WS3252 WS3252 High Precision CC/CV Primary-Side PWM Controller Features ■ 5uA ultra-low startup current ■ 2mA Low operating current ■±5% Constant Voltage Regulation at Universal AC input ■ Primary-side Sensing and Regulation Without TL431 and Opto-coupler ■ Programmable CV and CC Regulation ■ Built-in Primary winding inductance compensation ■ Programmable cable drop compensation ■ Built-in soft start ■ Built-in Leading-edge blanking ■ Cycle by cycle over current protection (OCP) ■ VCC over voltage clamp & under voltage lockout( UVLO) ■ Maximum Gate output voltage clamped at 12V ■ Frequency jittering General Description WS3252 is a high-integrated offline PWM controller, optemized for high poformance low power AC/DC charger and adapter adapter application. WS3252 operates in primary-side sensing and regulation. Consequently, opto-coupler and TL431 could be eliminated, thus reduce the cost. It can achieve ± 5% constant voltage precision in full input voltage range. CC/CV Control as shown in fig.1.In CC Control, the current and output power setting can be adjusted externally by the sense resistor Rs at CS pin. In CV control, multi-mode operations are utilized to achieve high performance and high efficiency. In addition, good load regulation is achieved by the built-in cable drop compensation. Device operates in PFM in CC mode as well at large load condition and it operates in PWM with frequency reduction at light/medium load. Vo 5% Applications Low power AC/DC offline SMPS for ■ Cell Phone Charger ■ Digital Cameras Charger ■ Small Power Adapter ■ Auxiliary Power for PC, TV etc. ■ Linear Regulator/RCC Replacement Typical Application Circuit Io Icc WS3252 offers power on soft start control and protection coverage with auto-recovery features including Cycle-by-Cycle current limiting, VCC OVP,VCC clamp and UVLO. The gate-driven output is clamped to maximum 12V to protect the internal MOSFET. Excellent EMI performance is achieved by using the soft-switching and frequency jittering at the totem-pole-gate-drive output. The WS3252 is the ideal substitute of the linear power supply or the RCC-mod e power, for a better performance of the whole switch power system and a lower cost. WS3252 is available in SOT23-6 package. Rev.A Sep.2011 Copyright@Winsemi Microelectronics Co., Ltd., All right reserved. WS3252 Pin Definition and Device Marking 1 GND VCC 6 2 GATE 52: WS3252 CO M P 5 Y: Year Code(0-9) WW: Week Code (1-52) 3 CS IN V 4 SOT23-6 Pin Function Description Pin Name Pin Number Pin Type GND 1 GND GATE 2 Gate-driven output Totem-pole gate driver output for power MOSFET. CS 3 Current Monitoring Current sense input. Function Description Ground. The voltage feedback from auxiliary winding. Connected to INV 4 Feedback Input resistor divider from auxiliary winding reflecting output voltage. PWM duty cycle is determined by EA output and current sense signal at pin3. COMP 5 Loop Compensation VCC 6 Power Loop Compensation for CV Stability Power supply Block Diagram GND 1 6 VCC Vcc_OVP G a te 2 Driver regulator UVLO Inter supply PO R CLK Generation Logic CC Controller LEB OCP 5 COM P PW M +& SS Drop Comp CS - 3 EA + Sampler 4 IN V 2V Sampling Controller 2/8 Steady, keep you advance WS3252 Ordering Information Package 6-Pin SOT23-6, Pb-free IC Marking Information Purchasing Device Name WS3252TP WS3252TP Recommended Operating Condition Symbol Parameter Value Unit VCC VCC supply voltage 10~30 V TA Operating temperature -20~85 ℃ Absolute Maximum Ratings Symbol Parameter Value Unit VCC DC supply voltage 30 V VINV INV input voltage -0.3~7 V VCS CS input voltage -0.3~7 V VCOMP COMP input voltage -0.3~7 V TJ Max. Operating junction temperature 150 ℃ TSTG Min./Max. Storage temperature -55~150 ℃ ICC VCC Clamp Continuous Current 10 mA Note Note: Stresses above those listed under 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 Recommended Operating Conditions section are not implied. Exposure to absolute maximum-rated conditions for extended periods may affect device reliability. 3/8 Steady, keep you advance WS3252 Electrical Characteristics (TA=25℃，VCC=16V, if not otherwise noted) Supply Voltage (VCC) symbol parameter Test condition I_VCC_ST Start up current I_VCC_OP Typ Max Unit VCC=13V 5 20 uA Operation Current VCC=18V,INV=2V,CS=0V 2 3 mA UVLO_ON Turn on threshold Voltage VCC falling 8.2 9.0 10.5 V UVLO_OFF Turn-off threshold Voltage VCC rising 13.5 14.8 16.0 V VCC_Clamp VCC Zener Clamp Voltage IVCC=10mA 28 29 31 V Ramp VCC until gate shut down 27 28.3 30 V 1.97 2 2.03 V Over voltage Min protection OVP Threshold Error Amplifier Section Vref_EA Reference voltage for EA Gain DC gain of EA Max. Cable 60 dB 37.5 uA 625 ns compensation I_comp_max INV=2V,COMP=0V current Current Sense Section TLEB Leading edge Blanking Time Zsense Input impedance TD_OC OCP control delay VTH_OC OCP threshold T_ss Soft start time 50 kΩ 110 0.88 0.91 ns 0.94 17 V ms Oscillator Section Freq_Max1 IC Maximum frequency System nominal 55 60 65 khz switch Freq_Nom 50 khz 14 khz ±6 % frequency Freq_startup ∆f/Freq INV=0V,COMP=5V Frequency shuffling range Gate Driver Output Section VOL Output Low Level Io=20mA VOH Output High Level Io=20mA V_clamp Output Clamp Voltage Level T_r Output Rising Time T_f Output Falling Time 1 6 V V 12 V CL=0.5nF 650 ns CL=0.5nF 40 ns Note Note: 1. Freq_Max indicates IC internal maximum clock frequency. In system application, the maximum operation frequency of 60kHz nominal occurs at maximum output power or the transition point from CV to CC. 4/8 Steady, keep you advance WS3252 Typical Operating Characteristics 5/8 Steady, keep you advance WS3252 Function Description winding. During MOSFET turn-on time, the load current WS3252 is a high-integrated offline PWM controller, is supplied from the output filter capacitor Co. The optemized for high poformance low power AC/DC current in the primary winding ramps up. When MOSFET charger and adapter adapter application. WS3252 turns off, the primary current transfers to the secondary operates at the amplitude of in Consequently, primary-side opto-coupler sensing and and TL431 regulation. could be Is = eliminated, thus reduce the cost. High presicion CC/CV control can meet most adapter and charger application requirements. NP *Ip Ns The auxiliary voltage reflects the output voltage, given by V AUX = N AUX * (Vo + ∆V ) NS Startup Current and Startup Control Where △ V indicates the drop voltage of the output Startup current of WS3252 is designed to be extremely Diode. low at 5uA, so that VCC could be charged up above Via a resistor divider connectrd between the auxiliary UVLO threshold level and device starts up quickly. A winding and INV, the auxiliary voltage is sampled at the large value startup resistor can therefore be used to end of the demagnetization and it is hold until the next minimize the power loss, predigest the design of startup sampling. The sampled voltage is compared with circuit and provides reliable startup in application. Vref(2V) and the error is amplified. The error amplifier output COMP reflects the load condition and controls the PWM switching frequency to regulate the output voltage, thus the constant output current can be achieved. Operating Current The operating current of WS3252 is low at 2mA. Excellent efficiency is achieved with low operating current together and multi-mode control circuit. When sampled voltage is below Vref and error amplifier output COMP reaches its maximum, the switching frequency is controlled by the sampled voltage thus the output voltage to regulate the output current, thus the constant output current can be achieved. CC/CV Operation WS3252 is designed to produce good CC/CV control Adjustable CC point and Output Power characteristic as shown in the fig.1. In charger In WS3252, the CC point and maximum output power applications, a discharged battery charging starts in the can be externally adjusted by eaternal current sense CC portion of the curve until it is nearly full charged and resistor Rs at CS pin. The output power is adjusted smoothly switches to operate in CV portion of the curve. through CC point change. The larger Rs, the smaller CC In an AC/DC adapter, the normal operation occurs only point is, and the smaller output power becomes, and on the CV portion of the curve. The CC portion provides vice versa. output current limiting. In CV operation, the output voltage is regulated through the primary side control. In Vo CC operation mode, WS3252 will regulate the output Large Rs current constant regardless of the output voltage drop. Small R s Principle of Operation To achieve high precision CC/CV control, system needs Io to be designed in DCM mode for flyback system. In DCM mode, the output voltage can be sensed via the auxiliary Fig.2 Adjustable output power by changing Rs 6/8 Steady, keep you advance WS3252 Operation switching frequency Programmable Cable Drop Compensation The switching frequency of WS3252 is adaptively Cable drop compensation is implemented to achieve controlled according to the load conditions and the good load regulation inWS3252. An offset voltage is operation modes. The operation switching frequency at generated at INV by an internal current flowing into the maximum output power is set to 60KHz internally. In resister divider. The current is inversely proportional to DCM mode, the maximum output power is given by the voltage across pin COMP, as a result, it is inversely PoMAX proportional to the output load current, thus the drop due 1 2 = LP FSW I P 2 to the cable loss can be compensated. As the load current decreases from full-load to no-load, the offset Where Lp indicate the inductance of primary winding and voltage at INV will increase. It can also be programmed Ip is peak current of primary winding. by adjusting the resistance of the divider to compensate The change of the primary winding inductance results in the drop for various cable lines used. the change of the maximum output power and constant output current in CC mode. To compensate the change from viariations of primary winding inductance, the switching frequency is locked by an internal loop such Gate Drive that the switching frequency is The gate drive strength which is too weak leads to over FSW = Since TDemag is switch loss of MOSFET while too strong gate drive 1 output compromises in the over EMI. A good tradeoff 2TDemag inversely between output strength and dead time control is proportional to the achieved through the design of the built-in totem pole inductance, as a result, the product Lp and Fsw is gate. The low standby dissipation and good EMI system constant, thus the maximum output power and constant design is easier to achieve through this dedicated devise. current in CC mode will not change as primary winding For MOSFET gate protection, an internal 12V clamp is inductance changes. Up to ±10% variation of the primary added at higher than expected VCC input. winding inductance can be compensation. Protection Controls Frequency Shuffling Excellent Excellent EMI performance is achieved by using comprehensive frequency jittering in WS3252 Cycle-by-Cycle current limiting (OCP), VCC Clamp, system stability protection is of achieved WS3252. by the Including Under Voltage Lockout on VCC (UVLO). Device restarts when VCC voltage drops below UVLO limit. It is clamped when VCC is higher than threshold Current Sensing and Leading Edge Blanking value. The power MOSFET is shut down when VCC Cycle-by-Cycle current limiting is offered in WS3252. drops below UVLO limit and device enters power on The switch current is detected by a sense resistor into start-up sequence thereafter. the sense pin. An internal leading edge blanking circuit chops off the sense voltage spike at initial MOSFET on state due to snubber diode reverse recovery so that the external RC filtering on sense input is no longer required. The current limit comparator is disabled and thus cannot turn off the internal MOSFET during the blanking period. PWM duty cycle is determined by the current sense input voltage and the EA output voltage. 7/8 Steady, keep you advance WS3252 SOT23-6 Package Outline Dimensions Symbol A A1 A2 b c D E E1 e e1 L θ Dimensions In Milimeters Min Max 1.000 1.300 0.000 0.150 1.000 1.200 0.300 0.500 0.100 0.200 2.800 3.020 1.500 1.700 2.600 3.000 0.950(BSC) 1.800 2.000 0.300 0.600 0° 8° Dimensions In Inches Min Max 0.039 0.051 0.000 0.006 0.039 0.047 0.012 0.020 0.004 0.008 0.110 0.119 0.059 0.067 0.102 0.118 0.037(BSC) 0.071 0.079 0.012 0.024 0° 8° 8/8 Steady, keep you advance