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Title
Reference Design Report for a 6 W Non-
Dimmable, Non-Isolated Buck LED Driver
Using LYTSwitchTM-0 LYT0006P
Specification 90 VAC – 265 VAC Input; 54 V, 110 mA Output
Application GU10 LED Driver Lamp Replacement
Author Applications Engineering Department
Document
Number RDR-355
Date June 18, 2013
Revision 1.0
Summary and Features
Single-stage power factor corrected (>0.75 at 120 V and >0.5 at 230 V) and accurate constant current
(CC) output
Low cost, low component count and small PCB footprint solution
Highly energy efficient, >91 % at 120 VAC input
Highly energy efficient, >90 % at 240 VAC input
Superior performance and end user experience
Fast start-up time (<20 ms) – no perceptible delay
Integrated protection and reliability features
Single shot no-load protection / output short-circuit protected with auto-recovery
Auto-recovering thermal shutdown with large hysteresis protects both components and PCB
No damage during brown-out conditions
Meets IEC ring wave, differential line surge and EN55015 conducted EMI
PATENT INFORMATION
The products and applications illustrated herein (including transformer construction and circuits external to the products) may be covered
by one or more U.S. and foreign patents, or potentially by pending U.S. and foreign patent applications assigned to Power Integrations. A
complete list of Power Integrations' patents may be found at www.powerint.com. Power Integrations grants its customers a license under
certain patent rights as set forth at <http://www.powerint.com/ip.htm>.
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Table of Contents
1Introduction ................................................................................................................. 4
2Power Supply Specification ........................................................................................ 6
3Schematic ................................................................................................................... 7
4Circuit Description ...................................................................................................... 8
4.1Input EMI Filtering ............................................................................................... 8
4.2LYTSwitch-0 ........................................................................................................ 8
4.3Output Rectification ............................................................................................. 8
4.4Output Feedback ................................................................................................. 8
4.5No-Load Protection ............................................................................................. 9
5PCB Layout .............................................................................................................. 10
6Bill of Materials ......................................................................................................... 12
7Inductor Specification ............................................................................................... 13
7.1Electrical Diagram ............................................................................................. 13
7.2Electrical Specifications ..................................................................................... 13
7.3Materials ............................................................................................................ 13
7.4Inductor Build Diagram ...................................................................................... 14
7.5Transformer Construction .................................................................................. 14
8Inductor Design Spreadsheet ................................................................................... 15
9Performance Data .................................................................................................... 17
9.1Active Mode Efficiency ...................................................................................... 18
9.2Output Current Regulation ................................................................................. 19
9.2.1Input Line and Load Voltage to Output Current Regulation ........................ 19
10Thermal Performance ........................................................................................... 20
10.1Equipment Used ................................................................................................ 20
11Thermal Result ...................................................................................................... 21
11.1Thermal Scan .................................................................................................... 22
12Waveforms ............................................................................................................ 23
12.1Drain Voltage Normal Operation ....................................................................... 23
12.2Drain Current at Normal Operation .................................................................... 24
12.3Drain Voltage and Current When Output Short ................................................. 26
12.4Drain Voltage and Current Start-up Profile ........................................................ 26
12.5Output Current Start-up Profile .......................................................................... 27
12.6Input-Output Profile ........................................................................................... 28
12.7Line Sag and Surge ........................................................................................... 29
12.8Brown-out/ Brown-in .......................................................................................... 30
13Line Surge ............................................................................................................. 31
14Conducted EMI ..................................................................................................... 33
15Audible Noise ........................................................................................................ 35
16Appendix ............................................................................................................... 36
17Revision History .................................................................................................... 39
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Important Note:
Although this board is designed to satisfy safety isolation requirements, the engineering
prototype has not been agency approved. Therefore, all testing should be performed
using an isolation transformer to provide the AC input to the prototype board.
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1 Introduction
This document describes a cost effective power supply utilizing the LYTSwitchTM-0 family
(LYT0006P) in a highly compact buck topology.
This power supply operates over an input voltage range of 90 VAC to 264 VAC. The DC
bus voltage is high enough to support a 54 V output when using a buck topology. In a
buck converter the output voltage must always be lower than the input voltage. The
output voltage is also limited by the maximum duty cycle of the LYTSwitch-0, which also
requires the input voltage to be larger than the output voltage.
Figure 1 – Populated Circuit Board Photograph, Top.
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Figure 2 – Populated Circuit Board Photograph, Bottom.
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2 Power Supply Specification
Description Symbol Min Typ Max Units Comment
Input
Voltage Operation VIN 90 265 VAC 2 Wire – no P.E.
Frequency fLINE 47 50/60 Hz
Operating frequency is not limited.
Adjust sense resistor if application
is for 400 Hz line.
Output
Output Voltage VOUT 52 54 56 V
Output Current IOUT 110 mA
±4% at 100 VAC - 240 VAC
Total Output Power
Continuous Output Power POUT 6
6.5 W
Efficiency
120 VAC; 54 V LED 91 % Measured at POUT 25 ºC
240 VAC; 54 V LED 90 %
Power Factor
120 VAC; 54 V LED PF 0.75 Measured at POUT 25 ºC
240 VAC; 54 V LED PF 0.5
Environmental
Conducted EMI Meets CISPR22B / EN55015B
Line Surge
Differential Mode (L1-L2) 0.5
kV
1.2/50 s surge, IEC 1000-4-5,
Series Impedance:
Differential Mode: 2
Ring Wave (100 kHz)
Differential Mode (L1-L2) 2.5
kV
500 A short circuit
Series Impedance:
Differential Mode: 2
Ambient Temperature TAMB -10 25 ºC Free convection, sea level
UUT can start-up at – (neg) 40 ºC
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3 Schematic
Figure 3 – Schematic. T1 can be replaced by a drum core inductor if final casing/housing has sufficient
room to avoid shorting the magnetic flux. Zener diode VR1 is an option and provides one-time no-load
protection.
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4 Circuit Description
The power supply shown in Figure 3 uses the LYT0006P (U1) in a high-side buck
configuration to deliver a constant 110 mA current at an output voltage of 54 VDC. The
power supply is designed for driving LEDs, which should always be driven with a
constant current (CC).
4.1 Input EMI Filtering
Fuse RF1 provides short circuit protection. Bridge BR1 provides full wave rectification for
good power factor. Capacitor C1, C2 and common-mode choke L1 form a π filter in order
meet conducted EMI standards. Capacitor C1 and C2 are also used for energy storage
reducing line noise and protecting against line surge.
4.2 LYTSwitch-0
LYTSwitch-0 is optimized to achieve a simple and cost effective LED driver with good line
and temperature regulation from 0 to 100C (LYTSwitch-0 case temperature). The PIXls
spreadsheet was used to achieve the best line regulation by balancing the power inductor
and the sense resistor. The total input capacitance will also have some effect but it can
be compensated for by adjusting the sense resistor (R2/R3) to optimize performance.
The LYTSwitch-0 family has built-in thermal limit to protect the power supply in case the
bulb is subjected to an excessive operating temperature.
The buck converter stage is consists of the integrated power MOSFET switch within
LYT0006P (U1), a freewheeling diode (D1), sense resistor (R2), power inductor L2 and
output capacitor (C5). The converter is operating mostly in DCM in order to limit the
cycles of reverse current. A fast freewheeling diode was selected to minimize the
switching losses.
Inductor L2 is a standard EE10 which will constrain the flux path and ensure the right
inductance in any casing. It can be replaced by a lower cost drum-core inductor once
positioned in a specific enclosure that has a known effect on the magnetic flux of the
inductor.
4.3 Output Rectification
Fast output diode (D1) was used to achieve good efficiency and for thermal
management. Normally for LED applications, the ambient temperature is above 70C. A
device with low tRR (<35 nS) is recommended.
4.4 Output Feedback
Regulation is maintained by skipping switching cycles. As the output current rises, the
voltage into the FB pin will rise. If this exceeds VFB then subsequent cycles will be
skipped until the voltage reduces below VFB. Current is sensed from R2 and filtered by
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C4, then fed to the FB pin for accurate regulation. The key to achieving good line
regulation is in balancing the power inductor and sense resistor values after the minimum
inductance has been calculated.
The bypass capacitor (C4) is connected between the FEEDBACK pin and the SOURCE
pin and helps reduce power loss during output current sensing. The capacitor acts to
sample-and-hold the feedback current information for the FB pin. No limiting resistor is
required between the FB pin and C4, because the peak voltage will not exceed the
maximum rating of the device.
4.5 No-Load Protection
Optional, one shot, no-load protection circuit is incorporated in this design. In case of
accidental no-load operation, the output capacitor is protected by VR1. Zener diode VR1
would need to be replaced after a failure.
In operation (LED retrofit lamp), the load is always connected, so VR1 can be removed to
save cost. To protect during board level testing (in manufacturing) 40 VAC can be applied
to the input; if no output current is measured then the load is not connected. This test will
allow safe, non-destructive initial power up of the board, without the need of an OV
protection circuit.
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5 PCB Layout
Figure 4 – Printed Circuit Layout. Top view.
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Figure 5 – Printed Circuit Layout. Bottom View.
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6 Bill of Materials
Item Qty Ref Des Description Manufacturer P/N Manufacturer
1 1 BR1 600 V, 0.5 A, Bridge Rectifier, SMD, MBS-1, 4-SOIC MB6S-TP Micro Commercial
2 1 C1 47 nF, 630 V, Film ECQ-E6473KF Panasonic
3 1 C2 330 nF, 450 V, METALPOLYPRO ECW-F2W334JAQ Panasonic
4 1 C3 100 nF, 25 V, Ceramic, X7R, 0603 VJ0603Y104KNXAO Vishay
5 1 C4 22 F, 16 V, Ceramic, X5R, 1206 EMK316BJ226ML-T Taiyo Yuden
6 1 C5 47 F, 63 V, Electrolytic, Gen. Purpose, (6.3 x 13) 63YXJ47M6.3X11 Rubycon
7 1 D1 600 V, 1 A, Ultrafast Recovery, 35 ns, SMB Case MURS160T3G On Semi
8 1 L1 4.7 mH, 0.150 A, 20% RL-5480-3-4700 Renco
9 1 R1 4.7 k, 5%, 1/8 W, Thick Film, 0805 ERJ-6GEYJ472V Panasonic
10 1 R2 18.7 , 1%, 1/4 W, Thick Film, 1206 ERJ-8ENF18R7V Panasonic
11 1 RF1 4.7 , 5%, 2 W, Metal Film Fusible FW20A4R70JA Bourns
12 1 RV1 275 V, 23 J, 7 mm, RADIAL V275LA4P Littlefuse
13 1 T1 EE10, Bobbin
Inductor
Custom
SNX-R1699
Kunshan Fengshunhe
Santronics USA
14 1 U1 LinkSwitch-0, DIP-8B LYT0006P Power Integrations
15 1 VR1 62 V, 5%, 1 W, DO-41 1N4759A Vishay
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7 Inductor Specification
7.1 Electrical Diagram
Figure 6 – Inductor Electrical Diagram.
7.2 Electrical Specifications
Primary Inductance Pins 4-5, all other windings open, measured at 100 kHz, 0.4 VRMS. 1.4 mH ±7%
7.3 Materials
Item Description
[1] Core: EE10; TDK-PC40EE10/11-Z; or equivalent.
[2] Bobbin: EE10; 8 pins (4/4), Horizontal, PI#: 25-00956-00.
[3] Magnet Wire: #31 AWG, double coated.
[4] Tape: Polyester film, 3M 1350-1, 6.5mm wide.
[5] Varnish.
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7.4 Inductor Build Diagram
Start (P4)
Finish (P5)
Figure 7 – Inductor Build Diagram.
7.5 Transformer Construction
Winding
Preparation
Place bobbin item [2] on the mandrel with pin side 1-4 on the right side.
Winding direction is clockwise direction.
Winding Start pin 4, wind 150 turns of wire item [3] from right to left then left to right in ~6
layers and finish at pin 5.
Tape Secure winding with tape item [4].
Final Assembly Gap cores to get the 1.35 mH inductance. Apply tape to secure both cores.
Remove pins: 2 and 3.
Figure 8 – Transformer Assembly Sample.
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8 Inductor Design Spreadsheet
ACDC_LYTSwitchZero_052813;
Rev.0.8; Copyright Power
Integrations 2013
INPUT INFO OUTPUT UNIT
LYTSwitchZero_Rev_0-8.xls:
LYTSwitchZero Design
Spreadsheet
INPUT VARIABLES
VACMIN 90 90 Volts Minimum AC Input Voltage
VACNOM 120 120
VACMAX 265 265 Volts Maximum AC Input Voltage
FL 60 60 Hertz Line Frequency
VO 54 54 Volts Output Voltage
IO 110 110 mA Output Current
Pout 5.94 W
EFFICIENCY 0.9
0.9
Overall Efficiency Estimate (Adjust to
match Calculated, or enter Measured
Efficiency)
CIN 0.38 0.38 uF Input Filter Capacitor
Input Stage Resistance 4.7 4.7 ohms
Input Stage Resistance, Fuse &
Filtering
Switching Topology Buck Type of Switching topology
DC INPUT VARIABLES
VMIN 54.00068302 Volts Minimum DC Bus Voltage
VMAX 374.766594 Volts
LYTSwitchZero
LYTSwitchZero LYT0006 LYT0006
ILIMIT 0.375 Amps Typical Current Limit
ILIMIT_MIN 0.33275 Amps Minimum Current Limit
ILIMIT_MAX 0.401 Amps Maximum Current Limit
FSMIN 62000 Hertz Minimum Switching Frequency
VDS
4.8375 Volts
Maximum On-State Drain To Source
Voltage drop
DIODE
VD 0.7 Volts
Freewheeling Diode Forward Voltage
Drop
VRR 600 Volts
Recommended PIV rating of
Freewheeling Diode
IF 1 Amps
Recommended Diode Continuous
Current Rating
Diode Recommendation BYV26C Suggested Freewheeling Diode
OUTPUT INDUCTOR
Core type Ferrite Ferrite
Select core type between Ferrite and
Off-the-Shelf
Core size EE10 EE10 Select core size
Custom Core
Enter custom core description (if
used)
AE 12.1 mm^2 Core Effective Cross Sectional Area
LE 26.1 mm Core Effective Path Length
AL 850 nH/T^2 Ungapped Core Effective Inductance
BW 6.6 mm Bobbin Physical Winding Width
NL 149.6667555 Number of turns on inductor
BP 3100 Gauss Peak flux density
LG 2.253983597 mm Gap length
OD
0.132293908
Maximum Primary Wire Diameter
including insulation
INS
0.031219467
Estimated Total Insulation Thickness
(= 2 * film thickness)
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DIA 0.101074441 Bare conductor diameter
AWG 39
Primary Wire Gauge (Rounded to
next smaller standard AWG value)
CM
12.69920842
Bare conductor effective area in
circular mils
CMA
0.112907248
!!! INCREASE CMA > 200 (increase
L(primary layers),decrease NS, use
larger Core)
L 3
LP 1400
1400 uH
Output Inductor, Recommended
Standard Value
L_R 2 2 Ohms DC Resistance of Inductor
IO_Average 112.474696 Average output current
ILRMS
112.474696 mA
Estimated RMS inductor current (at
VMAX)
FEEDBACK COMPONENTS
RFB 18.7
18.7 Ohms
Feedback Resistor. Use closest
standard 1% value
CFB 22 uF Feedback Capacitor
OUTPUT REGULATION
IO_VACMIN 109.393596 mA Output Current at VACMIN
IO_VACNOM 112.474696 mA Output Current at VACNOM
IO_VACMAX 114.3382366 mA Output Current at VACMAX
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9 Performance Data
All measurements performed at room temperature (≈25 ºC) otherwise specified.
Input Input Measurement LED Load Measurement Efficiency
(%)
Regulation
(%)
VAC
(VRMS)
Freq
(Hz)
VIN
(VRMS)
IIN
(mARMS)
PIN
(W) PF VOUT
(VDC)
IOUT
(mADC)
POUT
(W)
90 60 90.07 82.57 6.480 0.871 54.0400 108.050 5.918 91.33 -1.77
100 60 100.11 78.53 6.584 0.838 54.1400 110.150 6.024 91.49 0.14
115 60 110.12 73.24 6.555 0.813 54.1400 110.080 6.006 91.62 0.07
120 60 120.12 69.70 6.566 0.784 54.1600 110.500 6.021 91.70 0.45
132 60 135.16 67.07 6.564 0.724 54.1600 110.590 6.015 91.64 0.54
190 50 190.30 57.15 6.386 0.587 54.0200 107.810 5.836 91.39 -1.99
200 50 200.41 56.02 6.359 0.566 53.9900 107.310 5.805 91.29 -2.45
220 50 220.35 54.16 6.308 0.529 53.9400 106.430 5.749 91.14 -3.25
230 50 230.37 53.68 6.286 0.508 53.9200 106.010 5.723 91.04 -3.63
240 50 264.15 55.86 6.726 0.456 54.2500 112.380 6.098 90.66 2.16
265 50 90.07 82.57 6.480 0.871 54.0400 108.050 5.918 91.33 -1.77
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9.1 Active Mode Efficiency
Figure 9 – Efficiency with Respect to AC Input Voltage. 90-132 VAC (50 Hz) and 190-265 VAC (60 Hz)
Input.
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9.2 Output Current Regulation
9.2.1 Input Line and Load Voltage to Output Current Regulation
Figure 10 – Load Regulation, Room Temperature.
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10 Thermal Performance
10.1 Equipment Used
Chamber: Tenney Environmental Chamber
Model No: TJR-17 942
AC Source: Chroma Programmable AC Source
Model No: 6415
Wattmeter: Yokogawa Power Meter
Model No: WT2000
Data Logger: Yokogawa
Model: 2008-3-4-2-2-1D
SN: S5L409310
Figure 11 – Thermal Chamber Set-up Showing Box Used to Prevent Airflow Over UUT.
Figure 12 – Thermal Unit Thermocouple Measurement Set-up.
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11 Thermal Result
Input: 90 VAC / 60 Hz
Load: 54 V / 110 m A LED load.
Location Temperature Thermal
Shutdown
Thermal
Recovery
Ambient 23.3 38.7 47.9 58.4 70.0 80.0 90.0 100.0 107.9 40.5
Bridge 37.8 52.4 60.8 70.9 80.7 89.6 99.0 108.5 115.1 64.4
L1 37.2 52.7 60.9 71.2 81.9 90.6 100.4 109.9 117.8 60.2
L2 39.4 54.6 63.7 73.9 84.7 93.4 103.2 112.7 120.6 63.0
IC 40.9 56.9 66.1 76.9 87.6 97.5 107.5 117.8 125.0 61.7
Diode 38.0 53.5 62.8 73.5 83.9 93.3 103.1 113.0 120.1 59.4
Table 1 – Thermal Measurement.
Note: Unit will start reliably at -40 C. Tests were performed but are not shown here.
20
30
40
50
60
70
80
90
100
110
120
130
140
10 20 30 40 50 60 70 80 90 100 110 120
Device Temperature (ºC)
Ambient (ºC)
IC
Bridge
L2
L1
O/P Diode
Figure 13 – Thermal Performance Curve.
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11.1 Thermal Scan
Open-frame thermal measurement at 25C ambient. UUT was soaked for 1 hour to
achieve steady-state before the measurement.
Figure 14 – Temperature (C) at Top Side of PCB.
SP1 – U1, LYT0006P.
SP2 – L2, Power Inductor.
SP3 – L1, EMI Choke.
SP4 – FR1, Fusible Resistor.
Figure 15 – Temperature (C) at Bottom Side of PCB.
SP1 – BR1, Bridge Rectifier.
SP2 – PCB, Trace Temperature.
SP3 – D1, Freewheeling Diode.
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12 Waveforms
12.1 Drain Voltage Normal Operation
Figure 16 – 90 VAC, 60Hz, Full Load
F1(Orange): VDRAIN-SOURCE, 100 V / div.
Ch1(Yellow): VDRAIN-GND, 100 V / div.
Ch2(Red): VSOURCE-GND, 100 V, 2 ms / div.
Figure 17 – 265 VAC, Full Load
F1(Orange): VDRAIN-SOURCE, 200 V / div.
Ch1(Yellow): VDRAIN-GND, 200 V / div.
Ch2(Red): VSOURCE-GND, 200 V, 2 ms / div.
Figure 18 – 90 VAC, 60Hz, Full Load
F1(Orange): VDRAIN-SOURCE, 50 V / div.
Ch1(Yellow): VDRAIN-GND, 50 V / div.
Ch2(Red): VSOURCE-GND, 50 V, 2 ms / div.
Z1(Yellow): VDRAIN-GND, 50 V / div.
Z2(Red): VSOURCE-GND, 50 V, 20 s / div.
Figure 19 – 265 VAC, Full Load
F1(Orange): VDRAIN-SOURCE, 200 V / div.
Ch1(Yellow): VDRAIN-GND, 200 V / div.
Ch2(Red): VSOURCE-GND, 200 V, 2 ms / div.
Z1(Yellow): VDRAIN-GND, 200V / div.
Z2(Red): VSOURCE-GND, 200 V, 20 s / div.
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12.2 Drain Current at Normal Operation
Missing pulses are normal and are used to regulate the output current. These missing
pulses are present every time the sense resistor (R2) voltage-drop reaches 1.65 V. The
unit will enter into auto-restart if there is not at least one missing pulse within 50 ms. For
some designs wherein the power inductance is high and operating mostly in CCM, a
reverse current may be present. One way to avoid this is by increasing the device size or
increase input capacitance or adding a blocking diode in the drain. See AN-60 for more
details.
Figure 20 – 90 VAC, 60 Hz, 54 VLED
Ch2(Red): VBULK, 50V / div.
Ch4(Green): IDRAIN, 200 mA / div., 1 ms / div.
Z2(Green): IDRAIN, 100 mA / div., 20 s / div.
Figure 21 – 115 VAC, 60 Hz, 54 VLED
Ch2(Red): VBULK, 50 V / div.
Ch4(Green): IDRAIN, 200 mA / div., 1 ms /
div.
Z2(Green): IDRAIN, 100 mA / div., 20 s / div.
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Figure 22 – 240 VAC, 60 Hz, 54 VLED
Ch2(Red): VBULK, 50 V / div.
Ch4(Green): IDRAIN, 200 mA / div., 1 ms / div.
Z2(Green): IDRAIN, 100 mA / div., 20 s / div.
Figure 23 – 265 VAC, 60 Hz, 54 VLED
Ch2(Red): VBULK, 50 V / div.
Ch4(Green): IDRAIN, 200 mA / div., 1 ms / div.
Z2(Green): IDRAIN, 100 mA / div., 20 s / div.
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12.3 Drain Voltage and Current When Output Short
Device is operating within the range and no inductor saturation was observed.
Figure 24 – LYT0006P Output Short.
Ch4: IDRAIN; 0.2 A / div.
Time Scale: 20 ms / div.
Z4: VDS; 0.2 A / div.
Zoom Time Scale: 5 s / div.
Figure 25 – LYT0006P Output Short.
Ch4: IDRAIN; 0.2 A / div.
Time Scale: 20 ms / div.
Z4: VDS; 0.2 A / div.
Zoom Time Scale: 2 s / div.
12.4 Drain Voltage and Current Start-up Profile
Device is operating within the range and no inductor saturation was observed.
Figure 26 – 265 VAC / 50 Hz Start-up.
Ch1, Z1: SOURCE Pin to Ground; 100 V / div.
Ch2, Z2: Bulk Input; 100 V / div.
Ch4, Z4: IDRAIN; 0.2 A / div.
Time Scale: 100 s / div.
F1: VDS; 100 V / div.
Zoom Time Scale: 500 ns / div.
Figure 27 – 265 VAC / 50 Hz Start-up.
Ch1: SOURCE Pin to Ground; 100 V / div.
Ch2: Bulk Input; 100 V / div.
Ch4: IDRAIN; 0.2 A / div.
Time Scale: 500 ns / div.
F1: VDS; 100 V / div.
F2: Switching Power; 500 W / div.
Zoom Time Scale: 500 ns / div.
18-Jun-13 RDR-355 6 W Non-Isolated Buck Using LYT0006P
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12.5 Output Current Start-up Profile
Output current/light is present in just one AC cycle. <20 ms
Figure 28 – 90 VAC, 60Hz, Full Load
Ch1(Yellow): VIN, 200 V / div.
Ch2(Red): VOUT, 20 V,
Ch3(Blue): IIN, 0.5 A / div.
Ch4(Green): IOUT, 100 mA / div., 20 ms / div.
Figure 29 – 265 VAC, Full Load
Ch1(Yellow): VIN, 200 V / div.
Ch2(Red): VOUT, 20 V,
Ch3(Blue): IIN, 0.5 A / div.
Ch4(Green): IOUT, 100 mA / div., 20 ms / div.
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12.6 Input-Output Profile
There is no limitation to the amount of output capacitance that can be added. If the
application requires less output current ripple then increasing the output capacitance is
straight forward. Note that the output current waveform below will vary depending on LED
load impedance and will vary according to LED type.
Figure 30 – 120 VAC, 60 Hz, Full Load
Ch1(Yellow): VIN, 200 V / div.
Ch2(Red): VOUT, 20 V.
Ch3(Blue): IIN, 0.5 A / div.
Ch4(Green): IOUT, 100 mA / div, 10 ms / div.
Figure 31 – 240 VAC, Full Load
Ch1(Yellow): VIN, 200 V / div.
Ch2(Red): VOUT, 20 V.
Ch3(Blue): IIN, 0.5 A / div.
Ch4(Green): IOUT, 100 mA / div, 10 ms / div.
18-Jun-13 RDR-355 6 W Non-Isolated Buck Using LYT0006P
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12.7 Line Sag and Surge
The inherent advantage of the buck converter implemented with LYTSwitch-0 is the
imperceptible start-up delay, the driver will turn-on within 20 ms as shown in the figures
below. No failure of any component occurred during line fluctuation tests.
Figure 32 – Line sag test at 230 - 0 V at 1 Sec
Interval.
Ch1: VIN; 100 V / div.
Ch2: IOUT; 50 mA / div.
Time Scale: 5 s / div.
Figure 33 – Line Surge Test at 230 - 265 V at 1
Sec Interval.
Ch1: VIN; 100 V / div.
Ch2: IOUT; 50 mA / div.
Time Scale: 5 s / div.
Figure 34 – Line Surge Test at 230 - 265 V at 1 Sec
Interval.
Ch1: VIN; 100 V / div.
Ch2: IOUT; 50 mA / div.
Time Scale: 5 s / div.
Figure 35 – Line Sag Test at 230 - 265 V at 1 Sec
Interval.
Ch1: VIN; 100 V / div.
Ch2: IOUT; 50 mA / div.
Time Scale: 5 s / div.
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12.8 Brown-out/ Brown-in
No failure of any component during brownout test of 0.5 V / sec AC cut-in and cut-off.
Figure 36 – Brown-out Test at 0.5 V / s. The Unit is
Able to Operate Normally Without Any
Failure and Without Flicker.
Ch1: VIN; 100 V / div.
Ch2: IOUT; 50 mA / div.
Time Scale: 100 s / div.
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13 Line Surge
Differential input line 1.2 kV / 50 s surge testing was completed on a single test unit to
IEC61000-4-5. Input voltage was set at 230 VAC / 60 Hz. Output was loaded at full load
and operation was verified following each surge event.
Surge
Level (V)
Input
Voltage
(VAC)
Injection
Location
Injection
Phase (°)
Test Result
(Pass/Fail)
+500 230 L to N 90 Pass
-500 230 L to N 90 Pass
+500 230 L to N 270 Pass
-500 230 L to N 270 Pass
+500 230 L to N 0 Pass
-500 230 L to N 0 Pass
Unit passed under all test conditions.
Differential ring input line surge testing was completed on a single test unit to IEC61000-
4-5. Input voltage was set at 230 VAC / 60 Hz. Output was loaded at full load and
operation was verified following each surge event.
Surge
Level (V)
Input
Voltage
(VAC)
Injection
Location
Injection
Phase (°)
Test Result
(Pass/Fail)
+2500 230 L to N 90 Pass
-2500 230 L to N 90 Pass
+2500 230 L to N 270 Pass
-2500 230 L to N 270 Pass
+2500 230 L to N 0 Pass
-2500 230 L to N 0 Pass
Unit passed under all test conditions.
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Figure 37 – Differential Line Surge at 500 V / 90.
Peak Drain Voltage Recorded is 678 V.
Ch1: VIN; 200 V / div.
Ch2: VDRAIN; 200 V / div.
Ch3: VBULK; 200 V / div.
Time Scale: 1 ms / div.
Figure 38 – Differential Ring Surge at 2500 V / 90.
Peak Drain Voltage Recorded is 468 V.
Ch1: VIN; 200 V / div.
Ch2: VDRAIN; 200 V / div.
Ch3: VBULK; 200 V / div.
Time Scale:1 ms / div.
18-Jun-13 RDR-355 6 W Non-Isolated Buck Using LYT0006P
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14 Conducted EMI
9 kHz 30 MHz
dBµV
dBµV
2 A
V
CLRW
R
SGL
TDF
6DB
1 QP
CLRW
R
Att 10 dB AUTO
100 kHz 1 MHz 10 MHz
-20
-10
0
10
20
30
40
50
60
70
80
90
100
110
120
LIMIT CHECK PASS
EN55015A
EN55015Q
Figure 26 – Conducted EMI, Maximum Steady State Load, 120 VAC, 60 Hz, and EN55015 B Limits.
EDIT PEAK LIST (Final Measurement Results)
Trace1: EN55015Q
Trace2: EN55015A
Trace3: ---
TRACE FREQUENCY LEVEL dBµV DELTA LIMIT dB
2 Average 9.9415991287 kHz 22.25 N gnd
2 Average 67.8393045788 kHz 23.52 N gnd
2 Average 134.789536006 kHz 38.77 N gnd
1 Quasi Peak 165.693318812 kHz 47.45 L1 gnd -17.72
2 Average 167.350252 kHz 33.66 N gnd -21.42
2 Average 200.175581485 kHz 38.55 N gnd -15.05
1 Quasi Peak 204.199110673 kHz 45.87 N gnd -17.56
2 Average 267.135089486 kHz 34.58 N gnd -16.62
1 Quasi Peak 272.504504785 kHz 44.83 N gnd -16.20
2 Average 397.727746704 kHz 31.37 N gnd -16.53
1 Quasi Peak 401.705024172 kHz 41.34 N gnd -16.47
1 Quasi Peak 475.741040231 kHz 40.79 N gnd -15.62
1 Quasi Peak 536.076911993 kHz 39.85 N gnd -16.14
1 Quasi Peak 610.105531335 kHz 41.66 N gnd -14.33
1 Quasi Peak 806.126927408 kHz 43.14 N gnd -12.85
2 Average 806.126927408 kHz 33.29 N gnd -12.70
1 Quasi Peak 1.00339897152 MHz 39.33 N gnd -16.66
2 Average 2.03372014292 MHz 26.57 N gnd -19.42
1 Quasi Peak 29.2697736439 MHz 43.21 L1 gnd -16.78
2 Average 29.5624713804 MHz 34.37 L1 gnd -15.62
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Table 2 – Conducted EMI, Maximum Steady State Load, 120 VAC, 60 Hz, and EN55015 B Limits.
Power Integrations
9 kHz 30 MHz
dBµV
dBµV
2 A
V
CLRW
R
SGL
TDF
6DB
1 QP
CLRW
R
17.Oct 12 21:24
RBW 9 kHz
MT 500 ms
Att 10 dB AUTO
100 kHz 1 MHz 10 MHz
-20
-10
0
10
20
30
40
50
60
70
80
90
100
110
120
LIMIT CHECK PASS
EN55015A
EN55015Q
Figure 27 – Conducted EMI, Maximum Steady State Load, 230 VAC, 60 Hz, and EN55015 B Limits.
EDIT PEAK LIST (Final Measurement Results)
Trace1: EN55015Q
Trace2: EN55015A
Trace3: ---
TRACE FREQUENCY LEVEL dBµV DELTA LIMIT dB
2 Average 134.789536006 kHz 37.65 L1 gnd
2 Average 200.175581485 kHz 41.49 N gnd -12.10
2 Average 267.135089486 kHz 39.23 N gnd -11.97
2 Average 332.507282579 kHz 35.66 N gnd -13.72
2 Average 475.741040231 kHz 33.70 N gnd -12.71
1 Quasi Peak 592.16241791 kHz 45.66 N gnd -10.33
2 Average 592.16241791 kHz 35.36 N gnd -10.63
1 Quasi Peak 667.263434405 kHz 48.66 N gnd -7.33
2 Average 667.263434405 kHz 36.60 N gnd -9.39
1 Quasi Peak 744.444692652 kHz 48.12 N gnd -7.87
1 Quasi Peak 872.919948931 kHz 50.67 N gnd -5.32
2 Average 872.919948931 kHz 38.46 N gnd -7.53
1 Quasi Peak 954.699692378 kHz 47.91 N gnd -8.08
1 Quasi Peak 1.02356729084 MHz 47.16 N gnd -8.83
1 Quasi Peak 1.55458365781 MHz 43.77 N gnd -12.22
1 Quasi Peak 2.50634031306 MHz 42.47 N gnd -13.53
2 Average 2.93888112801 MHz 31.88 N gnd -14.11
1 Quasi Peak 29.2697736439 MHz 48.08 L1 gnd -11.91
2 Average 29.2697736439 MHz 40.24 L1 gnd -9.75
18-Jun-13 RDR-355 6 W Non-Isolated Buck Using LYT0006P
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Table 3 – Conducted EMI, Maximum Steady State Load, 230 VAC, 60 Hz, and EN55015 B Limits.
15 Audible Noise
Input voltage were sweep from 90V to 265Vac at 60Hz line input.
PI Standard Audio Noise (do not edit).at2
Color Line Style Thick Data Axi s
Cyan Solid 1Fft.Ch.1 Am pl Left
Green Solid 1Fft.Ch.1 Am pl Left
Yellow Solid 1Fft.Ch.1 Am pl Left
-30
+80
-20
-10
+0
+10
+20
+30
+40
+50
+60
+70
d
B
r
A
2k 22k4k 6k 8k 10k 12k 14k 16k 18k 20k
Hz
Figure 39 – Noise from the UUT at 1 cm from the Center of the Board to Microphone Receiver Position.
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16 Appendix
Types of overvoltage protection for a buck converter:
Figure 40 – Simple and cheapest approach is to add a Zener diode across the output terminals. In case of
no load, the Zener diode will short in order and protect the output capacitor. IC U1 will be limited by the
primary current limit. Note that the Zener diode will need to be replaced after this event.
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Figure 41 – Auto-recovery OVP latch protection. Once AC input is recycled for 2s, the unit will function
normally once load is connected. Advantage is lowest no-load consumption and non-damaging failure.
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Figure 42 – Constant voltage (CV) mode protection. Load can be connected anytime without AC recycle.
Disadvantage is it will require some pre-load in order to regulate, which decreases efficiency. Pre-load can
be replaced by a appropriately rated Zener in series with a resistor if efficiency is a concern.
OVP Protection Pros Cons
Zener 1. Cheapest and simple.
2. VOUT 0 V at no-load; safe.
1. Non-auto recovery. Replace
Zener once fault is removed.
SCR Latch
1. Auto-recovery.
2. Lowest no-load consumption.
3. VOUT 0 V at no-load; safe.
1. Cost.
2. Requires AC recycle for
recovery.
Constant
Voltage Mode
1. Hot-plug, load can be
connected anytime.
1. Consumes extra power.
2. Residual voltage at no-load.
3. Cost.
Table 4 – Overvoltage Protection Comparison.
18-Jun-13 RDR-355 6 W Non-Isolated Buck Using LYT0006P
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17 Revision History
Date Author Revision Description & changes Reviewed
18-Jun-13 JDC 1.0 Initial Release Apps & Mktg
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For the latest updates, visit our website: www.powerint.com
Power Integrations reserves the right to make changes to its products at any time to improve reliability or manufacturability.
Power Integrations does not assume any liability arising from the use of any device or circuit described herein. POWER
INTEGRATIONS MAKES NO WARRANTY HEREIN AND SPECIFICALLY DISCLAIMS ALL WARRANTIES INCLUDING,
WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
PURPOSE, AND NON-INFRINGEMENT OF THIRD PARTY RIGHTS.
PATENT INFORMATION
The products and applications illustrated herein (including transformer construction and circuits’ external to the products)
may be covered by one or more U.S. and foreign patents, or potentially by pending U.S. and foreign patent applications
assigned to Power Integrations. A complete list of Power Integrations’ patents may be found at www.powerint.com. Power
Integrations grants its customers a license under certain patent rights as set forth at http://www.powerint.com/ip.htm.
The PI Logo, TOPSwitch, TinySwitch, LinkSwitch, LYTSwitch, DPA-Switch, PeakSwitch, CAPZero, SENZero, LinkZero, HiperPFS,
HiperTFS, HiperLCS, Qspeed, EcoSmart, Clampless, E-Shield, Filterfuse, StackFET, PI Expert and PI FACTS are trademarks of Power
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