RT7302 Evaluate Report for T8 Internal Power (Flyback) ACDC BU / SLM Division Mar. 2016 http://www.richtek.com/LED CONFIDENTIAL RT7302 Brief introduction RT7302 is an active power factor correction controller specifically designed for using as a constant current LED driver. Supporting: Isolation: PSR mode Non-isolation: Buck-Boost mode Applications AC/DC LED lighting driver ……… 2 CONFIDENTIAL RT7302 Features Primary-Side Regulation PWM Controller and High PF LED Driver • Primary Side Regulation(PSR) • Power Factor Correction(PFC) • Compatible with TRIAC Dimmer • Built-in HV start-up Device • Critical conduction mode(CRM) • Max/Min switch frequency clamping • Max/Min on time limitation 3 CONFIDENTIAL RT7302 Advantage • Universal input voltage. (90Vac~264Vac) • Good LED current regulation. • No shunt regulator and photo to achieve the 2 nd regulation. • Protection: a. Open-circuit protection b. Short-circuit protection c. Output diode short-circuit protection d. Vdd under/over voltage protection e. Over temperature protection f . Cycle-by-cycle current limitation g. Excellent PF and THD. 4 CONFIDENTIAL Circuit 5 CONFIDENTIAL Electrical Performance 6 CONFIDENTIAL Efficiency 7 CONFIDENTIAL Power Factor 8 CONFIDENTIAL Current regulation Limit in 1.23% 9 CONFIDENTIAL Load regulation Frequency Vac [V] Vout [V] Iout [mA] 60Hz 60Hz 60Hz 50Hz 50Hz 50Hz 110 42.79 45.80 49.52 43.11 46.23 49.73 407 404 403 403 400 399 110 110 230 230 230 Load regulation 0.98% 0.99% 10 CONFIDENTIAL PCB layout Top Trace Bottom Trace 11 CONFIDENTIAL Demo board photo L LED- N LED+ Length Width Height 229mm 18mm 10mm PCB No : PCB022_V1 12 CONFIDENTIAL BOM Item Location Value Type 1 F1 T1.25A/300V SS-5F-2P 2 RV1 7N471K TVS-2P 3 LX2 30mH LRS-T14 4 CX1 0.1uF CFS-12X12 5 LX1 5mH LDS-D9X12 6 BD1 1A/600V DB-1A 7 C4 0.1uF/500V CFS-11X10 8 R6,R7,R9 2.2Mohm 0805 9 R19 43kohm 0603 10 C6 22nF/50V 0603 11 C7 2.2uF/25V 0805 12 R22 0ohm 0603 13 CONFIDENTIAL BOM Item Location Value Type 13 R8 10kohm 1206 14 R2 140kohm 1206 15 D2 FM4007 SOD123 16 C2 2.2nF/1kV 1206 17 R13 200R 0805 18 D4 1N4148 SOD-123 19 Q1 4A/600V TO-220 20 C9 100p/1kV 1206 21 LX3 T3.5*3*1.4 --- 22 R15,R16,R17 2.21ohm 1206 23 R14 2kohm 0603 24 C10 470p/1kV 1206 14 CONFIDENTIAL BOM Item Location Value Type 25 CY1 1000pF/250Vac CAP-10mm 26 R10 60kohm 0603 27 R18 8.06kohm 0603 28 C5 22pF 0603 29 D3 BAV21 SOD-123 30 R11 82R 0603 31 EC2 33uF/50V CES-5X11 32 T1 EDR28 EDR28 33 U1 RT7302 SOP-8 34 D1 SF26 DO-15 35 R1 33.2R 1206 36 C1 220p/1kV 1206 15 CONFIDENTIAL BOM Item Location Value Type 37 EC1 220uF/63V CES-10X25 38 L1 110uF LR-T9 39 R4 200kohm 1206 40 C8 47.5kohm 1206 Total : 44 pcs 16 CONFIDENTIAL Transformer top view 17 CONFIDENTIAL Power Component Stress Voltage Test condition: 90Vac input / 60V,300mA output Stead state Location Max rating (V) Measure De-rating Q1 600 304 50.67% D1 400 110 27.50% Transient State Location Max rating (V) Measure De-rating Q1 600 304 50.67% D1 400 110 27.50% 18 CONFIDENTIAL Power Component Stress Voltage Test condition: 264Vac input / 60V,300mA output Stead state Location Max rating (V) Measure De-rating Q1 600 568 94.67% D1 400 227 56.75% Transient State Location Max rating (V) Measure De-rating Q1 600 572 95.33% D1 400 230 57.50% Suggestion: If change the Q1 from 600V to 650V. The de-rating decrease to 87.38%(Stead state) and 88%(Transient state) . 19 CONFIDENTIAL Start up waveform Vac_in = 90V T_start up =760ms Vac_in = 264V T_start up =370ms 20 CONFIDENTIAL LED open protection Vac_in = 90V Ch2:Vout ; Ch3:Vzcd ; Ch4:Vdd Vac_in = 264V Ch2:Vout ; Ch3:Vzcd ; Ch4:Vdd When LED open , the output keeps rising and causing the VZCD rising accordingly. If Vzcd trigger the protected level(2.9V~3.3V), the IC latch down. IC will be auto-restarted when the output is recovered. 21 CONFIDENTIAL LED Short protection Vac_in = 90V Ch2:Vout ; Ch3:Vgate ; Ch4:Vcs Vac_in = 264V Ch2:Vout ; Ch3:Vgate ; Ch4:Vcs When LED short , the output level is 0V and the Vcs will rise to trigger the protected function. IC will be auto-restarted when the output is recovered. 22 CONFIDENTIAL Harmonic(IEC61000-3-2) 110V input Class C : Pass Class D : Pass 23 CONFIDENTIAL Harmonic(IEC61000-3-2) 230V input Class C : Pass Class D : Pass 24 CONFIDENTIAL Conduction-EMI 230V-LPass 230V-N Pass 25 CONFIDENTIAL Conduction-EMI 110V-LPass 110V-N Pass 26 CONFIDENTIAL Radiation-EMI 230V-V Pass 230V-H Pass 27 CONFIDENTIAL Radiation-EMI 110V-V Pass 110V-H Pass 28