NCL30088LED1GEVB - ON Semiconductor

November, 2014 − Rev. 0

1Publication Order Number:

EVBUM2285/D

NCL30088LED1GEVB

18 W High Power Factor

LED Driver Evaluation Board

User'sManual

Overview

This manual covers the specification, theory of operation,

testing and construction of the NCL30088LED1GEVB

demonstration board. The NCL30088 board demonstrates a

18 W high PF buck boost LED driver in a typical T8 outline.

Table 1. SPECIFICATIONS

Parameter Value Comment

Input voltage (Class 2 Input,

no ground)

100 − 277

V ac

Line Frequency 50 Hz / 60 Hz

Power Factor (100% Load) 0.9 Min

THD (Load > 30%) 20% Max

Output Voltage Range 90 − 180 V dc

Output Current 100 mA dc ±2%

Efficiency 92% Typical

Start Up Time < 500 msec Typical

EMI (conducted) Class B FCC/CISPR

Key Features

As illustrated, the key features of this evaluation board

include:

•Wide Mains

•Low THD across Line and Load

•High Power Factor across Wide Line and Load

•Integrated Auto Recovery Fault Protection (can be

latched by Choice of Options)

♦Over Temperature on Board (a PCB mounted NTC)

♦Over Current

♦Output and Vcc Over Voltage

Figure 1. Evaluation Board Picture (Top View)

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EVAL BOARD USER’S MANUAL

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THEORY OF OPERATION

Power Stage

The power stage for the demo board is a non−isolated

buck−boost based. The controller has a built in control

algorithm that is specific to the flyback transfer function.

Specifically:

Vout

Vin +Duty

(1*Duty)

This is applicable to flyback, buck−boost, and SEPIC

converters. The control is very similar to the control of the

NCL30080−83 with the addition of a power factor

correction control loop. The controller has a built in

hardware algorithm that relates the output current to a

reference on the primary side.

Iout +Vref Nps

2 Rsense

Nps +Npri

Nsec

Where Npri = Primary Turns and Nsec = Secondary Turns

We can now find Rsense for a given output current.

Rsense +Vref Nps

2 Iout

Line Feedforward

The controller is designed to precisely regulate output

current but variation input line voltage do have an impact.

R3 sets the line feedforward and compensates for power

stage delay times by reducing the current threshold as the

line voltage increases. R3 is also used by the shorted pin

detection. At start up the controller puts out a current to

check for a shorted pin. If R3 is zero, the current sense

resistor is too low a value and the controller will not start

because it will detect a shorted pin. So R3 is required to make

the controller operate properly. In practice, R3 should be

greater than 250 W.

Voltage Sense

The voltage sense pin has several functions:

1. Basis for the reference of the PFC control loop

2. Line Range detection

The reference scaling is automatically controller inside

the controller. While the voltage on Vs is not critical for the

PFC loop control, it is important for the range detection.

Generally the voltage on Vs should be 3.5 V peak at the

highest input voltage of interest. The voltage on Vs

determines which valley the power stage will operate in. At

low line and maximum load, the power stage operates in the

first valley (standard CrM operation). At the higher line

range, the power stage moves to the second valley to lower

the switching frequency while retaining the advantage of

CrM soft switching.

Auxiliary Winding

The auxiliary winding has 3 functions:

1. CrM timing

2. Vcc Power

3. Output voltage sense

CrM Timing

In the off time, the voltage on the transformer/inductor

forward biases Dout and D9. When the current in the

magnetic has reached zero, the voltage collapses to zero.

This voltage collapse triggers a comparator on the ZCD pin

to start a new switching cycle. The ZCD pin also counts rings

on the auxiliary winding for higher order valley operation.

A failure of the ZCD pin to reach a certain threshold also

indicates a shorted output condition.

Vcc Power

The auxiliary winding forward biases D9 to provide

power for the controller. This arrangement is called a

“bootstrap”. Initially the Cvcc, is charged through R4 and

R5. When the voltage on Cvcc reaches, the startup threshold,

the controller starts switching and providing power to the

output circuit and the Cvcc. Cvcc discharges as the

controller draws current. As the output voltage rises, the

auxiliary winding starts to provide all the power to the

controller. Ideally, this happens before Cvcc discharges to

the under voltage threshold where the controller stops

operating to allow Cvcc to recharge once again. The size of

the output capacitor will have a large effect on the rise of the

output voltage. Since the LED driver is a current source, the

rise of output voltage is directly dependent on the size of the

output capacitor.

There are tradeoffs in the selection of Cout and Cvcc. A

low output ripple will require a large Cout value. This

requires that Cvcc be large enough to support Vcc power to

the controller while Cout is charging up. A large value of

Cvcc requires that R4 and R5 be lower in value to allow a fast

enough startup time. Smaller values of R4 and R5 have

higher static power dissipation which lowers efficiency of

the driver.

Output Voltage Sense

The auxiliary winding voltage is proportional to the

output voltage by the turns ratio of the output winding and

the auxiliary winding. The controller has an overvoltage

limit on the Vcc pin at about 26 V minimum. Above that

threshold, the controller will stop operation and enter

overvoltage fault mode such as when an open LED string

occurs.

In cases where the output has a lot of ripple current and the

LED has high dynamic resistance, the peak output voltage

can be much higher than the average output voltage. The

auxiliary winding will charge the Cvcc to the peak of the

output voltage which may trigger the OVP sooner than

expected so in this case the peak voltage of the LED string

is critical.

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SD Pin

The SD pin is a multi−function protection input.

1. Thermal Foldback Protection

2. Programmable OVP

Thermal Protection

There is an internal current source from the SD pin.

Placing an NTC from the SD pin to ground will allow the

designer to choose the level of current foldback protection

from over temperature. Below 0.5 volts on SD, the controller

stops. Series or parallel resistors on the NTC and shape the

foldback curve. In the event that the pin is left open, there is

a soft voltage clamp at 1.35 V (nominal). Output current is

reduced when the voltage on the SD pin drops below 1 V.

Programmable OVP

While the SD pin has a current source for the OTP, it can

be overcome raising the voltage on the SD pin. At about

2.5 V, the SD pin detects an OVP and shuts down the

controller. Typically, a zener to Vcc is used for this. In this

way, the designer can set the OVP to a lower value that the

OVP threshold built into the Vcc pin.

Circuit Modifications

Output Current

The output current is set by the value of Rsense as shown

above. It’s possible to adjust the output current by changing

R7. Since the magnetic is designed for 18 W, it is possible

to increase the current while reducing the maximum LED

forward voltage within limits. Changes of current of ±10%

are within the existing EMI filter design and magnetic,

changes of more than 10% may require further adjustments

to the transformer or EMI filter.

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SCHEMATIC

Figure 2. Input Circuit

120nF 450V

3.3mH

+HVDC_iso

R11

5.1k

R10

5.1k

FUSE +

−

AC1

AC2

MB6S

+HVDC

AC_L 1

AC_N 1

1.5mH

120nF 450V

Figure 3. Main Schematic

+HVDC_iso

R14

75k 1/2W

Dout

US1K−TP

NCL30088D

Vcc 8

Cs 5

Gnd 6

Comp

ZCD

2Drv 7

BAS21DW5T1G

CVcc1

6.8uF

4.7

C11

R16

1 Meg

C10

1uF

C12

R15

75k 1/2W

620k

10k

Rsens

1.00

LED−

LED+

Rtco

100k Ohm NTC

Rzcd

56k

STU8N80K5

Cout

18uF 200V

620

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BILL OF MATERIAL

Table 2. BILL OF MATERIAL*

Qty Reference Part Manufacturer Mfr_PN PCB Footprint

Substitution

Allowed

1 Cvcc1 6.8 mFTDK C3216X7R1V685K160AC 1206 Yes

1 Cout 18 mF 200 V Rubycon 200LLE18MEFC10X12.5 ALEL_10X12M5_V

ERT

Yes

2C4, C5 120 nF 450 V Panasonic ECW−FD2W124KQ CAP_BOX_12M6X

4M6_LS10

Yes

1 C10 1 mFTaiyo Yuden TMK105BJ105MV−F 402 Yes

2C11, C12 1 n Kemet C0402C102K3GACTU 402 Yes

1 Dout US1K−TP MCC US1K−TP SMA Yes

1 D4 MB6S MCC MB6S MB6S Yes

1 D9 BAS21DW5T1G ON Semiconductor BAS21DW5T1G SC−88A No

1 F1 FUSE Littelfuse 0263.500WRT1L FUSE−HAIRPIN−L

S250

Yes

2L1, L2 3.3 mH Wurth 744772332 RAD_IND_LS5 Yes

1 L3 1.5 mH Wurth 744772152 RAD_IND_LS5 Yes

1 Q1 STU8N80KS ST STU8N80K5 IPAK Ye s

1 Rtco 100 kW NTC Epcos B57331V2104J60 603 Yes

1 Rzcd 56k Yaego RC1206FR−0756KL 1206 Yes

1 R1 620k Yaego RC1206FR−07620KL 1206 Yes

1 R2 10k Yaego RC0402FR−0710KL 402 Yes

1 R3 620 Yaego RC0402FR−07620RL 402 Yes

1 R5 4.7 Yaego RC1206FR−074R7L 1206 Yes

2R10, R11 5.1k Yaego RC1206FR−075K1L 1206 Yes

2R14, R15 75k ½ WStackpole RNCP1206FTD75K0 1206 Yes

1 R16 1 Meg Yaego RC1206JR−071ML 1206 Yes

1 T1 XFRM_LINEAR Wurth 750314731 RM6_4P Yes

6” W1 Wire, Red, 24AWG McMaster Carr 7587K922 UL1569 Yes

6” W2 Wire, Blk, 24AWG McMaster Carr 7587K921 UL1569 Yes

12” W3, W4 Wire, Wht, 24AWG McMaster Carr 7587K924 UL1569 Yes

*All Components to comply with RoHS 2002/95/EC

Construction Options

NCL30088B Revision 00

1 U2 NCL30088B ON Semiconductor NCL30088B SO8 No

1 Rsens 1.13 Yaego RC1206FR−071R13L 1206 Yes

1 R4 No Stuff Yaego RC0805JR−0710RL 805 Yes

NCL30088D Revision 01

1 U2 NCL30088D ON Semiconductor NCL30088D SO8 No

1 Rsens 1 Yaego RC1206FR−071RL 1206 Yes

1 R4 10 Yaego RC0805JR−0710RL 805 Yes

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GERBER VIEWS

Figure 4. Top Side PCB

Figure 5. Bottom Side PCB

Figure 6. PCB Outline

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Figure 7. Assembly Notes

1. Strip and tin lead wires to 6” ± 0.5” 4 Places.

Mark the appropriate Revision Here

White Wires Here

Black Wire HereRed Wire Here

Notch Here

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CIRCUIT BOARD FABRICATION NOTES

1. Fabricate per IPC−6011 and IPC6012. Inspect to

IPA−A−600 Class 2 or updated standard.

2. Printed Circuit Board is defined by files listed in

fileset.

3. Modification to copper within the PCB outline is

not allowed without permission, except where

noted otherwise. The manufacturer may make

adjustments to compensate for manufacturing

process, but the final PCB is required to reflect the

associated gerber file design ±0.001 in. for etched

features within the PCB outline.

4. Material in accordance with IPC−4101/21, FR4,

Tg 125°C min.

5. Layer to layer registration shall not exceed

±0.004 in.

6. External finished copper conductor thickness shall

be 0.0026 in. min. (ie 2oz)

7. Copper plating thickness for through holes shall be

0.0013 in. min. (ie 1oz)

8. All holes sizes are finished hole size.

9. Finished PCB thickness 0.031 in.

10. All un-dimensioned holes to be drilled using the

NC drill data.

11. Size tolerance of plated holes: ±0.003 in. :

non−plated holes ±0.002 in.

12. All holes shall be ±0.003 in. of their true position

U.D.S.

13. Construction to be SMOBC, using liquid photo

image (LPI) solder mask in accordance with

IPC−SM−B40C, Type B, Class 2, and be green in

color.

14. Solder mask mis-registration ±0.004 in. max.

15. Silkscreen shall be permanent non−conductive

white ink.

16. The fabrication process shall be UL approved and

the PCB shall have a flammability rating of

UL94V0 to be marked on the solder side in

silkscreen with date, manufactures approved logo,

and type designation.

17. Warp and twist of the PCB shall not exceed

0.0075 in. per in.

18. 100% electrical verification required.

19. Surface finish: electroless nickel immersion gold

(ENIG)

20. RoHS 2002/95/EC compliance required.

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BUCK BOOST INDUCTOR SPECIFICATION

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ECA PICTURES

Figure 8. Top View

Figure 9. Bottom View

TEST PROCEDURE

Equipment Needed

•AC Source – 90 to 305 V ac 50/60 Hz Minimum 500 W

capability

•AC Wattmeter – 300 W Minimum, True RMS Input

Voltage, Current, Power Factor, and THD 0.2%

accuracy or better

•DC Voltmeter – 300 V dc minimum 0.1% accuracy or

better

•DC Ammeter – 1 A dc minimum 0.1% accuracy or

better

•LED Load – 10 V – 30 V @ 1 A

Test Connections

1. Connect the LED Load to the red (+) and black (−)

leads through the ammeter shown in Figure 10.

CAUTION: Observe the correct polarity or the load may

be damaged.

2. Connect the AC power to the input of the AC

wattmeter shown in Figure 10. Connect the white

leads to the output of the AC wattmeter

3. Connect the DC voltmeter as shown in Figure 10.

Figure 10. Test Set Up

AC Power

Source

Wattmeter

UUT LED Test

Load

DC Ammeter

DC Voltmeter

NOTE: Unless otherwise specified, all voltage measurements are taken at the terminals of the UUT.

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Functional Test Procedure

1. Set the LED Load for 26 V output.

2. Set the input power to 120 V 60 Hz.

CAUTION: Do not touch the ECA once it is energized

because there are hazardous voltages

present.

LINE AND LOAD REGULATION

Table 3. 120 V / MAX LOAD

Output Current

100 mA + 3 mA Output Power Power Factor THD < 20%

90 V

135 V

180 V

Table 4. 230 V / MAX LOAD

Output Current

100 mA + 3 mA Output Power Power Factor THD < 20%

90 V

135 V

180 V

Efficiency +Vout Iout

Pin 100%

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TEST DATA

Figure 11. Power Factor over Line and Load

Figure 12. THD over Line and Load

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Figure 13. Efficiency over Line and Load

Figure 14. Regulation over Line

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Figure 15. Start Up with AC Applied 120 V Maximum Load

Figure 16. Start Up with AC Applied 230 V Maximum Load

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Figure 17. Conducted EMI Pre−compliance QP Data 150 kHz − 1 MHz

Figure 18. Conducted EMI Pre−compliance Peak Data 150 kHz − 30 MHz

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