NCP1013: Universal Input, 5 W, LED Ballast

DN06027/D
Design Note – DN06027/D
Universal Input, 5 W, LED Ballast
Device
Application
Input Voltage
Output Power
Topology
I/O Isolation
NCP1013
Solid State Lighting
85 – 265 Vac
5W
Flyback
Yes
Other Specifications
Output 1
10 Vmax
700 mA
Output Voltage
Nominal Current
PFC (Yes/No)
No
Target Efficiency
65 % at nominal load
Max Size
58 x 30 x 19 mm
Operating Temp Range
Cooling Method/Supply
Orientation
Signal Level Control
0 to +70°C (open frame)
Convection
No
Circuit Description
Key Features
The controller used in this application is a low cost
monolithic design, the NCP1013. This, and the other
members of the family, from the NCP1010 to the
NCP1014, allow for the design of low cost, yet fully
featured, switched mode powers supplies. They integrate
many peripheral circuits, from start-up to current limit,
whilst also adding the ability to run directly from the HV
bus, thus obviating the need for a bias winding, and an
overload feature ensuring low dissipation in overload and
short –circuit.
The design comprises and input filter, bridge rectifier
(using low cost 1N4007 diodes), bulk capacitors and line
inductor in π-filter arrangement, the power stage, rectifier
diode and smoothing capacitors. Feedback is CVCC,
constant current drive for the LED’s with a constant
voltage in the event of an open circuit output.
y Wide input voltage range – 85 Vac to 265 Vac
y Small size, and low cost
y Good line regulation
y High efficiency
y Overload and short circuit protection.
Number of LED’s
in series.
LED Current
350 mA
LUXEON® I
2
LUXEON® III
2
700 mA
1A
#NOTE1
2
1
1
1
#NOTE1
2
2
1
2
2
1
Vz (D7)
9V1
8V2
5V1
R3 & R4
3R6
1R8
1R2
®
®
®
LUXEON V
LUXEON K2
LUXEON Rebel
#NOTE1: Out of LED specification.
July 2008, Rev. 1
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DN06027/D
Schematic
LED Current
The light output of an LED is determined by the forward
current so the control loop will be constant current, with a
simple Zener to limit the maximum output voltage.
For a white LUXEON® K2 the VI characteristics are:
IF
VF
350 mA
3.42 V
700 mA
3.60 V
1000 mA
3.72 V
1500 mA
3.85 V
I LED =
0.6V
.........................................(Eq.1)
RSENSE
Total sense resistor power dissipation is:
PD = I LED × 0.6V ....................................(Eq.2)
Driving two LED’s at 700 mA thus gives an output
power of 5.04 W at 7.2 V.
Inductor selection
In a flyback converter the inductance required in the
transformer primary is dependant on the mode of
operation and the output power. Discontinuous operation
requires lower inductance but results in higher peak to
average current waveforms, and thus higher losses. For
low power designs, such as this ballast, the inductance is
designed to be just continuous (or just discontinuous)
under worst case conditions, that is minimum line and
maximum load.
The specification for this ballast is as follows:
• Universal input – 85 VAC to 265 VAC
• 5 W output power
• 700 mA output current
So for 700 mA we need a 0.9 Ω sense resistor capable
of dissipating 420 mW, two 330 mW surface mount
resistors, 1.8 Ω each in parallel, are used.
allowance will be made for this by using 100 V as the
minimum input voltage.
Assuming efficiency (η) of 85% we get an input power
of:
PIN =
POUT
η
= 5.9 W ...............................(Eq.3)
At a switching frequency of 100 kHz this gives an
energy per cycle requirement, that is the energy that must
be stored in the primary inductance on each cycle, of:
E=
This gives us a minimum DC input voltage of 120 V,
there will be some sag on the DC bulk capacitors so an
July 2008, Rev. 1
The output current is sensed by a series resistance, once
the voltage drop across this reaches the base-emitter
threshold of the PNP transistor current flows in the optocoupler diode and thus in the FB pin of the NCP101x.
The LED current is thus set by:
P
f SW
=
5.9
= 59 µJ ................(Eq.4)
100 ×10 3
For an inductor:
E = 12 LI 2 ................................................(Eq.5)
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DN06027/D
We therefore get N < 32 from (Eq.11) and N < 12.9
from (Eq.13), clearly we need to use the lower figure of
12.9.
Also:
V =L
di
..................................................(Eq.6)
dt
Rearranging and combining (Eq.5) and (Eq.6) gives:
Putting N=12.9 and VIN = 100 V into (Eq.9) we get
δ = 0.499, and from (Eq.8), dt = 4.99 µs. This gives us,
from (Eq.7), the minimum inductance required which is
2.1 mH. We shall use 2.3 mH.
We can now establish the peak primary current and
select the correct member of the NCP101x family.
V 2 dt 2
L=
..............................................(Eq.7)
2E
Where;
V is VIN(min) = 100 V,
E is the energy per cycle = 59 µJ
dt =
and dt is the on time;
δ
f SW
Rearranging (Eq.6) we get:
...............(Eq.8)
di =
For a flyback topology the duty cycle is:
δ=
VOUT
Thus di = 217 mA which, as stated earlier, is equal to
IPK in discontinuous mode.
.....................................(Eq.9)
VIN
+ VOUT
N
where N is the transformer turns ratio.
For the NCP101x family of regulators the turn’s ratio is
determined from the constraints of not exceeding the
700 V maximum rating on the DRAIN pin, and also not
taking the DRAIN pin below ground.
N × (VOUT + V f ) + VIN (max ) + Vleak ≤ 700 (Eq.10)
Or
N≤
(700 − V
(V
IN ( max )
OUT
− Vleak )
+Vf
)
N × (VOUT + V f ) ≤ VIN (min) .....................(Eq.12)
(V
OUT
+Vf
)
IPK(nom)
IPK(max)
NCP1010
90
100
110
NCP1011
#1
225
250
275
NCP1012
#2
225
250
275
NCP1013
#2
315
350
385
NCP1014
#2
405
450
495
#1
22Ω FET
#2
11Ω FET
IC Consumption
The IC internal consumption is quoted as a maximum
1.15 mA, typically 0.95 mA. This is dissipated as loss in
the regulator itself and is in addition to our estimated 85%
efficiency that just relates to the transformer throughput.
This loss goes from typically 115 mW at 85 Vac to 356
mW at 265 Vac with a maximum, at 265 VAC, of 431 mW.
Or
VIN (min)
IPK(min)
#1
Whilst the NCP1011 has a current limit inception point
between 225 mA and 275 mA there is little margin for
spikes and parameter variances so the NCP1013 will be
the regulator used.
.................(Eq.11)
And
N≤
Vdt
...............................................(Eq.14)
L
..................................(Eq.13)
Where:
VIN(max) is the maximum rectified input = 375 V.
VIN(min) is the minimum rectified input = 100 V.
VOUT is 7.2 V (5 W @ 700 mA).
Vleak is the leakage spike associated with the leakage
inductance of the transformer. A well constructed
transformer with a low leakage inductance and some
snubbing of the DRAIN pin will keep this value down. A
figure of 80 V will allow for a safety margin.
Vf is the forward drop of the output rectifier diode, in
this case a Schottky so 0.5 V.
July 2008, Rev. 1
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DN06027/D
MAGNETICS DESIGN DATA SHEET
Project / Customer:
ON Semiconductor/Future Lighting Solution
Part Description:
5 W Transformer
Schematic ID:
-
Core Type:
-
Core Gap:
Gap for 2.3 mH
Inductance:
2.3 mH
Bobbin Type:
-
Windings (in order):
Winding # / type
Turns / Material / Gauge / Insulation Data
N1, Primary
Start on pin 1 and wind 128 turns, of Grade 2 ECW, in one neat
layer across the entire bobbin width. Finish on pin 2.
N2, Secondary
Start on pin 8 and wind 10 turns, of Tex E triple insulated wire or
equivalent, distributed evenly across the entire bobbin width. Finish
on pin 5. Sleeving and insulation between primary and secondary
as required to meet requirements of double insulation.
Primary leakage inductance (pins 5 and 8 shorted together) to be < 70 µH
NIC part number: NLT181814W2NT128UT10P8C2F
Hipot: 3 kV between pins 1,2 and pins 5,8 for 60 secs.
Lead Breakout / Pinout
Schematic
(Bottom View – looking at pins)
1
N1
2
July 2008, Rev. 1
5
N2
4
5
3
6
2
7
1
8
Pins 6 & 7
Cropped flush with
bobbin or removed
8
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DN06027/D
Bill of Materials
Ref.
Part Type
Qty.
per
Description
Manufacturer
1
X2-class EMI suppression capacitor
NIC
C10
3.3nF,
250/275VAC
1µF, 16V
1
NIC
C2 & C3
4.7µF, 400V
2
C4
220pF, 1kV
1
NIC
C5
22µF, 16V
1
C6
1.0nF, 10V
1
Ceramic chip capacitor
General purpose high voltage
electrolytic
Ceramic chip capacitor
General purpose low voltage
electrolytic
Ceramic chip capacitor
C7
1nF
1
Ceramic Y Capacitor
Murata
C8 & C9
470µF
2
Miniature low impedance electrolytic
NIC
D1 - D4
1N4007
4
D5
MBRA340
D6
MURA160
D7
C1
NIC
NIC
NIC
Part No.
Com m ent
NPX332M275VX2
(Alt. SMD: NPX332M275VX2F)
NMC1206X7R105K16
NREH4R7M400V10X16F
(Alt. SMD: NACV4R7M400V10X10.8TR13F)
NMC-H1210NP0221K1KVTRPF
NRSA220M16V5X11F
(Alt. SMD: NACE220M16V4X5.5TR13F)
NMC0805X7R102K10
250VAC/275VAC X2
16V X7R
1kV
10V X7R
DE1E3KX102MN4AL01
NRSH471M16V8X11.5F
(Alt. SMD: NACK471M35V12.5X14TR13F)
Y1
1N4007RLG
1000V
0.06Ohms
1
Axial Lead Standard Recovery
Rectifier 1A, 1000V
40V 3A Schottky diode
ON Semiconductor
MBRA340T3G
1
600V 1A Ultrafast rectifier
ON Semiconductor
MURA160T3G
9V1
1
200mW SOD-323 Zener diode
ON Semiconductor
MM3Z9V1T1G
9.1V, 5%
IC1
NCP1013
1
Self-Supplied Monolithic Sw itcher for
ON Semiconductor
Low Standby-Pow er Offline SMPS
NCP1013ST100T3G
NCP1013100T3G
100kHz
IC2
HCPL-817
1
Opto-coupler HCPL-817 - Wide pitch
Agilent
HCPL-817-W0AE
Wide pitch
L1
1mH, 250mA
1
Pow er inductor
Coilcraft
ON Semiconductor
Q1
BC857
1
General purpose PNP
ON Semiconductor
RFB0807-102L
(Alt. SMD: NIC NPIS104T102KTRF)
BC857ALT1G
R1
15R, 1W
1
Axial lead carbon film resistor
NIC
NRC100J150TRF
R2
91k, 1W
1
Axial lead carbon film resistor
NIC
NRC100J913TRF
1W
R3 & R4
1.8R
2
Resistor thick film NRC
NIC
NRC25J1R8TR
0.33W
R5
47R
1
Resistor thick film NRC
NIC
NRC10J470TR
0.125W
R6
200R
1
Resistor thick film NRC
NIC
NRC10J201TR
0.125W
TX1
Custom
1
5W Flyback transformer
NIC
NLT181814W2NT128UT10P8C2F
250mA
1W
All parts can be ordered from Future Electronics
Component locations
Top view.
July 2008, Rev. 1
Bottom view.
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DN06027/D
PCB Tracks
Results
Drain waveform at 110 VAC
Drain waveform at 230 VAC
I OUT vs VOUT
Efficiency vs VOUT
0.9
80%
0.8
75%
0.7
70%
65%
Efficiency
IOUT (A)
0.6
0.5
0.4
0.3
230 VAC
0.2
110 VAC
0.1
60%
55%
50%
45%
230 VAC
40%
110 VAC
35%
0.0
30%
0.0
2.0
4.0
6.0
8.0
10.0
12.0
0.0
VOUT (V)
July 2008, Rev. 1
2.0
4.0
6.0
8.0
10.0
12.0
V OUT (V)
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© 2008 ON Semiconductor.
Disclaimer: ON Semiconductor is providing this design note “AS IS” and does not assume any liability arising from its use; nor
does ON Semiconductor convey any license to its or any third party’s intellectual property rights. This document is provided only to
assist customers in evaluation of the referenced circuit implementation and the recipient assumes all liability and risk associated
with its use, including, but not limited to, compliance with all regulatory standards. ON Semiconductor may change any of its
products at any time, without notice.
Design note created by Anthony Middleton, e-mail: [email protected]
July 2008, Rev. 1
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