NCL30001 D

NCL30001
High-Efficiency Single
Stage Power Factor
Correction and Step-Down
Offline LED Driver
The NCL30001 is a highly integrated controller for implementing
power factor correction (PFC) and isolated step down ac−dc power
conversion in a single stage, resulting in a lower cost and reduced part
count solution. This controller is ideal for LED Driver power supplies
with power requirements between 40 W and 150 W. The single stage
is based on the flyback converter and it is designed to operate in
continuous conduction (CCM).
The NCL30001 can be configured as as constant current driver or a
fixed output driver for two stage LED lighting applications. In
addition, the controller features a proprietary Soft−Skip™ to reduce
acoustic noise at light loads. Other features found in the NCL30001
include a high voltage startup circuit, voltage feedforward, brown out
detector, internal overload timer, latch input and a high accuracy
multiplier. The multi−function latch off pin can also be used to
implement an overtemperature shutdown circuit.
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MARKING
DIAGRAM
NCL30001G
AWLYWW
SOIC−16
D SUFFIX
CASE 751B
A
WL
YY
WW
G
= Assembly Location
= Wafer Lot
= Year
= Work Week
= Pb−Free Package
Features
•
•
•
•
•
•
•
•
•
•
Voltage Feedforward Improves Loop Response
Frequency Jittering Reduces EMI Signature
Proprietary Soft−Skip at Light Loads Reduces Acoustic Noise
Brown Out Detector
Internal 160 ms Fault Timer
Independent Latch−Off Input Facilitates Implementation of
Overvoltage and Overtemperature Fault Detectors
Average Current Mode Control (ACMC), Fixed Frequency Operation
High Accuracy Multiplier Reduces Input Line Harmonics
Adjustable Operating Frequency from 20 kHz to 250 kHz
These Devices are Pb−Free and are RoHS Compliant
LED Street Lights
Low Bay LED Lighting
High Power LED Drivers
Architectural LED Lighting
© Semiconductor Components Industries, LLC, 2015
February, 2015 − Rev. 1
16 Startup
CT 1
Ramp Comp 2
15 GND
14 NC
AC IN 3
FB 4
13 DRV
VFF 5
12 VCC
CM 6
11 Ispos
AC COMP 7
10 Iavg
Latch−Off 8
9 TEST
(Top View)
Typical Applications
•
•
•
•
PIN CONNECTIONS
ORDERING INFORMATION
See detailed ordering and shipping information on page 30 of
this data sheet.
1
Publication Order Number:
NCL30001/D
NCL30001
FB overload
comparator
Jitter
FB
CT
+
Jitter
Adj.
+
−
Overload
Timer
tOVLD
Enable
S
Q
R
VOVLD
Clock
Oscillator
DC Max
Sawtooth
DC Max
VFF
+
V Brown−Out
FF
Comparator
−
+
VBO
Ramp. Comp.
OVLD
Startup
Enable
x2
counter
Reset
Out
Dual HV
start−up
current source
BO
Ramp Comp
Adj.
VCC(off) HV current
Reset
Ramp
Comp
+
−
+
VCC
Management
Start
VDD
Reset
V
CCOK
AC In skip
comparator
VDD
VSSKIP(sync)
VDD
GND
Clock
Soft−skip Ramp
R
FB
FB skip
Comparator
+
DC Max
Delay
tSSKIP
Start
Terminate
+
−
VSSKIP
AC IN
+
Transient Load Detect
Comparator
+
−
VSSKIP(TLD)
DRV
Output
Driver
PWM Skip
Comparator
21.33kW
V−to−I
Reference
Generator
+
gm
−
V−to−I
+ inverter
+
−
AC error
Amplifier
VFF
21.33kW
VCC
PWM
comparator
+
OVLD
4V
CM
BO
Latch
Blanking
tLEB
VCCOK
gm
AC COMP
−
+
FB
VFF
Q
R
−
V−to−I
FB
S
+
Ramp Comp
Ispos
Current sense
amplifier
VDD
OVP Comparator
+
Ilatch(clamp)
Iavg
+
−
Vlatch(high)
blanking
tLatch(delay)
Latch−Off
OTP Comparator
Ilatch(shdn)
Vlatch(clamp)
+
S
−
+
Q
R
Vlatch(low)
Reset
Figure 1. Detailed Block Diagram
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2
Latch
TEST
NCL30001
PIN FUNCTION DESCRIPTION
Pin
Symbol
Description
1
CT
An external timing capacitor (CT) sets the oscillator frequency. A sawtooth between 0.2 V and 4 V sets the
oscillator frequency and the gain of the multiplier.
2
RAMP COMP
A resistor (RRC) between this pin and ground adjust the amount of ramp compensation that is added to the
current signal. Ramp compensation is required to prevent subharmonic oscillations. This pin should not be
left open.
3
AC IN
The scaled version of the full wave rectified input ac wave is connected to this pin by means of a resistive
voltage divider. The line voltage information is used by the multiplier.
4
FB
An error signal from an external error amplifier circuit is fed to this pin via an optocoupler or other isolation
circuit. The FB voltage is a proportional of the load of the converter. If the voltage on the FB pin drops below 0.41 V (typical) the controller enters Soft−Skip to reduce acoustic noise.
5
VFF
Feedforward input. A scaled version of the filtered rectified line voltage is applied by means of a resistive
divider and an averaging capacitor. The information is used by the Reference Generator to regulate the
controller.
6
CM
Multiplier output. A capacitor is connected between this pin and ground to filter the modulated output of the
multiplier.
7
AC COMP
Sets the pole for the ac reference amplifier. The reference amplifier compares the low frequency component of the input current to the ac reference signal. The response must be slow enough to filter out most of
the high frequency content of the current signal that is injected from the current sense amplifier, but fast
enough to cause minimal distortion to the line frequency information. The pin should not be left open.
8
Latch
Latch−Off input. Pulling this pin below 1.0 V (typical) or pulling it above 7.0 V (typical) latches the controller.
This input can be used to implement an overvoltage detector, an overtemperature detector or both. Refer
to Figure 60 for a typical implementation.
9
TEST
This pin is a TEST pin. A nominal 50K $10% resistor must be connected to GND for proper operation.
10
IAVG
An external resistor and capacitor connected from this terminal to ground, to set and stabilizes the gain of
the current sense amplifier output that drives the ac error amplifier.
11
ISpos
Positive current sense input. Connects to the positive side of the current sense resistor.
12
VCC
Positive input supply. This pin connects to an external capacitor for energy storage. An internal current
source supplies current from the STARTUP pin VCC. Once the voltage on VCC reaches approximately 15.3
V, the current source turns off and the outputs are enabled. The drivers are disabled once VCC reaches
approximately 10.2 V. If VCC drops below 0.83 V (typical), the startup current is reduced to less than
500 mA.
13
DRV
Drive output for the main flyback power MOSFET or IGBT. DRV has a source resistance of 10.8 W (typical)
and a sink resistance of 8 W (typical).
14
NC
15
GND
16
HV
No Connect
Ground reference for the circuit.
Connect the rectified input line voltage directly to this pin to enable the internal startup regulator. A constant current source supplies current from this pin to the capacitor connected to the VCC pin, eliminating
the need for a startup resistor. The charge current is typically 5.5 mA. Maximum input voltage is 500 V.
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3
NCL30001
MAXIMUM RATINGS (Notes 1 and 2)
Rating
Symbol
Value
Unit
Start_up Input Voltage
Start_up Input Current
VHV
IHV
−0.3 to 500
$100
V
mA
Power Supply Input Voltage
Power Supply Input Current
VCC
ICC
−0.3 to 20
$100
V
mA
VLatch
ILatch
−0.3 to 10
$100
V
mA
−0.3 to 6.5
$100
V
mA
Latch Input Voltage
Latch Input Current
All Other Pins Voltage
All Other Pins Current
Thermal Resistance, Junction−to−Air
0.1 in” Copper
0.5 in” Copper
qJA
130
110
Thermal Resistance, Junction−to−Lead
RΘJL
Maximum Power Dissipation @ TA = 25°C
PMAX
0.77
W
TJ
−40 to 125
°C
TSTG
−55 to 150
°C
Operating Temperature Range
Storage Temperature Range
50
°C/W
°C/W
Stresses exceeding those listed in the Maximum Ratings table may damage the device. If any of these limits are exceeded, device functionality
should not be assumed, damage may occur and reliability may be affected.
1. This device contains ESD protection and exceeds the following tests:
Pin 1−15: Human Body Model 2000 V per JEDEC Standard JESD22, Method A114E.
Machine Model Method 200 V per JEDEC Standard JESD22, Method A114A.
Pin 16 is the high voltage startup of the device and is rated to the maximum rating of the part, 500 V.
2. This device contains Latchup protection and exceeds ±100 mA per JEDEC Standard JESD78.
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4
EMI Filter
FB
Latch
5
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Figure 2. Typical Application Schematic
LATCH
AC COMP
CM
TEST
Iavg
Ispos
VCC
VFF
NCL30001
DRV
GND
HV
FB
AC IN
Ramp Comp
CT
9
16
VCC
FB
Î
Î
7
OUT2
1
OUT1
ÎÎ
ÎÎÎ
8
1
NTC
Latch
VCC
8
−
+
IN2−
IN2+
GND
+
4
IN1+
− IN1−
NCS1002
VCC
3
2
6
5
R LED
NCL30001
NCL30001
ELECTRICAL CHARACTERISTICS (VCC = 15 V, VAC IN = 3.8 V, VFB = 2.0 V, VFF = 2.4 V, VLatch = open, VISPOS = −100 mV,
CDRV = 1 nF, CT = 470 pF, CIAVG = 0.27 nF, CLatch = 0.1 nF, CM = 10 nF, RIAVG = 76.8 kW,
RTEST = 50 kW, RRC = 43 kW, For typical Value TJ = 25°C, for min/max values TJ = −40°C to 125°C, unless otherwise noted)
Symbol
Min
Typ
Max
Unit
fosc
90
100
110
kHz
Frequency Modulation in Percentage
of fOSC
–
6.8
–
%
Frequency Modulation Period
–
6.8
–
ms
Parameter
Test Condition
OSCILLATOR
Frequency
Ramp Peak Voltage
VCT(peak)
–
4.0
–
V
Ramp Valley Voltage
VCT(valley)
–
0.10
–
V
D
94
−
–
%
VRCOMP(peak)
–
4
–
V
40
–
mV
Maximum Duty Ratio
RTEST = open
Ramp Compensation Peak Voltage
AC ERROR AMPLIFIER
Input Offset Voltage (Note 3)
Ramp IAVG, VFB = 0 V
Error Amplifier Transconductance
ACVIO
gm
–
100
–
mS
Source Current
VAC COMP = 2.0 V, VAC IN = 2.0 V,
VFF = 1.0 V
IEA(source)
25
70
–
mA
Sink Current
VAC COMP = 2.0 V, VA C_IN = 2.0 V,
VFF = 5.0 V
IEA(sink)
−25
−70
–
mA
VISPOS = 0 V
CAIbias
40
53
80
mA
VAC COMP = 5.0 V, VISpos = 0 V
CAVIO
−20
0
20
mV
force DRV high, VAC COMP = 3.0 V,
ramp VISPOS, VRamp_Comp = open
VILIM
0.695
0.74
0.77
V
tLEB
–
200
–
ns
–
1.5
–
MHz
PWMk
4.0
5.3
6.0
V/V
ISVk
15.4
18.5
23
V/V
k
–
0.55
–
V
CURRENT AMPLIFIER
Input Bias Current
Input Offset Voltage
Current Limit Threshold
Leading Edge Blanking Duration
Bandwidth
PWM Output Voltage Gain
Current Limit Voltage Gain (See
Current Sense Section)
PWMk +
4
(V ILIM * C AVIO)
ISVK +
V (AVG)
VI SPOS
REFERENCE GENERATOR
Reference Generator Gain
k+
V AC_REF @ V FF 2
V FB @ V AC_IN
Reference Generator output voltage
(low input ac line and full load)
VAC IN = 1.2 V, VFF = 0.765 V,
VFB = 4 V
RGout1
3.61
4.36
4.94
Vpk
Reference Generator output voltage
(high input ac line and full load)
VAC IN = 3.75 V, VFF = 2.39 V,
VFB = 4.0 V
RGout2
1.16
1.35
1.61
Vpk
Reference Generator output Voltage
(low input as line and minimum load)
VAC IN = 1.2 V, VFF = 0.765 V,
VFB = 2.0 V
RGout3
1.85
2.18
2.58
Vpk
Reference Generator output voltage
(high input ac line and minimum load)
VAC IN = 3.75 V, VFF = 2.39 V,
VFB = 2.0 V
RGout4
0.55
0.65
0.78
Vpk
RGoffset
−100
–
100
mV
Reference Generator output offset
voltage
Product parametric performance is indicated in the Electrical Characteristics for the listed test conditions, unless otherwise noted. Product
performance may not be indicated by the Electrical Characteristics if operated under different conditions.
3. Guaranteed by Design
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6
NCL30001
ELECTRICAL CHARACTERISTICS (VCC = 15 V, VAC IN = 3.8 V, VFB = 2.0 V, VFF = 2.4 V, VLatch = open, VISPOS = −100 mV,
CDRV = 1 nF, CT = 470 pF, CIAVG = 0.27 nF, CLatch = 0.1 nF, CM = 10 nF, RIAVG = 76.8 kW,
RTEST = 50 kW, RRC = 43 kW, For typical Value TJ = 25°C, for min/max values TJ = −40°C to 125°C, unless otherwise noted)
Parameter
Test Condition
Symbol
Min
Typ
Max
Unit
IAC IN(IB)
–
0.01
–
mA
RSNK
RSRC
–
–
8
10.8
18
24
Rise Time (10% to 90%)
DRV
tr
–
40
–
ns
Fall Time (90% to 10%)
DRV
tf
–
20
–
ns
IDRV = 100 mA
VDRV(low)
–
1.0
100
mV
Skip Synchronization to ac Line
Voltage Threshold
VACIN Increasing, VFB = 1.5 V
VSSKIP(SYNC)
210
267
325
mV
Skip Synchronization to ac Line
Voltage Threshold Hysteresis
VACIN Decreasing
VSSKIP
(SYNCHYS)
–
40
–
mV
Skip Ramp Period (Note 3)
tSSKIP
−
2.5
–
ms
Skip Voltage Threshold
VSSKIP
360
410
460
V
Skip Voltage Hysteresis
VSSKIP(HYS)
45
90
140
mV
Skip Transient Load Detect Threshold
(Note 3)
VSSKIP(TLD)
−
1.75
−
V
IFB
600
750
920
mA
RFB
–
6.7
–
kW
VFB(open)
5.3
5.7
6.3
V
VCC Increasing
VCC Decreasing
VCC Decreasing
VCC(on)
VCC(off)
VCC(reset)
14.3
9.3
–
15.4
10.2
7.0
16.3
11.3
–
VHV = 40 V, Iinhibit = 500 mA
Vinhibit
−
0.83
1.15
V
VHV = 40 V, VCC = 0.8 * Vinhibit
Iinhibit
40
-
500
mA
Istart = 0.5 mA, VCC = VCC(on) – 0.5 V
Vstart(min)
–
–
40
V
VCC = VCC(on) – 0.5 V, VFB = Open
Istart
3.0
5.62
8.0
mA
VHV = 400 V, TJ = 25°C
TJ = −40°C to 125°C
IHV(off)
–
–
17
15
40
80
VFB = Open
fOSC [ 100 kHz
ICC1
ICC2
–
–
0.72
6.25
1.2
7.2
tOVLD
120
160
360
AC INPUT
Input Bias Current Into Reference
Multiplier & Current Compensation
Amplifier
DRIVE OUTPUT
Drive Resistance (Thermally Limited)
DRV Sink
DRV Source
Driver Out Low Voltage
DRV
VDRV = 1 V
IDRV = 100 mA
W
Soft−Skip
FEEDBACK INPUT
Pull−Up Current Source
VFB = 0.5 V
Pull−Up Resistor
Open Circuit Voltage
STARTUP AND SUPPLY CIRCUITS
Supply Voltage
Startup Threshold
Minimum Operating Voltage
Logic Reset Voltage
Inhibit Threshold Voltage
Inhibit Bias Current
Minimum Startup Voltage
Startup Current
Off−State Leakage Current
Supply Current
Device Disabled (Overload)
Device Switching
V
mA
mA
FAULT PROTECTION
Overload Timer
ms
Product parametric performance is indicated in the Electrical Characteristics for the listed test conditions, unless otherwise noted. Product
performance may not be indicated by the Electrical Characteristics if operated under different conditions.
3. Guaranteed by Design
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7
NCL30001
ELECTRICAL CHARACTERISTICS (VCC = 15 V, VAC IN = 3.8 V, VFB = 2.0 V, VFF = 2.4 V, VLatch = open, VISPOS = −100 mV,
CDRV = 1 nF, CT = 470 pF, CIAVG = 0.27 nF, CLatch = 0.1 nF, CM = 10 nF, RIAVG = 76.8 kW,
RTEST = 50 kW, RRC = 43 kW, For typical Value TJ = 25°C, for min/max values TJ = −40°C to 125°C, unless otherwise noted)
Parameter
Test Condition
Symbol
Min
Typ
Max
Unit
VOVLD
4.7
4.9
5.2
V
FAULT PROTECTION
Overload Detect Threshold
Brown−Out Detect Threshold (entering
fault mode)
VFF Decreasing, VFB = 2.5 V,
VAC IN = 2.0 V
VBO(low)
0.41
0.45
0.49
V
Brown−Out Exit Threshold (exiting
fault mode)
VFF Increasing, VFB = 2.5 V,
VAC IN = 2.0 V
VBO(high)
0.57
0.63
0.69
V
VBO(HYS)
−
174
−
mV
Brown−Out Hysteresis
LATCH INPUT
Pull−Down Latch Voltage Threshold
VLatch Decreasing
Vlatch(low)
0.9
0.98
1.1
V
Pull−Up Latch Voltage Threshold
VLatch Increasing
Vlatch(high)
5.6
7.0
8.4
V
VLatch = Vlatch(high)
tlatch(delay)
30
56
90
ms
VLatch = 1.5 V
Ilatch(clamp)
42
51
58
mA
ILatch = 50 mA
Vlatch(clamp)
2.5
3.27
4.5
V
VLatch Increasing
Ilatch(shdn)
−
95
−
mA
Latch Propagation Delay
Latch Clamp Current (Going Out)
Latch Clamp Voltage (ILatch Going In)
Latch−Off Current Shutdown
(Going In)
Product parametric performance is indicated in the Electrical Characteristics for the listed test conditions, unless otherwise noted. Product
performance may not be indicated by the Electrical Characteristics if operated under different conditions.
3. Guaranteed by Design
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8
NCL30001
8.0
OSCILLATOR FREQUENCY
MODULATION (%)
fOSC, OSCILLATOR FREQUENCY (kHz)
110
105
100
95
90
−50
−25
0
25
50
75
100
125
7.5
7.0
6.5
6.0
−50
150
−25
Figure 3. Oscillator Frequency (fOSC) vs.
Junction Temperature
VCT(peak), OSCILLATOR RAMP PEAK
VOLTAGE (V)
7.0
6.5
−25
0
25
50
75
100
125
150
75
100
125
150
4.05
4.0
3.95
3.9
3.85
3.8
−50
−25
0
25
50
75
100
125
TJ, JUNCTION TEMPERATURE (°C)
TJ, JUNCTION TEMPERATURE (°C)
Figure 5. Oscillator Frequency Modulation
Period vs. Junction Temperature
Figure 6. Ramp Peak Voltage vs. Junction
Temperature
100
D, MAXIMUM DUTY RATIO (%)
50
4.1
7.5
98
96
94
92
90
−50
25
Figure 4. Oscillator Frequency Modulation in
Percentage of fOSC vs. Junction Temperature
8.0
6.0
−50
0
TJ, JUNCTION TEMPERATURE (°C)
−25
0
25
50
75
100
125
TJ, JUNCTION TEMPERATURE (°C)
150
VCOMP(peak), RAMP COMP PEAK VOLTAGE (V)
OSCILLATOR FREQUENCY MODULATION PERIOD (ms)
TJ, JUNCTION TEMPERATURE (°C)
150
4.1
4.05
4.0
3.95
3.9
3.85
3.8
−50
Figure 7. Maximum Duty Ratio vs. Junction
Temperature
−25
0
25
50
75
100
125
150
TJ, JUNCTION TEMPERATURE (°C)
Figure 8. Ramp Compensation Peak Voltage
vs. Junction Temperature
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NCL30001
IEA(SINK), ERROR AMPLIFIER SINK
CURRENT (mA)
IEA(SOURCE), ERROR AMPLIFIER
SOURCE CURRENT (mA)
90
85
80
75
70
65
60
55
50
−50
−25
0
25
50
75
100
125
90
85
80
75
70
65
60
55
50
−50
150
−25
0
25
50
75
100
125
TJ, JUNCTION TEMPERATURE (°C)
TJ, JUNCTION TEMPERATURE (°C)
Figure 9. Error Amplifier Source Current vs.
Junction Temperature
Figure 10. Error Amplifier Sink Current vs.
Junction Temperature
150
CAVBIAS, CURRENT AMPLIFIER INPUT BIAS CURRENT (mA)
60.0
57.5
55.0
52.5
50.0
47.5
45.0
42.5
40.0
−50
−25
0
25
50
75
100
125
150
TJ, JUNCTION TEMPERATURE (°C)
770
6.0
PWMk, PWM VOLTAGE GAIN (V/V)
VILIM, CURRENT LIMIT THRESHOLD
(mV)
Figure 11. Current Amplifier Input Bias
Current vs. Junction Temperature
760
750
740
730
720
710
700
−50
−25
0
25
50
75
100
125
150
5.8
5.6
5.4
5.2
5.0
−50
−25
0
25
50
75
100
125
TJ, JUNCTION TEMPERATURE (°C)
TJ, JUNCTION TEMPERATURE (°C)
Figure 12. Current Limit Threshold vs.
Junction Temperature
Figure 13. PWM Output Voltage Gain vs.
Junction Temperature
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10
150
NCL30001
5.25
RGout, REFERENCE GENERATOR
OUTPUT VOLTAGE (V)
ISVk, CURRENT LIMIT VOLTAGE
GAIN (V/V)
22
21
20
19
18
17
16
−50
−25
0
25
50
75
100
125
150
4.25
3.75
3.25
2.75
RGout3
2.25
1.75
RGout2
1.25
RGout4
0.75
0.25
−50
−25
0
25
50
75
100
125
TJ, JUNCTION TEMPERATURE (°C)
TJ, JUNCTION TEMPERATURE (°C)
Figure 14. Oscillator CS Limit Voltage Gain vs.
Junction Temperature
Figure 15. Oscillator Reference Generator
Output Voltage vs. Junction Temperature
150
16
RSRC1, DRV SOURCE RESISTANCE
(W)
14
RSNK1, DRV SINK DRIVE RESISTANCE (W)
RGout1
4.75
12
10
8.0
6.0
4.0
−50
−25
0
25
50
75
100
125
150
14
12
10
8.0
6.0
−50
−25
0
25
50
75
100
125
150
TJ, JUNCTION TEMPERATURE (°C)
TJ, JUNCTION TEMPERATURE (°C)
Figure 16. DRV Sink Resistance vs. Junction
Temperature
Figure 17. DRV Source Drive Resistance vs.
Junction Temperature
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11
NCL30001
VDRV(low), DRV LOW VOLTAGE (mV)
130
110
90
70
50
30
−50
−25
0
25
50
75
100
125
TJ, JUNCTION TEMPERATURE (°C)
150
Figure 18. DRV Low Voltage vs. Junction
Temperature
VSSKIP, SKIP VOLTAGE THRESHOLD (V)
VSSKIP(SYNC), SKIP SYNC TO AC
LINE VOLTAGE THRESHOLD (mV)
300
280
260
240
220
200
−50
−25
0
25
50
75
100
125
150
0.410
0.408
0.406
0.404
0.402
0.400
0.398
0.396
0.394
0.392
0.390
−50
−25
0
25
50
75
100
125
150
TJ, JUNCTION TEMPERATURE (°C)
TJ, JUNCTION TEMPERATURE (°C)
Figure 19. Skip Synchronization to ac Line
Voltage Threshold vs. Junction Temperature
Figure 20. Skip Voltage Threshold vs. Junction
Temperature
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12
100
780
IFB, FEEDBACK PULL−UP CURRENT
SOURCE (mA)
VSSKIP, SKIP VOLTAGE HYSTERESIS
(mV)
NCL30001
95
90
85
80
−50
−25
0
25
50
75
100
125
150
730
705
680
−50
−25
0
25
50
75
100
125
150
TJ, JUNCTION TEMPERATURE (°C)
TJ, JUNCTION TEMPERATURE (°C)
Figure 21. Skip Voltage Hysteresis vs.
Junction Temperature
Figure 22. Feedback Pull−Up Current Source
vs. Junction Temperature
15.75
VCC(on), STARTUP THRESHOLD (V)
6.2
6.0
5.8
5.6
5.4
5.2
−50
−25
0
25
50
75
100
125
150
15.55
15.35
15.15
14.95
14.75
−50
−25
0
25
50
75
100
125
TJ, JUNCTION TEMPERATURE (°C)
TJ, JUNCTION TEMPERATURE (°C)
Figure 23. Feedback Open Circuit Voltage vs.
Junction Temperature
Figure 24. Startup Threshold vs. Junction
Temperature
10.5
VCC(off), MINIMUM OPERATING
VOLTAGE (V)
VFB(open), FEEDBACK OPEN CIRCUIT VOLTAGE (V)
755
10.3
10.1
9.9
9.7
9.5
−50
−25
0
25
50
75
100
TJ, JUNCTION TEMPERATURE (°C)
125
Figure 25. Minimum Operating Voltage vs.
Junction Temperature
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13
150
150
NCL30001
Iinhibit, INHIBIT BIAS CURRENT (mA)
950
900
850
800
750
700
650
−50
Vstartup(min), MINIMUM STARTUP
VOLTAGE (V)
25.0
24.5
−25
0
25
50
75
100
125
310
290
270
250
−50
−25
0
25
50
75
100
125
TJ, JUNCTION TEMPERATURE (°C)
Figure 27. Inhibit Bias Current vs. Junction
Temperature
23.5
23.0
22.5
−25
0
25
150
6.0
50
75
100
125
150
5.8
5.6
5.4
5.2
5.0
−50
−25
0
25
50
75
100
125
TJ, JUNCTION TEMPERATURE (°C)
TJ, JUNCTION TEMPERATURE (°C)
Figure 28. Minimum Startup Voltage vs.
Junction Temperature
Figure 29. Startup Current vs. Junction
Temperature
150
850
ICC1, SUPPLY CURRENT DEVICE
DISABLED (mA)
30
IHV(off), OFF−STATE LEAKAGE CURRENT (mA)
330
TJ, JUNCTION TEMPERATURE (°C)
24.0
25
20
15
10
−50
350
Figure 26. Inhibit Threshold Voltage vs.
Junction Temperature
VCC = VCC − 0.5 V
Istart = 0.5 mA
22.0
−50
150
Istart, STARTUP CURRENT (mA)
Vinhibit, INHIBIT THRESHOLD VOLTAGE (V)
1000
−25
0
25
50
75
100
125
150
825
800
775
750
725
700
675
650
−50
−25
0
25
50
75
100
125
TJ, JUNCTION TEMPERATURE (°C)
TJ, JUNCTION TEMPERATURE (°C)
Figure 30. Off−State Leakage Current vs.
Junction Temperature
Figure 31. Supply Current Device Disabled
(Overload) vs. Junction Temperature
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14
150
NCL30001
200
tOVLD, OVERLOAD TIMER (ms)
ICC2, SUPPLY CURRENT DEVICE
SWITCHING (mA)
6.75
6.55
6.35
6.15
5.95
5.75
−50
−25
0
25
50
75
100
125
150
140
120
100
−50
25
50
75
100
125
TJ, JUNCTION TEMPERATURE (°C)
150
500
5.1
4.9
4.7
−25
0
25
50
75
100
125
TJ, JUNCTION TEMPERATURE (°C)
150
480
460
440
420
400
−50
−25
Figure 34. Overload Detect Threshold vs.
Junction Temperature
0
25
50
75
100
125
TJ, JUNCTION TEMPERATURE (°C)
150
Figure 35. Brown−Out Detect Threshold vs.
Junction Temperature
180
VBO(HYS), BROWN−OUT HYSTERESIS (mV)
650
VBO(high), BROWN−OUT EXIT
THRESHOLD (mV)
0
Figure 33. Overload Timer vs. Junction
Temperature
5.3
640
630
620
610
600
−50
−25
TJ, JUNCTION TEMPERATURE (°C)
VBO(low), BROWN−OUT DETECT
THRESHOLD (mV)
VOVLD, OVERLOAD DETECT
THRESHOLD (V)
160
Figure 32. Supply Current Device Switching
vs. Junction Temperature
5.5
4.5
−50
180
−25
0
25
50
75
100
125
150
175
170
165
160
−50
−25
0
25
50
75
100
125
150
TJ, JUNCTION TEMPERATURE (°C)
TJ, JUNCTION TEMPERATURE (°C)
Figure 36. Brown−Out Exit Threshold vs.
Junction Temperature
Figure 37. Brown−Out Hysteresis vs. Junction
Temperature
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15
NCL30001
VLATCH(low_HYS), LATCH PULL−UP
THRESHOLD (V)
7.5
980
960
940
920
−25
0
25
50
75
100
125
7.3
7.1
6.9
6.7
6.5
−50
150
−25
0
25
50
75
100
125
TJ, JUNCTION TEMPERATURE (°C)
TJ, JUNCTION TEMPERATURE (°C)
Figure 38. Latch Pull−Down Voltage Threshold
vs. Junction Temperature
Figure 39. Latch Pull−Up Threshold vs.
Junction Temperature
7.5
7.3
7.1
6.9
6.7
6.5
−50
150
60
VLATCH(delay), LATCH PROPAGATION
DELAY (ms)
VLATCH(lhigh), LATCH PULL−UP VOLTAGE THRESHOLD (V)
900
−50
−25
0
25
50
75
100
125
150
58
56
54
52
50
−50
−25
0
25
50
75
100
125
TJ, JUNCTION TEMPERATURE (°C)
TJ, JUNCTION TEMPERATURE (°C)
Figure 40. Latch Pull−Up Voltage Threshold
vs. Junction Temperature
Figure 41. Latch Propagation Delay vs.
Junction Temperature
55
ILATCH(clamp), LATCH CLAMP CURRENT (mA)
VLATCH(low), LATCH PULL−DOWN
VOLTAGE THRESHOLD (mV)
1000
54
53
52
51
50
−50
−25
0
25
50
75
100
TJ, JUNCTION TEMPERATURE (°C)
125
Figure 42. Latch Clamp Current vs. Junction
Temperature
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16
150
150
NCL30001
100
VLATCH(shdn), LATCH−OFF CURRENT
SHUTDOWN (mA)
VLATCH(clamp), LATCH CLAMP VOLTAGE (V)
3.5
3.4
3.3
3.2
3.1
3.0
−50
−25
0
25
50
75
100
125
150
98
96
94
92
90
−50
−25
0
25
50
75
100
125
TJ, JUNCTION TEMPERATURE (°C)
TJ, JUNCTION TEMPERATURE (°C)
Figure 43. Latch Clamp Voltage vs. Junction
Temperature
Figure 44. Latch−Off Current Shutdown vs.
Junction Temperature
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17
150
NCL30001
DETAILED DEVICE DESCRIPTION
Introduction
components. But, because it processes the power twice, the
search is always on for a more compact and power efficient
solution.
The NCL30001 controller offers the convenience of
shrinking the front−end converter (PFC preregulator) and
the dc−dc converter into a single power processing stage as
shown in Figure 46.
The NCL30001 is a highly integrated controller
combining PFC and isolated step down power conversion in
a single stage, resulting in a lower cost and reduced part
count solution. This controller is ideal for LED Lighting
applications with power requirements between 40 W and
150 W with an output voltage greater than 12 V. The single
stage is based on the flyback converter and it is designed to
operate in CCM mode.
AC
Input
Power Factor Correction (PFC) Introduction
Power factor correction shapes the input current of
off−line power supplies to maximize the real power
available from the mains. Ideally, the electrical appliance
should present a load that emulates a pure resistor, in which
case the reactive power drawn by the device is zero. Inherent
in this scenario is the freedom from input current harmonics.
The current is a perfect replica of the input voltage (usually
a sine wave) and is exactly in phase with it. In this case the
current drawn from the mains is at a minimum for the real
power required to perform the needed work, and this
minimizes losses and costs associated not only with the
distribution of the power, but also with the generation of the
power and the capital equipment involved in the process.
The freedom from harmonics also minimizes interference
with other devices being powered from the same source.
Another reason to employ PFC in many of today’s power
supplies is to comply with regulatory requirements. Today,
lighting equipment in Europe must comply with
IEC61000−3−2 Class C. This requirement applies to most
lighting applications with input power of 25 W or greater,
and it specifies the maximum amplitude of line−frequency
harmonics up to and including the 39th harmonic. Moreover
power factor requirements for commercial lighting is
included within the ENERGY STAR® Solid State Lighting
Luminaire standard regardless of the applications power
level.
PFC
Preregulator
DC−DC
Converter
with isolation
Vout
This approach significantly reduces the component count.
The NCL30001 based solution requires only one each of
MOSFET, magnetic element, output rectifier (low voltage)
and output capacitor (low voltage). In contrast, the 2−stage
solution requires two or more of the above−listed
components. Elimination of certain high−voltage
components (e.g. high voltage capacitor and high voltage
PFC diode) has significant impact on the system design. The
resultant cost savings and reliability improvement are often
worth the effort of designing a new converter.
Single PFC Stage
While the single stage offers certain benefits, it is
important to recognize that it is not a recommended solution
for all requirements. The following three limitations apply
to the single stage approach:
• The output voltage ripple will have a 2x line frequency
component (120 Hz for North American applications)
that can not be eliminated easily. The cause of this
ripple is the elimination of the energy storage element
that is typically the boost output capacitor in the
2−stage solution. The only way to reduce the ripple is to
increase the output filter capacitance. The required
value of capacitance is inversely proportional to the
output voltage. Normally the presence of this ripple is
not a issue for most LED lighting applications.
• The hold−up time will not be as good as the 2−stage
approach – again due to the lack of an intermediate
energy storage element.
• In a single stage converter, one FET processes all the
power – that is both a benefit and a limitation as the
stress on that main MOSFET is relatively higher.
Similarly, the magnetic component (flyback
transformer/inductor) can not be optimized as well as in
the 2−stage solution. As a result, potentially higher
leakage inductance induces higher voltage spikes (like
the one shown in Figure 47) on the MOSFET drain.
This may require a MOSFET with a higher voltage
A typical power supply consists of a boost PFC
preregulator creating an intermediate X400 V bus and an
isolated dc−dc converter producing the desired output
voltage as shown in Figure 45. This architecture has two
power stages.
Rectifier
&
Filter
NCL30001 Based
Single−Stage
Flyback Converter
Figure 46. Single Stage Power Converter
Typical Power Supply with PFC
AC
Input
Rectifier
&
Filter
Vout
Figure 45. Typical Two Stage Power Converter
A two stage architecture allows optimization of each
individual power stage. It is commonly used because of
designer familiarity and a vast range of available
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18
NCL30001
a slightly higher cost and dissipates power only when the
drain voltage exceeds the voltage rating of the TVS.
Other features found in the NCL30001 include a high
voltage startup circuit, voltage feedforward, brown out
detector, internal overload timer, latch input and a high
accuracy multiplier.
rating compared to similar dc−input flyback
applications.
NCL30001 PFC Loop
The NCL30001 incorporates a modified version of
average current mode control used for achieving the unity
power factor. The PFC section includes a variable reference
generator, a low frequency voltage regulation error
amplifier (AC error AMP), ramp compensation (Ramp
Comp) and current shaping network. These blocks are
shown in the lower portion of the bock diagram (Figure 45).
The inputs to the reference generator include feedback
signal (FB), scaled AC input signal (AC_IN) and
feedforward input (VFF). The output of the reference
generator is a rectified version of the input sine−wave scaled
by the FB and VFF values. The reference amplitude is
proportional to the FB and inversely proportional to the
square of the VFF. This, for higher load levels and/or lower
input voltage, the signal would be higher.
The function of the AC error amp is to force the average
current output of the current sense amplifier to match the
reference generator output. The output of the AC error
amplifier is compensated to prevent response to fast events.
This output (Verror) is fed into the PWM comparator through
a reference buffer. The PWM comparator sums the Verror and
the instantaneous current and compares it to a 4.0 V
threshold to provide the desired duty cycle control. Ramp
compensation is also added to the input signal to allow CCM
operation above 50% duty cycle.
Figure 47. Typical Drain Voltage Waveform of a
Flyback Main Switch
There are two methods to clamp the voltage spike on the
main switch, a resistor−capacitor−diode (RCD) clamp or a
transient voltage suppressor (TVS).
RCD
Clamp
Vin
R
C
Vout
D
High Voltage Startup Circuit
Figure 48. RCD Clamp
TVS
Clamp
Vin
The NCL30001 internal high voltage startup circuit
eliminates the need for external startup components and
provides a faster startup time compared to an external
startup resistor. The startup circuit consists of a constant
current source that supplies current from the HV pin to the
supply capacitor on the VCC pin (CCC). The startup current
(Istart) is typically 5.5 mA.
The DRV driver is enabled and the startup current source
is disabled once the VCC voltage reaches VCC(on), typically
15.4 V. The controller is then biased by the VCC capacitor.
The drivers are disabled if VCC decays to its minimum
operating threshold (VCC(off)) typically 10.2 V. Upon
reaching VCC(off) the gate driver is disabled. The VCC
capacitor should be sized such VCC is kept above VCC(off)
while the auxiliary voltage is building up. Otherwise, the
system will not start.
The controller operates in double hiccup mode while in
overload or VCC(off). A double hiccup fault disables the
drivers, sets the controller in a low current mode and allows
VCC to discharge to VCC(off). This cycle is repeated twice to
minimize power dissipation in external components during
Vout
TVS
Figure 49. TVS Clamp
Both methods result in dissipation of the leakage energy
in the clamping circuits – the dissipation is proportional to
LI2 where L is the leakage inductance of the transformer and
I is the peak of the switch current at turn−off. An RCD
snubber is simple and has the lowest cost, but constantly
dissipates power. A TVS provides good voltage clamping at
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19
NCL30001
During this mode, VCC never drops below VCC(reset), the
controller logic reset level. This prevents latched faults to be
cleared unless power to the controller is completely
removed (i.e. unplugging the supply from the AC line).
a fault event. Figure 50 shows double hiccup mode
operation. A soft−start sequence is initiated the second time
VCC reaches VCC(on). If the controller is latched upon
reaching VCC(on), the controller stays in hiccup mode.
VCC
VCC(on)
VCC(off)
t
DRV
t
Fault Timer
(internal)
Overload
applied
t
tOVLD
Figure 50. VCC Double Hiccup Operation with a Fault Occurring while the Startup Circuit is Disabled
typically 0.85 V. Once VCC exceeds Vinhibit, the startup
current source is enabled. This behavior is illustrated in
Figure 51. This slightly increases the total time to charge
VCC, but it is generally not noticeable.
An internal supervisory circuit monitors the VCC voltage
to prevent the controller from dissipating excessive power
if the VCC pin is accidentally grounded. A lower level
current source (Iinhibit) charges CCC from 0 V to Vinhibit,
Figure 51. Startup Current at Various VCC Levels
The rectified ac line voltage is provided to the power stage
to achieve accurate PFC. Filtering the rectified ac line
voltage with a large bulk capacitor distorts the PFC in a
single stage PFC converter. A peak charger is needed to bias
the HV pin as shown in Figure 52. Otherwise, the HV pin
follows the ac line and the startup circuit is disabled every
time the ac line voltage approaches 0 V. The VCC capacitor
is sized to bias the controller during power up.
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20
NCL30001
Peak Charger
VOUT
VIN
HV
DRV
NCL30001
Figure 52. Peak charger
and it is applied to the non inverting input of the EA. The
filtered input current, Iin, is the current sense signal at the
ISpos pin multiplied by the current sense amplifier gain. It
is applied to the inverting input of the AC EA.
The AC EA is a transconductance amplifier. A
transconductance amplifier generates an output current
proportional to its differential input voltage. This amplifier
has a nominal gain of 100 mS (or 0.0001 A/V). That is, an
input voltage difference of 10 mV causes the output current
to change by 1.0 mA. The AC EA has typical source and sink
currents of 70 mA.
The filtered input current is a high frequency signal. A low
frequency pole forces the average input current to follow the
reference generator output. A pole-zero pair is created by
placing a (RCOMP) and capacitor (CCOMP) series
combination at the output of the AC EA. The AC COMP pin
provides access to the AC EA output.
The output of the AC EA is inverted and converted into a
current using a second transconductance amplifier. The
output of the inverting transconductance amplifier is
VACEA(buffer). Figure 53 shows the circuit schematic of the
AC EA buffer. The AC EA buffer output current, IACEA(out),
is given by Equation 1.
The startup circuit is rated at a maximum voltage of 500 V.
Power dissipation should be controlled to avoid exceeding
the maximum power dissipation of the controller. If
dissipation on the controller is excessive, a resistor can be
placed in series with the HV pin. This will reduce power
dissipation on the controller and transfer it to the series
resistor.
Drive Output
DRV has a source resistance of 10.8 W (typical) and a sink
resistance of 8.0 W (typical). The driver is enabled once VCC
reaches VCC(on) and there are no faults present. They are
disabled once VCC discharges to VCC(off). The high current
drive capability of DRV may generate voltage spikes during
switch transitions due to parasitic board inductance.
Shortening the connection length between the driver and the
load and using wider connections will reduce
inductance−induced spikes.
AC Error Amplifier and Buffer
The AC error amplifier (EA) shapes the input current into
a high quality sine wave by forcing the filtered input current
to follow the output of the reference generator. The output
of the reference generator is a full wave rectified ac signal
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21
NCL30001
VDD
x4
IACEA(out)
+
+
−
2.8V
VAC_REF
21.33kW
+
IAVG
To PWM
comparator
37.33kW
gm = 100mS
gm
+
−
−
AC error
amplifier
RIAVG
AC COMP
RAC_COMP
Figure 53. AC EA Buffer Amplifier
I ACEA(out) +
ǒ
Ǔ
2.8 * V ACEA
37.33k
@4
amplifier is a wide bandwidth amplifier with a differential
input. The current sense amplifier has two outputs, PWM
Output and IAVG Output. The PWM Output is the
instantaneous switch current which is filtered by the internal
leading edge blanking (LEB) circuitry prior to applying it to
the PWM Comparator non inverting input. The second
output is a filtered current signal resembling the average
value of the input current. Figure 54 shows the internal
architecture of the current sense amplifier.
(eq. 1)
The voltage at the PWM non-inverting input is
determined by IACEA(out), the instantaneous switch current
along and the ramp compensation current. DRV is
terminated once the voltage at the PWM non-inverting input
reaches 4 V.
Current Sense Amplifier
A voltage proportional to the main switch current is
applied to the current sense input, ISPOS. The current sense
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22
NCL30001
Ip
Ispos
gm = 250mS
+
−
RCS
blanking
gm
Inst. current
To PWM
tLEB
comparator
Current sense
amplifier
IAVG
VIAVG
To AC error
amplifier
CIAVG
RIAVG
Figure 54. Current Sense Amplifier
Caution should be exercised when designing a filter
between the current sense resistor and the ISPOS input, due
to the low impedance of this amplifier. Any series resistance
due to a filter creates a voltage offset (VOS) due to its input
bias current, CAIbias. The input bias current is typically
60 mA. The voltage offset is given by Equation 2.
V OS + CA Ibias @ R external
I CS + I IN +
V ISPOS
4k
(eq. 3)
The PWM Output delivers current to the positive input of
the PWM input where it is added to the AC EA and ramp
compensation signal.
The IAVG Output generates a voltage signal to a buffer
amplifier. This voltage signal is the product of IAVG and an
external RIAVG resistor filtered by the capacitor on the IAVG
pin, CIAVG. The pole frequency, fP, set by CIAVG should be
significantly below the switching frequency to remove the
high frequency content. But, high enough to not to cause
significant distortion to the input full wave rectified
sinewave waveform. A properly filtered average current
signal has twice the line frequency. Equation 4 shows the
relationship between CIAVG (in nF) and fP (in kHz).
(eq. 2)
The offset adds a positive offset to the current sense signal.
The ac error amplifier will then try to compensate for the
average output current which appears never to go to zero and
cause additional zero crossing distortion.
A voltage proportional to the main switch current is
applied to the ISPOS pin. The ISPOS pin voltage is converted
into a current, i1, and internally mirrored. Two internal
currents are generated, ICS and IAVG. ICS is a high frequency
signal which is a replica of the instantaneous switch current.
IAVG is a low frequency signal. The relationship between
VISPOS and ICS and IAVG is given by Equation 3.
C IAVG +
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23
1
2 @ p @ R IAVG @ f P
(eq. 4)
NCL30001
Oscillator
The gain of the low frequency current buffer is set by the
resistor at the IAVG pin, RIAVG. RIAVG sets the scaling factor
between the primary peak and primary average currents.
The gain of the current sense amplifier, ACA, is given by
Equation 5.
A CA +
RI AVG
The oscillator controls the switching frequency, f, the jitter
frequency and the gain of the multiplier. The oscillator ramp
is generated by charging the timing capacitor on the CT Pin,
CT, with a 200 mA current source. This current source is
tightly controlled during manufacturing to achieve a
controlled and repeatable oscillator frequency. The current
source turns off and CT is immediately discharged with a
pull down transistor once the oscillator ramp reaches its peak
voltage, VCT(peak), typically 4.0 V. The pull down transistor
turns off and the charging current source turns on once the
oscillator ramp reaches its valley voltage, VCT(valley).
Figure 55 shows the resulting oscillator ramp and control
circuitry.
(eq. 5)
4k
The current sense signal is prone to leading edge spikes
during the switch turn on due to parasitic capacitance and
inductance. This spike may cause incorrect operation of the
PWM Comparator. The NCL30001 incorporates LEB
circuitry to block the first 200 ns (typical) of each current
pulse. This removes the leading edge spikes without filtering
the current signal waveform.
VDD
x 1.2
To PWM
comparator
Ramp Comp
To PWM skip
−
+
comparator
RRC
VDD
CT
+
CT
−
+
4.0 V / 0.1 V
Oscillator
Figure 55. Oscillator Ramp and Control Circuitry
The relationship between the oscillator frequency in kHz
and timing capacitor in pF is given by Equation 6.
CT +
47000
f
A low frequency oscillator modulates the switching
frequency, reducing the controller EMI signature and
allowing the use of a smaller EMI filter. The frequency
modulation or jitter is typically ±6.8% of the oscillator
frequency.
(eq. 6)
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24
NCL30001
Output Overload
260 mV. A new Soft−Skip period starts once the voltage on
the AC−IN pin increases to 260 mV.
An increase in output load current terminates a Soft−Skip
event. A transient load detector terminates a Soft−Skip
period once VFB voltage exceeds VSSKIP (1.75 V nominal).
This ensures the required output power is delivered during
a load transient and the output voltage does not fall out of
regulation. Figure 57 shows the relationship between
Soft−Skip and the transient load detector.
The Feedback Voltage, VFB, is directly proportional to the
output power of the converter. An internal 6.7 kW resistor
pulls−up the FB voltage to the internal 6.5 V reference. An
external optocoupler pulls down the FB voltage to regulate
the output voltage of the system. The optocoupler is off
during power up and output overload conditions allowing
the FB voltage to reach its maximum level.
The NCL30001 monitors the FB voltage to detect an
overload condition. A typical startup time of a single PFC
stage converter is around 100 ms. If the converter is out of
regulation (FB voltage exceeds 5.0 V) for more that 160 ms
(typical) the drivers are disabled and the controller enters the
double hiccup mode to reduce the average power
dissipation. A new startup sequence is initiated after the
double hiccup is complete. This protection feature is critical
to reduce power during an output short condition.
Soft−Skip™ Cycle Mode
The FB voltage reduces as the output power demand of the
converter reduces. Once VFB drops below the skip
threshold, VSSKIP, 410 mV (typical) the driver is disabled.
The skip comparator hysteresis is typically 90 mV.
The converter output voltage starts to decay because no
additional output power is delivered. As the output voltage
decreases the feedback voltage increases to maintain the
output voltage in regulation. This mode of operation is
known as skip mode. The skip mode frequency is dependent
of load loop gain and output capacitance and can create
audible noise due to mechanical resonance in the
transformer and snubber capacitor. A proprietary Soft−Skip
mode reduces audible noise by slowly increasing the
primary peak current until it reaches its maximum value.
The minimum skip ramp period, tSSKIP, is 2.5 ms. Figure 56
shows the relationship between VFB, VSSKIP and the
primary current.
VSSKIP
VFB
Figure 57. Load transient during Soft−Skip
The output of the Soft−Skip Comparator is or−ed with the
PWM Comparator output to control the duty ratio. The
Soft−Skip Comparator controls the duty ratio in skip mode
and the PWM Comparator controls the duty cycle during
normal operation. In skip mode, the non−inverting input of
the Soft−Skip Comparator exceeds 4 V, disabling the
drivers. As the FB voltage increases, the voltage at the
non−inverting input is ramp down from 4 V to 0.2 V to
enable the drivers.
Multiplier and Reference Generator
The NCL30001 uses a multiplier to regulate the average
output power of the converter. This controller uses a
proprietary concept for the multiplier used within the
reference generator. This innovative design allows greatly
improved accuracy compared to a conventional linear
analog multiplier. The multiplier uses a PWM switching
circuit to create a scalable output signal, with a very well
defined gain.
The output of the multiplier is the ac-reference signal. The
ac-reference signal is used to shape the input current. The
multiplier has three inputs, the error signal from an external
error amplifier (VFB), the full wave rectified ac input
(AC_IN) and the feedforward input (VFF).
The FB signal from an external error amplifier circuit is
applied to the VFB pin via an optocoupler or other isolation
circuit. The FB voltage is converted to a current with a V-I
Figure 56. Soft−Skip Operation
Skip mode operation is synchronized to the ac line
voltage. The NCL30001 disables Soft−Skip when the
rectified ac line voltage drops to its valley level. This ensures
the primary current always ramp up reducing audible noise.
A skip event occurring as the ac line voltage is decreasing,
causes the primary peak current to ramp down instead of
ramp up. Once the skip period is over the primary current is
only determined by the ac line voltage. A Soft−Skip event
terminates once the AC−IN pin voltage decreases below
VCC
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25
NCL30001
factored by the AC_IN comparator output. The resulting
signal is filtered by the low pass R-C filter on the CM pin.
The low pass filter removes the high frequency content. The
gain of the multiplier is determined by the V-I converter, the
resistor on the CM pin, and the peak and valley voltages of
the oscillator sawtooth ramp.
converter. There is no error in the output signal due to the
series rectifier as shown in Figure 58.
The scaled version of the full wave rectified input ac wave
is applied to the AC_IN pin by means of a resistive voltage
divider. The multiplier ramp is generated by comparing the
scaled line voltage to the oscillator ramp with the AC_IN
Comparator. The current signal from the V-I converter is
FB
Multiplier
V−to−I
+
AC IN
V
−
V
AC_REF
[email protected]
Oscillator
CM
FB
@V
V
AC_IN
FF
2
AC_REF
Divide
VFF2
VFF
Square
Figure 58. Reference Generator
The third input to the reference generator is the VFF signal.
The VFF signal is a dc voltage proportional to the ac line
voltage. A resistive voltage divider attenuates the full wave
rectified line voltage between 0.7 and 5.0 V. The full wave
rectified line is then averaged with a capacitor. The ac
average voltage must be constant over each half cycle of the
line. Line voltage ripple (120 Hz or 100 Hz) ripple on the
VFF signal adds ripple to the output of the multiplier. This
will distort the ac reference signal and reduce the power
factor and increase the line current distortion. Excessive
filtering delays the feedforward signal reducing the line
transient response. A good starting point is to set the filter
time constant to one cycle of the line voltage. The user can
then optimize the filter for line transient response versus
power factor. The average voltage on the VFF pin is:
V FF +
2
Vac Ǹ2a
p
V AC_REF +
V FB @ V AC_IN
V FF
2
@k
(eq. 8)
The multiplier transfer function is given by Equation 8.
The output of the multiplier is the AC_REF. It connects to
the AC Error Amplifier.
where, k is the reference generator gain, typically 0.55. The
output of the reference generator is clamped at 4.5 V to limit
the maximum output power.
Feedforward maintains a constant input power
independent of the line voltage. That is, for a given FB
voltage, if the line voltage doubles (AC_IN), the
feedforward term quadruples and reduces the output of the
error amplifier in half to maintain the same input power.
AC Error Amplifier Compensation
A pole-zero pair is created by placing a series combination
of RCOMP and CCOMP at the output of the AC error amplifier
(EA). The value of the compensation components is
(eq. 7)
Where, a is the voltage divider ratio, normally 0.01.
www.onsemi.com
26
NCL30001
dependent of the average input current and the instantaneous
switch current. The gain of the average input current or slow
loop is given by Equation 9.
A LF +
ǒ Ǔ
R IAVG
4k
@ ǒgm @ R AC_COMPǓ @ (2.286)
where, Vin(LL) is the low line ac input voltage, D is the duty
ratio, Pout is the output power, Pin is the input power, h is the
efficiency, LP is the primary inductance and ton is the on
time. Typical efficiency for this topology is around 88%.
The current sense resistor is selected to achieve maximum
signal resolution at the input of the ac reference amplifier.
The maximum voltage input of the ac reference amplifier to
prevent saturation is 4.5 V. This together with the
instantaneous peak current is used to calculate the current
sense resistor, RCS, using Equation 16.
(eq. 9)
The low frequency gain is the product of the current sense
averaging circuit, the transconductance amplifier and the
gain of the AC error amplifier.
A current proportional to the instantaneous current is
generated using a 4 kW resistor in the current sense amplifier
input. This proportional current is applied to a 21.33 kW at
the PWM comparator input to generate a current sense
voltage signal. The high frequency or fast loop gain, AHF, is
calculated using Equation 10.
A HF +
21.33k
4k
+ 5.333
R CS + 4.5
R IAVG
4k
@ ǒgm @ R AC_COMPǓ @ (2.286) t
Subharmonic oscillations are observed in peak
current-mode controllers operating in continuous
conduction mode with a duty ratio greater than 50%.
Injecting a compensation ramp on the current sense signal
eliminates the subharmonic oscillations. The amount of
compensation is system dependent and it is determined by
the inductor falling di/dt.
The NCL30001 has built in ramp compensation to
facilitate system design. The amount of ramp compensation
is set by the user with a resistor, RRCOMP, between the Ramp
Comp pin and ground. The Ramp Comp pin buffers the
oscillator ramp generated on the CT pin. The current across
RRCOMP is internally mirrored with a 1:1.2 ratio. The
inverted ac error amplifier and the instantaneous switch
current signals are added to the ramp compensation mirrored
current. The resulting current signal is applied to an internal
21.33 kW between the PWM Comparator non inverting
input and ground as shown in Figure 55.
The maximum voltage contribution of the ramp
compensation signal to the error signal, VRCOMP, is given by
Equation 17.
(eq. 10)
5.333
(eq. 11)
2
Equation 12 is obtained by re-arranging Equation 11 for
RAC_COMP. This equation provides the maximum value for
RAC_COMP.
R AC_COMP t
4666
R IAVG @ gm
(eq. 12)
The control loop zero, fZ, is calculated using Equation 13.
The control loop zero should be set at approximately at
1/10th of the oscillator frequency, fOSC. The compensation
capacitor is calculated using Equation 14.
fz +
1
2p @ C AC_COMP @ R AC_COMP
C AC_COMP +
1
2p @
f
OSC
10
(eq. 13)
(eq. 14)
@ R AC_COMP
V RCOMP +
Current Sense Resistor
Ǹ2 @ P
out
h @ V in(LL) @ D
)
V in(LL) @ t on
0.88 @ 2 @ L P
(1.2) @ ǒV CT(peak)Ǔ @ (21.33k)
R RCOMP
(eq. 17)
+
102.38k
R RCOMP
where, VCT(peak) is the oscillator ramp peak voltage,
typically 4.0 V.
For proper ramp compensation, the ramp signal should
match the falling di/dt (which has been converted to a dv/dt)
of the inductor at 50% duty cycle. Both the falling di/dt and
output voltage need to be reflected by the transformer turns
ratio to the primary side. Equations 18 through 23 assist in
the derivation of equations for RCS and RCOMP.
The PFC stage has two control loops. The first loop
controls the average input current and the second loop
controls the instantaneous current across the main switch.
The current sense signal affects both loops. The current
sense signal is fed into the positive input of the error
amplifier to control the average input current. In addition,
the current sense information together with the ramp
compensation and error amplifier signal control the
instantaneous primary peak current.
The primary peak current, IPK, is calculated using
Equation 15,
I PK +
(eq. 16)
R IAVG @ P in @ Ǹ2
Ramp Compensation
Equation 11 shows system stability requirements. That is,
the low frequency gain has to be less than one half of the high
frequency gain.
ǒ Ǔ
4k @ ǒV in(LL) @ DǓ
di
dt secondary
di
(eq. 15)
dt primary
www.onsemi.com
27
+
+
V out
LS
di
dt secondary
+
@
V out
LP
NS
NP
+
@
ǒ Ǔ
NP
NS
V out N P
LP NS
2
(eq. 18)
(eq. 19)
NCL30001
di
V RCOMP +
NS
R CS +
NP
dt primary
@
@ T @ R CS @ A HF
L P @ 102.38k
T @ A HF @ V out @ R RCOMP
latch is Set dominant which means that if both R and S are
high the S signal will dominate and Q will be high, which
will hold the power switch off.
The NCL30001 uses a pulse width modulation scheme
based on a fixed frequency oscillator. The oscillator
generates a voltage ramp as well as a pulse in sync with the
falling edge of the ramp. The pulse is an input to the PWM
Logic and Driver block. While the oscillator pulse is present,
the latch is reset, and the output drive is in its low state. On
the falling edge of the pulse, the DRV goes high and the
power switch begins conduction.
The instantaneous inductor current is summed with a
current proportional to the ac error amplifier output voltage.
This complex waveform is compared to the 4 V reference
signal on the PWM comparator inverting input. When the
signal at the non-inverting input to the PWM comparator
exceeds 4 V, the output of the PWM comparator toggles to
a high state which drives the Set input of the latch and turns
the power switch off until the next clock cycle.
(eq. 20)
(eq. 21)
At low line and full load, the output of the ac error
amplifier output is nearly saturated in a low state. While the
ac error amplifier output is saturated, IACEA is zero and does
not contribute to the voltage across the internal 21.33 kW
resistor on the PWM comparator non-inverting input. In this
operation mode, the voltage across the 21.33 kW resistor is
determined solely by the ramp compensation and the
instantaneous switch current as given by Equation 22.
ǒ
V ref(PWM) + V RCOMP @
Ǔ)V
t on
T
INST
(eq. 22)
The voltage reference of the PWM Comparator,
VREF(PWM), is 4 V. For these calculations, 3.8 V is used to
provide some margin. The maximum instantaneous switch
current voltage contribution, VINST, is given by
Equation 23.
V INST + I PK @ R CS @ A HF
Brown−Out
The NCL30001 incorporates a brown−out detection
circuit to prevent the controller operate at low ac line
voltages and reduce stress in power components. A scaled
version of the rectified line voltage is applied to the VFF Pin
by means of a resistor divider. This voltage is used by the
brown out detector.
A brown−out condition exists if the feedforward voltage
is below the brown−out exit threshold, VBO(high), typically
0.45 V. The brown−out detector has 175 mV hysteresis. The
controller is enabled once VFF is above 0.63 V and VCC
reaches VCC(on). Figure 59 shows the relationship between
the brown−out, VCC and DRV signals.
(eq. 23)
Substituting Equation 23 in Equation 22, setting
VREF(PWM) at 3.8 V (provides margin) and solving for
RRCOMP, Equation 24 is obtained.
R RCOMP +
102.38k
ǒ3.8 * 5.333 @ IPK @ R CSǓ
@
t on
T
(eq. 24)
Replacing Equation 24 in Equation 21 we obtain:
R CS +
ǒ
3.8
N
P
N
S
@
A
@V
HF
L
Ǔ ) 5.333 I
[email protected]
P
(eq. 25)
PK
PWM Logic
The PWM and logic circuits are comprised of a PWM
comparator, an RS flip-flop (latch) and an OR gate. The
www.onsemi.com
28
NCL30001
VCC
VCC(on)
VCC(off)
t
DRV
t
VFF
VBO(low)
VBO(high)
Brown−Out
t
Figure 59. Relationship Between the Brown−Out, VCC, and DRV
Vaux or VCC
VDD
OVP comparator
+
−
+
Vlatch(high)
Ilatch(clamp)
blanking
tlatch(delay)
Latch−Off
OTP comparator
−
I latch(shdn)
S
Q
+
+
Latch
R
Vlatch(low)
NTC
Vlatch(clamp)
Reset
Figure 60.
Latch Input
Latch−Off pin voltage is pulled below 1 V or above 6.5 V.
Figure 61 shows the relationship between the Latch−Off,
VCC and DRV signals.
The NCL30001 has a dedicated latch input to easily latch
the controller during overtemperature and overvoltage
faults (See Figure 60). The controller is latched if the
www.onsemi.com
29
NCL30001
VCC
VCC(on)
VCC(off)
t
DRV
t
Latch−Off
Vlatch(high)
Latch−Off
Vlatch(low)
Latch−Off
t
Figure 61. Relationship Between the Latch−Off, VCC, and DRV
The Latch−Off pin is clamped at 3.5 V. A 50 mA (typical)
pull−up current source is always on and a 100 mA (typical)
pull−down current source is enabled once the Latch−Off pin
voltage reaches 3.5 V (typical). This effectively clamps the
Latch−Off pin voltage at 3.5 V. A minimum pull−up or
pull−down current of 50 mA is required to overcome the
internal current sources and latch the controller. The
Latch−Off input features a 50 ms (typical) filter to prevent
latching the controller due to noise or a line surge event.
The startup circuit continues to cycle VCC between
VCC(on) and VCC(off) while the controller is in latch mode.
The controller exits the latch mode once power to the system
is removed and VCC drops below VCC(reset).
APPLICATION INFORMATION
The electronic design tool allows the user to easily
determine most of the system parameters of a single PFC
stage The tool evaluates the power stage as well as the
frequency response of the system.
ON Semiconductor provides an electronic design tool,
facilitate design of the NCL30001 and reduce development
cycle time. The design tool can be downloaded at
www.onsemi.com.
ORDERING INFORMATION
Device
NCL30001DR2G
Package
Shipping†
SO−16
(Pb−Free)
2500 / Tape & Reel
†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.
www.onsemi.com
30
NCL30001
PACKAGE DIMENSIONS
SOIC−16
CASE 751B−05
ISSUE K
−A−
16
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2. CONTROLLING DIMENSION: MILLIMETER.
3. DIMENSIONS 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.
9
−B−
1
P
8 PL
0.25 (0.010)
8
B
M
S
DIM
A
B
C
D
F
G
J
K
M
P
R
G
R
K
F
X 45 _
C
−T−
SEATING
PLANE
J
M
D
MILLIMETERS
MIN
MAX
9.80
10.00
3.80
4.00
1.35
1.75
0.35
0.49
0.40
1.25
1.27 BSC
0.19
0.25
0.10
0.25
0_
7_
5.80
6.20
0.25
0.50
INCHES
MIN
MAX
0.386
0.393
0.150
0.157
0.054
0.068
0.014
0.019
0.016
0.049
0.050 BSC
0.008
0.009
0.004
0.009
0_
7_
0.229
0.244
0.010
0.019
16 PL
0.25 (0.010)
M
T B
S
A
S
SOLDERING FOOTPRINT*
8X
6.40
16X
1.12
1
16
16X
0.58
1.27
PITCH
8
9
DIMENSIONS: MILLIMETERS
*For additional information on our Pb−Free strategy and soldering
details, please download the ON Semiconductor Soldering and
Mounting Techniques Reference Manual, SOLDERRM/D.
Soft−Skip is a trademark of Semiconductor Components Industries, LLC (SCILLC).
ENERGY STAR and the ENERGY STAR mark are registered U.S. marks.
ON Semiconductor and the
are registered trademarks of Semiconductor Components Industries, LLC (SCILLC) or its subsidiaries in the United States and/or other countries.
SCILLC owns the rights to a number of patents, trademarks, copyrights, trade secrets, and other intellectual property. A listing of SCILLC’s product/patent coverage may be accessed
at www.onsemi.com/site/pdf/Patent−Marking.pdf. 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
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Phone: 303−675−2175 or 800−344−3860 Toll Free USA/Canada
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Phone: 421 33 790 2910
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Phone: 81−3−5817−1050
www.onsemi.com
31
ON Semiconductor Website: www.onsemi.com
Order Literature: http://www.onsemi.com/orderlit
For additional information, please contact your local
Sales Representative
NCL30001/D