Texas Instruments Using the UCC28911EVM-718 User guide

Using the UCC28911EVM-718

User's Guide

Literature Number: SLUUBA1

March 2015

1

2

3

4

5

1

±5%

1.5 2.0

±5%

Typical

Application

Output Voltage (V)

Output Current (A)

Typical Target Output V-I Characteristic

User's Guide

SLUUBA1–March 2015

Using the UCC28911EVM-718 7.5W Universal Off-Line

Flyback Converter with Primary-Side Regulation

1 Introduction

The UCC28911EVM-718 evaluation module is an offline flyback power supply that provides isolated

output voltage and current regulation without the use of an optocoupler. The input accepts a voltage range

of 85 V

AC

to 265 V

AC

, 47 Hz to 64 Hz.

2 Description

The evaluation module uses the UCC28911 CV/CC PWM HV Switcher. This device integrates a 700-V

power MOSFET and controller that processes operating information from an auxiliary flyback winding and

from the power MOSFET to provide precise output voltage and current control. Control algorithms in the

UCC28911 allow operating efficiencies to meet or exceed applicable standards. Discontinuous Conduction

Mode (DCM) with valley switching is used to reduce switching losses. A combination of switching

frequency and peak-primary current amplitude modulation is used to keep conversion efficiency high

across the full load and input voltage range. Figure 1 below details the output V-I characteristic.

Low-system parts count and built-in advanced protection features result in a cost-effective solution that

meets stringent world-wide energy efficiency requirements.

This user’s guide provides the schematic, component list, assembly drawing, art work, and test set up

necessary to evaluate the UCC28911 in a typical off-line converter application.

Figure 1. Output Voltage as a Function of Output Load

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Description

2.1 Applications

The UCC28911 is suited for use in isolated off-line systems requiring high efficiency and advanced fault

protection features including:

• USB Compliant Adapters for Cell Phones, Tablets and Cameras

• 7-W to 10-W AC-to-DC Power Supplies

2.2 Features

The UCC28911EVM-718 features include:

• Isolated 7.5-W, 5-V Output

• Universal Off-Line Input Voltage Range

• Meets USB Specification 1.1

• Multiple Operating Modes and Valley Switching (for optimum efficiency over entire operating range)

• Primary-Side Control Eliminates Need for Optocoupler

• Output Over-Voltage Protection

• Input Under-Voltage Protection

• Primary Over-Current protection

• Thermal Shutdown

• Controlled Start Up and Restart After Fault Protection

CAUTION

High voltage levels are present on the evaluation module when energized.

Proper precautions must be taken when working with the EVM. The large bulk

capacitors, C1 and C2, and the output capacitors, C7 and C8, must be

completely discharged before the EVM can be handled. Serious injury can

occur if proper safety precautions are not followed.

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Electrical Performance Specifications

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3 Electrical Performance Specifications

Table 1. UCC28911EVM-718 Electrical Performance Specifications

PARAMETER TEST CONDITIONS Min NOM MAX UNITS

Input Characteristics

V

IN

Input voltage 85 115/230 265 V

f

LINE

Frequency 47 50/60 64 Hz

P

NL

No-load power V

IN

= V

NOM

I

OUT

= 0 A 15 20 mW

V

IN(uvlo)

Brownout voltage I

OUT

= I

NOM

70 V

V

INOV

Brownout recovery voltage 80 V

I

IN

Input current V

IN

= V

MIN

I

OUT

= I

OUT(max)

0.3 A

Output Characteristics

V

OUT

Output voltage V

IN

= V

MIN

to V

MAX

I

OUT

= 0 to I

NOM

4.75 5 5.25 V

I

OUT(max)

Maximum output current V

IN

= V

MIN

to V

MAX

1.425 1.5 1.575 A

I

OUT(min)

Minimum output current V

IN

= V

MIN

to V

MAX

0 A

ΔV

OUT

Output voltage ripple V

IN

= V

MIN

to V

MAX

I

OUT

= 0 to I

NOM

150 mV

P

OUT

Output power V

IN

= V

MIN

to V

MAX

7.5 W

System Characteristics

η Average efficiency V

IN

= V

NOM

I

OUT

= 25%, 75%

50%,,75%,,100% of I

OUT

Mechanical

W Width 3.5 in

L Dimensions Length 5 in

H Component Height 1 in

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6.8k

R1

10 F

400V

C2

1.50k

R5

100k

R6

6.8k

R2

33.0

R7

100.0k

R9

30.0k

R8

15.0k

R4

1.27k

R3

2200pF

C6

180

R11

6.8k

R12

430.0k

R10

1

3

2

D5

1200 F

C7

10

F

C5

D4

D3

~

3

~

4

D1

1mH

L1

1mH

L2

170V

D2

FKN1WSJR-52-4R7

RF1

J1

J2

100pF

C3

0.1 F

C8

HV

i

600V

LINE

NEUTRAL

+VOUT

-VOUT

LINE

NEUTRAL

+VOUT

-VOUT

88 VAC TO 265 VAC

47 Hz TO 63 Hz

I IN MAX. =

300 mA

0.1

F

C4

CAUTION! HIGH VOLTAGE

+5V 1.5A

10

F

400V

C1

GND

1

GND

2

GND

3

IPK

4

VS

5

VDD

6

DRAIN

8

U1

UCC28911D

7

8

9

6

1

2

4

5

T1

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Schematic

4 Schematic

Figure 2. UCC28911EVM-718 Schematic

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Circuit Description

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5 Circuit Description

A brief description of the circuit elements follows:

• Diode Bridge D1, input capacitors C1 and C2, transformer T1, UCC28911 switcher U1, Schottky

rectifier D5 and capacitor C7 form the power stage of the converter.

NOTE: The UCC28911 U1 is also part of the power stage since the high-voltage MOSFET is

internal to U1.

• Capacitor C8 filters the high-frequency noise directly across the electrolytic output capacitor.

• The input EMI filter is made up of C1 and C2 and differential mode inductors, L2 and L3.

• R1, R2 serve the dual function of dampening input filter oscillations and prevent a large voltage being

developed across L2 and L3 in the event of an ESD pulse.

• Input-current protection is provided by fusible resistor, RF1.

• Resistors R5 and R6, capacitor C3, and diodes D2 and D3 make up the primary-side voltage clamp.

The clamp prevents the drain voltage on U1 from exceeding its maximum rating. A secondary function

of the clamp is to alleviate the EMI currents associated with the turnoff voltage of U1.

• Operating bias to the controller is provided by the auxiliary winding on T1, diode D4, resistor R7 and

bulk capacitor C5.

• Capacitor C4 is a decoupling capacitor which should always be good quality low ESR/ESL type

capacitors placed as close to the device pins as possible and returned directly to the device ground

reference.

• Secondary-side snubber C6 and R11are used to reduce the effects switching noise of D5.

• Resistor R9 programs the start-up voltage threshold.

• Resistors R8 and R10 program the output voltage set point.

• Resistors R3 and R4 program the maximum output current.

• Resistor R12 is used to adjust the no-load output voltage.

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EVM Test Set Up

6 EVM Test Set Up

Figure 3 shows the equipment set up when measuring the input power consumption during no load.

During the no-load test, the power analyzer should be set for long averaging in order to include several

cycles of operation and an appropriate current scale factor should be used. Figure 4 shows the basic test

set up recommended to evaluate the UCC28911EVM-718 with a load.

WARNING

High voltages that may cause injury exist on this evaluation

module (EVM). Please ensure all safety procedures are followed

when working on this EVM. Never leave a powered EVM

unattended.

6.1 Test Equipment

See Figure 3 and Figure 4 for recommended test set ups.

AC Input Source: The input source shall be an isolated variable AC source capable of supplying between

85 V

RMS

and 265 V

RMS

at no less than 15 W and connected as shown in Figure 3 and Figure 4. For

accurate efficiency calculations, a power meter should be inserted between the AC source and the EVM.

For highest accuracy, connect the voltage terminals of the power meter directly across the power source.

NOTE: Connecting the voltage terminals directly to the EVM results in a small current error. This is

very significant when measuring no load power.

Load: For the output load, a programmable electronic load set to constant current mode and capable of

sinking 0 to 1.5 A

DC

at 10 V

DC

shall be used. For highest accuracy, V

OUT

can be monitored by connecting a

DC voltmeter, DMM V1, directly across the V

OUT

and –V

OUT

terminals as shown in Figure 3 and Figure 4. A

DC current meter, DMM A1, should be placed in series with the electronic load for accurate output current

measurements.

Power Meter: The power analyzer (PM1) shall be capable of measuring low-input current, typically less

than 100 µA, and a long averaging mode if low-power standby mode input-power measurements are to be

taken. An example of such an analyzer is the Yokogawa WT210 Digital Power Meter. To measure the

intermittent bursts of current and power drawn from the line during no-load operation, the WT210 should

be set to integrate.

Multimeters: Two digital multimeters are used to measure the regulated output voltage (DMM V1) and

load current (DMM A1).

Oscilloscope: A digital or analog oscilloscope with a 500-MHz scope probe is recommended.

Recommended Wire Gauge: a minimum of AWG 24 wire is recommended. The wire connections

between the AC source and the EVM, and the wire connections between the EVM and the load should be

less than two feet long.

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AC

SOURCE

LINE

NEUT

V_HI

V_LO

A_HI A_LO

DMM V1

+

-

DMM A1

Electronic

Load

AC

SOURCE

LINE

NEUT

V_HI

V_LO

A_HI A_LO

DMM V1

+

-

EVM Test Set Up

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6.2 Recommended Test Set Up for Operation Without a Load

Figure 3. UCC28911EVM-718 Recommended Test Set Up without a Load

6.3 Recommended Test Set Up for Operation With a Load

Figure 4. UCC28911EVM-718 Recommended Test Set Up With a Load

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Test Procedure

7 Test Procedure

All tests should use the set up as described in Section 5 of this user’s guide. The following test procedure

is recommended primarily for power up and shutting down the evaluation module. Never leave a powered

EVM unattended for any length of time.

7.1 Applying Power to the EVM

1. Set up the EVM as shown in Section 6 of this user’s guide.

(a) If no-load input power measurements are to be made, set the power analyzer to long averaging or

integrating power measurement mode.

(b) For operation with a load, as shown in Figure 4, set the electronic load to constant resistance

mode.

2. Prior to turning on the AC source, set the voltage to between 85 V

AC

and 265 V

AC

.

3. Turn on the AC source.

4. Monitor the output voltage on DMM V1.

5. Monitor the output current on DMM A1.

6. The EVM is now ready for testing.

7.2 No-Load Power Consumption

1. Use the test set up shown in Figure 3.

(a) Set the power analyzer to integrating average power mode.

(b) Set the current measurement scale to 0.25 A.

(c) Set the voltage range to 300 V.

(d) Set the measurement mode to RMS.

2. Apply power to the EVM per Section 7.1.

3. Monitor the input power on the power analyzer while varying the input voltage.

4. Make sure the input power is off and the bulk capacitor and output capacitors are completely

discharged before handling the EVM.

7.3 Output Voltage Regulation and Efficiency

1. For load regulation:

(a) Use the test set up shown in Figure 4.

(b) Set the AC source to a constant voltage between 85 V

AC

and 265 V

AC

.

(c) Apply power to the EVM per Section 7.1.

(d) Vary the load current from 0 A up to 1.5 A, as measured on DMM A1.

(e) Observe that the output voltage on DMM V1 remains between 4.75 V and 5.25 V from no load up

to 1.5 A and thereafter the current remains between 1.425 A and 1.575 A until the output voltage

drops to 2 V or lower. See Figure 1 for details.

2. For line regulation:

(a) Set the load to sink 1.5 A.

(b) Vary the AC source from 85 V

AC

to 265 V

AC

.

(c) Observe that the output voltage on DMM V1 remains between 4.75 V and 5.25 V.

3. Make sure the input power is off and the bulk capacitor and output capacitors are completely

discharged before handling the EVM.

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Test Procedure

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7.4 Output Voltage Ripple

1. For output ripple measurements, solder a 0.1-µF, 50-V ceramic capacitor and 4.7-µF, 35-V tantalum

capacitor on a BNC adapter as shown in Figure 5 below. Connect the red test lead to the V

OUT

output

and the black test lead to the –V

OUT

on the EVM.

2. Connect the other end of the BNC cable to the oscilloscope and monitor the output ripple on the

oscilloscope.

3. Apply power to the EVM per Section 7.1.

Figure 5. Typical Example of Tip Measurement Technique

7.5 Equipment Shutdown

1. Ensure the load is at maximum; this quickly discharges the output capacitors.

2. Turn off the AC source.

3. Make sure the bulk capacitors, C1, C2 and output capacitor, C7 are completely discharged before

handling the EVM.

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Output Current (A)

Output Voltage (V)

1 1.1 1.2 1.3 1.4 1.5 1.6

1

2

3

4

5

6

D001

100 V

IN

115 V

IN

230 V

IN

265 V

IN

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Performance Data and Typical Characteristic Curves

8 Performance Data and Typical Characteristic Curves

Figure 6 through Figure 14 present typical performance curves for the UCC28911EVM-718.

Figure 6. Typical V-I Characteristic

Table 2. Average and 10% Load Efficiency

V

IN

(V) f (Hz) P

IN

(W) I

OUT

(A) V

OUT

(V) P

OUT

(W) Eff (%) Avg Eff (%)

115 60 10.27 1.497 5.131 7.68 74.79 75.48

7.654 1.122 5.123 5.75 75.10

5.047 0.747 5.118 3.82 75.75

2.495 0.372 5.115 1.90 76.26

1.042 0.148 5.119 0.76 72.71

230 50 10.02 1.493 5.148 7.69 76.71 76.32

7.476 1.119 5.133 5.74 76.83

4.964 0.744 5.122 3.81 76.77

2.527 0.370 5.120 1.89 74.97

1.052 0.145 5.117 0.74 70.53

Table 3. No-Load Power Consumption

V

IN

(V) f (Hz) P

IN

(mW) V

OUT

(V)

115 60 11.4 5.21

230 50 13.5 5.21

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Table 4. Typical V-I Test Data

100 V

AC

115 V

AC

230 V

AC

265 V

AC

I

OUT

(A) V

OUT

(V) I

OUT

(A) V

OUT

(V) I

OUT

(A) V

OUT

(V) I

OUT

(A) V

OUT

(V)

1.387 5.147 1.387 5.148 1.387 5.148 1.387 5.148

1.401 5.147 1.401 5.148 1.401 5.149 1.401 5.148

1.415 5.147 1.416 5.148 1.416 5.149 1.416 5.149

1.429 5.147 1.43 5.149 1.431 5.149 1.43 5.148

1.444 5.147 1.445 5.149 1.445 5.149 1.445 5.149

1.46 5.147 1.46 5.149 1.461 5.149 1.461 5.149

1.472 5.136 1.476 5.15 1.476 5.149 1.476 5.149

1.473 5.086 1.48 5.108 1.492 5.15 1.492 5.15

1.474 5.033 1.481 5.058 1.508 5.15 1.508 5.15

1.476 4.987 1.482 5.004 1.513 5.11 1.525 5.15

1.477 4.933 1.483 4.952 1.514 5.057 1.524 5.089

1.477 4.88 1.484 4.902 1.515 5.004 1.525 5.037

1.478 4.829 1.485 4.85 1.516 4.951 1.526 4.983

1.479 4.777 1.485 4.796 1.517 4.899 1.527 4.93

1.48 4.726 1.486 4.743 1.518 4.843 1.527 4.874

1.481 4.673 1.487 4.691 1.519 4.791 1.528 4.821

1.482 4.621 1.488 4.64 1.519 4.736 1.529 4.766

1.483 4.568 1.489 4.585 1.52 4.681 1.53 4.712

1.483 4.516 1.49 4.532 1.521 4.629 1.531 4.659

1.484 4.461 1.49 4.479 1.521 4.574 1.531 4.603

1.485 4.409 1.491 4.426 1.522 4.519 1.532 4.547

1.486 4.357 1.491 4.373 1.523 4.465 1.533 4.494

1.486 4.302 1.492 4.32 1.523 4.41 1.533 4.438

1.487 4.25 1.493 4.267 1.524 4.355 1.534 4.384

1.487 4.195 1.494 4.214 1.524 4.3 1.534 4.328

1.488 4.143 1.494 4.158 1.525 4.244 1.535 4.273

1.489 4.091 1.495 4.106 1.525 4.189 1.536 4.217

1.489 4.036 1.495 4.051 1.526 4.136 1.536 4.162

1.49 3.982 1.496 3.999 1.526 4.08 1.537 4.106

1.49 3.928 1.497 3.944 1.527 4.022 1.537 4.051

1.49 3.874 1.497 3.89 1.527 3.969 1.537 3.993

1.491 3.82 1.497 3.835 1.528 3.914 1.538 3.939

1.492 3.767 1.497 3.781 1.528 3.859 1.539 3.884

1.493 3.713 1.499 3.727 1.529 3.803 1.539 3.827

1.493 3.659 1.499 3.672 1.53 3.747 1.54 3.771

1.494 3.605 1.499 3.618 1.53 3.692 1.541 3.718

1.495 3.551 1.5 3.563 1.531 3.636 1.541 3.661

1.495 3.497 1.501 3.51 1.531 3.581 1.542 3.606

1.495 3.443 1.502 3.455 1.532 3.525 1.542 3.549

1.496 3.388 1.502 3.401 1.532 3.469 1.543 3.493

1.497 3.334 1.502 3.347 1.533 3.413 1.543 3.436

1.498 3.281 1.503 3.292 1.533 3.358 1.543 3.381

1.498 3.225 1.503 3.237 1.534 3.302 1.544 3.325

1.498 3.171 1.504 3.181 1.534 3.246 1.544 3.267

1.499 3.117 1.504 3.127 1.534 3.188 1.546 3.213

1.498 3.062 1.504 3.072 1.535 3.133 1.546 3.157

1.5 3.011 1.505 3.016 1.535 3.077 1.546 3.1

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Performance Data and Typical Characteristic Curves

Table 4. Typical V-I Test Data (continued)

100 V

AC

115 V

AC

230 V

AC

265 V

AC

I

OUT

(A) V

OUT

(V) I

OUT

(A) V

OUT

(V) I

OUT

(A) V

OUT

(V) I

OUT

(A) V

OUT

(V)

1.5 2.951 1.505 2.961 1.535 3.021 1.547 3.042

1.5 2.896 1.505 2.906 1.536 2.964 1.547 2.986

1.501 2.841 1.505 2.85 1.536 2.907 1.546 2.929

1.5 2.786 1.505 2.794 1.536 2.851 1.547 2.873

1.501 2.729 1.506 2.74 1.536 2.794 1.548 2.815

1.501 2.675 1.505 2.683 1.536 2.738 1.548 2.758

1.501 2.621 1.506 2.626 1.537 2.682 1.547 2.7

1.502 2.565 1.506 2.572 1.536 2.624 1.547 2.642

1.502 2.509 1.506 2.516 1.537 2.568 1.547 2.585

1.502 2.453 1.506 2.46 1.537 2.51 1.547 2.527

1.501 2.397 1.506 2.405 1.537 2.453 1.547 2.47

1.502 2.341 1.506 2.349 1.537 2.396 1.547 2.412

1.502 2.286 1.506 2.292 1.537 2.339 1.547 2.355

1.501 2.23 1.506 2.237 1.536 2.281 1.547 2.296

1.502 2.174 1.505 2.181 1.536 2.224 1.546 2.239

1.501 2.119 1.505 2.124 1.536 2.167 1.546 2.181

1.501 2.062 1.505 2.067 1.535 2.11 1.546 2.124

1.501 2.006 1.505 2.011 1.535 2.052 1.545 2.066

1.501 1.949 1.504 1.956 1.535 1.994 1.546 2.008

1.5 1.894 1.504 1.898 1.534 1.936 1.545 1.95

1.499 1.838 1.503 1.841 1.533 1.879 1.544 1.892

1.5 1.782 1.503 1.786 1.533 1.821 1.544 1.834

1.498 1.725 1.502 1.73 1.532 1.764 1.543 1.776

1.497 1.668 1.501 1.673 1.531 1.705 1.542 1.718

1.497 1.612 1.501 1.616 1.531 1.648 1.541 1.659

1.496 1.555 1.5 1.559 1.53 1.591 1.54 1.601

1.495 1.499 1.498 1.503 1.528 1.532 1.539 1.543

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Performance Data and Typical Characteristic Curves

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Figure 7. Ripple with 5 V, 1.5 A Out, 115 V

AC

in 20 mV/div 100 µs/div

Figure 8. Ripple with 5 V, 1 A Out, 115 V

AC

in 20 mV/div 100 µs/div

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Performance Data and Typical Characteristic Curves

Figure 9. Step Load 1.5 A to 0.5 A, C4 200 mV/div, C3 2 A/div 200 ms/div

Figure 10. Step Load 1.5 A to 0 A, C4 500 mV/div, C3 2 A/div 200 ms/div

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Performance Data and Typical Characteristic Curves

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Figure 11. Output Voltage Start 115 V

AC

, 1.5-A load, 1 V/div 50 mS/div

Figure 12. Output Voltage Start, 230 V

AC

, 1.5-A load, 1 V/div 50 ms/div

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Performance Data and Typical Characteristic Curves

Figure 13. Primary-Side Switching Waveforms 85 V

AC

(1.5-A Load Drain Voltage, CH 1 100 V/div and Current, CH3 0.5 A/div 2 µs/div)

Figure 14. Primary-Side Switching Waveforms 265 V

AC

(1.5-A Load Drain Voltage, CH 1 100 /div and Current,CH4 0.5 A/div 2 µs/div)

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EVM Assembly Drawing and Layout

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9 EVM Assembly Drawing and Layout

The following figures show the design of the UCC28911EVM-718 printed circuit board.

Figure 15. UCC28911EVM-718 (top view)

Figure 16. PCB (top)

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EVM Assembly Drawing and Layout

Figure 17. PCB (bottom)

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List of Materials

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10 List of Materials

10.1 Flyback Transformer

10.1.1 Material List

• EE16/8/5 ferrite core pair.

• EE16/8/5 9-pin through hole, horizontal bobbin.

• 0.18-mm OD enamel copper wire.

• 0.35-mm Furukawa TEX-E triple insulated copper wire or equivalent.

• 10.6-mm wide mylar tape.

10.1.2 Winding Table

Table 5. Winding Table

WINDING START FINISH WIRE WINDING TURNS COMMENTS

DIRECTION

WDG 1 2 0.18-mm OD CW 50 WDG 1 is full single layer. Finish of WDG1

is lead out towards pin 2 and becomes

start of WDG2.

Tape CW 2

WDG 2 5 0.18-mm OD CW 49 WDG 1 is full single layer. Finish of WDG1

is lead out towards pin 2 and becomes

start of WDG2.

10.6-mm CW 2

tape

WDG 3 4 x 0.18-mm OD CW 25 WDG 3 wound bifilar. single layer

10.6-mm CW 2

tape

WDG 4 x 4 0.18-mm OD CW 25 WDG 4 wound bifilar, single layer

10.6-mm CW 2

tape

WDG 5 1 4 0.18-mm OD CW 21 WDG 5 wound bifilar. single layer

10.6-mm CW 2

tape

WDG 6 3 NC 0.18-mm OD CW 28 WDG 6 wound bifilar, single layer

10.6-mm CW 2

tape

WDG 7 6 8 0.35-mm CCW 6 WDG 7 wound bifilar

TEX

10.6-mm CCW 2

tape

WDG 8 7 9 0.35-mm CCW 6 WDG 8 wound bifilar

TEX

10.6-mm CCW 2

tape

20

Using the UCC28911EVM-718 7.5W Universal Off-Line Flyback Converter SLUUBA1–March 2015

with Primary-Side Regulation

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Texas Instruments Using the UCC28911EVM-718 User guide

Texas Instruments Using the UCC28911EVM-718 User guide

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