ON NCP1200P60G Pwm current−mode controller for low−power universal off−line supply Datasheet

NCP1200
PWM Current−Mode
Controller for Low−Power
Universal Off−Line Supplies
Housed in SOIC−8 or PDIP−8 package, the NCP1200 represents a
major leap toward ultra−compact Switchmode Power Supplies. Due to
a novel concept, the circuit allows the implementation of a complete
offline battery charger or a standby SMPS with few external
components. Furthermore, an integrated output short−circuit
protection lets the designer build an extremely low−cost AC−DC wall
adapter associated with a simplified feedback scheme.
With an internal structure operating at a fixed 40 kHz, 60 kHz or
100 kHz, the controller drives low gate−charge switching devices like
an IGBT or a MOSFET thus requiring a very small operating power.
Due to current−mode control, the NCP1200 drastically simplifies the
design of reliable and cheap offline converters with extremely low
acoustic generation and inherent pulse−by−pulse control.
When the current setpoint falls below a given value, e.g. the output
power demand diminishes, the IC automatically enters the skip cycle
mode and provides excellent efficiency at light loads. Because this
occurs at low peak current, no acoustic noise takes place.
Finally, the IC is self−supplied from the DC rail, eliminating the
need of an auxiliary winding. This feature ensures operation in
presence of low output voltage or shorts.
Features
•
•
•
•
•
•
•
•
•
•
•
•
No Auxiliary Winding Operation
Internal Output Short−Circuit Protection
Extremely Low No−Load Standby Power
Current−Mode with Skip−Cycle Capability
Internal Leading Edge Blanking
250 mA Peak Current Source/Sink Capability
Internally Fixed Frequency at 40 kHz, 60 kHz and 100 kHz
Direct Optocoupler Connection
Built−in Frequency Jittering for Lower EMI
SPICE Models Available for TRANsient and AC Analysis
Internal Temperature Shutdown
Pb−Free Packages are Available
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MARKING
DIAGRAMS
8
200Dy
ALYW
G
SOIC−8
D SUFFIX
CASE 751
8
1
1
8
PDIP−8
P SUFFIX
CASE 626
1200Pxxx
AWL
YYWWG
8
1
1
xxx
y
= Device Code: 40, 60 or 100
= Device Code:
4 for 40
6 for 60
1 for 100
A
= Assembly Location
L
= Wafer Lot
Y, YY = Year
W, WW = Work Week
G, G
= Pb−Free Package
PIN CONNECTIONS
Adj
1
8
HV
FB
2
7
NC
CS
3
6
VCC
GND
4
5
Drv
(Top View)
Typical Applications
• AC−DC Adapters
• Offline Battery Chargers
• Auxiliary/Ancillary Power Supplies (USB, Appliances, TVs, etc.)
© Semiconductor Components Industries, LLC, 2006
September, 2006 − Rev. 15
1
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 14 of this data sheet.
Publication Order Number:
NCP1200/D
NCP1200
C3
10 mF
400 V
*
+
1
D2
1N5819
HV 8
Adj
2 FB
NC 7
3 CS
VCC 6
M1
MTD1N60E
4 GND Drv 5
6.5 V @ 600 mA
+ C2
470 mF/10 V
Rf
470
EMI
Filter
+
C5
10 mF
Rsense
D8
5 V1
Universal Input
*Please refer to the application information section
Figure 1. Typical Application
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PIN FUNCTION DESCRIPTION
Pin No.
Pin Name
Function
Description
1
Adj
Adjust the Skipping Peak Current
This pin lets you adjust the level at which the cycle skipping process takes
place.
2
FB
Sets the Peak Current Setpoint
By connecting an Optocoupler to this pin, the peak current setpoint is adjusted accordingly to the output power demand.
3
CS
Current Sense Input
This pin senses the primary current and routes it to the internal comparator
via an L.E.B.
4
GND
The IC Ground
5
Drv
Driving Pulses
The driver’s output to an external MOSFET.
6
VCC
Supplies the IC
This pin is connected to an external bulk capacitor of typically 10 mF.
7
NC
No Connection
This un−connected pin ensures adequate creepage distance.
8
HV
Generates the VCC from the Line
Connected to the high−voltage rail, this pin injects a constant current into
the VCC bulk capacitor.
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2
NCP1200
Adj
8
1
HV Current
Source
75.5 k
FB
1.4 V
+
2
HV
Skip Cycle
Comparator
UVLO
High and Low
Internal Regulator
Internal
VCC
−
7
NC
29 k
Current
Sense
Ground
8k
4
+
−
Vref
5.2 V
Set
40, 60 or
100 kHz
Clock
250 ns
L.E.B.
3
Q Flip−Flop
DCmax = 80%
Q
6
Reset
VCC
+
60 k
5
−
1V
20 k
Drv
±250 mA
Overload?
Fault Duration
Figure 2. Internal Circuit Architecture
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MAXIMUM RATINGS
Rating
Symbol
Value
Units
Power Supply Voltage
VCC
16
V
Thermal Resistance Junction−to−Air, PDIP−8 version
Thermal Resistance Junction−to−Air, SOIC version
RqJA
RqJA
100
178
°C/W
Maximum Junction Temperature
Typical Temperature Shutdown
TJmax
150
140
°C
−
Tstg
−60 to +150
°C
ESD Capability, HBM Model (All Pins except VCC and HV)
−
2.0
kV
ESD Capability, Machine Model
−
200
V
Maximum Voltage on Pin 8 (HV), pin 6 (VCC) Grounded
−
450
V
Maximum Voltage on Pin 8 (HV), Pin 6 (VCC) Decoupled to Ground with 10 mF
−
500
V
Minimum Operating Voltage on Pin 8 (HV)
−
30
V
Storage Temperature Range
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
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3
NCP1200
ELECTRICAL CHARACTERISTICS (For typical values TJ = +25°C, for min/max values TJ = −25°C to +125°C, Max TJ = 150°C,
VCC= 11 V unless otherwise noted)
Rating
Pin
Symbol
Min
Typ
Max
Unit
DYNAMIC SELF−SUPPLY (All Frequency Versions, Otherwise Noted)
VCC Increasing Level at Which the Current Source Turns−off
6
VCCOFF
10.3
11.4
12.5
V
VCC Decreasing Level at Which the Current Source Turns−on
6
VCCON
8.8
9.8
11
V
VCC Decreasing Level at Which the Latchoff Phase Ends
6
VCClatch
−
6.3
−
V
Internal IC Consumption, No Output Load on Pin 5
6
ICC1
−
710
880
Note 1
mA
Internal IC Consumption, 1 nF Output Load on Pin 5, FSW = 40 kHz
6
ICC2
−
1.2
1.4
Note 2
mA
Internal IC Consumption, 1 nF Output Load on Pin 5, FSW = 60 kHz
6
ICC2
−
1.4
1.6
Note 2
mA
Internal IC Consumption, 1 nF Output Load on Pin 5, FSW = 100 kHz
6
ICC2
−
1.9
2.2
Note 2
mA
Internal IC Consumption, Latchoff Phase
6
ICC3
−
350
−
mA
High−voltage Current Source, VCC = 10 V
8
IC1
2.8
4.0
−
mA
High−voltage Current Source, VCC = 0 V
8
IC2
−
4.9
−
mA
Output Voltage Rise−time @ CL = 1 nF, 10−90% of Output Signal
5
Tr
−
67
−
ns
Output Voltage Fall−time @ CL = 1 nF, 10−90% of Output Signal
5
Tf
−
28
−
ns
Source Resistance (drive = 0, Vgate = VCCHMAX − 1 V)
5
ROH
27
40
61
W
Sink Resistance (drive = 11 V, Vgate = 1 V)
5
ROL
5
12
25
W
Input Bias Current @ 1 V Input Level on Pin 3
3
IIB
−
0.02
−
mA
Maximum internal Current Setpoint
3
ILimit
0.8
0.9
1.0
V
Default Internal Current Setpoint for Skip Cycle Operation
3
ILskip
−
350
−
mV
Propagation Delay from Current Detection to Gate OFF State
3
TDEL
−
100
160
ns
Leading Edge Blanking Duration
3
TLEB
−
230
−
ns
INTERNAL CURRENT SOURCE
DRIVE OUTPUT
CURRENT COMPARATOR (Pin 5 Un−loaded)
INTERNAL OSCILLATOR (VCC = 11 V, Pin 5 Loaded by 1 kW)
Oscillation Frequency, 40 kHz Version
−
fOSC
36
42
48
kHz
Oscillation Frequency, 60 kHz Version
−
fOSC
52
61
70
kHz
Oscillation Frequency, 100 kHz Version
−
fOSC
86
103
116
kHz
Built−in Frequency Jittering, FSW = 40 kHz
−
fjitter
−
300
−
Hz/V
Built−in Frequency Jittering, FSW = 60 kHz
−
fjitter
−
450
−
Hz/V
Built−in Frequency Jittering, FSW = 100 kHz
−
fjitter
−
620
−
Hz/V
Maximum Duty Cycle
−
Dmax
74
80
87
%
Internal Pullup Resistor
2
Rup
−
8.0
−
kW
Pin 3 to Current Setpoint Division Ratio
−
Iratio
−
4.0
−
−
Default skip mode level
1
Vskip
1.1
1.4
1.6
V
Pin 1 internal output impedance
1
Zout
−
25
−
kW
FEEDBACK SECTION (VCC = 11 V, Pin 5 Loaded by 1 kW)
SKIP CYCLE GENERATION
1. Max value @ TJ = −25°C.
2. Max value @ TJ = 25°C, please see characterization curves.
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4
NCP1200
60
11.70
50
11.60
40
11.50
VCCOFF (V)
LEAKAGE (mA)
100 kHz
30
11.40
40 kHz
20
11.30
10
11.20
0
−25
0
25
50
75
100
11.10
−25
125
60 kHz
0
25
50
75
100
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 3. HV Pin Leakage Current vs.
Temperature
Figure 4. VCC OFF vs. Temperature
9.85
125
900
100 kHz
9.80
850
60 kHz
800
9.70
ICC1 (mA)
VCCON (V)
9.75
9.65
9.60
40 kHz
750
700
9.55
650
9.50
9.45
−25
100 kHz
60 kHz
40 kHz
0
25
50
75
100
600
−25
125
0
25
50
75
100
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 5. VCC ON vs. Temperature
Figure 6. ICC1 vs. Temperature
2.10
110
104
100 kHz
1.90
125
100 kHz
98
92
FSW (kHz)
ICC2 (mA)
1.70
1.50
60 kHz
1.30
86
80
74
68
60 kHz
62
56
40 kHz
1.10
50
40 kHz
44
0.90
−25
0
25
50
75
100
38
−25
125
0
25
50
75
100
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 7. ICC2 vs. Temperature
Figure 8. Switching Frequency vs. TJ
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5
125
NCP1200
6.50
460
430
6.45
370
6.40
ICC3 (mA)
VCCLATCHOFF (V)
400
6.35
6.30
340
310
280
250
6.25
220
6.20
−25
0
25
50
75
100
190
−25
125
100
Figure 10. ICC3 vs. Temperature
125
1.00
Source
CURRENT SETPOINT (V)
W
75
Figure 9. VCC Latchoff vs. Temperature
40
30
20
Sink
10
0
25
50
75
100
0.96
0.92
0.88
0.84
0.80
−25
125
0
25
50
75
100
125
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 11. DRV Source/Sink Resistances
Figure 12. Current Sense Limit vs. Temperature
86.0
1.33
84.0
DUTY−MAX (%)
1.34
1.32
Vskip (V)
50
TEMPERATURE (°C)
50
1.31
1.30
1.29
1.28
−25
25
TEMPERATURE (°C)
60
0
−25
0
82.0
80.0
78.0
76.0
0
25
50
75
100
74.0
−25
125
0
25
50
75
100
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 13. Vskip vs. Temperature
Figure 14. Max Duty Cycle vs. Temperature
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6
125
NCP1200
APPLICATIONS INFORMATION
INTRODUCTION
The NCP1200 implements a standard current mode
architecture where the switch−off time is dictated by the
peak current setpoint. This component represents the ideal
candidate where low part−count is the key parameter,
particularly in low−cost AC−DC adapters, auxiliary
supplies etc. Due to its high−performance High−Voltage
technology, the NCP1200 incorporates all the necessary
components normally needed in UC384X based supplies:
timing components, feedback devices, low−pass filter and
self−supply. This later point emphasizes the fact that ON
Semiconductor’s NCP1200 does NOT need an auxiliary
winding to operate: the product is naturally supplied from
the high−voltage rail and delivers a VCC to the IC. This
system is called the Dynamic Self−Supply (DSS).
Dynamic Self−Supply
The DSS principle is based on the charge/discharge of the
VCC bulk capacitor from a low level up to a higher level. We
can easily describe the current source operation with a bunch
of simple logical equations:
POWER−ON: IF VCC < VCCOFF THEN Current Source
is ON, no output pulses
IF VCC decreasing > VCCON THEN Current Source is
OFF, output is pulsing
IF VCC increasing < VCCOFF THEN Current Source is
ON, output is pulsing
Typical values are: VCCOFF = 11.4 V, VCCON = 9.8 V
To better understand the operational principle, Figure 15’s
sketch offers the necessary light:
VCCOFF = 11.4 V
VCC
10.6 V Avg.
VCCON = 9.8 V
ON
OFF
Current
Source
Output Pulses
10.00M
30.00M
50.00M
70.00M
90.00M
Figure 15. The Charge/Discharge Cycle
Over a 10 mF VCC Capacitor
. 0.16 = 256 mW. If for design reasons this contribution is
still too high, several solutions exist to diminish it:
1. Use a MOSFET with lower gate charge Qg
2. Connect pin through a diode (1N4007 typically) to
one of the mains input. The average value on pin 8
The DSS behavior actually depends on the internal IC
consumption and the MOSFET’s gate charge, Qg. If we
select a MOSFET like the MTD1N60E, Qg equals 11 nC
(max). With a maximum switching frequency of 48 kHz (for
the P40 version), the average power necessary to drive the
MOSFET (excluding the driver efficiency and neglecting
various voltage drops) is:
Fsw @ Qg @ V cc
2*V
mains PEAK. Our power contribution
becomes
p
example drops to: 160 mW.
with
Fsw = maximum switching frequency
Qg = MOSFET’s gate charge
VCC = VGS level applied to the gate
To obtain the final driver contribution to the IC
consumption, simply divide this result by VCC: Idriver =
Fsw @ Qg = 530 mA. The total standby power consumption
at no−load will therefore heavily rely on the internal IC
consumption plus the above driving current (altered by the
driver’s efficiency). Suppose that the IC is supplied from a
400 V DC line. To fully supply the integrated circuit, let’s
imagine the 4 mA source is ON during 8 ms and OFF during
50 ms. The IC power contribution is therefore: 400 V . 4 mA
Dstart
1N4007
C3
4.7 mF
400 V
EMI
Filter
+
NCP1200
1
HV 8
2
Adj
FB
NC 7
3
CS
VCC 6
4
GND Drv 5
Figure 16. A simple diode naturally reduces the
average voltage on pin 8
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7
NCP1200
3. Permanently force the VCC level above VCCH with
an auxiliary winding. It will automatically
disconnect the internal startup source and the IC
will be fully self−supplied from this winding.
Again, the total power drawn from the mains will
significantly decrease. Make sure the auxiliary
voltage never exceeds the 16 V limit.
When FB is above the skip cycle threshold (1.4 V by
default), the peak current cannot exceed 1 V/Rsense. When
the IC enters the skip cycle mode, the peak current cannot go
below Vpin1 / 4 (Figure 19). The user still has the flexibility
to alter this 1.4 V by either shunting pin 1 to ground through
a resistor or raising it through a resistor up to the desired
level.
Skipping Cycle Mode
The NCP1200 automatically skips switching cycles when
the output power demand drops below a given level. This is
accomplished by monitoring the FB pin. In normal
operation, pin 2 imposes a peak current accordingly to the
load value. If the load demand decreases, the internal loop
asks for less peak current. When this setpoint reaches a
determined level, the IC prevents the current from
decreasing further down and starts to blank the output
pulses: the IC enters the so−called skip cycle mode, also
named controlled burst operation. The power transfer now
depends upon the width of the pulse bunches (Figure 18 ).
Suppose we have the following component values:
Lp, primary inductance = 1 mH
FSW, switching frequency = 48 kHz
Ip skip = 300 mA (or 350 mV / Rsense)
The theoretical power transfer is therefore:
P1
P2
P3
Figure 18. Output pulses at various power levels
(X = 5 ms/div) P1<P2<P3
Max Peak
Current
1 @ Lp @ Ip 2 @ Fsw + 2.2 W
2
If this IC enters skip cycle mode with a bunch length of
10 ms over a recurrent period of 100 ms, then the total power
transfer is: 2.2 . 0.1 = 220 mW.
To better understand how this skip cycle mode takes place,
a look at the operation mode versus the FB level
immediately gives the necessary insight:
Skip Cycle
Current Limit
FB
4.8 V
3.8 V
Figure 19. The skip cycle takes place at low peak
currents which guarantees noise free operation
Normal Current Mode Operation
Skip Cycle Operation
Ipmin = 350 mV / Rsense
1.4 V
Figure 17. Feedback Voltage Variations
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8
NCP1200
Power Dissipation
The NCP1200 is directly supplied from the DC rail
through the internal DSS circuitry. The current flowing
through the DSS is therefore the direct image of the
NCP1200 current consumption. The total power dissipation
can be evaluated using: (V HVDC * 11 V) @ ICC2. If we
operate the device on a 250 VAC rail, the maximum rectified
voltage can go up to 350 VDC. As a result, the worse case
dissipation occurs on the 100 kHz version which will
dissipate 340 . 1.8 mA@Tj = −25°C = 612 mW (however
this 1.8 mA number will drop at higher operating
temperatures). Please note that in the above example, ICC2
is based on a 1 nF capacitor loading pin 5. As seen before,
ICC2 will depend on your MOSFET’s Qg: ICC2 = ICC1 + Fsw
x Qg. Final calculations shall thus account for the total
gate−charge Qg your MOSFET will exhibit. A DIP8
package offers a junction−to−ambient thermal resistance
of RqJ−A 100°C/W. The maximum power dissipation can
thus be computed knowing the maximum operating
ambient temperature (e.g. 70°C) together with the
maximum allowable junction temperature (125°C):
Pmax +
Overload Operation
In applications where the output current is purposely not
controlled (e.g. wall adapters delivering raw DC level), it is
interesting to implement a true short−circuit protection. A
short−circuit actually forces the output voltage to be at a low
level, preventing a bias current to circulate in the
optocoupler LED. As a result, the FB pin level is pulled up
to 4.1 V, as internally imposed by the IC. The peak current
setpoint goes to the maximum and the supply delivers a
rather high power with all the associated effects. Please note
that this can also happen in case of feedback loss, e.g. a
broken optocoupler. To account for this situation, the
NCP1200 hosts a dedicated overload detection circuitry.
Once activated, this circuitry imposes to deliver pulses in a
burst manner with a low duty cycle. The system recovers
when the fault condition disappears.
During the startup phase, the peak current is pushed to the
maximum until the output voltage reaches its target and the
feedback loop takes over. This period of time depends on
normal output load conditions and the maximum peak
current allowed by the system. The time−out used by this IC
works with the VCC decoupling capacitor: as soon as the
VCC decreases from the VCCOFF level (typically 11.4 V) the
device internally watches for an overload current situation.
If this condition is still present when VCCON is reached, the
controller stops the driving pulses, prevents the self−supply
current source to restart and puts all the circuitry in standby,
consuming as little as 350 mA typical (ICC3 parameter). As
a result, the VCC level slowly discharges toward 0. When
this level crosses 6.3 V typical, the controller enters a new
startup phase by turning the current source on: VCC rises
toward 11.4 V and again delivers output pulses at the
UVLOH crossing point. If the fault condition has been
removed before UVLOL approaches, then the IC continues
its normal operation. Otherwise, a new fault cycle takes
place. Figure 20 shows the evolution of the signals in
presence of a fault.
T Jmax * T Amax
= 550 mW. As we can see, we do not
R RqJ*A
reach the worse consumption budget imposed by the 100
kHz version. Two solutions exist to cure this trouble. The
first one consists in adding some copper area around the
NCP1200 DIP8 footprint. By adding a min−pad area of 80
mm2 of 35 m copper (1 oz.) RqJ−A drops to about 75°C/W
which allows the use of the 100 kHz version. The other
solutions are:
1. Add a series diode with pin 8 (as suggested in the
above lines) to drop the maximum input voltage
down to 222 V ((2
350)/pi) and thus dissipate
less than 400 mW
2. Implement a self−supply through an auxiliary
winding to permanently disconnect the self−supply.
SOIC−8 package offers a worse RqJ−A compared to that of
the DIP8 package: 178°C/W. Again, adding some copper
area around the PCB footprint will help decrease this
number: 12 mm x 12 mm to drop RqJ−A down to 100°C/W
with 35 m copper thickness (1 oz.) or 6.5 mm x 6.5 mm with
70 m copper thickness (2 oz.). One can see, we do not
recommend using the SOIC package for the 100 kHz version
with DSS active as the IC may not be able to sustain the
power (except if you have the adequate place on your PCB).
However, using the solution of the series diode or the
self−supply through the auxiliary winding does not cause
any problem with this frequency version. These options are
thoroughly described in the AND8023/D.
http://onsemi.com
9
NCP1200
VCC
Regulation
Occurs Here
11.4 V
Latchoff
Phase
9.8 V
6.3 V
Time
Drv
Driver
Pulses
Driver
Pulses
Time
Internal
Fault
Flag
Fault is
Relaxed
Time
Startup Phase
Fault Occurs Here
Figure 20. If the fault is relaxed during the VCC natural fall down sequence, the IC automatically resumes.
If the fault persists when VCC reached UVLOL, then the controller cuts everything off until recovery.
Calculating the VCC Capacitor
As the above section describes, the fall down sequence
depends upon the VCC level: how long does it take for the
VCC line to go from 11.4 V to 9.8 V? The required time
depends on the startup sequence of your system, i.e. when
you first apply the power to the IC. The corresponding
transient fault duration due to the output capacitor charging
must be less than the time needed to discharge from 11.4 V
to 9.8 V, otherwise the supply will not properly start. The test
consists in either simulating or measuring in the lab how
much time the system takes to reach the regulation at full
load. Let’s suppose that this time corresponds to 6ms.
Therefore a VCC fall time of 10 ms could be well
appropriated in order to not trigger the overload detection
circuitry. If the corresponding IC consumption, including
the MOSFET drive, establishes at 1.5 mA, we can calculate
the required capacitor using the following formula:
Protecting the Controller Against Negative Spikes
As with any controller built upon a CMOS technology, it
is the designer’s duty to avoid the presence of negative
spikes on sensitive pins. Negative signals have the bad habit
to forward bias the controller substrate and induce erratic
behaviors. Sometimes, the injection can be so strong that
internal parasitic SCRs are triggered, engendering
irremediable damages to the IC if they are a low impedance
path is offered between VCC and GND. If the current sense
pin is often the seat of such spurious signals, the
high−voltage pin can also be the source of problems in
certain circumstances. During the turn−off sequence, e.g.
when the user unplugs the power supply, the controller is still
fed by its VCC capacitor and keeps activating the MOSFET
ON and OFF with a peak current limited by Rsense.
Unfortunately, if the quality coefficient Q of the resonating
network formed by Lp and Cbulk is low (e.g. the MOSFET
Rdson + Rsense are small), conditions are met to make the
circuit resonate and thus negatively bias the controller. Since
we are talking about ms pulses, the amount of injected
charge (Q = I x t) immediately latches the controller which
brutally discharges its VCC capacitor. If this VCC capacitor
is of sufficient value, its stored energy damages the
controller. Figure 21 depicts a typical negative shot
occurring on the HV pin where the brutal VCC discharge
testifies for latchup.
Dt + DV @ C, with DV = 2V. Then for a wanted Dt of 10 ms,
i
C equals 8 mF or 10 mF for a standard value. When an
overload condition occurs, the IC blocks its internal
circuitry and its consumption drops to 350 mA typical. This
appends at VCC = 9.8 V and it remains stuck until VCC
reaches 6.5 V: we are in latchoff phase. Again, using the
calculated 10 mF and 350 mA current consumption, this
latchoff phase lasts: 109 ms.
http://onsemi.com
10
NCP1200
Figure 21. A negative spike takes place on the Bulk capacitor at the switch−off sequence
Simple and inexpensive cures exist to prevent from
internal parasitic SCR activation. One of them consists in
inserting a resistor in series with the high−voltage pin to
keep the negative current to the lowest when the bulk
becomes negative (Figure 22). Please note that the negative
spike is clamped to –2 x Vf due to the diode bridge. Please
refer to AND8069/D for power dissipation calculations.
Another option (Figure 23) consists in wiring a diode from
VCC to the bulk capacitor to force VCC to reach UVLOlow
sooner and thus stops the switching activity before the bulk
capacitor gets deeply discharged. For security reasons, two
diodes can be connected in series.
3
Rbulk
> 4.7 k
2
+
Cbulk
1
8
2
7
3
6
4
5
3
+
Cbulk
1 +
CVCC
Figure 22. A simple resistor in series avoids any
latchup in the controller
1
8
2
7
3
6
4
5
D3
1N4007
1 +
CVCC
Figure 23. or a diode forces VCC to reach
UVLOlow sooner
A Typical Application
Figure 24 depicts a low−cost 3.5 W AC−DC 6.5 V wall
adapter. This is a typical application where the wall−pack
must deliver a raw DC level to a given internally regulated
apparatus: toys, calculators, CD players etc. Due to the
inherent short−circuit protection of the NCP1200, you only
need a bunch of components around the IC, keeping the final
cost at an extremely low level. The transformer is available
from different suppliers as detailed on the following page.
http://onsemi.com
11
NCP1200
R7
Clamping
Network
L5
330 mH
L4
2.2 mH
6.5 V @ 600 mA
Rclamp
C3 +
4.7 mF
400 V
C2
4.7 mF
400 V
D3
1N5819
+
Clamp
1
Dclamp
HV 8
2
Adj
FB
NC 7
3
CS
VCC 6
4
GND Drv 5
Universal
Input
L6
330 mH
M1
MTD1N60E
C10
4.7 mF/
10 V
R2
220
Optional
Networks
CSnubber
R6
2.8
C9
10 mF
C5
470 mF/
10 V
+
Snubber
RSnubber
+
R9
10
T1
NCP1200
+
IC1
SFH615A−2
D6
5 V1
Figure 24. A typical AC−DC wall adapter showing the reduced part count due to the NCP1200
T1: Lp = 2.9 mH, Np:Ns = 1:0.08, leakage = 80 mH, E16 core, NCP1200P40
To help designers during the design stage, several manufacturers propose ready−to−use transformers for the above
application, but can also develop devices based on your particular specification:
Eldor Corporation Headquarter
Via Plinio 10,
22030 Orsenigo
(Como) Italia
Tel.: +39−031−636 111
Fax : +39−031−636 280
Email: [email protected]
www.eldor.it
ref. 1: 2262.0058C: 3.5 W version
(Lp = 2.9 mH, Lleak = 80 mH, E16)
ref. 2: 2262.0059A: 5 W version
(Lp = 1.6 mH, Lleak = 45 mH, E16)
Atelier Special de Bobinage
125 cours Jean Jaures
38130 ECHIROLLES FRANCE
Tel.: 33 (0)4 76 23 02 24
Fax: 33 (0)4 76 22 64 89
Email: [email protected]
ref. 1: NCP1200−10 W−UM: 10 W for USB
(Lp = 1.8 mH, 60 kHz, 1:0.1, RM8 pot core)
Coilcraft
1102 Silver Lake Road
Cary, Illinois 60013 USA
Tel: (847) 639−6400
Fax: (847) 639−1469
Email: [email protected]
http://www.coilcraft.com
ref. 1: Y8844−A: 3.5 W version
(Lp = 2.9 mH, Lleak = 65 mH, E16)
ref. 2: Y8848−A: 10 W version
(Lp = 1.8 mH, Lleak = 45 mH, 1:01, E core)
http://onsemi.com
12
NCP1200
Improving the Output Drive Capability
The NCP1200 features an asymmetrical output stage used
to soften the EMI signature. Figure 25 depicts the way the
driver is internally made:
1
8
2
7
3 NCP1200
6
4
5
2N2222
Rd
To Gate
VCC
Q
2
2N2907
7
40
Figure 26. Improving Both Turn−On and
Turn−Off Times
1
12
1
5
Q\
2
3
8
NCP1200
7
3
6
4
5
1N4148
To Gate
2N2907
Figure 25. The higher ON resistor slows down
the MOSFET while the lower OFF resistor
ensures fast turn−off.
In some cases, it is possible to expand the output drive
capability by adding either one or two bipolar transistors.
Figures 26, 27, and 28 give solutions whether you need to
improve the turn−on time only, the turn−off time or both. Rd
is there to damp any overshoot resulting from long copper
traces. It can be omitted with short connections. Results
showed a rise fall time improvement by 5X with standard
2N2222/2N2907:
Figure 27. Improving Turn−Off Time Only
1
2
8
NCP1200
7
3
6
4
5
2N2222
To Gate
1N4148
Figure 28. Improving Turn−On Time Only
http://onsemi.com
13
NCP1200
If the leakage inductance is kept low, the MTD1N60E can
withstand accidental avalanche energy, e.g. during a
high−voltage spike superimposed over the mains, without
the help of a clamping network. If this leakage path
permanently forces a drain−source voltage above the
MOSFET BVdss (600 V), a clamping network is mandatory
and must be built around Rclamp and Clamp. Dclamp shall
react extremely fast and can be a MUR160 type. To calculate
the component values, the following formulas will help you:
Rclamp =
2@ V
clamp
@ (V
clamp
L
leak
Vripple: the clamping ripple, could be around 20 V
Another option lies in implementing a snubber network
which will damp the leakage oscillations but also provide
more capacitance at the MOSFET’s turn−off. The peak
voltage at which the leakage forces the drain is calculated
by:
V max + Ip @
clamp
+
L
leak
C
lump
where Clump represents the total parasitic capacitance seen
at the MOSFET opening. Typical values for Rsnubber and
Csnubber in this 4W application could respectively be 1.5
kW and 47 pF. Further tweaking is nevertheless necessary to
tune the dissipated power versus standby power.
* (V
out ) Vf sec) @ N)
@ Ip 2 @ Fsw
V
C
Ǹ
clamp
V
ripple
@ Fsw @ R
Available Documents
“Implementing the NCP1200 in Low−cost AC−DC
Converters”, AND8023/D.
“Conducted EMI Filter Design for the NCP1200’’,
AND8032/D.
“Ramp Compensation for the NCP1200’’, AND8029/D.
TRANSient and AC models available to download at:
http://onsemi.com/pub/NCP1200
NCP1200 design spreadsheet available to download at:
http://onsemi.com/pub/NCP1200
clamp
with:
Vclamp: the desired clamping level, must be selected to be
between 40 V to 80 V above the reflected output voltage
when the supply is heavily loaded.
Vout + Vf: the regulated output voltage level + the secondary
diode voltage drop
Lleak: the primary leakage inductance
N: the Ns:Np conversion ratio
FSW: the switching frequency
ORDERING INFORMATION
Marking
Package
Shipping †
NCP1200P40
1200P40
PDIP−8
50 Units / Rail
NCP1200P40G
1200P40
PDIP−8
(Pb−Free)
50 Units / Rail
200D4
SOIC−8
2500 / Tape & Reel
200D4
SOIC−8
(Pb−Free)
2500 / Tape & Reel
NCP1200P60
1200P60
PDIP−8
50 Units / Rail
NCP1200P60G
1200P60
PDIP−8
(Pb−Free)
50 Units / Rail
200D6
SOIC−8
2500 / Tape & Reel
200D6
SOIC−8
(Pb−Free)
2500 / Tape & Reel
NCP1200P100
1200P100
PDIP−8
50 Units / Rail
NCP1200P100G
1200P100
PDIP−8
(Pb−Free)
50 Units / Rail
200D1
SOIC−8
2500 / Tape & Reel
200D1
SOIC−8
(Pb−Free)
2500 / Tape & Reel
Device
NCP1200D40R2
Type
FSW = 40 kHz
NCP1200D40R2G
NCP1200D60R2
FSW = 60 kHz
NCP1200D60R2G
NCP1200D100R2
NCP1200D100R2G
FSW = 100 kHz
†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging
Specifications Brochure, BRD8011/D.
http://onsemi.com
14
NCP1200
PACKAGE DIMENSIONS
SOIC−8 NB
CASE 751−07
ISSUE AH
NOTES:
1. DIMENSIONING AND TOLERANCING PER
ANSI Y14.5M, 1982.
2. CONTROLLING DIMENSION: MILLIMETER.
3. DIMENSION A AND B DO NOT INCLUDE
MOLD PROTRUSION.
4. MAXIMUM MOLD PROTRUSION 0.15 (0.006)
PER SIDE.
5. DIMENSION D DOES NOT INCLUDE DAMBAR
PROTRUSION. ALLOWABLE DAMBAR
PROTRUSION SHALL BE 0.127 (0.005) TOTAL
IN EXCESS OF THE D DIMENSION AT
MAXIMUM MATERIAL CONDITION.
6. 751−01 THRU 751−06 ARE OBSOLETE. NEW
STANDARD IS 751−07.
−X−
A
8
5
0.25 (0.010)
S
B
1
M
Y
M
4
K
−Y−
G
C
N
DIM
A
B
C
D
G
H
J
K
M
N
S
X 45 _
SEATING
PLANE
−Z−
0.10 (0.004)
H
D
0.25 (0.010)
M
Z Y
S
X
M
J
S
SOLDERING FOOTPRINT*
1.52
0.060
7.0
0.275
4.0
0.155
0.6
0.024
1.270
0.050
SCALE 6:1
mm Ǔ
ǒinches
*For additional information on our Pb−Free strategy and soldering
details, please download the ON Semiconductor Soldering and
Mounting Techniques Reference Manual, SOLDERRM/D.
http://onsemi.com
15
MILLIMETERS
MIN
MAX
4.80
5.00
3.80
4.00
1.35
1.75
0.33
0.51
1.27 BSC
0.10
0.25
0.19
0.25
0.40
1.27
0_
8 _
0.25
0.50
5.80
6.20
INCHES
MIN
MAX
0.189
0.197
0.150
0.157
0.053
0.069
0.013
0.020
0.050 BSC
0.004
0.010
0.007
0.010
0.016
0.050
0 _
8 _
0.010
0.020
0.228
0.244
NCP1200
PACKAGE DIMENSIONS
PDIP−8
P SUFFIX
CASE 626−05
ISSUE L
8
NOTES:
1. DIMENSION L TO CENTER OF LEAD WHEN
FORMED PARALLEL.
2. PACKAGE CONTOUR OPTIONAL (ROUND OR
SQUARE CORNERS).
3. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
5
−B−
1
4
F
−A−
NOTE 2
L
C
J
−T−
MILLIMETERS
MIN
MAX
9.40
10.16
6.10
6.60
3.94
4.45
0.38
0.51
1.02
1.78
2.54 BSC
0.76
1.27
0.20
0.30
2.92
3.43
7.62 BSC
−−−
10_
0.76
1.01
INCHES
MIN
MAX
0.370
0.400
0.240
0.260
0.155
0.175
0.015
0.020
0.040
0.070
0.100 BSC
0.030
0.050
0.008
0.012
0.115
0.135
0.300 BSC
−−−
10_
0.030
0.040
N
SEATING
PLANE
D
H
DIM
A
B
C
D
F
G
H
J
K
L
M
N
M
K
G
0.13 (0.005)
M
T A
M
B
M
The product described herein (NCP1200), may be covered by the following U.S. patents: 6,271,735, 6,362,067, 6,385,060, 6,429,709, 6,587,357. There may
be other patents pending.
ON Semiconductor and
are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice
to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability
arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages.
“Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All
operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. SCILLC does not convey any license under its patent rights
nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications
intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death may occur. Should
Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees, subsidiaries, affiliates,
and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death
associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part. SCILLC is an Equal
Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.
PUBLICATION ORDERING INFORMATION
LITERATURE FULFILLMENT:
Literature Distribution Center for ON Semiconductor
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Phone: 303−675−2175 or 800−344−3860 Toll Free USA/Canada
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16
ON Semiconductor Website: www.onsemi.com
Order Literature: http://www.onsemi.com/orderlit
For additional information, please contact your local
Sales Representative
NCP1200/D