A 6 W/12 W Universal Mains Adapter with the NCP101X

AND8142/D
A 6.0 W/12 W Universal
Mains Adapter with the
NCP101X
Prepared by: Christophe Basso
ON Semiconductor
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APPLICATION NOTE
controller. The resistor in series with the auxiliary winding
limits the current in the active VCC clamp, in case the
auxiliary winding is connected. Please note that this option
enables the optocoupler fail−safe protection: if the loop gets
accidentally opened, the VCC grows−up and imposes an
abnormal current into the VCC pin. The internal circuitry
detects it and the controller is fully latched−off. The user
must unplug the converter from the mains until VCC
collapses below 4.0 V to reset all internal logic blocks.
The present report depicts a demonstration board built
around the NCP1013P06, a new monolithic high−voltage
switcher. Delivering 6.0 W from 90 VAC to 250 VAC, the
board complies with EMI testing CISPR0022 and offers the
ability to either use the Dynamic Self−Supply or an auxiliary
winding. With this latter, the converter passes less than
100 mW in a no−load situation at 230 VAC.
Schematic Description
Figure 1 portrays the board application schematic whose
heart is powered by the NCP1013 operating at 65 kHz. This
frequency is selected for a) passing the CISPR0022 EMI
specification (that starts at 150 kHz) more easily
b) reducing the switching losses.
As one can see from Figure 1, a jumper exists and offers
the ability to disconnect the Dynamic Self−Supply (DSS):
when left open, the DSS powers the controller and
introduces frequency jittering thanks to the VCC ripple
injected inside the circuit. It also offers a precise
short−circuit trip point since the decision is taken
independently of any loosely coupled auxiliary winding.
The input power consumption is directly the current needed
to power the controller multiplied by the rectified bulk
voltage. If we assume an average controller current of
1.0 mA and a bulk level of 330 VDC, the input power will
be around 330 mW in a no−load situation. If the jumper is
now put in place, the DSS disconnects itself and the standby
power reduces below 100 mW. Precise numbers are given in
a summary table at the end of this document.
An RCD network safely clamps the maximum drain
excursion below 700 V at the highest mains conditions, e.g.
Vbulk = 370 V. A small 1.0 nF capacitor decouples the FB
to ground and prevents any noise from coupling inside the
 Semiconductor Components Industries, LLC, 2004
January, 2004 − Rev. 0
Practical Measurements
Some typical measurements are detailed below and
highlight the impact between the DSS or the auxiliary
winding implementation. All measurements were carried in
a 25°C operating temperature.
Standby Power
When the load is removed, it becomes possible to measure
the power absorbed by the demoboard in both operating
modes, DSS or auxiliary winding. It is required to let the
converter warm up for 15 minutes before recording the
numbers:
DSS: Vin = 120 VDC, Iout = 0, Pin = 130 mW
Vin = 330 VDC, Iout = 0, Pin = 320 mW
Aux.: Vin = 120 VDC, Iout = 0, Pin = 69 mW
Vin = 330 VDC, Iout = 0, Pin = 66 mW
The slight difference in the low/high numbers with the
auxiliary winding is due to the startup leakage current
(35 A), although very low, this number decreases as the
junction heats up (the internal controller consumption too).
With 330 VDC, the die temperature is slightly higher than
with 120 VDC and it explains the minor difference.
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Publication Order Number:
AND8142/D
1N4148
D4
JP1
2
J3
1
C8
2.2 nF
400 V
T1
Aux
+ C10
47 F/35 V
R7
150 k/
1W
+
T1
A9619−C
2x15 mH CM
L1
Schaffner RN112−06/2
Universal Input
220 nF
C1
X2
C6a C6b
470 F/16 V
R3
1k
NCP1013P06
+ C2
47 F/
400 V
+
12 V @
0.85
+ 47 F/16 V
C7
GND
D3
MUR160
R2
3.3 k
B1
SMD
L2
10 H
D2
MBRS360T3
R5
39 k
1 VCC GND 8
2 NC
NC 7
3 NC
NC 6
4 FB
D 5
IC3
+ 47 F/16 V
C3
C4
C9
1 nF
IC1
SFH615A−2
100 nF
IC2
TLV431
C5
2.2 nF
Y1 Type
R6
4.3 k
AND8142/D
2
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Figure 1. The Electrical Schematic of the 6.0 W Power Supply
Supply Jumper
Off: DSS Activated
On: Aux. Winding
R_L322
AND8142/D
Efficiency
Output Voltage Versus Output Current
As the DSS is directly drawing current from the rectified
rail via the drain pin, the average consumption permanently
present (though lowered when skip is activated) slightly
degrades the efficiency at light loads and low output power.
Nevertheless, efficiency is still above 50% at 730 mW output
power. Figures 2 and 3 portray the efficiency evolution at both
input voltages with either DSS or auxiliary winding.
Using the DSS or an auxiliary winding makes a big
difference in the ability to let the power supply detect an over
current condition. Both versions will be protected against
real short−circuits (Rload = 0), but the DSS will naturally
offer an improved performance when a precision trip point
is needed. This is mainly due to the poor coupling between
the auxiliary winding and the power winding which prevents
proper collapsing when Vout goes low. Also, the built−in
OVP forces us to grow the auxiliary voltage, which does not
play in our favor either.
90
80
Aux
14
DSS
60
12
50
OUTPUT VOLTAGE (V)
EFFICIENCY (%)
70
40
30
20
10
0
0
1
2
3
4
5
OUTPUT POWER (W)
6
7
6
4
DSS
0
Aux
0
0.5
1
1.5
2
2.5
OUTPUT CURRENT (A)
3
3.5
DSS
70
Operating Curves
It is important to check that critical parameters are well
within control before releasing the board to production.
Following are some curves captured on the demonstration
board with their individual comments.
60
50
40
30
20
10
0
Aux
Figure 4. Vout vs Iout (330 Vdc)
The DSS Offers a Better Performance to Detect an
Overcurrent Condition
90
EFFICIENCY (%)
8
2
Figure 2. Efficiency vs Power, Vin = 330 Vdc
Efficiency at High Input Line
80
10
0
1
2
3
4
5
OUTPUT POWER (W)
6
7
Figure 3. Efficiency vs Power, Vin = 120 Vdc
Efficiency at Low Input Line
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AND8142/D
Drain−Source Waveform
585 V
Vds(t)
Figure 5. Drain−Source Voltage Captured at Vin = 370 VDC with
Maximum Output Power
the loop is closed (e.g. Vout reaches its target). The displayed
level of 585 V gives sufficient room when compared to the
internal MOSFET BVdss of 700 V.
This shot has been taken just before the maximum current
trip point is reached. It corresponds to the highest peak
power and the largest reflected voltage on the drain. This
event also occurs during the start−up sequence, just before
Feedback Loop Closure
Loop is closed here . . .
Vfb
Error is checked here
Vcc
Figure 6. It is Important to Check for a Safe Start−Up Sequence
At power−on, the controller delivers the maximum peak
current. During this time, an error flag is internally raised,
signalling that the power supply has reached the maximum
peak limit. The fault management circuitry consists in
checking the presence of this flag every time the ripple on the
VCC pin comes down to 7.5 V. If the error flag is activated at
this time, the controller considers the presence of a fault and
it triggers the protective burst mode. As a result, since the VCC
capacitor must be sized to give enough room to let Vout reach
the target before the VCC ripple touches the 7.5 V setpoint.
Worse case corresponds to 120 VDC and maximum output
power, e.g. 6.0 W in our case.
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AND8142/D
Short−Circuit Protection
Vds
Vcc
Figure 7. A Short−Circuit has Occurred, the Controller Enters Burst−Mode
start−up source is re−activated and a new start−up attempt is
made. This is an auto−recovery system: if the fault fades
away, the power supply resumes its operation.
As we explained above, when the 7.5 V internal check
reveals that the error flag is raised, the controller stops
pulsing and reduces its consumption. VCC thus falls down
until another lower level is reached (VCClatch) where the
Optocoupler Fail−Safe Protection
22 V
Unloaded
Vout
Loaded
Figure 8. Fail−Safe Optocoupler Protection Triggered by a Short on the Secondary LED
fully latches off and all activity is stopped. The DSS keeps
going up and down, but the power supply is permanently
stopped. The user needs to reset the controller by unplugging
the converter to have VCC falling down below 4.0 V where
the latch is reset.
When the feedback loop is broken, the auxiliary and
output voltages run away. When the VCC pin is supplied by
the auxiliary winding (jumper is on), an internal circuitry
clamps to 8.7 V typical (a kind of active zener diode). When
the auxiliary level runs away, it pushes more current into the
active zener. If this current exceeds a given level, the circuit
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AND8142/D
Fault
Margin
Normal Startup
Vaux
Figure 9. It’s also important that start−up overshoots do not have the
bad luck to trigger the fail−safe circuitry.
supply gets latched at start−up. Figure 9 confirms the
adequate margin with the demo. Playing on R2 will offer a
reduction of the overvoltage level, but can affect the margin
as well as the standby consumption (e.g. if the active zener
is turned on in standby, it is more difficult to go below
100 mW).
A 100 nF capacitor connected over the TL431 offers a
pure integral compensation. Despite its simplicity, this kind
of capacitive network can engender start−up overshoots. If
the overshoot is low, as on this board, there is no problem.
However, it is important to check that, again, a sufficient
margin exists between a normal start−up and a real fault
detection. If this margin is too small, there are risks that the
Conducted EMI Sweeps
QP
QP
AV
AV
Figure 10. When the DSS is on, EMI Jittering
is Active
Figure 11. The Aux Winding Deactivates the
Jittering
winding is put in place, it disconnects the frequency sweep.
Nevertheless, the power supply still passes the limit.
Figures 12 and 13 show the same plots but when the
converter is powered from a 230 VAC input source. EMI
effects are also visible on Figure 12.
Figures 10 and 11 portray the conducted EMI sweeps
captured at Vin = 100 VAC. One can see the nice spreading
effect of the frequency sweep on Figure 10 where the
high−frequency noise is artificially reduced: it naturally
offers more margin to pass the limit. When the auxiliary
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AND8142/D
Conducted EMI Sweeps
QP
QP
AV
AV
Figure 12. When the DSS is on, the
Frequency Jitters
Figure 13. The Aux Winding Stops the
Jittering
Stability Check
By pulsing the converter output, it becomes possible to
detect any oscillations in the way the converter reacts.
Figure 14 shows stable results at low and high line, for a
10% to 100% current excursion.
High Line
Low Line
Figure 14. Pulsing the Output Current Confirms the Stability at Both
High and Low Line Conditions
Increasing the Output Power
The current demonstration board is supplied with a
Coilcraft A9619−C transformer featuring a primary
inductance of 3.0 mH. This device allows an output power
of 6.0 W continuous on a 70°C ambient temperature.
However, with the same board, it is possible to raise the
output power up to 12 W on a 230 VAC 15% application.
1. Plug another transformer, the Coilcraft B0570−B
that features a 3.4 mH primary inductor but whose
turn ratio is higher. The pinout is compatible with
the PCB, it is thus easy to wire it.
2. Replace the NCP1013P06 by an NCP1013P10, the
100 kHz version.
3. Replace the 150 k RCD resistor (R7) by a
100 k/2.0 W value.
The rest is kept unchanged. Please note that the board is
now able to deliver up to 12 W output power. Experiments
have shown that if the NCP1013P10 layout is improved
(more copper area), the new board can experimentally
deliver up to 19 W of continuous power in a 60°C ambient
temperature.
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AND8142/D
Conclusion
This board shows how to build, and test for reliability, a
power supply made around the new NCP101X device.
Despite a DIP8 package, the converter can be used in a
variety of applications ranging from auxiliary power
supplies up to a few watts converters. Once the chip
specification is understood, it becomes a child’s play to
make it work!
6.0 W − Universal Mains NCP101X Demonstration Board Part List
Reference
Value
Part Number
Manufacturer
Comment
R2
3.3 k
−
Any
1/4 W Thru Holes
R3
1.0 k
−
Any
1206 SMD
R4
−
−
−
Not Wired
R5
39 k
−
Any
1/4 W Thru Holes
R6
4.3 k
−
Any
1206 SMD
R7
150 k
2322 194 13154
BC Comp.
PRO1 Thru Holes
R_L3
22 −
Any
1/4 W Thru Holes
Replaces L3
L1
2 x 15 mH
RN112−0.6/02
Schaffner
CM Mode
L2
10 H
744 772 100
Wurth Elect.
LC Filter
L3
−
−
−
Not Wired
B1
800 V/1.0 A
DF08M
General Semiconductor
DIP8
D2
MBRS360T3
−
ON Semiconductor
SMD Type
D3
MUR160
−
ON Semiconductor
Axial
D4
1N4148
−
Any
Axial
C1
220 nF/X2
2222 335 5224
BC Comp.
X2 Type
C2
47 F/400 V
ECA2GM470
Panasonic
Radial
C3
47 F/16 V
ECA1CM470
Panasonic
−
C4
100 nF/25 V
−
Any
1206 SMD
C5
2.2 nF
WKP222MCMBFOK
Vishay
Y1
C6b
470 F/16 V
ECA1CM471
Panasonic
Radial
C6a
470 F/16 V
ECA1CM471
Panasonic
Radial
C7
47 F/16 V
ECA1CM470
Panasonic
Radial
C8
2.2 nF/400 V
R82MC1220DQ02J
Arcotronics
−
C9
1.0 nF/10 V
−
Any
1206 SMD
C10
47 F/35 V
ECA1VM470
Panasonic
Radial
C11
−
−
−
Not Wired
IC1
SFH615A−2
−
Siemens
SMD
IC2
TLV431ALP
−
ON Semiconductor
TO92
IC3
NCP1013P06
−
ON Semiconductor
DIP8
T1
A9619−C
−
Coilcraft
−
J1
Connector
PX0786/PC
Bulgin
Mains Inlet
J2
Connector
L145202010002
LMI
12 V Output
J3
Connector
4710334140400
Kontek
−
JP1
Jumper Shunts
−
Any
−
Feet
Board Feet
LCBS−TF−M4−6−01
Richco
9.5 mm Height
Coilcraft
1102 Silver Lake Road
Cary IL 60013
Tel. US: 800−322−2645
Tel. (WW) : 847−639−6400
Fax: 847−639−1469
www.coilcraft.com
www.coilcraft.com.cn
email: [email protected]
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8
AND8142/D
Figure 15. PCB Layout and Component Views
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AND8142/D
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