WS2268 Primary Side AC/DC Controller Features ■ Lower no-load power ■ Lower start-up current ■ Built-in cable compensation ■ Built-in peak current compensation ■ Random frequency modulation to reduce system EMI ■ Built-in leading edge blanking ■ Current limited protection in each cycle ■ Over voltage protection ■ Open circuit protection ■ Under voltage lockout Gerneral Description The WS2268 is a high performance AC/DC power supply controller for battery charger and adapter applications. The device uses Pulse Frequency Modulation (PFM) method to build discontinuous conduction mode (DCM) flyback power supplies. The WS2268 provides accurate constant voltage, constant current (CV/CC) regulation without requiring the opto-coupler and the secondary control circuitry. It also eliminates the need of loop compensation circuitry while maintaining stability. The WS2268 achieves excellent regulation and high power efficiency, the no-load power consumption is less than 100mW. The WS2268 is available in SOP8 package. Application ■ Adapters/Chargers for Cell/Cordless phones, PDAs, MP3 and other portable apparatus ■ Standby and Auxiliary power supplies Typical Application WS2268 Rev. 2 Jan.2012 Copyright@Winsemi Mircroelectronics.,Ltd.,All rights reserved. T21-2 WS2268 Genenral Information Pin Configuration Marking Information WS2268SP DVf YWW Line1 W :Winsemi Logo Line2 Device Name(WS2268SP) Line 3 Lot Code Y: Year code(0:2010,1:2011……) ww: Week code(1-52) Termianl Assignments Pin number Pin name Function 1 IP The primary current sense 2 VP Supply voltage 3 G This pin drives the base of external power NPN switch 4 GND Ground 5 PCC This pin connects a resistor for peak current compensation 6 U The voltage feedback from the auxiliary winding 7 CDC This pin connects a resistor for cable compensation 8 - Null Block Diagram Constant voltage control Constant Current control 2/8 Steady, keep for your advance WS2268 Recommended Condition Parameter Value Unit Supply voltage（VP） 10~30 V Operating temperature -20~85 ℃ Absolute Maximum Ratings(Note 1) Value Parameter Unit Supply voltage（VP） 30 V Feedback voltage（U） -40~10 V others（IP, G, PCC, CDC） -0.3~7 V Output current at G Internally limited A Power dissipation at Ta=25℃ 0.657 W Operating junction temperature 150 ℃ Storage temperature -65~150 ℃ Thermal resistance junction-to-ambient 190 ℃/W Note 1：Stresses greater than those listed under “Absolute Maximum Rating” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under “Recommended operating conditions” is not implied. Exposure to “Absolute Maximum Rating” for extended periods may affect device reliability. Electrical Characteristics (Tc = 25°C) Parameter Symbol Conditions Min Typ Max Unit Start-up section Start-up threshold Vstu 18 20 22 V UVLO threshold Vlo 7 9 11 V Start-up current Istart VP=Vstu-0.5V 3 5 uA IIS Static 600 900 uA 500 525 mV Operating current Current sense section IP compare threshold Vip 475 Leading edge blanking Tleb 500 ns Vs&href 4 V 350 KΩ Feedback section Feedback threshold voltage Input resistor Ru Dynamic Over voltage protection Vovp 7 8 9 V Open circuit protection vlotage Vockp -1.2 -1 -0.8 V 0.8 V Drive output section Output low voltage VOL Io = -20mA Output high voltage VOH Io = 20mA Output clamp 8 VClamp V 19 V Rise time Tr CL = 1nf 200 ns Fall time Tf CL = 1nf 70 ns 3/8 Steady, keep for your advance WS2268 ESD Information Symbol Parameter Value Unit VESD_HBM Human model 2000 V VESD_MM Machine model 400 V Ordering Information Package IC marking information Purchasing device name 8 Pin SOP8, Pb-free WS2268SP WS2268 4/8 Steady, keep for your advance WS2268 Typical Operating Characteristics Vstop Vs Temp Vstart VS Temp 9 20.45 20.4 8.9 20.35 8.8 20.3 Vstop(V) Vstart(V) 20.25 8.7 20.2 8.6 20.15 20.1 8.5 20.05 8.4 20 8.3 19.95 -40 0 40 80 120 -40 160 0 40 80 120 160 Temp(℃) Temp(℃) Ist VS Temp Iop VS Temp 2.5 900 800 2 700 Iop(uA) Ist(uA) 600 1.5 1 500 400 300 200 0.5 100 0 -40 0 0 40 80 120 160 -40 0 Temp(℃) 40 80 Temp(℃) 5/8 Steady, keep for your advance 120 160 WS2268 Operration Description 1. Startup Mode The output voltage. Assuming the secondary winding is At the phase of power-on, the rectified high voltage DC master, the auxiliary winding is slave during the D1 on-time charges the capacitor of VP through the start-up resistor. When The auxiliary voltage is given by: VP rises to 20V, the IC enters normal operation, then switching Vaux Vs = Naux Ns begins and the output voltage begins to rise. The VP bypass capacitor must supply the IC until the output voltage builds up Vs = Vo + Vd enough to provide power from the auxiliary winding to sustain So, Vaux = Naux ⋅ (Vo + Vd ) the VP. The under-voltage threshold of VP is 9V, and therefore, the voltage on the VP capacitor must Ns not drop more than 11V Vaux = Vu * (1 + while the output is charging up. R2 ) R3 Where Vd is the diode forward drop voltage. 2. Constant Primary Peak Current The primary current ip(t) is sensed by a current sense resistor Rcs, the current rises up linearly at a rate of: dip (t ) Vg (t ) = dt Lm （1） Auxiliary voltage waveform Primary current waveform The output voltage is different from the secondary As illustrated in top figure，when the current ip(t) rises up to Ipk, the switch turns off. The constant peak current is given by: Ipk = Vcs Rcs （2） voltage in a diode forward drop voltage that depends on the current. If the secondary voltage is always detected at a fixed secondary current, the difference between the output voltage and the secondary voltage will be a fixed .The energy stored in the magnetizing inductance Lm each cycle is : Vd. The voltage detection point is at two-thirds of the D1 on-time. The CV loop control function of WS2268 then Eg = 1 × Lm × Ipk 2 2 （3） So the power transferring from the input to the output is given generates a D1 off-time to regulate the output voltage. 4、Constant Current Operation by: P= 1 × Lm × Ipk 2 × f sw 2 Where f sw （4） is the switching frequency. When the peak current Ipk is constant, the output power depends on the switching frequency f sw . Secondary current waveform In CC operation, the CC loop control function of 3. Constant Voltage Operation WS2268 will keep a fixed proportion between D1 on-time The WS2268 captures the auxiliary winding feedback voltage at Tons and D1 off-time Toffs by discharging or charging the U pin and operates in constant-voltage (CV) mode to regulate capacitance. The fixed proportion is: 6/8 Steady, keep for your advance WS2268 disabled and the gate driver can not be switched off. Tons 4 = Toffs 3 6. CCM Protection The relationship between the output constant-current Iout The WS2268 is designed to operate in discontinuous and secondary peak current Ipks is given by: conduction mode (DCM) in both CV and CC modes. To 1 Tons × Ipks × 2 Tons + Toffs avoid operating in continuous conduction mode (CCM), Iout = At the instant of D1 turn-on, the primary current transfers to the secondary at an amplitude of: Ipks = voltage on each cycle. If a 0.1V falling edge of U is not detected, the WS2268 will stop switching. Np × Ipk Ns 7. OVP & OCkP Thus the output constant-current is given by: Iout = the WS2268 detects the falling edge of the U input 1 Np Tons 2 Np × × Ipk × = × × Ipk 2 Ns Tons + Toffs 7 Ns 5. Leading Edge Blanking WS2268 include output over-voltage protection (OVP) and open circuit protection (OckP) circuitry. If the voltage at U pin exceeds 8V, 100% above the normal detection voltage, or the -1V falling edge of U input can not be When the power switch is turned on, a turn-on spike will monitored, the WS2268 will immediately shut off and occur on the sense-resistor. To avoid false-termination of the enter hiccup mode. The WS2268 sends out a fault switching pulse, a 430ns leading-edge blanking is built in. detection pulse every 19ms in hiccup mode until the fault During this blanking period, the current sense comparator is has been removed. 7/8 Steady, keep for your advance WS2268 SOP8 Package Information Unit:mm(inch) 8/8 Steady, keep for your advance