WS2268

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 Application ■ Adapters/Chargers for Cell/Cordless phones, PDAs, MP3 and other portable apparatus 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. ■ 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 Line2 Line 3 W :Winsemi Logo Device Name(WS2268SP) Lot Code Y: Year code(0:2010,1:2011……) ww: Week code(1-52) Termianl Assignments Pin number 1 2 3 4 5 6 7 8 IP VP G GND PCC U CDC - Pin name The primary current sense Supply voltage Function This pin drives the base of external power NPN switch Ground This pin connects a resistor for peak current compensation The voltage feedback from the auxiliary winding This pin connects a resistor for cable compensation Null Block Diagram Constant voltage control Constant Current control 2/8 Steady, keep for your advance WS2268 Recommended Condition Parameter Supply voltage（VP） Operating temperature Value 10~30 -20~85 Unit V ℃ Absolute Maximum Ratings(Note 1) Parameter Supply voltage（VP） Feedback voltage（U） others（IP, G, PCC, CDC） Output current at G Power dissipation at Ta=25℃ Operating junction temperature Storage temperature Thermal resistance junction-to-ambient 30 -40~10 -0.3~7 Internally limited 0.657 150 -65~150 190 Value Unit V V V A W ℃ ℃ ℃/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 Start-up section Start-up threshold UVLO threshold Start-up current Operating current Vstu Vlo Istart IIS VP=Vstu-0.5V Static 18 7 20 9 3 600 22 11 5 900 V V uA uA Symbol Conditions Min Typ Max Unit Current sense section IP compare threshold Leading edge blanking Vip Tleb 475 500 500 525 mV ns Feedback section Feedback threshold voltage Input resistor Over voltage protection Open circuit protection vlotage Vs&href Ru Vovp Vockp Dynamic 7 -1.2 4 350 8 -1 9 -0.8 V KΩ V V Drive output section Output low voltage Output high voltage Output clamp Rise time Fall time VOL VOH VClamp Tr Tf CL = 1nf CL = 1nf Io = -20mA Io = 20mA 8 19 200 70 0.8 V V V ns ns 3/8 Steady, keep for your advance WS2268 ESD Information Symbol VESD_HBM VESD_MM Parameter Human model Machine model Value 2000 400 Unit V V Ordering Information Package 8 Pin SOP8, Pb-free IC marking information WS2268SP Purchasing device name WS2268 4/8 Steady, keep for your advance WS2268 Typical Operating Characteristics Vstart VS Temp 20.45 20.4 20.35 20.3 Vstart(V) 20.25 20.2 20.1 20.05 20 19.95 -40 0 40 Temp(℃) 80 120 160 20.15 Vstop Vs Temp 9 8.9 8.8 Vstop(V) 8.7 8.6 8.5 8.4 8.3 -40 0 40 Temp(℃) 80 120 160 Ist VS Temp 2.5 2 Iop VS Temp 900 800 700 600 Ist(uA) Iop(uA) 0 40 Temp(℃) 80 120 160 1.5 1 500 400 300 0.5 200 100 0 -40 0 -40 0 40 Temp(℃) 80 120 160 5/8 Steady, keep for your advance WS2268 Operration Description 1. Startup Mode At the phase of power-on, the rectified high voltage DC charges the capacitor of VP through the start-up resistor. When VP rises to 20V, the IC enters normal operation, then switching begins and the output voltage begins to rise. The VP bypass The output voltage. Assuming the secondary winding is master, the auxiliary winding is slave during the D1 on-time The auxiliary voltage is given by: Vaux Vs = Naux Ns capacitor must supply the IC until the output voltage builds up enough to provide power from the auxiliary winding to sustain the VP. The under-voltage threshold of VP is 9V, and therefore, the voltage on the VP capacitor must while the output is charging up. not drop more than 11V Vs = Vo + Vd So, Vaux = Naux ⋅ (Vo + Vd ) Ns Vaux = Vu * (1 + 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 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: The output voltage is different from the secondary 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 Vd. The voltage detection point is at two-thirds of the D1 on-time. The CV loop control function of WS2268 then Ipk = Vcs Rcs （2） .The energy stored in the magnetizing inductance Lm each cycle is : Eg = 1 × Lm × Ipk 2 2 （3） generates a D1 off-time to regulate the output voltage. So the power transferring from the input to the output is given by: 4、Constant Current Operation P= 1 × Lm × Ipk 2 × f sw 2 （4） Where f sw 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 The WS2268 captures the auxiliary winding feedback voltage at U pin and operates in constant-voltage (CV) mode to regulate WS2268 will keep a fixed proportion between D1 on-time Tons and D1 off-time Toffs by discharging or charging the capacitance. The fixed proportion is: 6/8 Steady, keep for your advance WS2268 Tons 4 = Toffs 3 The relationship between the output constant-current Iout and secondary peak current Ipks is given by: disabled and the gate driver can not be switched off. 6. CCM Protection The WS2268 is designed to operate in discontinuous conduction mode (DCM) in both CV and CC modes. To avoid operating in continuous conduction mode (CCM), the WS2268 detects the falling edge of the U input voltage on each cycle. If a 0.1V falling edge of U is not detected, the WS2268 will stop switching. Iout = 1 Tons × Ipks × 2 Tons + Toffs At the instant of D1 turn-on, the primary current transfers to the secondary at an amplitude of: Ipks = Np × Ipk Ns 7. OVP & OCkP 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 monitored, the WS2268 will immediately shut off and enter hiccup mode. The WS2268 sends out a fault detection pulse every 19ms in hiccup mode until the fault has been removed. Thus the output constant-current is given by: Iout = 1 Np Tons 2 Np × × Ipk × =× × Ipk 2 Ns Tons + Toffs 7 Ns 5. Leading Edge Blanking When the power switch is turned on, a turn-on spike will occur on the sense-resistor. To avoid false-termination of the switching pulse, a 430ns leading-edge blanking is built in. During this blanking period, the current sense comparator is 7/8 Steady, keep for your advance WS2268 SOP8 Package Information Unit:mm(inch) 8/8 Steady, keep for your advance