply
Device
Application
Input Voltage
Output Power
Topology
I/O Isolation
NCP1027
Industrial Equipment
90 to 270 Vac
10 W (12W peak)
Flyback / Buck
Yes
Other Specifications
Output Voltage
Ripple
Nominal Current
Max Current
Min Current
Others
Output 1
Output 2
Output 3
Output 4
24 Vdc
200 mV
400 mA
500 mA
zero
5.0 Vdc
100 mV
250 mA
500 mA
zero
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
80% minimum
Operating Temp. Range
Cooling Method/Supply
Orientation
0 to +70°C
Convection
Both outputs regulated.
Circuit Description
Key Features
This design note features a low power, off-line dual
output power supply intended for industrial control
applications. ON Semiconductor’s NCP1027 integrated
monolithic controller is implemented in a discontinuous
conduction mode (DCM) flyback topology to provide 24
volts for powering motors or relays and an additional 5
volt output is provided utilizing the LM2574-5 Buck
switching regulator. This latter output is useful for logic
level power and is derived from the 24 Vdc main output.
With the exception of T1, all magnetics are “off-the-shelf”
parts from Coilcraft. The NCP1027 main controller
features current mode control and ac mains “brown-out”
sensing. Additional features of this chip not specifically
used in this application include slope compensation for
continuous conduction mode topologies and a power limit
function (see NCP1027 data sheet at www.onsemi.com).
The circuit also includes a conducted EMI filter
composed of C1, C9, and L1.
y Two regulated dc output voltages (24V, 5V) for
industrial controls or similar applications.
y Low cost yet robust 10 watt output power with 12 watt
surge capability.
y Mains brown-out sensing.
y Input conducted EMI filter.
y Efficient, low noise DCM flyback topology
y Monolithic current mode controller plus 700 V MOSFET
in single DIP-8 package.
August 2006, Rev. 0
www.onsemi.com
1
DN06012/D
Schematic
R1
15, 2W
AC
input
D1, 2, 3, 4
1N4007 x 4
L1, 1 mH
C1
1
10nf
"x"
C2
4.7uf,
400Vdc
x2
7,8
C4
1.5 nf
1 kV
C3
T1
D7
MBR1100
C5A C5B
R2
47K,
1W
C6
0.1
50V
D5
MUR160
5,6
D6
+24V @
400 mA
Com
470uf
35V x 2
4
3
1N4148A
R8
3M, 0.5W
R9
750
2
C9 ("Y" cap)
U1
NCP1027
(100kHz)
C12
1nF
R6
1M
D8
1N5252B
(24V, 400mW
5
3
R7
18K
2.2 nF
2
R4
4
4
7
U2
1
1
8
+ C11
10uf
25V
C10
100pf
100
R5
200
3
opto
2
U3
LM2574-5
C8
5
0.1
50V
3
1
8
6 4 2
L2
1mH
+5V @
250 mA
7
D9
1N5819
C7
220
6.3V
NOTES:
1. L1, L2 are Coilcraft inductor part # RFB0807-102L (1 mH @ 250 mA).
2. U2 is 4 pin optocoupler with CTR of 50% minimum(Vishay recommended)
3. See Magnetics Data Sheet for T1 construction details (EF-16 core & horizontal bobbin.)
4. U3 can be 5 volt or 3.3 volt version of LM2574 (DIP8 package).
5. D7 zener sets main Vout: Vout = Vz + 0.85V.
6. Fuse resistor recommended for R1 (inrush limiting).
7. Crossed schematic lines are not connected.
8. C5B optional depending on output ripple requirements.
9. Components shown are "generic" through-hole devices. SMD versions can be
substituted for most of the components if desired.
10. All semiconductors are manufactured by ON Semiconductor except U2 (optocoupler).
11. C1, C9, and L1 required for conducted EMI compliance.
12. All resistors are 1/4W unless otherwise specified.
August 2006, Rev. 0
www.onsemi.com
10 Watt, Dual Output,
Universal AC Input
Power Supply
ON Semiconductor
Power Design Group
2
DN06012/D
1
MAGNETICS DESIGN DATA SHEET
Project : 10 Watt, NCP1027 based off-line supply
Part Description: 10 watt flyback transformer, 100 kHz, 24V / 500mA
Schematic ID: T1
Core Type: EF16 (E16/8/5); 3C90 material or similar
Core Gap: Gap for 1.3 mH
Inductance: 1.3 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.
24V Secondary (5, 6 - 7, 8)
20 turns of #28H wound over one layer with
0.050" (1.3mm) end margins. Insulate with tape.
Vacuum varinish assembly.
Hipot: 3 kV from boost/primary to secondary for 1 minute.
Lead Breakout / Pinout
Schematic
(Bottom View - facing pins)
1
8
7
4
4
3
2
1
6
5
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]
August 2006, Rev. 0
www.onsemi.com
3