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FL7701 PAR20 LED Lighting & Dimming Demo

Steve Mappus,

January 31, 2012

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FL7701 Features

• Digital PFC Function

• Self Biasing

• Cycle-by-Cycle OCP

• Programmable Frequency

• Programmable LED Output Current

• Internal Soft Start

• Flicker-Free Analog Dimming

• Open & Short LED Protection

• High Voltage, AC or DC Input

• 8-Pin Narrow Body SOIC

FL7701 Smart LED Driver with PFC

GND

RT OUT

HVVCC

Reference

ADIM

JFET

AOCP

IAD

UVLO

QR

S

TSD

Leading Edge

Blanking

ZCD

DAC

Soft start

Digital Block

CS

Oscillator

-

+

LEB

-

+

time

VCC

ZCD

2.5V

1

2

83

5

4

6

FL77011

2

3

4 5

6

7

8

NC

HV

GND

ADIMRT

VCC

OUT

CS

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FL7701 Typical Applications

• Non-isolated, low-power (<10W) LED lamps operating from US or EU, AC line voltage

• Residential, non-dimming, LED luminaries (A, E, MR, PAR, GU, etc)

• Decorative LED lighting

• Low-power LED driver with 1V-10V analog or PWM dimming

• T-style LED ballast

• LED desk lamps with step dimming

FL7701 Benefits

• High power factor

• High efficiency

• Maintains high PF during analog dimming

• Non-isolated buck topology uses commonly available, low-cost, off-the-shelf inductors

• Non-isolated buck topology requires no output bulk capacitor

• Low component count, small form factor

FL7701 Applications & Benefits

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Measured Bulb Performance

• VIN=120VAC

• VOUT=12.15V

• IOUT=430mA, 4 Series LEDs

• PIN=7.2W

• PF=0.82

• POUT=5.22W

• η=72.6%

Utilitech Pro PAR20 LED Bulb (Rated 7.5W, 360 Lumens, 40W Incandescent Equivalent)

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• Removed all Potting Material

• Removed Utilitech LED Driver Power Supply

• Machined Bulb Base and Aluminum Heatsink to Allow Cutaway View of Exposed Bulb Base

• Redesigned FL7701, FEBL031-2 EVB to Meet Electrical and Mechanical Requirements of Utilitech Pro PAR20 Bulb Housing

• Utilitech Pro PAR20 LED Bulb used as Load to Demonstrate FL7701 Technology Features

Utilitech Pro PAR20 LED Bulb Cutaway Bulb Base

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FEBL020-2, FL7701 EVB Modification

• Original Unmodified

FEBL031-2 EVB

• FEBL031-2A EVB Modified to Meet Utilitech Pro PAR20 Electrical Requirements and Demonstrate Analog Dimming Function

FL77011

2

3

4 5

6

7

8

NC

HV

GND

ADIMRT

VCC

OUT

CS

L1

15mH

L2

10mH

R2

560Ω

D2

ES3J

D3

1N4148

R7

100Ω

R6

2.43Ω

R5

2.43Ω

L3

5.5mHC1

33nF

C2

47nF

C4

100pF

C3

1µF

Q1

FQD1N60C

D1

MB6S

220VAC

R7

56KΩ

1W

FL77011

2

3

4 5

6

7

8

NC

HV

GND

ADIMRT

VCC

OUT

CS

Utilitech PAR20

LED Luminaire

12V, 430mA

L2

10mH

Wurth, 744742103

R1

249Ω

R2

249Ω

D2

ES3J

D3

1N4148

R7

100Ω

R6

1.21Ω

R5

1.21Ω

R3

250

KΩ

R4

64.9

KΩ

L3

1mH

Wurth

7447709102

C1

33nF

C2

47nF

C4

100nF

C3

1µF

Q1

FQD1N60C

D1

MB6S

120VAC

R7

56KΩ

1W

L1

10mH

Wurth, 744742103

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FL7701 Utilitech PAR20 Schematic

FL77011

2

3

4 5

6

7

8

NC

HV

GND

ADIMRT

VCC

OUT

CS

Utilitech PAR20

LED Luminaire

12V, 430mA

L2

10mH

Wurth, 744742103

R1

249Ω

R2

249Ω

D2

ES3J

D3

1N4148

R7

100Ω

R6

1.21Ω

R5

1.21Ω

R3

250

KΩ

R4

64.9

KΩ

L3

1mH

Wurth

7447709102

C1

33nF

C2

47nF

C4

100nF

C3

1µF

Q1

FQD1N60C

D1

MB6S

120VAC

R7

56KΩ

1W

L1

10mH

Wurth, 744742103

NOTE: Open RT (pin 4) defaults to 45kHz switching frequency, Otherwise frequency is set by:

𝑅𝑇 =2.02 × 109

𝐹𝑂𝑆𝐶

𝛺

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LED Driver Electrical Performance Comparison

• Utilitech Pro PAR20 Power Supply Topology is Isolated Flyback that is Triac Dimmable

• FL7701 Topology is Non-Isolated Buck that is self-biased from the AC line voltage and is therefore not Triac Dimmable

• FL7701 Flicker-Free, Analog Dimming is Demonstrated BUT is not Feasible for Residential LED Replacement Bulbs Requiring Dimming

• FL7701 Solution has Fewer Components, Higher Power Factor and Comparably Similar Efficiency

VIN(V) PIN(W) VOUT(V) IOUT(mA) POUT(W) PF η

Utilitech PAR20

Power Supply

120 7.2 12.15 430 5.22 0.82 72.6%

FEBL031-2

(Unmodified)

220 8.71 32.8 260 7.56 0.95 86.8%

FEBL031-2A

(Modified)

120 7.2 12.17 431 5.25 0.942 72.8%

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FEBL031-2A Typical Test Set Up

Required Test Equipment:

1. Plugs into any standard 120VAC US line wall outlet

2. (3) battery powered DVMs (VIN, VLED, ILED)

3. (1) Oscilloscope

4. (2) Current Probes

5. (2) High Voltage Differential Probes (DO NOT USE GROUNDED VOLTAGE PROBES)

Recommended Test Equipment:

1. (1) Power meter can be used to show PF and THD verses dimming. Depending upon the capabilities of the oscilloscope, PF may be shown using oscilloscope calculation measurement (as done in test set up shown above).

WARNING

• Do not use standard oscilloscope voltage probes to probe any signals from back of demo box. The demo is operating directly from AC, off-line and is non-isolated so attaching any scope ground will damage the circuit.

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FEBL031-2A, PAR20 Demo Operation

• (A) Non-operational Static FEBLO31-2A EVB (shows reverse side of EVB from what is shown inside LED bulb)

• (B) LIVE operational demo protected by acrylic cover. Everything on the demo is safe to touch.

• (C) Open LED momentary push button (when pushed and held, bulb output disables and recovers when push button is released)

• (D) Short LED momentary push button (when pushed and held, bulb output disables and recovers when push button is released)

• (E) Dimming function potentiometer varies the FL7701 ADIM voltage. LED bulb can turn on in any DIM position.

• (F) ON/OFF rocker switch provides AC power to bulb

A

B

C D E

F

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FEBL031-2A, PAR20 Demo Back Panel

• (A) High Voltage Diff Probe (measure AC line voltage, oscilloscope channel 1)

• (B) Battery powered DVM (measure AC line RMS voltage)

• (C) 5A replaceable AC line Fuse

• (D) AC line cord is split apart in this location to allow current probe connection (measure AC line current, oscilloscope channel 2)

• (E) ON/OFF switch for blue light on front panel “power symbol”. The blue LED is independent from AC line voltage and is powered by 2 AA batteries.

• (F) High Voltage Diff Probe (measure LED voltage, oscilloscope channel 3), OR connect a battery powered DVM here to display the RMS LED voltage

• (G) Battery powered DVM (measure LED RMS voltage). IMPORTANT NOTE: Must connect either the DVM (set to measure current), OR shunt jumper (shown) to allow current to flow to the PAR20 LED array. Current probe (measure LED current, oscilloscope channel 4) can now be connected to either the DVM lead or the shunt jumper.

A

B

C

D

E

F

G

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• 0% Dimming, IOUT=433mA

• PF=0.942

FEBL031-2A Analog Dimming Waveforms CH1=VIN, CH2=IIN, CH3=VLED, CH4=ILED

• 50% Dimming, IOUT=194mA

• PF=0.945

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• 75% Dimming, IOUT=100mA

• PF=0.891

FEBL031-2A Analog Dimming Waveforms CH1=VIN, CH2=IIN, CH3=VLED, CH4=ILED

• Max Dimming, IOUT=50mA

• PF=0.724

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• Open LED Fault

• LED Current is Zero

• LED Voltage is Peak AC Line

Voltage

FEBL031-2A LED Fault Testing CH1=VIN, CH2=IIN, CH3=VLED, CH4=ILED

• Short LED (String) Fault

• LED Current is Max Limited

by FL7701 OCP Function

• LED Voltage is Zero

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• 120VAC Soft Start

• AC Phase is detected on VCC

• EA voltage reference set to AC

• CS voltage threshold set to 0.365V

FEBL031-2A AC vs. DC Soft Start CH1=VIN, CH2=IIN, CH3=VLED, CH4=ILED

• 170VDC Soft Start

• No AC phase detected on VCC

• EA voltage reference set to DC

• CS voltage reference set to 0.5V

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FEBL031-2A LED Capacitor Comparison CH1=VIN, CH2=IIN, CH3=VLED, CH4=ILED

CLED=10µF, 16V, 33% Ripple Reduction

CLED=470µF, 16V, 72% Ripple Reduction CLED=1000µF, 16V, 78% Ripple Reduction

CLED=0

380mA

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FEBL031-2A LED Capacitor Comparison

Cap VIN(VAC) PIN(W) VOUT(V) IOUT(mA) POUT(W) η PF THD

0 120 7.3 11.86 441 5.23 71.6% .944 29.78%

10µF 120 7.3 11.93 441 5.26 72.06% .944 29.16%

470µF 120 7.3 12.00 442 5.3 72.6% .934 29.18%

1000µF 120 7.3 12.04 442 5.32 72.8% .934 29.74%

• Reduced output LED, high frequency, ripple current is sometimes desirable for improving LED reliability

• Aluminum electrolytic capacitor can be added in parallel with LED load

• 16V rated capacitor voltage used for 12V LED output

• During open LED condition, LED output voltage equals peak AC line voltage so appropriately rated high voltage capacitor is necessary

• For residential LED bulb applications, high voltage output capacitors may not be feasible due to their large size

• For LED loads that include open LED shunt protection, capacitor voltage rating can be rated for clamped LED voltage (16V)

• 16V rated capacitor easily fits within residential Edison based LED bulb bases

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FL7701 OVP Output LED Voltage Clamp

• Recommended FL7701 configuration for LED loads that DO NOT include parallel open LED shunt protection

• When LED voltage is greater than zener voltage, the BJT is turned on and discharges the VDD capacitor

• LED voltage is now limited to the zener voltage allowing the use of low voltage output bulk capacitor on LED output

AC input85Vac~265Vac

LED

FUSE

FRD

Lm

C

VD

DH

V

GN

D

FL7701

Varistor

N.C

Adim

R

RT

CS

GATE

EMI FILTER

R

C

R

R

D

ZD

C

OVP Protection

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FEBL031-2A LED Driver THD and PF (Chroma 61502 Programmable AC Source)

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FEBL031-2A LED Driver, THD (Chroma 61502 Programmable AC Source)

0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.016

0.018

3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39

Ha

rmo

nic

C

urr

en

t (A

)

Harmonic Number

FEBL031-2A Measured THD EN61000-3-2, 115VAC

Measured Harmonic Current

Class C (Lighting) Limit

• FEBL031-2A, EMI filter not optimized resulting in AC line current distortion

• Measured THD is close to Class C limits and could be improved by optimizing EMI filter