NCP1217: 18 to 24 V, 85 W, Off-line PSU with Short Term, High Surge Current Capability

DN06038/D
Design Note – DN06038/D
18 to 24 Volt, 85 Watt, Off-line PSU with
Short Term, High Surge Current Capability
Device
Application
Input Voltage
Output Power
Topology
I/O Isolation
NCP1217
Industrial – motors,
solenoids, etc.
90 to 265 Vac
85 Watts
CCM Flyback
Yes – 3 kV
Other Specifications
Output Voltage
Ripple
Nominal Current
Max Current
Min Current
Others
Output 1
Output 2
Output 3
Output 4
18 to 24 V
Less than 1%
3.5 A
7–8A
Zero
N/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
N/A
N/A
PFC (Yes/No)
No
Minimum Efficiency
85%
Inrush Limiting / Fuse
3 A fuse, Thermistor inrush limiter
Operating Temp. Range
Cooling Method/Supply
Orientation
Signal Level Control
0 to +60°C
Convection
None
High output surge current capability for several seconds.
Circuit Description
This Design Note is a modification/upgrade to ON
Semiconductor’s Application Note AND8076. The
NCP1217 current mode controller (100 kHz version) has
been used to eliminate the additional discrete circuitry
required by the original NCP1200/NCP1203 controller for
ramp compensation and OVP functions. By using a
continuous conduction mode (CCM) flyback topology,
which has a constant power output characteristic, this
power supply is capable of supplying short term, high
surge currents of over 7 A for powering industrial
equipment such as motors, solenoids or other inductive
loads. Overcurrent protection is initiated at approximately
3.6 A. However, the output current will increase up to
double this as the output voltage decreases due to the
overload. At a threshold determined by the value of
resistor R8, the supply will enter “hiccup” mode overcurrent
protection for reduced dissipation in the event of a “hard”
short circuit. For the given flyback transformer design, the
output voltage is adjustable via R14 from 18 volts to about
24 volts to suit the intended application. The OVP trip level
March 2008, Rev. 0
is determined by zener Z1. The overcurrent point is set by
parallel resistors R6A and B, and ramp compensation for
CCM operation is adjusted by R11. Additional details on
basic circuit operation, critical components, and the
NCP1217 characteristics can be found in the Application
Note AND8076 and the data sheet for the NCP1217
controller. The CCM flyback transformer T1 is available
from Coilcraft as part number Z9260-A or Z9007-B. EMI
inductor L2 is Coilcraft E3505-AL (or similar), and L1 is an
optional output ripple inductor that is Coilcraft part PCV-0472-05L.
Key Features
y 3.5 A continuous output with over 7 A surge capability with
adjustability on the latter threshold
y Overvoltage and overcurrent protection
y Input EMI filter for conducted emissions attenuation
y Thermistor input surge current limiting at turn-on
y Measured efficiencies of 85% at 120 Vac and 87% at 230
Vac input at full load
y Adjustable 18 to 24 volt output range (via R14)
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DN06038/D
Schematic
1
BD1
6A, 600V
AC
in
L2
TH1
5 ohms
3A
R1
0.33uf 1.0M
"X2" 1/2W
0.33uf
"X2"
D2
R4
4.7K,
0.5W
L1
4.7uH
D4
MBR20100
+
C9
C5
Q1
FQP6N60
C2
C1
T1
D1
MRA4007T
C3
270uF
400Vdc
MSD4148A
F1
3A
C4
R3 100nF
R2
39K
2W
x2
C7
C6
C8
0.1
18 - 24 V,
3.5 A
output
_
2,200uF
35V x 3
R6A,B
0.27 ohm,
0.5W
x2
R5
15
220uF
C10
D3
2.2 nF
"Y1"
R7
MMSD4148A 10
R8
2.4K
NCP1217
(100 kHz)
R9
100
R13
C15
47uf
35V
MMSZ5252BT
8
6
Z1
24V
(OVP)
1.2K,
0.5W
R11
2.4K
5
U1
SFH6156A-2
2
1
U2
4
R10
4.7K
C13
47uF,
35V
C14
0.1uF
C12
1nf
Opto
R14
39K
(20V)
C11
U3
TL431A
Notes:
1. Crossed schematic lines are not connected.
2. Heavy schematic lines indicate recommend ground plane areas.
3. Q1 and D4 require heatsinks.
4. R8 sets U1 Vcc level for overcurrent "hiccup" mode threshold.
5. R11 sets ramp compensation for U1.
6. R6A, B (paralleled resistors) set overcurrent trip level.
7. R14 sets Vout.
8. All resistors 1/8 or 1/4 watt unless otherwise noted.
Vout
Adj.
R12
1K
3
0.1uf
R15
5.6K
18 - 24 Vout, 85 Watt, Off-Line CCM Flyback Power Supply
Additional collateral from ON Semiconductor
y NCP1217: Current Mode Controller Fixed Frequency Operation
y MMSD4148: 100 V Switching Diode
y TL431A: Programmable Precision Reference
y MBR20100: 20 A, 100 V Schottky Rectifier
y Application Note AND8076: a 70 W Low Standby Power Supply with NCP120x Series
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© 2008 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]
March 2008, Rev. 0
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