FSQ0265

FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 — Green Mode Fairchild Power Switch (FPS™) September 2007 FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 Green Mode Fairchild Power Switch (FPS™) for Valley Switching Converter - Low EMI and High Efficiency Features Optimized for Valley Switching (VSC) Low EMI through Variable Frequency Control and Inherent Frequency Modulation High-Efficiency through Minimum Voltage Switching Narrow Frequency Variation Range over Wide Load and Input Voltage Variation Advanced Burst-Mode Operation for Low Standby Power Consumption Pulse-by-Pulse Current Limit Various Protection Functions: Overload Protection (OLP), Over-Voltage Protection (OVP), Abnormal Over-Current Protection (AOCP), Internal Thermal Shutdown (TSD) Under-Voltage Lockout (UVLO) with Hysteresis Internal Start-up Circuit Internal High-Voltage SenseFET (650V) Built-in Soft-Start (15ms) Description A Valley Switching Converter generally shows lower EMI and higher power conversion efficiency than a conventional hard-switched converter with a fixed switching frequency. The FSQ-series is an integrated Pulse-Width Modulation (PWM) controller and SenseFET specifically designed for valley switching operation with minimal external components. The PWM controller includes an integrated fixed-frequency oscillator, Under-Voltage Lockout, Leading Edge Blanking (LEB), optimized gate driver, internal soft-start, temperature-compensated precise current sources for loop compensation, and self-protection circuitry. Compared with discrete MOSFET and PWM controller solutions, the FSQ-series reduces total cost, component count, size and weight; while simultaneously increasing efficiency, productivity, and system reliability. This device provides a basic platform that is well suited for costeffective designs of valley switching fly-back converters. Applications Power Supply for DVP Player and DVD Recorder, Set-Top Box Adapter Auxiliary Power Supply for PC, LCD TV, and PDP TV Related Application Notes AN-4137, AN-4141, AN-4147, AN-4150 (Flyback) AN-4134 (Forward) FPSTM is a trademark of Fairchild Semiconductor Corporation. © 2006 Fairchild Semiconductor Corporation FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 Rev. 1.0.5 www.fairchildsemi.com FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 — Green Mode Fairchild Power Switch (FPS™) Ordering Information Product Number(5) FSQ311 FSQ311L FSQ321 FSQ321L FSQ0165RN PKG. Operating Temp. Current Limit Maximum Output Power(1) RDS(ON) Max. 230VAC±15%(2) Adapter(3) Open-Frame(4) 85-265VAC Adapter(3) Open-Frame(4) Replaces Devices 8-DIP 8-LSOP 8-DIP 8-LSOP 8-DIP -40 to +85C 0.6A 19Ω 7W 10W 6W 8W FSDL321 FSDM311 FSDL321 FSDM311 FSDL0165RN FSDM0265RN FSDM0265RNB FSDM0365RN FSDM0365RNB -40 to +85°C 0.6A 19Ω 8W 12W 7W 10W FSQ0165RL 8-LSOP FSQ0265RN 8-DIP -40 to +85°C 0.9A 10Ω 10W 15W 9W 13W FSQ0265RL 8-LSOP FSQ0365RN 8-DIP -40 to +85°C 1.2A 6Ω 14W 20W 11W 16W FSQ0365RL 8-LSOP -40 to +85°C 1.5A 4.5Ω 17.5W 25W 13W 19W Notes: 1. The junction temperature can limit the maximum output power. 2. 230VAC or 100/115VAC with doubler. The maximum power with CCM operation. 3. Typical continuous power in a non-ventilated enclosed adapter measured at 50°C ambient temperature. 4. Maximum practical continuous power in an open-frame design at 50°C ambient. 5. Pb-free package per JEDEC J-STD-020B. © 2006 Fairchild Semiconductor Corporation FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 Rev. 1.0.5 2 www.fairchildsemi.com FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 — Green Mode Fairchild Power Switch (FPS™) Typical Circuit VO AC IN Vstr PWM Vfb Vcc Drain Sync GND FSQ0365RN Rev.00 Figure 1. Typical Flyback Application Internal Block Diagram Sync 4 + 0.7V/0.2V + VCC Vref Idelay IFB 3R R SoftStart PWM LEB 200ns S Q Gate driver 0.35/0.55 VBurst OSC + Vref VCC good 8V/12V Vstr 5 Vcc 2 Drain 67 8 Vfb 3 RQ AOCP 6V TSD 2.5μs time delay VCC good FSQ0365RN Rev.00 S Q 1 VOCP (1.1V) VSD GND Sync Vovp 6V RQ Figure 2. Functional Block Diagram © 2006 Fairchild Semiconductor Corporation FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 Rev. 1.0.5 3 www.fairchildsemi.com FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 — Green Mode Fairchild Power Switch (FPS™) Pin Configuration GND Vcc Vfb Sync FSQ0365RN Rev.01 D 8-DIP 8-LSOP V D D Vstr Figure 3. Pin Configuration (Top View) Pin Definitions Pin # 1 2 Name GND Vcc Description SenseFET source terminal on primary side and internal control ground. Positive supply voltage input. Although connected to an auxiliary transformer winding, current is supplied from pin 5 (Vstr) via an internal switch during startup (see Internal Block Diagram Section). It is not until VCC reaches the UVLO upper threshold (12V) that the internal start-up switch opens and device power is supplied via the auxiliary transformer winding. The feedback voltage pin is the non-inverting input to the PWM comparator. It has a 0.9mA current source connected internally while a capacitor and optocoupler are typically connected externally. There is a time delay while charging external capacitor Cfb from 3V to 6V using an internal 5μA current source. This time delay prevents false triggering under transient conditions but still allows the protection mechanism to operate under true overload conditions. This pin is internally connected to the sync-detect comparator for valley switching. Typically the voltage of the auxiliary winding is used as Sync input voltage and external resistors and capacitor are needed to make time delay to match valley point. The threshold of the internal sync comparator is 0.7V/0.2V. This pin is connected to the rectified AC line voltage source. At start-up the internal switch supplies internal bias and charges an external storage capacitor placed between the Vcc pin and ground. Once the Vcc reaches 12V, the internal switch is opened. The drain pins are designed to connect directly to the primary lead of the transformer and are capable of switching a maximum of 700V. Minimizing the length of the trace connecting these pins to the transformer will decrease leakage inductance. 3 Vfb 4 Sync 5 Vstr 6,7,8 Drain © 2006 Fairchild Semiconductor Corporation FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 Rev. 1.0.5 4 www.fairchildsemi.com FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 — Green Mode Fairchild Power Switch (FPS™) Absolute Maximum Ratings Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be operable above the recommended operating conditions and stressing the parts to these levels is not recommended. In addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. The absolute maximum ratings are stress ratings only. TA = 25°C, unless otherwise specified. Symbol VSTR VDS VCC VFB VSync Vstr Pin Voltage Drain Pin Voltage Supply Voltage Characteristic Min. 500 650 Max. Unit V V 20 -0.3 -0.3 FSQ0365 FSQ0265 FSQ0165 FSQ321/311 FSQ0365 FSQ0265 FSQ0165 FSQ321/311 9.0 9.0 12 8 4 1.5 230 140 50 10 1.5 -40 -40 -55 Internally limited 85 150 CLASS1 C CLASS B V V V Feedback Voltage Range Sync Pin Voltage Range IDM Drain Current Pulsed(6) A EAS Single Pulsed Avalanche Energy(7) mJ PD TJ TA TSTG ESD Total Power Dissipation Recommended Operating Junction Temperature Operating Ambient Temperature Storage Temperature Human Body Model(8) Machine Model(8) W °C °C °C Notes: 6. Repetitive rating: Pulse width limited by maximum junction temperature. 7. L=51mH, starting TJ=25°C. 8. Meets JEDEC standards JESD22-A114 and JESD22-A115. Thermal Impedance Symbol 8-DIP(9) θJA(10) θJC(11) θJT(12) Junction-to-Ambient Thermal Resistance Junction-to-Case Thermal Resistance Junction-to-Top Thermal Resistance 80 20 35 °C/W Parameter Value Unit Notes: 9. All items are tested with the standards JESD 51-2 and 51-10 (DIP). 10. Free-standing, with no heat-sink, under natural convection. 11. Infinite cooling condition - refer to the SEMI G30-88. 12. Measured on the package top surface. © 2006 Fairchild Semiconductor Corporation FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 Rev. 1.0.5 5 www.fairchildsemi.com FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 — Green Mode Fairchild Power Switch (FPS™) Electrical Characteristics TA = 25°C unless otherwise specified. Symbol SenseFET Section BVDSS IDSS Parameter Drain Source Breakdown Voltage Zero-Gate-Voltage Drain Current FSQ0365 Drain-Source On-State Resistance(13) FSQ0265 FSQ0165 FSQ321/311 FSQ0365 FSQ0265 FSQ0165 FSQ321/311 FSQ0365 FSQ0265 FSQ0165 FSQ321/311 FSQ0365 Reverse Transfer Capacitance FSQ0265 FSQ0165 FSQ321/311 FSQ0365 FSQ0265 FSQ0165 FSQ321/311 FSQ0365 FSQ0265 FSQ0165 FSQ321/311 FSQ0365 FSQ0265 FSQ0165 FSQ321/311 FSQ0365 FSQ0265 FSQ0165 FSQ321/311 Condition VCC = 0V, ID = 100µA VDS = 560V Min. Typ. Max. Unit 650 100 3.5 4.5 6.0 10.0 19.0 Ω 5.0 8.0 14.0 315 550 250 162 47 38 25 18 9.0 17.0 10.0 3.8 11.2 20.0 12.0 9.5 34 15 4 19 28.2 55.0 30.0 33.0 32 25 10 42 V µA RDS(ON) TJ = 25°C, ID = 0.5A CSS Input Capacitance VGS = 0V, VDS = 25V, f = 1MHz pF COSS Output Capacitance VGS = 0V, VDS = 25V, f = 1MHz pF CRSS VGS = 0V, VDS = 25V, f = 1MHz pF td(on) Turn-On Delay Time VDD = 350V, ID = 25mA ns tr Rise Time VDD = 350V, ID = 25mA ns td(off) Turn-Off Delay Time VDD = 350V, ID = 25mA ns tf Fall Time VDD = 350V, ID = 25mA ns Control Section tON.MAX1 tON.MAX2 tB1 tB2 Maximum On Time1 Maximum On Time2 Blanking Time1 Blanking Time2 All but Q321 Q321 All but Q321 Q321 TJ = 25°C TJ = 25°C 10.5 6.35 13.2 7.5 12.0 7.06 15.0 8.2 13.5 7.77 16.8 µs µs µs µs © 2006 Fairchild Semiconductor Corporation FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 Rev. 1.0.5 6 www.fairchildsemi.com FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 — Green Mode Fairchild Power Switch (FPS™) Electrical Characteristics (Continued) TA = 25°C unless otherwise specified. Symbol tW fS1 fS2 ΔfS IFB DMIN VSTART VSTOP tS/S1 tS/S2 VBURH VBURL VBUR(HYS) Protection Section Parameter Detection Time Window Initial Switching Freq.1 Initial Switching Freq.2 Feedback Source Current Minimum Duty Cycle UVLO Threshold Voltage Internal Soft-Start Time1 Internal Soft-Start Time2 All but Q321 Q321 All but Q321 Q321 Condition TJ = 25°C, Vsync = 0V Min. Typ. Max. Unit 3.0 50.5 84.0 55.6 89.3 ±5 700 11 7 900 12 8 15 10 0.45 0.55 0.35 200 0.65 0.45 61.7 95.2 ±10 1100 0 13 9 µs kHz kHz % µA % V V ms ms V V mV 1.68 1.34 1.0 0.67 0.67 6.5 6 6.5 4 155 0.85 0.26 V µA ns V µs °C V V ns 5 450 1.00 mA µA mA V A Switching Frequency Variation(14) -25°C < TJ < 85°C VFB = 0V VFB = 0V After turn-on With free-running frequency With free-running frequency Burst Mode Section Burst-Mode Voltage TJ = 25°C, tPD = 200ns(15) 0.25 FSQ0365 FSQ0265 ILIM Peak Current Limit FSQ0165 FSQ321 FSQ311 VSD IDELAY tLEB VOVP tOVP TSD VSH VSL tSync IOP ISTART ICH VSTR Shutdown Feedback Voltage Shutdown Delay Current Leading-Edge Blanking Time(14) Over-Voltage Protection Over-Voltage Protection Blanking Time Thermal Shutdown Temperature(14) TJ = 25°C, di/dt = 240mA/µs TJ = 25°C, di/dt = 200mA/µs TJ = 25°C, di/dt = 175mA/µs TJ = 25°C, di/dt = 125mA/µs TJ = 25°C, di/dt = 112mA/µs VCC = 15V VFB = 5V VCC = 15V, VFB = 2V 1.32 1.06 0.8 0.53 0.53 5.5 4 5.5 2 125 0.55 0.14 1.50 1.20 0.9 0.60 0.60 6.0 5 200 6.0 3 140 0.70 0.20 300 Sync Section Sync Threshold Voltage Sync Delay Time(14)(16) VCC = 15V VCC = VSTART - 0.1V (before VCC reaches VSTART) VCC = 0V, VSTR = min. 40V 1 270 0.65 Total Device Section Oper. Supply Current (Control Part Only) Start Current Start-up Charging Current Minimum VSTR Supply Voltage 3 360 0.85 26 Notes: 13. Pulse test: Pulse-Width=300μs, duty=2% 14. Though guaranteed, it is not 100% tested in production. 15. Propagation delay in the control IC. 16. Includes gate turn-on time. © 2006 Fairchild Semiconductor Corporation FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 Rev. 1.0.5 7 www.fairchildsemi.com FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 — Green Mode Fairchild Power Switch (FPS™) Comparison Between FSDM0x65RNB and FSQ-Series Function Operation method EMI reduction FSDM0x65RNB Constant frequency PWM Frequency modulation FSQ-Series Valley switching operation Valley switching & inherent frequency modulation FSQ-Series Advantages Improved efficiency by valley switching Reduced EMI noise Reduce EMI noise by two ways Improved standby power by valley switching also in burst-mode Because the current peak during burst operation is dependent on VFB, it is easier to solve audible noise Improved reliability through precise abnormal over-current protection Burst-mode operation Fixed burst peak Advanced burst-mode Protection AOCP © 2006 Fairchild Semiconductor Corporation FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 Rev. 1.0.5 8 www.fairchildsemi.com FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 — Green Mode Fairchild Power Switch (FPS™) Typical Performance Characteristics These characteristic graphs are normalized at TA= 25°C. 1.2 1.0 1.2 1.0 Normalized 0.8 0.6 0.4 0.2 0.0 -25 0 25 50 75 100 125 Normalized 0.8 0.6 0.4 0.2 0.0 -25 0 25 50 75 100 125 Temperature [°C] Temperature [°C] Figure 4. Operating Supply Current (IOP) vs. TA Figure 5. UVLO Start Threshold Voltage (VSTART) vs. TA 1.2 1.0 1.2 1.0 Normalized 0.8 0.6 0.4 0.2 0.0 -25 0 25 50 75 100 125 Normalized 0.8 0.6 0.4 0.2 0.0 -25 0 25 50 75 100 125 Temperature [°C] Temperature [°C] Figure 6. UVLO Stop Threshold Voltage (VSTOP) vs. TA Figure 7. Start-up Charging Current (ICH) vs. TA 1.2 1.0 1.2 1.0 Normalized 0.8 0.6 0.4 0.2 0.0 -25 0 25 50 75 100 125 Normalized 0.8 0.6 0.4 0.2 0.0 -25 0 25 50 75 100 125 Temperature [°C] Temperature [°C] Figure 8. Initial Switching Frequency (fS) vs. TA © 2006 Fairchild Semiconductor Corporation FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 Rev. 1.0.5 9 Figure 9. Maximum On Time (tON.MAX) vs. TA www.fairchildsemi.com FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 — Green Mode Fairchild Power Switch (FPS™) Typical Performance Characteristics (Continued) These characteristic graphs are normalized at TA= 25°C. 1.2 1.0 1.2 1.0 Normalized 0.8 0.6 0.4 0.2 0.0 -25 0 25 50 75 100 125 Normalized 0.8 0.6 0.4 0.2 0.0 -25 0 25 50 75 100 125 Temperature [°C] Temperature [°C] Figure 10. Blanking Time (tB) vs. TA Figure 11. Feedback Source Current (IFB) vs. TA 1.2 1.0 1.2 1.0 Normalized Normalized 0.8 0.6 0.4 0.2 0.0 -25 0 25 50 75 100 125 0.8 0.6 0.4 0.2 0.0 -25 0 25 50 75 100 125 Temperature [°C] Temperature [°C] Figure 12. Shutdown Delay Current (IDELAY) vs. TA Figure 13. Burst-Mode High Threshold Voltage (Vburh) vs. TA 1.2 1.0 1.2 1.0 Normalized Normalized 0.8 0.6 0.4 0.2 0.0 -25 0 25 50 75 100 125 0.8 0.6 0.4 0.2 0.0 -25 0 25 50 75 100 125 Temperature [°C] Temperature [°C] Figure 14. Burst-Mode Low Threshold Voltage (Vburl) vs. TA Figure 15. Peak Current Limit (ILIM) vs. TA © 2006 Fairchild Semiconductor Corporation FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 Rev. 1.0.5 10 www.fairchildsemi.com FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 — Green Mode Fairchild Power Switch (FPS™) Typical Performance Characteristics (Continued) These characteristic graphs are normalized at TA= 25°C. 1.2 1.0 1.2 1.0 Normalized 0.8 0.6 0.4 0.2 0.0 -25 0 25 50 75 100 125 Normalized 0.8 0.6 0.4 0.2 0.0 -25 0 25 50 75 100 125 Temperature [°C] Temperature [°C] Figure 16. Sync High Threshold Voltage (VSH) vs. TA Figure 17. Sync Low Threshold Voltage (VSL) vs. TA 1.2 1.0 1.2 1.0 Normalized 0.8 0.6 0.4 0.2 0.0 -25 0 25 50 75 100 125 Normalized 0.8 0.6 0.4 0.2 0.0 -25 0 25 50 75 100 125 Temperature [°C] Temperature [°C] Figure 18. Shutdown Feedback Voltage (VSD) vs. TA Figure 19. Over-Voltage Protection (VOP) vs. TA © 2006 Fairchild Semiconductor Corporation FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 Rev. 1.0.5 11 www.fairchildsemi.com FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 — Green Mode Fairchild Power Switch (FPS™) Functional Description 1. Startup: At startup, an internal high-voltage current source supplies the internal bias and charges the external capacitor (Ca) connected to the Vcc pin, as illustrated in Figure 20. When VCC reaches 12V, the FPS begins switching and the internal high-voltage current source is disabled. The FPS continues its normal switching operation and the power is supplied from the auxiliary transformer winding unless VCC goes below the stop voltage of 8V. 2.2 Leading Edge Blanking (LEB): At the instant the internal SenseFET is turned on, a high-current spike usually occurs through the SenseFET, caused by primary-side capacitance and secondary-side rectifier reverse recovery. Excessive voltage across the Rsense resistor would lead to incorrect feedback operation in the current mode PWM control. To counter this effect, the FPS employs a leading edge blanking (LEB) circuit. This circuit inhibits the PWM comparator for a short time (tLEB) after the SenseFET is turned on. VCC Idelay Vref IFB OSC VDC VO FOD817A VFB CB 3 D1 D2 + VFB* R 3R SenseFET Ca KA431 Gate driver - 2 VCC 5 ICH Vstr VSD FSQ0365RN Rev. 00 OLP Rsense 8V/12V VCC good Vref Figure 21. Pulse-Width-Modulation (PWM) Circuit 3. Synchronization: The FSQ-series employs a valley switching technique to minimize the switching noise and loss. The basic waveforms of the valley switching converter are shown in Figure 22. To minimize the MOSFET's switching loss, the MOSFET should be turned on when the drain voltage reaches its minimum value, as shown in Figure 22. The minimum drain voltage is indirectly detected by monitoring the VCC winding voltage, as shown in Figure 22. Vds FSQ0365RN Rev.00 Internal Bias Figure 20. Start-up Circuit 2. Feedback Control: FPS employs current mode control, as shown in Figure 21. An opto-coupler (such as the FOD817A) and shunt regulator (such as the KA431) are typically used to implement the feedback network. Comparing the feedback voltage with the voltage across the RSENSE resistor makes it possible to control the switching duty cycle. When the reference pin voltage of the shunt regulator exceeds the internal reference voltage of 2.5V, the opto-coupler LED current increases, thus pulling down the feedback voltage and reducing the duty cycle. This event typically happens when the input voltage is increased or the output load is decreased. 2.1 Pulse-by-Pulse Current Limit: Because current mode control is employed, the peak current through the SenseFET is limited by the inverting input of PWM comparator (VFB*), as shown in Figure 21. Assuming that the 0.9mA current source flows only through the internal resistor (3R + R = 2.8k), the cathode voltage of diode D2 is about 2.5V. Since D1 is blocked when the feedback voltage (VFB) exceeds 2.5V, the maximum voltage of the cathode of D2 is clamped at this voltage, thus clamping VFB*. Therefore, the peak value of the current through the SenseFET is limited. VRO VRO VDC Vsync tF Vovp (6V) 0.7V 0.2V 300ns Delay MOSFET Gate ON ON FSQ0365RN Rev.00 Figure 22. Valley Resonant Switching Waveforms www.fairchildsemi.com 12 © 2006 Fairchild Semiconductor Corporation FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 Rev. 1.0.5 FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 — Green Mode Fairchild Power Switch (FPS™) 4. Protection Circuits: The FSQ-series has several self-protective functions, such as Overload Protection (OLP), Abnormal Over-Current protection (AOCP), OverVoltage Protection (OVP), and Thermal Shutdown (TSD). All the protections are implemented as autorestart mode. Once the fault condition is detected, switching is terminated and the SenseFET remains off. This causes VCC to fall. When VCC falls down to the Under-Voltage Lockout (UVLO) stop voltage of 8V, the protection is reset and start-up circuit charges VCC capacitor. When the VCC reaches the start voltage of 12V, the FSQ-series resumes normal operation. If the fault condition is not removed, the SenseFET remains off and VCC drops to stop voltage again. In this manner, the auto-restart can alternately enable and disable the switching of the power SenseFET until the fault condition is eliminated. Because these protection circuits are fully integrated into the IC without external components, the reliability is improved without increasing cost. voltage. If the output consumes more than this maximum power, the output voltage (VO) decreases below the set voltage. This reduces the current through the optocoupler LED, which also reduces the opto-coupler transistor current, thus increasing the feedback voltage (VFB). If VFB exceeds 2.8V, D1 is blocked and the 5µA current source starts to charge CB slowly up to VCC. In this condition, VFB continues increasing until it reaches 6V, when the switching operation is terminated, as shown in Figure 24. The delay time for shutdown is the time required to charge CB from 2.8V to 6V with 5µA. A 20 ~ 50ms delay time is typical for most applications. VFB 6.0V FSQ0365RN Rev.00 Overload protection 2.8V Fault occurs Fault removed VDS Power on t12= CFB*(6.0-2.8)/Idelay t1 t2 t Figure 24. Overload Protection 4.2 Abnormal Over-Current Protection (AOCP): When the secondary rectifier diodes or the transformer pins are shorted, a steep current with extremely high-di/dt can flow through the SenseFET during the LEB time. Even though the FSQ-series has OLP (Overload Protection), it is not enough to protect the FSQ-series in that abnormal case, since severe current stress is imposed on the SenseFET until OLP triggers. The FSQ-series has an internal AOCP (Abnormal Over-Current Protection) circuit as shown in Figure 25. When the gate turn-on signal is applied to the power SenseFET, the AOCP block is enabled and monitors the current through the sensing resistor. The voltage across the resistor is compared with a preset AOCP level. If the sensing resistor voltage is greater than the AOCP level, the set signal is applied to the latch, resulting in the shutdown of the SMPS. 3R VCC 12V 8V t Normal operation Fault situation Normal operation FSQ0365RN Rev. 00 Figure 23. Auto Restart Protection Waveforms 4.1 Overload Protection (OLP): Overload is defined as the load current exceeding its normal level due to an unexpected abnormal event. In this situation, the protection circuit should trigger to protect the SMPS. However, even when the SMPS is in the normal operation, the overload protection circuit can be triggered during the load transition. To avoid this undesired operation, the overload protection circuit is designed to trigger only after a specified time to determine whether it is a transient situation or a true overload situation. Because of the pulse-by-pulse current limit capability, the maximum peak current through the Sense FET is limited, and therefore the maximum input power is restricted with a given input OSC PWM LEB 200ns S Q R Q Gate driver R Rsense AOCP FSQ0365RN Rev.00 + VOCP - 1 GND Figure 25. Abnormal Over-Current Protection © 2006 Fairchild Semiconductor Corporation FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 Rev. 1.0.5 13 www.fairchildsemi.com FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 — Green Mode Fairchild Power Switch (FPS™) 4.3 Over-Voltage Protection (OVP): If the secondary side feedback circuit malfunctions or a solder defect causes an opening in the feedback path, the current through the opto-coupler transistor becomes almost zero. Then, VFB climbs up in a similar manner to the overload situation, forcing the preset maximum current to be supplied to the SMPS until the overload protection triggers. Because more energy than required is provided to the output, the output voltage may exceed the rated voltage before the overload protection triggers, resulting in the breakdown of the devices in the secondary side. To prevent this situation, an OVP circuit is employed. In general, the peak voltage of the sync signal is proportional to the output voltage and the FSQ-series uses a sync signal instead of directly monitoring the output voltage. If the sync signal exceeds 6V, an OVP is triggered, shutting down the SMPS. To avoid undesired triggering of OVP during normal operation, the peak voltage of the sync signal should be designed below 6V. 4.4 Thermal Shutdown (TSD): The SenseFET and the control IC are built in one package. This makes it easy for the control IC to detect the abnormal over temperature of the SenseFET. If the temperature exceeds ~150°C, the thermal shutdown triggers. 5. Soft-Start: The FPS has an internal soft-start circuit that increases PWM comparator inverting input voltage with the SenseFET current slowly after it starts up. The typical soft-start time is 15ms, The pulse width to the power switching device is progressively increased to establish the correct working conditions for transformers, inductors, and capacitors. The voltage on the output capacitors is progressively increased with the intention of smoothly establishing the required output voltage. This mode helps prevent transformer saturation and reduces stress on the secondary diode during startup. 6. Burst Operation: To minimize power dissipation in standby mode, the FPS enters burst-mode operation. As the load decreases, the feedback voltage decreases. As shown in Figure 26, the device automatically enters burst-mode when the feedback voltage drops below VBURL (350mV). At this point, switching stops and the output voltages start to drop at a rate dependent on standby current load. This causes the feedback voltage to rise. Once it passes VBURH (550mV), switching resumes. The feedback voltage then falls and the process repeats. Burst-mode operation alternately enables and disables switching of the power SenseFET, thereby reducing switching loss in standby mode. VO VOset VFB 0.55V 0.35V IDS VDS time FSQ0365RN Rev.00 t1 Switching disabled t2 t3 Switching disabled t4 Figure 26. Waveforms of Burst Operation 7. Switching Frequency Limit: To minimize switching loss and EMI (Electromagnetic Interference), the MOSFET turns on when the drain voltage reaches its minimum value in valley switching operation. However, this causes switching frequency to increases at light load conditions. As the load decreases, the peak drain current diminishes and the switching frequency increases. This results in severe switching losses at light-load condition, as well as intermittent switching and audible noise. Because of these problems, the valley switching converter topology has limitations in a wide range of applications. To overcome this problem, FSQ-series employs a frequency-limit function, as shown in Figures 27 and 28. Once the SenseFET is turned on, the next turn-on is prohibited during the blanking time (tB). After the blanking time, the controller finds the valley within the detection time window (tW) and turns on the MOSFET, as shown in Figures 27 and 28 (Cases A, B, and C). If no valley is found during tW, the internal SenseFET is forced to turn on at the end of tW (Case D). Therefore, our devices have a minimum switching frequency of 55kHz and a maximum switching frequency of 67kHz, as shown in Figure 28. © 2006 Fairchild Semiconductor Corporation FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 Rev. 1.0.5 14 www.fairchildsemi.com FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 — Green Mode Fairchild Power Switch (FPS™) tsmax=18μs IDS IDS When the resonant period is 2μs 67kHz 59kHz 55kHz A B C Constant frequency A tB=15μs ts D Burst mode IDS IDS B tB=15μs ts FSQ0365RN Rev. 00 PO Figure 28. Switching Frequency Range IDS IDS C tB=15μs ts IDS IDS tB=15μs D tW=3μs tsmax=18μs FSQ0365RN Rev. 00 Figure 27. Valley Switching with Limited Frequency © 2006 Fairchild Semiconductor Corporation FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 Rev. 1.0.5 15 www.fairchildsemi.com FSQ0365, FSQ0265, FSQ0165, FSQ321, FSQ311 — Green Mode Fairchild Power Switch (FPS™) Typical Application Circuit of FSQ0365RN Application DVD Player Power Supply FPS Device Input Voltage Range 85-265VAC Rated Output Power Output Voltage (Max. Current) 5.1V (1.0A) 3.4V (1.0A) 12V (0.4A) 16V (0.3A) FSQ0365RN 19W Features High efficiency ( >77% at universal input) Low standby mode power consumption (70% at universal input) Low standby mode power consumption (