NCP1075: Universal AC Input, 12 Vout,10 W E-Meter Power Supply

DN05018/D
Universal AC Input,
12 V Output, 10 W E‐meter
Power Supply
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DESIGN NOTE
Table 1. DEVICE DETAILS
Device
Application
Input Voltage
Output Power
Topology
I/O Isolation
NCP1075,
NCP431
Smart Meters,
Electric Meters,
White Goods
85 to 300 Vac
5 to 10 W
Flyback
Isolated
(3 kV)
Characteristic
Output Specification
Output Voltage
12 Vdc
Ripple
150 mV p/p @ Full Load
Nominal Current
800 mA
Max Current
1.0 A Maximum
Min Current
Zero
PFC (Yes/No)
No, (Pout < 25 W)
Efficiency
77% per Energy Star
Inrush Limiting/Fuse
Inrush Resistor (R1) & Fuse
Operating Temp. Range
0 to +50°C
Cooling Method/Supply Orientation
Convection
Signal Level Control
None
Circuit Description
Performance characteristics for efficiency, output ripple,
and internal MOSFET drain switching characteristics are
shown in the figures and plots below. Enhanced input
transient protection (lightning, etc.) can be accomplished
with the addition of an appropriate TVS device across C2.
This design note describes a simple, low power (10 W or
less), universal AC input, constant voltage power supply
intended for powering utility electric meters or similar
industrial equipment or white goods where isolation from
the AC mains is required and low cost and high efficiency
is essential.
The featured power supply is a simple flyback topology
utilizing ON Semiconductor’s new NCP1075 SOT−223
monolithic switcher. This Design Note provides the
complete circuit schematic details and transformer design
for a 12 V, 800 mA amp power supply. Other output voltages
from 3.3 Vdc up to 28 Vdc are easy to implement by
modifying the values (or ratings) of a few of the secondary
side output components and the flyback transformer’s
secondary winding (T1). The simple input EMI filter is
adequate to pass Level B for FCC conducted EMI
compliance and the NCP431 plus optocoupler feedback
scheme provides for excellent line and load regulation along
with high input-to-output isolation.
© Semiconductor Components Industries, LLC, 2015
January, 2015 − Rev. 1
Key Features
• Universal AC Input Range (85–300 Vac).
• Input Filter (Pi-network) for Conducted EMI
•
•
•
•
1
Attenuation and Input Transient Protection
Very Low Standby (No Load) Power Consumption
Frequency Foldback under Light Load and/or
Over-current Conditions
Secondary Circuit Easily Configured for Different
Output Voltages
Inherent Over-current, Over-voltage and
Over-temperature Protection
Publication Order Number:
DN05018/D
4.7 ohms
3W
R1
C1
0.1uF
”X”
1.5A
F1
C2
1 mH
0.1uF
”X”
L1B
1 mH
L1A
R2B
3.3M
3.3M
R2A
Primary
Ground
Plane
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2
R4
C7
1nF
1K
R3
D5
C4
1nF
1kV
4.7uF
50V
D6
C6
10
MMSD
4148A R5
1N4937
68K
1/2W
C8
T1
5,6
7,8
3
4
MBRS
260T3
D7
2
1 1K
R7
R6
1K
C10
U3
0.1uF
50V
Secondary
Ground
Plane
U2
1nF ”Y1”
2
3
4
1
10 W NCP1075 Power Supply with Universal AC Input
C5
22uF
25V
(100 kHz)
NCP1075
1
22uF
400V
U1
3
4 2
D1−D4
MRA4007
X4
C3
Notes:
1. Crossed lines on schematic are NOT connected.
2. R4 value dependent on AUX winding turns.
3. R1 is optional inrush limiting resistor.
4. U1 tab (pin 4) and D7 should have heatsinking clad pours.
5. Heavy lines indicate recommended ground plane areas.
6. L1A/L1B are Coilcraft RFB0810−102L.
7. U2 is Vishay SFH6156A−4 optocoupler or similar.
AC Input
J1
NCP431
10K
0.1
R10 C12
1000uF, 16V
C9A C9B
10K
R9
R8
39K
0.1uF
50V
C11
+
_
Vout
J2
DN05018/D
CIRCUIT SCHEMATIC
DN05018/D
12 V Transformer Design
Project/Customer: ON Semiconductor − NCP1075 10W PSU
Part Description: 10 W Flyback Transformer, 100 kHz, 12 V/0.8 A Out
Schematic ID: T1
Core Type: EF16 (E16/8/5); 3C90 Material or Similar
Core Gap: Gap for 1.7 to 2 mH Inductance across Primary (Pins 1 − 4)
Inductance: 1.85 mH ±5%
Bobbin Type: 8 Pin Horizontal Mount for EF16
Windings (in order):
Winding #/Type
Turns/Material/Gauge/Insulation Data
Primary (4 − 1)
100 turns of #35HN over 2 layers evenly. Insulate with a layer of Mylar
tape.
12 V Secondary (7, 8 − 5, 6)
10 turns of #24 triple insulated wire over one layer. Self leads to pins
per drawing. Insulate with a layer of Mylar tape.
Vcc/Boost (3 − 2)
10 turns of #35HN spiral wound over 1 layer with 2 mm end margins.
Insulate with tape for 3 kV.
Varnish assembly
Hipot: 3 kV from Vcc/primary to secondary.
Schematic
1
4
3
Lead Breakout/Pinout
(Bottom View − Facing Pins)
8
7
6
5
4
5
3
6
2
7
1
8
2
Note: Transformer is Wurth Electronics part #750312597
A 5 Vout version of this transformer is available on request.
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3
DN05018/D
Average efficiency for both 120 Vac and 230 Vac was 77%.
Figure 1. Efficiency vs. Load Curves
Standby (No Load) Input Power
120 Vac: 74 mW
230 Vac: 107 mW
Figure 2. Full Load Output Ripple @ 120 Vac Input
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4
DN05018/D
Figure 3. MOSFET Drain Voltage (120 Vac Input, 12 V, 1 A Load on Output)
Figure 4. MOSFET Drain Voltage (120 Vac Input, 12 V, 250 mA Output)
dBuV
NCP1075 Flyback 12V 800mA
120 v ac input
80
70
60
EN 55022; Class B Conducted, Quasi−Peak
EN 55022; Class B Conducted, Average
50
40
30
20
10
0
Average
−10
−20
1
10
9/14/2011 8:00:53 AM
(Start = 0.15, Stop = 30.00) MHz
Figure 5. EMI Profile
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5
DN05018/D
BILL OF MATERIALS
Table 2. BILL OF MATERIALS FOR 12 Vout, 10 W NCP1075 FLYBACK
Footprint
Manufacturer
Manufacturer
Part Number
Substitution
Allowed
2 A, 60 V
SMB
ON Semiconductor
MBRS260T3
No
Designator
Qty
Description
Value
D7
(12 Vout)
1
Schottky Diode
Tolerance
D7 (5 Vout)
1
Schottky Diode
3 A, 40 V
SMB
ON Semiconductor
MBRS2040L
No
D1, D2, D3,
D4
4
Diode − 60 Hz
1 A, 800 V
SMA
ON Semiconductor
MRA4007
No
D5
1
Diode − Fast Recov.
1 A, 600 V
Axial Lead
ON Semiconductor
1N4937
No
D6
1
Signal Diode
100 mA, 100 V
SOD−123
ON Semiconductor
MMSD4148A
No
U3
1
Programmable Zener
2.5 V
SOIC8/
SOT23
ON Semiconductor
NCP431A
No
U2
1
Optocoupler
CTR >/= 0.5
4-pin
Vishay or NEC
SFH6156A−4 or
PS2561L−1
Yes
U1
1
Switcher IC −
NCP1075
100 kHz
SOT223
ON Semiconductor
NCP1075ST100
No
C1, C2
2
“X” Cap, Box Type
100 nF, X2
LS = 15 mm
Rifa, Wima
TBD
Yes
C8
1
“Y1” Cap, Disc Type
1 nF, Y1
LS = 7.5 mm
Rifa, Wima
TBD
Yes
C4
1
Ceramic Cap, Disc
1 nF, 1 kV
5%
LS = 7.5 mm
Rifa, Wima
TBD
Yes
C7
1
Ceramic Cap,
Monolythic
1 nF, 50 V
10%
1206
AVX, Murata
TBD
Yes
C10, C11,
C12
3
Ceramic Cap,
Monolythic
100 nF, 50 V
10%
1206
AVX, Murata
TBD
Yes
C3
1
Electrolytic Cap
22 mF,
400/450 V
10%
LS = 7.5 mm,
D = 16 mm
UCC, Panasonic
TBD
Yes
C6
1
Electrolytic Cap
4.7 mF, 50 Vdc
10%
LS = 2.5 mm,
D = 6.3 mm
UCC, Panasonic
TBD
Yes
C5
1
Electrolytic Cap
22 mF, 25 V
10%
LS = 2.5 mm,
D = 6.3 mm
UCC, Panasonic
TBD
Yes
C9A, C9B
2
Electrolytic Cap
1000 mF, 16 V
10%
LS = 5 mm,
D = 12.5 mm
UCC, Panasonic
TBD
Yes
R1
1
Resistor, 3 W, Wire
Wound
4.7 W, 3 W
10%
LS = 7.5 mm,
D = 7 mm
Ohmite, Dale
TBD
Yes
R3
1
Resistor, 0.5 W,
Metal Film
68 kW, 0.5 W
10%
Axial Lead;
LS = 12.5 mm
Ohmite, Dale
TBD
Yes
R2A, R2B
2
Resistor, 1/4 W SMD
3.3 MW
5%
SMD 1206
AVX, Vishay, Dale
TBD
Yes
R5
1
Resistor, 1/4 W SMD
10 W
5%
SMD 1206
AVX, Vishay, Dale
TBD
Yes
R4
1
Resistor, 1/4 W SMD
1 kW
5%
SMD 1206
AVX, Vishay, Dale
TBD
Yes
R9, R10
2
Resistor, 1/4 W SMD
10 kW
1%
SMD 1206
AVX, Vishay, Dale
TBD
Yes
R7
1
Resistor, 1/4 W SMD
1 kW
1%
SMD 1206
AVX, Vishay, Dale
TBD
Yes
R6
(12 Vout)
1
Resistor, 1/4 W SMD
1 kW
1%
SMD 1206
AVX, Vishay, Dale
TBD
Yes
R6 (5 Vout)
1
Resistor, 1/4 W SMD
240 W
1%
SMD 1206
AVX, Vishay, Dale
TBD
Yes
R8
(12 Vout)
1
Resistor, 1/4 W SMD
39 kW
5%
SMD 1206
AVX, Vishay, Dale
TBD
Yes
R8 (5 Vout)
1
Resistor, 1/4 W SMD
10 kW
1%
SMD 1206
AVX, Vishay, Dale
TBD
Yes
F1
1
Fuse, TR−5 Style
1.5 A
TR−5,
LS = 5 mm
Minifuse
L1A/B
2
Inductor (EMI Choke)
1 mH, 500 mA
See Wurth
Drawing
LS = 5 mm,
D = 8 mm
T1
(12 Vout)
1
Transformer
E20/10/6 Core
See Mag
Drawing
Wurth Magnetics
J1, J2
2
Screw Terminal
LS = 0.2″
DigiKey
NOTE: Grey indicates part change with Vout change.
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6
Yes
7447728102
Yes
Yes
# 281−1435−ND
Yes
DN05018/D
REFERENCES
[3] ON Semiconductor Application Note AND8489/D
[1] ON Semiconductor Data Sheet for NCP1251/D
Controller in TSOP6 Package.
[2] ON Semiconductor Design Notes DN05012/D,
DN05014/D, DN05017/D.
ON Semiconductor and the
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DN05018/D