3x1w led driver solution using ap3766

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10.5V 350mA Led Driver solution using AP3766

Version 2.0 1


BCD Semiconductor Manufacturing Limited

11/12/2009

Summary of Report

Specifications 85~264Vac, 10.5V/350mA

Applications Led Driver

Key features

Primary Side Regulation (PSR) solution without opto-coupler

±10% constant current regulation

Pass EN55022 Class B with over 6dB margin with output grounding

High reliability guaranteed by built-in multi-protection functions,

e.g. soft-start, OVP, OCkP (Open Circuit Protection) and SCP (Short

Circuit Protection) functions

Cost effective total charger solution ,22 components in all



10.5V 350mA LED Driver Solution Using AP3766

Version 2.02

Contents

1. Introduction........................................................................................................................... 3

2.Specifications......................................................................................................................... 5

3.Schematic............................................................................................................................... 6

4.Circuit Description ............................................................................................................... 6

4.1. AC input filter:........................................................................................................... 6

4.2. Power converter:........................................................................................................ 6

4.3. AP3766 related circuitry: ........................................................................................... 7

5.BOM and transformer specifications.................................................................................. 8

5.1. BOM .......................................................................................................................... 8

5.2. Transformer specifications......................................................................................... 9

5.2.1. Electrical Diagram......................................................................................... 9

5.2.2. Electrical Specifications................................................................................ 9

5.2.3. Materials........................................................................................................ 9

5.2.4. Transformer Build Diagram ........................................................................ 10

5.2.5. Transformer Construction............................................................................ 10

6.PCB layout............................................................................................................................11

7.Electrical performance....................................................................................................... 12

7.1. Current Test &Active mode efficiency .................................................................... 12

7.2. No load input power ................................................................................................ 13

8.Thermal performance ........................................................................................................ 14

9.Key Operating Waveforms ................................................................................................ 14

9.1. Output ripple Current............................................................................................... 14

10. EMI test results................................................................................................................. 17

10.1. Conducted EMI...................................................................................................... 17

11. Summary of test results .................................................................................................. 18

12. Revision history ............................................................................................................... 18




Version 2.0 3

1. Introduction

This report describes a 3W constant current universal input power supply for LED

Driver or similar applications. This design was based on BCD’s new generation 5-Star

Primary Side Regulation (PSR) controller, AP3766. The mechanic dimensions are 26mm in

length, 17 mm in width and 18mm in height.

Figure 1. Photo of 10.5V 350mA Led Driver demo board (Top view and bottom view)

The AP3766 is a general use AC/DC power supply controller for the cost effective

battery charger and adapter application. It can achieve constant voltage and constant current

(CV and CC) regulation without requiring an opto-coupler and secondary control circuitry.

Meanwhile, it also eliminates the need of loop compensation circuitry while maintaining

system stability. With the unique random frequency dithering technique, AP3766 system can

get good EMI performance.

Compared with the traditional Pulse Width Modulation control for CV and CC control

technique, this device uses Pulse Frequency Modulation (PFM) technique to achieve tight CV

and CC regulation, which guarantees high efficiency at light loading and makes the charger

system built with AP3766 easily to pass the active mode efficiency criteria of Energy Star

EPS 2.0. Designed to work in Discontinuous Current Mode (DCM), the power system using

the AP3766 operates with constant primary peak current and the CV regulation is realized by

modulating switching frequency. So the switching frequency presents a linear characteristic

with the change of the loading. The CC regulation is implemented by a fixed ratio between

the conduction time and off time of the secondary schottky rectifier. The detailed operation

principle can refer to the datasheet of AP3766.

The AP3766 consists of a 5V regulator, CV feedback and logic circuitry, constant peak




Version 2.04

current setting circuit, leading edge blanking circuit, optimized BJT driver circuitry, over

voltage/open circuit protection (OVP/OCkP) circuitry and a PFM controller for CV and CC

frequency modulation.

With the built-in soft-start, OVP, OCkP and SCP (Short Circuit Protection) functions,

the AP3766 can achieve high reliability in abnormal conditions without additional

components and cost.

This document contains the power supply specification, schematic, BOM (bill of

materials) including transformer architecture, PCB layout and key performance features with

detailed test data and waveforms.




Version 2.0 5

2. Specifications

Description Min Typ Max Units Conditions

Input

Voltage

Frequency

No Load Input Power

85

47 50/60

264

63

150

VAC

Hz

mW

Output

Output Voltage

Output Ripple VoltageOutput Current

Output Power (Pno)

Output Voltage rise Time

8.4

315

10

350

3.5

11

300385

20

V

mAppmA

W

ms

20M bandwidth

Efficiency

Average Efficiency at

25,50,75 and 100 % of

Pno (EPS 2.0) ---note 1

70 %

EMI Pass EN55022 Class B with 6dB margin

Surge test IEC61000-4-5 Class 3

ESD IEC6100-4-2 Class 4

Note 1:

The active mode average efficiency criterion of Energy Star EPS 2.0 was

calculated as follow:

Table 1. EPS 2.0 Active Mode Efficiency Criteria

Low voltage Model

(Nameplate Vo< 6V and

nameplate Io≥ 550mA)

1< to <49W [0.075*Ln(Pno)]+0.561

Standard Model 1< to <49W [0.0626*Ln(Pno)]+0.622




Version 2.06

3. Schematic

+

ACBD1

C1

FR1

D1T1

D2

C2

OUT

C4

+

R9

FB

R6

R1

R4Out

R7R5

CS

GND

AP3766SOT-23-5

Q1

C3

U1

R3

L1

Vcc

R8

1

2

3

4

5

R2

RV1

APT27TO-92

Figure 2. Schematic of 10.5V 350mA Led Driver demo board

4. Circuit Description

The power supply use AP3766 to realize a primary side regulation flyback converter.

4.1. AC input filter:The AC line voltage is rectified by BD1 to a DC bus voltage. L1, and C1 compose a

filter to achieve good EMI performance in attenuating the differential mode EMI noise. FR1

is used to limit the input surge current and also work as a fuse for ultimate protection in any

catastrophic failure.

4.2. Power converter:

In the main power supply topology of a layback converter, the transformer T1 is

magnetized and demagnetized by on/off control of the BJT transistor Q1. Thus the DC bus

voltage in the primary side is converted to AC voltage on the secondary winding of T1. By an

optimized driving circuitry within the AP3766, the maximum allowable peak voltage across

the collector of Q1 is Vces, which makes the use of popular BJT transistor with 450V Vceo

and 700V Vces feasible.

The output rectification circuitry is made up of a schottky diode D2 and an electrolytic

capacitors C2. A dummy load R6 is used to control the output voltage in no load condition to




Version 2.0 7

an acceptable level.

4.3. AP3766 related circuitry:

A common auxiliary winding is adopted in this schematic for both CV feedback and

bias supply. CV feedback and bias supply can be separated as two windings to achieve tighter

CV regulation. In the CV feedback network, R4 and R5 are required to use the resistors with

1% precision. And D1 and C3 constitute the bias supply circuitry for the AP3766. In order to

ensure good driving effect for Q1, C3 should be placed as close as possible to Vcc pin of the

AP3766

R1 and R3 compose the startup resistor and 1.5M ohm is recommended for the sum of

these two resistors considering the tradeoff between a reasonable startup time and guaranteed

reliable startup at low AC line. The primary peak current of the flyback converter is set by the

current sense resistor R7 with 1% precision. The ratio of RV1 to R2 determine the line

compensation to eliminate the variation of CC regulation with the line voltage.




Version 2.08

5. BOM and transformer specifications

5.1. BOM

Item Description QTY

C1 4.7uF/400V, 85°C, 8*12 electrolytic 1

C2 22uF/16V, 85°C, Tan Capacitor 1

C3 4.7uF/25V, 1206 X7R 1

C4 1000pF/100V,1206,X7R 1

D1 RS1M Fast Recovery Diode SMD 1

D2 SS110, Schottky DIODE,SMA 1

BD1 1UB60, Diode Bridge 1

L1 4.7mH,Inductor 1

FR1 12 ohm, 1/2 W, Fuse resistor 1

R1 2Mohm, 1%,1206, resistor 1

R2 5.1M ohm, 5%,0603, resistor 1

R3 470Kohm, 5%, 0603, resistor 1

R4 20K ohm, 5%, 0603, resistor 1

R5 5.1k ohm, 5%, 0603, resistor 1

R6 15k ohm, 5%,0603, resistor 1

R7 2ohm, 1%,1206, resistor 1

R8 10ohm 5%,0805, resistor 1

R9 43 ohm, 5%,1206, resistor 1

RV1 4.7k ohm, 5%,0603, resistor 1

T1 EPC13 5+5pin 1.8mH 8%,Transformer 1

U1 AP3766KTR-G1, SOT23-5, BCD’s IC 1

Q1 APT27ZTR-G1, TO-92, BCD’s BJT 1




Version 2.0 9

5.2. Transformer specifications

5.2.1. Electrical Diagram

Figure 3. Transformer electrical diagram

5.2.2. Electrical Specifications

Primary InductancePin3-4 all other windings open, measured at

1kHz, 0.4VRMS1.8mH,±8%

Primary Leakage

Inductance

Pin3-4,all other windings shorted, measured at

10kHz, 0.4VRMS50uH (Max)

Electrical Strength 60 seconds, 60HZ, from Pin 3-4 to Pin9-8 3000Vac

5.2.3. Materials

Item Description

[1] Core:EPC13, PC40 or equivalent

[2] Bobbin: EPC13, Horizontal, 10 Pin, (5/5)

[3] Wire: ø0.1mm, for Auxiliary Winding

[4] Wire: ø0.1mm, for Primary Winding

[5] Triple Insulated Wire: ø0.25mm for Secondary Winding

[6] Tape: 0.05mm thick, 7.0 mm wide

[7] Copper film: 0.05mm thick, 6.5 mm wide 27mm longth

[8] Glue




Version 2.010

5.2.4. Transformer Build Diagram

Figure 4. Transformer Build Diagram

5.2.5. Transformer Construction

Winding Sequence: Begin from the central column of the Bobbin. Primary side of the bobbin is

laced on the left hand side, and secondary side of the bobbin is placed on the right hand side.

WD 1Auxiliary winding

Start at Pin2. Wind 44 turns of ø0.1mm wire [3] from left to right. Wind tightl

& spread evenly in the middle.

Insulation 1 Layers of insulation tape [6], 0.05mm thick, 8.0mm wide.

WD 2

Primary Winding

Start at Pin 4. Wind 48 turns of ø0.1mm wire [4] from left to right. Wind

the next 46 turns on the next layer from right to left. Wind the last 44

turns from right to left on the side of primary. Finish on Pin 3. Wind

tightly & spread evenly.

Insulation 1 Layer of insulation tape [6], 0.05mm thick, 7.0mm wide.

ShieldCopper shield [7], 6.5mm wide, 27mm long. Connected to Pin 1 on the side of

primary.


WD 3

Secondary winding

Start at Pin 9. Wind 29 turns of ø0.25mm Triple Insulated Wire [5] from right

to left (to the opposite direction). Terminate on Pin 8. Wind tightly & spread

evenly.




Version 2.0 11


Glue Glue core and bobbin[8]

6. PCB layout

The PCB layout rules are highlighted as follow:

1. The loop area composed by the input capacitor, the primary winding of the

transformer, power transistor Q1 and current sense resistor R7 should be minimized

for better EMI performance

2. The power ground and signal ground should be connected by one node.

Figure 5. Printed circuit layout




Version 2.012

7. Electrical performance

All the test results were obtained at room temperature unless otherwise specified, with

50 Hz line voltage Load 3 LED..

7.1. Current Test &Active mode efficiency

The charger system passes active mode average efficiency criteria of Energy Star EPS

2.0 final version. The active efficiency criteria follow the formula for low voltage mode and

can be calculated as 70%.

Table 2. Iout and efficiency test results

AC Vin(V) Iout(mA) Vout(V) Pin(W) Efficiency(%)85 349 9.65 4.647 69.6

90 352 9.64 4.613 70.4

110 357 9.617 4.566 72.4

150 360 9.61 4.494 73.8

180 361 9.59 4.48 73.6

230 348 9.59 4.657 72.3

240 342 9.57 4.752 72.1264 342 9.55 4.83 71.0

Figure 6. Vin Vs Iout




Version 2.0 13

Figure 7. Vin Vs Efficiency

7.2. No load input power

The readings of input power were recorded only after the power supply had worked for

5 minutes under no load condition.

Table 3. No Load Input Power

No.

Input

Voltage

(V)

Input Power(mW) No.

Input

Voltage

(V)

Input Power(mW)

85 182 85 180

115 186 115 181

145 197 145 195

180 212 180 210

230 244 230 243

1#

264 275

2#

264 272

Less than 300mW@230Vac




Version 2.014

8. Thermal performance

The thermal performance was measured in a carton without the airflow, which was put

into a 75 O

C chamber, and after the power supply had worked for 1 hour under full load

condition. Two thermocouples were attached to the case of U1 and Q1 firmly.

Table 4. Thermal performance of key components

Item 115Vac 230Vac

U1

(AP3766)98

．

C 99．

C

Q1

(APT27) 94

．

C 95

．

CD1

(SS110)98

．

C 100．

C

T1 98．

C 100．

C

TA 75．

C 75．

C

9. Key Operating Waveforms9.1. Output ripple Current

All measurements were made with an oscilloscope with 20 MHz bandwidth and the

output was bypassed at the connector with a 0.1 µF ceramic disk capacitor and a 10 µF

electrolytic capacitor.




Version 2.0 15

Figure 8. Ripple,115Vac, Full Load, 20us,

50mA/div, peak-peak: 358mA

Figure 9. Ripple, 230Vac, Full Load, 20us

50mA/div, peak-peak: 434mA

9.2 Startup characterize

Figure 10. Vo start up waveform@Vin=115V Full load




Version 2.016

Figure 11 Vo start up waveform@Vin=230V full load

9.3. Collector voltage of power transistor

Figure 12. Collector voltage, Vin=265Vac, full load. 100V, 20us/div.




Version 2.0 17

10. EMI test results

10.1. Conducted EMI

RBW 9 kHz

MT 1 s

PREAMP OFFAtt 10 dB

TDF

6DB

dBµV

dBµV

2 AV

CLRWR

SGL

TDF

6DB

1 PK

CLRWR

1 MHz 10 MHz

-10

0

10

20

30

40

50

60

70

-10 0 10 20 30 40 50 60 70

FREQUENCY 24.0620000 MHz

LEVEL AV 37.69 dBµV

-10 0 10 20 30 40 50 60 70



-10 0 10 20 30 40 50 60 70



EN55022A

EN55022Q

EDIT PEAK LIST (Final Measurement Results)

Trace1: EN55022Q

Trace2: EN55022A

Trace3: ---

TRACE FREQUENCY LEVEL dBµV DELTA LIMIT dB

1 Quasi Peak 302 kHz 48.17 -12.00

2 Average 326 kHz 35.00 -14.54

1 Quasi Peak 382 kHz 49.61 -8.62

2 Average 382 kHz 40.06 -8.17

2 Average 1.85 MHz 27.65 -18.34

1 Quasi Peak 2.074 MHz 40.19 -15.80

2 Average 3.718 MHz 34.88 -11.12

1 Quasi Peak 4.406 MHz 41.89 -14.10

1 Quasi Peak 6.198 MHz 40.70 -19.29

2 Average 6.842 MHz 26.87 -23.12

1 Quasi Peak 20.098 MHz 29.64 -30.36

2 Average 20.098 MHz 22.11 -27.88

Figure 13. Conducted EMI, 230VAC/50Hz, full load, Neutral

RBW 9 kHz

MT 1 s

PREAMP OFFAtt 10 dB

TDF

6DB

dBµV

dBµV

2 AV

CLRWR

SGL

TDF

6DB

1 PK

CLRWR

1 MHz 10 MHz

-10

0

10

20

30

40

50

60

70

-10 0 10 20 30 40 50 60 70



-10 0 10 20 30 40 50 60 70



-10 0 10 20 30 40 50 60 70



EN55022A

EN55022Q

na easuremen esu s)

Trace1: EN55022Q

Trace2: EN55022A

Trace3: ---

TRACE FREQUENCY LEVEL dBµV DELTA LIMIT dB2 Average 322 kHz 39.12 -10.53

1 Quasi Peak 326 kHz 48.14 -11.41

1 Quasi Peak 378 kHz 48.10 -10.21

2 Average 378 kHz 42.21 -6.11

1 Quasi Peak 1.146 MHz 44.09 -11.90

2 Average 1.146 MHz 35.89 -10.10

1 Quasi Peak 3.898 MHz 46.08 -9.91

2 Average 4.726 MHz 33.16 -12.83

1 Quasi Peak 6.746 MHz 42.96 -17.03

2 Average 6.746 MHz 27.19 -22.80

1 Quasi Peak 24.058 MHz 33.78 -26.21

2 Average 24.062 MHz 33.73 -16.26

Figure 14. Conducted EMI, 230VAC/50Hz, full load, Line



5V/350mA Battery Charger Solution Using AP3766

Version 1.0 18

11. Summary of test results

Description Min Typ Max Units Tested results

Input

Voltage

Frequency

No Load Input Power

85

47 50/60

264

63

150

VAC

Hz

mW <110mW@230

Vac

Output

Output Voltage

Output Ripple Current

Output Current

Output Power (Pno)

Output Voltage rise Time

8.4

315

10

350

3.5

11

300

385

20

V

mApp

mA

W

ms

Pass

<154

Pass

Pass

Pass

Efficiency

Average Efficiency at

25,50,75 and 100 % of

Pno (EPS 2.0) ---note 1

70 %

72 at 115Vac;

72 at 230Vac

(26# cable)

EMI Pass EN55022 Class B with 6dB margin Pass

12. Revision history

Versions Date Author Descriptionfor changes

Reviewed

Version 1.0 12/25/2008 Jiao Yu Initial release

Version 2.0 11/12/09 Simon.ZhuUpdate to

AP3766

3x1w led driver solution using ap3766

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