SY5881FAC

Applications Note: SY5881 Single Stage Buck And PFC Controller With Primary Side Control For LED Lighting And Mutiple Dimming Option Advanced Design Specification Features General Description The SY5881 is a single stage Buck and PFC controller targeting at LED lighting applications with PWM or Analog dimming. It is a primary side controller without applying any secondary feedback circuit for low cost, and drives the Buck converter in the quasi-resonant mode to achieve higher efficiency. It keeps the Buck converter in constant on time operation to achieve high power factor. Ordering Information SY5881 □(□□)□ Package type SO8 • • • Temperature Code Package Code Optional Spec Code Ordering Number SY5881FAC • • • Note ---- • • • • High dimming accuracy Dimming Range from 5.5% to 100.0% CV mode for Bias supply at 0.90 Compact package: SO8 Applications • LED lighting Typical Applications PWM Signal Input VS. IOUT 100 80 60 40 20 0 2.5 5.5 20 40 60 80 90 100 PWM Duty(%) Figure.1a Analog dimming with PWM signal input AN_SY5881 Rev.0.0 Silergy Corp. Confidential- Prepared for Customer Use Only 1 IOUT(%) AN_SY5881 Figure.1b Dimming curve of analog dimming IOUT(mA) IOUT(mA) Test Condition: VIN=220VAC, VOUT=80V, IOUT=300mA Figure.1c Actual curve of analog dimming VS. PWM input AN_SY5881 Rev.0.0 Silergy Corp. Confidential- Prepared for Customer Use Only 2 AN_SY5881 Pinout (top view) （SO8） Top Mark: BEHxyz (device code: BEH, x=year code, y=week code, z= lot number code) Pin Name Pin number COMP 1 ZCS 2 ISEN 3 Pin Description Loop compensation pin. Connect a RC network across this pin and ground to stabilize the control loop. Inductor current zero-crossing detection pin. This pin receives the auxiliary winding voltage by a resister divider and detects the inductor current zero crossing point. This pin also provides over voltage protection and line regulation modification function simultaneously. If the voltage on this pin is above VZCS,OVP, the IC would enter over voltage protection mode. Good line regulation can be achieved by adjusting the upper resistor of the divider. Current sense pin. Connect this pin to the source of the primary switch. Connect the sense resistor across the source of the primary switch and the GND pin. = (current sense resister R : R S GND DRV 4 5 VIN 6 ADIM 7 PWM 8 AN_SY5881 Rev.0.0 S V REF 2×I ) OUT Ground pin Gate driver pin. Connect this pin to the gate of primary MOSFET. Power supply pin. This pin also provides output over voltage protection along with ZCS pin. Bypass this pin to GND with enough capacitance to hold on internal voltage reference. PWM dimming input pin, this pin detects the PWM dimming signal Silergy Corp. Confidential- Prepared for Customer Use Only 3 AN_SY5881 Block Diagram COMP VIN UVLO ISEN IO Estimator Gm &BIAS PWM Logic VREF V REF DRV & Driver GND VISEN,MAX Valley Detect ZCS Buffer OVP DIM Control PWM VREF ADIM Figure.3 Block Diagram Absolute Maximum Ratings (Note 1) VIN, DRV -------------------------------------------------------------------------------------------------------------------0.3V~25V Supply current IVIN ----------------------------------------------------------------------------------------------------------------7mA ZCS, PWM ------------------------------------------------------------------------------------------------------------------0.3V~23V ADIM ------------------------------------------------------------------------------------------------------------------------0.3V~15V ISEN, COMP ----------------------------------------------------------------------------------------------------------------0.3~ 3.6V Power Dissipation, @ TA = 25°C SO8 ----------------------------------------------------------------------------------------1.1W Package Thermal Resistance (Note 2) SO8, θ JA -----------------------------------------------------------------------------------------------------------------------88°C/W SO8, θ JC -----------------------------------------------------------------------------------------------------------------------45°C/W Temperature Range --------------------------------------------------------------------------------------------------- - 40°C to 150°C Lead Temperature (Soldering, 10 sec.) ---------------------------------------------------------------------------------------260°C Storage Temperature Range ----------------------------------------------------------------------------------------- - 65°C to 150°C Recommended Operating Conditions (Note 3) VIN, DRV ---------------------------------------------------------------------------------------------------------------------- AN_SY5881 Rev.0.0 Silergy Corp. Confidential- Prepared for Customer Use Only 8V~20V 4 AN_SY5881 Electrical Characteristics (VIN = 12V (Note 3), TA = 25°C unless otherwise specified) Parameter Power Supply Section VIN turn-on threshold VIN turn-off threshold VIN OVP voltage Start up Current Shunt current in OVP mode Error Amplifier Section Internal reference voltage Current Sense Section Current limit reference voltage ZCS pin Section ZCS pin OVP voltage threshold Gate Driver Section Gate driver voltage Maximum source current Minimum sink current Max ON Time Min ON Time Max OFF Time Min OFF Time Maximum switching frequency ADIM function Section ADIM Enable ON ADIM Enable OFF Symbol V VIN_ON V VIN_OFF V VIN_OVP I ST I Test Conditions Min Typ Max Unit 19 20 22 V 8.0 8.5 V 7.5 VIN ON+3.0 V 34 µA 7 mA REF 300 mV ISEN_MAX 750 mV 1.5 V VIN_OVP V V VIN VIN_OVP V V V ZCS_OVP V Gate 12 V SOURCE 200 mA SINK 650 mA I I T ON_MAX T ON_MIN T VCOMP=2.6V 24 µs 300 ns OFF_MAX 120 µs OFF_MIN 0.5 µs MAX 120 kHz 75 mV 37 mV FB 145 °C SD 160 °C T f V ADIM_ON V ADIM_OFF Thermal Section Thermal Fold back Temperature Thermal shut down Temperature PWM function Section PWM ON voltage PWM OFF voltage T T V PWM_ON V PWM_OFF 1.2 0.5 V V Note 1: Stresses beyond the “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only. Functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Note 2: ſJA is measured in the natural convection at TA = 25°C on a low effective single layer thermal conductivity test board of JEDEC 51-3 thermal measurement standard. Test condition: Device mounted on 2” x 2” FR-4 substrate PCB, 2oz copper, with minimum recommended pad on top layer and thermal vias to bottom layer ground plane. Note 3: Increase VIN pin voltage gradually higher than VVIN_ON voltage then turn down to 12V. AN_SY5881 Rev.0.0 Silergy Corp. Confidential- Prepared for Customer Use Only 5 AN_SY5881 Operation The SY5881 is a single stage Buck and PFC controller targeting at LED lighting applications with multiple dimming function. The Device provides primary side control to eliminate the opto-couplers or the secondary feedback circuits, which would cut down the cost of the system. High power factor is achieved by constant on operation mode, with which the control scheme and the circuit structure are both simple. SY5881 is compatible with Analog dimming and PWM dimming for different application. In order to reduce the switching losses and improve EMI performance, Quasi-Resonant switching mode is applied, which means to turn on the power MOSFET at voltage Fig.4 Start up The start up resistor RST and CVIN are designed by rules below: (a) Preset start-up resistor RST, make sure that the current through RST is larger than IST and smaller than IVIN_OVP V I BUS V 176V × 1.414 15µA =16.59MΩ , = 264V×1.414 =186.7kΩ BUS I 2mA VIN_OVP Set RST R ST =300kΩ × 2=600kΩ (b) Design CVIN ( C VBUS R = ST VIN -I ST ) × tST V VIN_ON ( = 176V × 1.414 600kΩ -34µA)×500ms 22V =8.6µF Set CVIN CVIN =10µF #6 Set COMP pin Refer to Internal pre-charge design for quick start up Parameters designed R C COMP 1.5kΩ COMP1 2µF V C COMP_IC 900mV COMP2 0 #7 Set current sense resistor to achieve ideal output current Refer to constant-current control Known conditions at this step V REF 0.3V The current sense resistor is AN_SY5881 Rev.0.0 I OUT 0.3A Silergy Corp. Confidential- Prepared for Customer Use Only 15 AN_SY5881 V 0.3 R S = 2 × I OUT = 2 × 0.3A = 0.5Ω REF #8 set ZCS pin Refer to Line regulation modification and Over Voltage Protection (OVP) & Open Loop Protection (OLP) First identify RZCSU need for line regulation. Known conditions at this step Parameters Designed R ZCSU 200kΩ k 1 Then compute RZCSD Conditions V V V 1.42V 24V ZCS_OVP OUT 68 OVP 35V AUX 45 Parameters designed R 200kΩ 100 ZCSU N ≤ NS N V N OVP 3 × 12 AUX = 35 36 ≈1 V ZCS_OVP R < V × NS OUT ZCSD 1- V V ZCS_OVP OUT ×R N AUX ZCSU N ×N S AUX 1.5V ×1 = 24V × 200kΩ 1-1.5V ×1 24V = 13.3kΩ RZCSD is set to R ZCSD =13kΩ #9 set ADIM and PWM pin Refer to Analog Dimming Mode Design Conditions V PWM_ON 0.8V Parameters Designed 200kΩ RPWM_UP 10 −3 C ADIM = f PWM F × Hz = 10−3 F=1uF 1000 AN_SY5881 Rev.0.0 Silergy Corp. Confidential- Prepared for Customer Use Only 16 AN_SY5881 Hence CADIM is set to CADIM=1uF #10 final result AN_SY5881 Rev.0.0 Silergy Corp. Confidential- Prepared for Customer Use Only 17 AN_SY5881 1.55 SO8 Package Outline & PCB Layout Design 5.80 - 6.20 4 . 0 0 - 5.40 . 8 0 1.27 TYP 0.30 – 0.50 0.60 1 . 4 0 1 . 6 0 4 0.180.25 0.25 - 0.50 0.08-0.25 2 5 b a s e Recommended Pad Layout 4.80 - 5.00 5° -8° 0 0.60 - 0.85 1.27 (TYP) Notes: All dimensions are in millimeters. All dimensions don’t include mold flash & metal burr. AN_SY5881 Rev.0.0 Silergy Corp. Confidential- Prepared for Customer Use Only 18