Drvg_HB_LED_HP Ind_Light Fix

1 Driving HB-LEDs in High-Power Industrial Lighting Fixtures Steve Mappus 2 Agenda • High-brightness LED characteristics • LED system requirements • LED driver topologies - Single-stage vs. two-stage • LED load control - Parallel LED strings • 100 W industrial LED design example - Power stage calculations - Test results • Summary 3 High-Power Industrial LED Fixtures T y p ic a l A p p li c a ti o n s L E D A d v a n ta g e s Highway Light Parking Lot Streetlight Tunnel Lighting High & Low Bay Airports Bridges Manufacturing Efficiency Reliability Maintenance Instant-on Dimming Light Quality UV-Free Mercury Free Typical Power, 50 W 4 HB-LED Characteristics VF, Forward Voltage (V) I F , F o rw a rd C u rr e n t (m A ) 0 0.5 1.5 2 2.5 3 3.5 4 4.5 100 200 300 400 500 600 700 800 900 0 200mA (50%) 100 °C 25 °C 200mV (6%) • PN junction devices - Negative temperature coefficient - T↑, VF↓, IF↑, T↑ - Not easily paralleled • Steep IF vs. VF curve • Small ΔVF→Large ΔIF - LED color shift - Thermal imbalance - Decreased reliability • VF varies with temperature • VF can vary by 20%~30% • Operate best from a Constant Current (CC), Constant Voltage (CV) power source (Typical I-V curve for 1 A, HB-LED) 5 CC-CV Characteristic Curve (Typical CC-CV Curve for 75 W LED Driver) • Constant Current = 1.5 A • Constant Voltage = 50 V • Overvoltage Protection = 60 V • CC-CV LED Driver Provides: - Signal Conditioning (PFC) - Power Conversion - Load Control (75 W CC-CV LED Driver) CC-CV LED DRIVER OUT GND VLED=50V 500 mA VF VF VF VF VF VF VF VF VF VF VF VF 500 mA ILED=1.5A 500 mA ILED, LED Current (A) V L E D , L E D V o lt a g e ( V ) 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 20 30 40 50 60 70 0 10 Current Foldback OVP 6 HB-LED System Requirements AC-DC DC-DC CC-CV LOAD CONTROL AC ANALOG DIM PWM DIM LED DRIVER PFC EMI BIAS (OPTIONAL) • Input voltage range of 85 VRMS 7 Single-Stage: CC-CV PFC Flyback Advantages • Best for simple, low-cost fixtures where POUT 8 Two-Stage: PFC and CC-CV LLC Advantages • Best for any power level 50 W 9 Two-Stage: PFC and Two-Switch Flyback Advantages • Best for 50 W 10 LED Load Control Single Series String Control VCS VBUSIF VF VF VF VF CC LED DRIVER OUT FB GND Advantages • Can drive 100s of series LEDs • IF is same for every LED - No current sharing necessary • Easy to control in CC or CV Disadvantages • HIGH STRING VOLTAGE • Efficiency impact due to high voltage power stage components • LED shunts needed to account for open LED failure • UL 1310 safety→VBUS 11 LED Load Control Linear Regulator Control VOLTAGE PRE-REG OUT FB GND VBUSIF1 VF VF VF VF VF VF VF VF VF VF VF VF IF2 IFN ILED CC REG CC REG CC REG Disadvantages • VBUS> ∑VF +VREG • Additional VBUS margin voltage is dropped across linear regulator • Increase in regulator voltage→increase power dissipation→lower efficiency • Max current and power dissipation limit the use of linear regulators for high-power industrial LED lighting • Matched VF (Binning) can increase efficiency but increase LED cost Advantages • Driver operates in CV • Each string independently regulated • Single string can fail while remaining strings regulate in CC • Low EMI 12 LED Load Control Switching Buck Regulator Control VOLTAGE PRE-REG OUT FB GND VBUS IF1 VF VF VF VF ILED SW CS VIN GND RCS1 CC BUCK IF2 VF VF VF VF SW CS VIN GND RCS2 CC BUCK IFN VF VF VF VF SW CS VIN GND RCSN CC BUCK Advantages • Driver operates in CV • Each string independently regulated • Single string can fail while remaining strings regulate in CC • Typical 20%-30% efficiency improvement over linear regulators Disadvantages • High component count • Must operate at high frequency to minimize inductor size - EMI impact • Current sharing accuracy tolerances→5% considered good 13 LED Load Control FAN7346, 4-Channel LED Controller FAN7346 CURRENT BALANCE OVR FB1 GND VCS1 VBUS IF1 VF VF VF VF VF VF VF VF VF VF VF VF IF2 IFN ILED VCS2 VCSN FB2 FBN CC-CV LED DRIVER OUT GND FB FB OUT1 OUT2 OUTN CH1 CH2 CHN ADIM PWMN FO Q1 Q2 QN Advantages • Driver operates in CC-CV • VLED minimized→higher efficiency • Each string independently regulated • Single string can fail while remaining strings regulate in CC • Low EMI • Analog and PWM dimming • Used with any LED driver topology • Master/slave configurable for additional LED channels • Secondary (shown) or primary (opto) side control • Fault output (FO) • ±1.5% current sharing accuracy 14 100 W, LED Design Specification Two-Stage, BCM PFC and Two-Switch Flyback Parameter Min. Typ. Max. BCM PFC Stage VAC 85VRMS 308VRMS fVIN(AC_ 50Hz 60Hz 65Hz VOUT_PFC Fixed Regulation 440V 450V 465V VOUT_PFC Boost Follower 245V VIN(PK)+30V 465V POUT_PFC 120W tSOFT_START 50ms tON_OVERSHOOT 10V η_PFC 0.9 0.95 Two-Switch Flyback DC-DC LED Stage VIN 250V 460V VOUT_LED 30V 60V IOUT_LED Single Channel 2A IOUT_LED 4-Channel (Per Channel) 350mA POUT_LED 100W fSW_LED 50kHz 150kHz η_LED 0.9 0.95 Total System η_120V 0.90 η_230V 0.90 PF_120V 0.95 0.99 PF_230V 0.95 Mechanical and Thermal Height 30mm TJ 60⁰C Primary Design Goals 1. Wide input 85 VRMS 15 BCM, PFC Design FL7930C 1 2 3 4 5 6 7 8 OUT VCC GND ZCDCS COMP RDY INV PBIAS ZCD ZCD AC EMI FILTER RDY (TO FLYBACK) BF ON OFF VOUT (TO FLYBACK) 1 2 3 R5 R6 C4 C5 R7 R8 R9 R10 R11 D6 D7 Q3 Q4 Q5 L1 D8 C6 C7 NB NAUX VIN RZCD RCS J1 0V VDS tREStOFF tON TS 0V VAUX 0V VZCD 0.65V 0A IL 0V VGS VIN VOUT 2x(VIN – VOUT) 1.4V t ZCD Delay (150ns) NAUX NB x (VOUT – VIN) NAUX NB x VIN 1.5V IL(PK) • Constant on-time, variable frequency • Switching period, TS = tOFF + tRES + tON • Inductor current switches from 0A (ZCS) • VDS - ZVS→VOUT 16 BCM, PFC Design Boost Follower Operation Time (ms) V o lt a g e ( V ) 0 20 40 60 80 100 120 140 160 50 100 150 200 250 300 350 400 450 0 500 180 200 VOUT=465V 250V 17 BCM, PFC Design Boost Follower Design Procedure 1. Set VOUT divider: 𝑅5 = 𝑉𝑅𝐸𝐹 𝐼2 = 2.5𝑉 150𝜇𝐴 = 16.7𝑘Ω 𝑅4 = 𝑅5 × 𝑉𝑂1 − 𝑉𝑅𝐸𝐹 𝑉𝑅𝐸𝐹 = 16.7𝑘Ω × 250𝑉 − 2.5𝑉 2.5𝑉 = 1.65𝑀Ω 2. Boost follower ON for VAC >150 VRMS: 𝐼1 = 0𝐴, 𝑓𝑜𝑟 𝑉𝐴𝐶 < 150𝑉𝑅𝑀𝑆 3. Set Vb≈2 V when VAC =308 VRMS: 𝑉𝑐𝑡𝑟𝑙 = 𝑉𝑏 − 𝑉𝑏𝑒 = 2𝑉 − 0.7𝑉 = 1.3𝑉 5. Set VAC divider: R1 R2 Vf Vbe R3 R4 R5 1 3 COMP INV VREF (2.5V) FL7930C 85VRMS 18 BCM, PFC Design Boost Follower Design Procedure (Cont.) 6. Verify Vctrl over 85 VRMS 19 𝐼𝐿(𝑃𝐾) = 4 × 𝑃𝑂𝑈𝑇 𝜂 × 2 × 𝑉𝐴𝐶(𝑀𝐼𝑁) = 4 × 144𝑊 0.95 × 2 × 85𝑉𝑅𝑀𝑆 = 5𝐴𝑃𝐾 𝐿 = 𝜂 × 2 × 𝑉𝐴𝐶(𝑀𝐼𝑁) 2 4 × 𝐹𝑀𝐼𝑁 × 𝑃𝑂𝑈𝑇 × 1 + 2 × 𝑉𝐴𝐶(𝑀𝐼𝑁) 𝑉𝑂𝑈𝑇 − 2 × 𝑉𝐴𝐶(𝑀𝐼𝑁) = 0.9 × 2 × 160𝑉𝑅𝑀𝑆 2 4 × 45𝑘𝐻𝑧 × 144𝑊 × 1 + 2 × 160𝑉𝑅𝑀𝑆 250𝑉 − 2 × 160𝑉𝑅𝑀𝑆 = 168𝜇𝐻 ≅ 170𝜇𝐻 1. Peak inductor current: 2. Inductor value (POUT Max +20% Margin = 144 W): 3. Maximum on-time: 𝑡𝑂𝑁(𝑀𝐴𝑋) = 𝐿 × 𝐼𝐿(𝑃𝐾) 2 × 𝑉𝐴𝐶(𝑀𝐼𝑁) = 170𝜇𝐻 × 5𝐴𝑃𝐾 2 × 85𝑉𝑅𝑀𝑆 = 7𝜇𝑠 < 35𝜇𝑠 (𝐹𝐿7930 𝑡𝑂𝑁 𝑀𝐴𝑋 ) (6) (1) NB=41 NA=3 (10) (9) Core: EFD30, Wurth Custom PN 750313579 Winding Pins (S→F) Wire Layers Turns Boost 6→1 40/38, Served Litz 2 41 AUX 9→10 2/38, Bifilar 1 3 BCM, PFC Design Power Stage, Inductor Calculation 20 4. Output capacitor: ≥ 144𝑊 250𝑉 × 2 × π × 50𝐻𝑧 × (0.05 × 250𝑉) = 150𝜇𝐹 • Holdup not typically required for LED • COUT calculated based upon maximum allowable output ripple voltage, ΔVOUT = 5%×VOUT(MIN) • VOUT(MAX)= 460 V→need COUT rated for 500 V • To maintain low-profile: - COUT = 2 x 330 µF, 250 V aluminum radial leaded capacitors in series BCM, PFC Design Power Stage, Capacitor Calculation 𝐶𝑂𝑈𝑇 ≥ 𝑃𝑂𝑈𝑇 𝑉𝑂𝑈𝑇(𝑀𝐼𝑁) × 2𝜋 × 𝐹𝐿(𝑀𝐼𝑁) × ΔV𝑂𝑈𝑇 21 Two-Switch Flyback Design CC CVFB FAN6300H 1 2 3 4 5 6 7 8 NC HV VDD GATEGND CS FB DET FAN7382 1 2 3 4 5 6 7 8 HO VB VS LOCOM LIN HIN VCCPBIAS VIN R1 R2 R3 Q1 Q2 D1 D2 D3 D4D5 ACIN R4 C1 VA VLED VHS C2 C3 (FROM PFC) (FROM PFC) RDY PBIAS 22 0V VDS 0A IDS tftOFF tON TS 0A ID VA VA 0V 0V VDET 0V VIN PBIAS VIN+VHS VGS(HS) VGS(LS) 0.7V 5µs 2.5V VO OVP IDET(SOURCE)>30µA tDELAY=200ns VRO 2 VRO 2 VIN 2 VIN 2 • Quasi-resonant, variable frequency • HS and LS MOSFETs switch synchronously • Switching period, TS = tOFF + tf + tON • Inductor current switches from 0 A (ZCS) every switching cycle • VDS - Valley switching - Extended valley switching • Gate turn-on - IDET>30 µA→delay 200 ns→turn-on • VDET>2.5 V→OVP (latching) Two-Switch Flyback Design Key Switching Waveforms 23 FAN7382 1 2 3 4 5 6 7 8 HO VB VS LOCOM LIN HIN VCCPBIAS VIN R1 R2 R3 Q1 Q2 D1 D2 D4D5 VA VHS C2 C3 DETPWM (FROM PFC) 0V 0V 0V PBIAS VHS UVLO VGS(HS) VGS(LS) • FAN7382 HVIC • HIN and LIN shorted • Q1 and Q2 MOSFETs switch synchronously…but • During start-up - HO not switching - LO switching charges C2 only when HO not switching • During steady-state - C2 charged from VHS Two-Switch Flyback Design Gate Drive Operation 24 1. Transformer turns ratio: 2. Primary magnetizing inductance: 3. Primary current: 𝑛 = 𝑉𝐼𝑁 𝑀𝐼𝑁 × 𝐷𝑀𝐴𝑋 1 − 𝐹𝑀𝐼𝑁 × 𝑡𝑓 − 𝐷𝑀𝐴𝑋 × 1 𝑉𝑂 + 𝑉𝑓 = 250𝑉 × 0.45 1 − 50𝑘𝐻𝑧 × 600𝑛𝑠 − 0.45 × 1 60𝑉 + 2𝑉 = 3.48 𝐿𝑀 = 𝑉𝐼𝑁(𝑀𝐼𝑁) × 𝐷𝑀𝐴𝑋 2 2 × 𝑃𝑂 𝑛 × 𝐹𝑀𝐼𝑁 = 250𝑉 × 0.45 2 2 × 100𝑊 0.9 × 50𝑘𝐻𝑧 = 1.14𝑚𝐻 ≈ 1𝑚𝐻 𝐼𝐷𝑆(𝑃𝐾) = 𝑉𝐼𝑁(𝑀𝐼𝑁) × 𝐷𝑀𝐴𝑋 𝐿𝑀 × 𝐹𝑀𝐼𝑁 = 250𝑉 × 0.45 1.14𝑚𝐻 × 50𝑘𝐻𝑧 = 2𝐴𝑃𝐾 𝐼𝐷𝑆(𝑅𝑀𝑆) = 𝐷𝑀𝐴𝑋 3 × 𝐼𝐷𝑆(𝑃𝐾) = 0.45 3 × 2𝐴𝑝𝑘 = 775𝑚𝐴𝑅𝑀𝑆 𝑡𝑓 = 𝜋 × 𝐿𝑀 × 𝐶𝑂𝑆𝑆 2 tf: • Estimate tf to start • Calculate tf after power stage design complete Two-Switch Flyback Design Transformer Calculations 25 4. Area-product core size estimate: 5. Choose EER28L, calculate primary turns: 6. Secondary turns: 𝐴𝑒 × 𝐴𝑤 = 𝑃𝑂 × 10 8 × 𝐹𝐾 2 × 𝐹𝑀𝐼𝑁 × 𝐵𝑃𝐾 × 𝑊𝐹 × 𝐶𝐷 × 𝑈𝐹 = 100𝑊 × 108 × 1 2 × 50𝑘𝐻𝑧 × 3000𝐺 × 0.25 × 350 × 1 = 0.38𝑐𝑚2𝑐𝑚2 Where: FK = Cooling Factor (1=no cooling, 0.3=100 CFM) BPK = AC Flux Density (Gauss) WF = Window Factor ( 26 7. EER28L transformer winding structure: 1 NP(2-3)=38T NLED=22T 4 3 11,12 9,10 NHS(1-2)=3T 2 5 6 NP(3-4)=44T NDET(6-5)=4T Winding Pins (S→F) Wire Layers Turns ½ Primary 2→3 15/38, Served Litz 1 38 Secondary (LED) 9→11 30/38, Served Litz 1 22 Secondary (LED) 10→12 30/38, Served Litz 1 22 ½ Primary 3→4 15/38, Served Litz 1+ 44 Secondary (DET) 6→5 2/38, Bifilar 1 4 Secondary (HS) 2→1 2/38, Bifilar 1 3 EER28L ferrite core Two-Switch Flyback Design Transformer Winding Structure 27 • Can be used with any power topology • Constant current, U1a - Set V-, initially to ~200 mV - ILED through R12 will reach -200 mV - U1a output goes high→regulates ILED - ILED regulates CC as long as VLED 28 FAN7346 1 2 3 4 25 26 27 28GND VMIN CMP FB OVR 21 22 23 24 17 18 19 20 15 16 8 7 6 5 12 11 10 9 14 13 PWM2 PWM3 PWM4 FO SLPR ADIM ENA PWM1 VCC REF FB1 OUT1 CH1 CH3 FB2 OUT2 CH2 OUT4 CH4 FB3 OUT3 FB4 VDD VL SBIAS ADIM ON OFF 1 2 3 SBIAS ADIM PWM1 PWM2 PWM3 PWM4 ADIM FB FOD817A U2 30V 29 • Constant current, ICHx - ICHx sensed by RSx (FBx) - FBx compared to VADIM/10 - 4 V1.42 V→FB proportionally pulled low - ICHx is reduced, VLED clamped to OVR set voltage level RSx VADIM/10 1V Vf VDS VS Gm OVR DCDC OUT FB CMP FB CHx OUTx FBxFAN7346 ICHx 1.42V ILED 50mV 30 Power Board Schematic PFC, Boost Follower Enable, Inrush Limit BOOST FOLLOWER 1. OFF = 450 V 2. ON = BF 3. OPEN = 250 V 31 Power Board Schematic 2-Switch Flyback, PWM Dimmers 32 Power Board Schematic High-Voltage Flyback Bias Power Supply • 85 VRMS 33 Controller Daughter Card Schematic Single String CC-CV LED Controller • Sources current into optocoupler anode (OPTO_A) • Constant LED current set to 2 A • Constant LED voltage set to 50 V 34 Controller Daughter Card Schematic 4-Channel LED Controller • Sinks current through optocoupler cathode (OPTO_C) • Constant LED current set to 350 mA • OVR set to 62 V PDIM 1. OFF = 5 V 2. ON = PWM DIM 35 Power Board Dimensions 228.6 mm (9 in) 76.2 mm (3 in) 25 mm (0.99 in) 36 Power Board Partitioning 1 2 3 4 5 6 7 1. AC input, EMI filter, inrush current limiting 2. Flyback bias regulator 3. BCM PFC 4. 2-switch, quasi-resonant, flyback converter 5. Removable controller card (4-Channel Controller Shown) 6. PWM dimmer circuits 7. LED output terminal block 37 LED CC-CV Controller Cards OR 4-Channel, 50 V, 350 mA per Channel Single Channel, 50 V, 2 A J19 J23 38 • VIN = 120 VAC • VOUT = 450 V vs. boost follower • POUT = 120 W = 100% • Δη = 1.8%, @ 20% POUT • ηPK = 97%, @ 90% POUT BCM PFC Measured Efficiency & PF • VIN = 120 VAC, 230 VAC • VOUT = 450 V • POUT = 120 W = 100% • PF = 0.994 • LED power is constant so PFC should operate within 50% 39 • Measured - 80 VRMS 40 • VIN = step 115 VRMS to 300 VRMS • VOUT(BF) = 250 V to 450 V • POUT = 60 W BCM PFC Boost Follower Voltage Tracking CH1 = VIN(AC), CH2 = VOUT(BF) • VIN = step 300 VRMS to 115 VRMS • VOUT(BF) = 450 V to 250 V • POUT = 60 W 41 2-Switch Flyback CH1 = VGS(HO), CH2 = VGS(LO), CH3 = V(CBOOT) • Boost Follower Benefit - η = 94.75% peak @ 300 VDC - VIN = VOUT(BF) = 250 V to 470 V - 250 VIN corresponds to 120 VAC - Without boost follower, VIN = 450 V for 85 VRMS 42 2-Switch Flyback CH1 = VDS(LO), CH3 = VGS(LO) • Extended valley switching - VIN = VOUT(BF) = 250 V - D = 11% - fS = 68 kHz - POUT = 24 W (Dim, 60 V, 4 x 100 mA) • VDS valley switching on first valley - VIN = VOUT(BF)=250 V - D = 42% - fS = 63kHz - POUT = 85 W (60 V, 4 x 350 mA) 43 System Performance CH1 = PBIAS, CH2 = RDY, CH3 = VLED, CH4 = VOUT(PFC) • Shut-Down - RDY LOW, stops PFC and 2-switch flyback - RDY HIGH, starts 2-SW flyback - VLED slowly discharges - POUT = 70 W (LED Load) • Start-Up - PBIAS HIGH, starts PFC - RDY HIGH, starts 2-switch flyback - VLED monotonic soft-start - POUT = 70 W (LED Load) 44 System Performance CH1 = VIN(AC), CH2 = IIN(AC) • VIN(AC) = 300 VRMS - PF = 0.915 - POUT = 85 W (LED load) • VIN(AC) = 85 VRMS - PF = 0.994 - POUT = 85 W (LED load) 45 • Inrush current limiting - NTC R7 and R12 limit inrush to 3.18 A during startup - RDY signal (12 V) applied to U1-3, comparator output is HIGH, relay shorts across R7 + R12 to maintain high efficiency during steady state operation - Relay shorting time can be further adjusted by R16, C10 - Relay short is removed during power supply turn-off System Performance CH1 = VIN(AC), CH2 = IIN(AC), CH3 = VLED 46 System Performance CH1 = VIN(AC), CH2 = IIN(AC), CH3 = VLED • Inrush circuit enabled - VIN(AC) = 120 VRMS - POUT = 70 W (LED load) - IPK = 3.18 APK - 79.2% reduction • Inrush circuit disabled - VIN(AC) = 120 VRMS - POUT = 70 W (LED load) - IPK = 15.25 APK 47 • PWM Dimming “chops” LED DC current • FPWM = 250 Hz • DCH1 = DCH2 = 50%, DCH3 = 10%, DCH4 = 100% • ILEDCH1 = ILEDCH2 = 35 mA • ILEDCH3 = 176 mA • ILEDCH4 = 350 mA • η = 87.02% • PF =.971 during dimming System Performance CH1=PWMCH3, CH2=PWMCH1_CH2, CH3=ILEDCH3, CH4=ILEDCH1_CH2 • 2,on-board PWM dimmers • PDIM1 controls channels 1, 2 • PDIM2 control channels 3, 4 • FPWM = 250 Hz, 1% 48 System Performance Dimming • FAN7346 analog dimming - All four strings dim simultaneously - 0.5 V 49 System Performance EN61000-3-2, Class C (PIN>25 W) • VIN(AC) = 115 VRMS - VOUT(PFC) = 250 V - POUT = 85.41 W (60 V, 4×350 mA) - η = 91.05% - THD = 8.91% - Passes EN61000-3-2,Class C • VIN(AC) = 230 VRMS - VOUT(PFC) = 400 V - POUT = 86.2 W (60 V, 4×350 mA) - η = 91.51% - THD = 21.52% - Passes EN61000-3-2,Class C 50 System Performance Efficiency • POUT comparison - POUT = 70 W vs. 85 W - η>90% over entire range for 85 W 51 System Performance Power Factor & CC-CV • System PF • PF>90% for 85 W 52 Summary • High-power, industrial LED lighting requirements were reviewed • Several power solutions for CC-CV LED load control were introduced • 100 W, dual-stage, QR flyback, LED driver was designed - Wide AC input voltage range - High efficiency - Configurable for single-string or 4-string CC-CV LED operation • Techniques for maximizing efficiency were verified