FAN7930 Critical Conduction Mode PFC Controller Features Description The FAN7930 is an active power factor correction (PFC) controller for boost PFC applications that operate in critical conduction mode (CRM). It uses a voltage-mode PWM that compares an internal ramp signal with the error amplifier output to generate a MOSFET turn-off signal. Because the voltage-mode CRM PFC controller does not need rectified AC line voltage information, it saves the power loss of an input voltage sensing network necessary for a current-mode CRM PFC controller. PFC Ready Signal Input Voltage Absent Detection Circuit Maximum Switching Frequency Limitation Internal Soft-Start and Startup without Overshoot Internal Total Harmonic Distortion (THD) Optimizer Precise Adjustable Output Over-Voltage Protection Open-Feedback Protection and Disable Function Zero Current Detector 150μs Internal Startup Timer MOSFET Over-Current Protection Under-Voltage Lockout with 3.5V Hysteresis Low Startup and Operating Current Totem-Pole Output with High State Clamp +500/-800mA Peak Gate Drive Current Related Resources 8-Pin SOP AN-8035 — Design Consideration Conduction Mode PFC Using FAN7930 Applications FAN7930 provides over-voltage protection, openfeedback protection, over-current protection, inputvoltage-absent detection, and under-voltage lockout protection. The PFC-ready pin can be used to trigger other power stages when PFC output voltage reaches the proper level with hysteresis. The FAN7930 can be disabled if the INV pin voltage is lower than 0.45V and the operating current decreases to a very low level. Using a new variable on-time control method, THD is lower than the conventional CRM boost PFC ICs. for Boundary Adapter Ballast LCD TV, CRT TV SMPS Ordering Information Part Number Operating Temperature Range Top Mark -40 to +125°C FAN7930 Package Packing Method Rail FAN7930M FAN7930MX © 2010 Fairchild Semiconductor Corporation FAN7930 • Rev. 1.0.1 8-Lead Small Outline Package (SOP) Tape & Reel www.fairchildsemi.com FAN7930 — Critical Conduction Mode PFC Controller April 2010 Figure 1. Typical Boost PFC Application Internal Block Diagram Figure 2. © 2010 Fairchild Semiconductor Corporation FAN7930 • Rev. 1.0.1 FAN7930 — Critical Conduction Mode PFC Controller Application Diagram Functional Block Diagram www.fairchildsemi.com 2 Figure 3. Pin Configuration (Top View) Pin Definitions Pin # Name Description 1 INV This pin is the inverting input of the error amplifier. The output voltage of the boost PFC converter should be resistively divided to 2.5V. 2 RDY This pin is used to detect PFC output voltage reaching a pre-determined value. When output voltage reaches 89% of rated output voltage, this pin is pulled HIGH, which is an (open drain) output type. 3 COMP 4 CS 5 ZCD This pin is the input of the zero-current detection block. If the voltage of this pin goes higher than 1.5V, then goes lower than 1.4V, the MOSFET is turned on. 6 GND This pin is used for the ground potential of all the pins. For proper operation, the signal ground and the power ground should be separated. 7 OUT This pin is the gate drive output. The peak sourcing and sinking current levels are +500mA and 800mA, respectively. For proper operation, the stray inductance in the gate driving path must be minimized. 8 VCC This is the IC supply pin. IC current and MOSFET drive current are supplied using this pin. FAN7930 — Critical Conduction Mode PFC Controller Pin Configuration This pin is the output of the transconductance error amplifier. Components for the output voltage compensation should be connected between this pin and GND. This pin is the input of the over-current protection comparator. The MOSFET current is sensed using a sensing resistor and the resulting voltage is applied to this pin. An internal RC filter is included to filter switching noise. © 2010 Fairchild Semiconductor Corporation FAN7930 • Rev. 1.0.1 www.fairchildsemi.com 3 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. Symbol VCC Parameter Min. Supply Voltage Max. Unit VZ V IOH, IOL Peak Drive Output Current -800 +500 mA ICLAMP Driver Output Clamping Diodes VO>VCC or VO<-0.3V -10 +10 mA Detector Clamping Diodes -10 +10 mA -0.3 8.0 -10.0 6.0 IDET VIN Error Amplifier Input, Output, ZCD and RDY Pin CS Input Voltage (2) TJ Operating Junction Temperature TA Operating Temperature Range Storage Temperature Range TSTG ESD (1) Electrostatic Discharge Capability V +150 °C -40 +125 °C -65 +150 °C Human Body Model, JESD22-A114 2.5 Charged Device Model, JESD22-C101 2.0 kV Notes: 1. When this pin is supplied by external power sources by accident, its maximum allowable current is 50mA. 2. In case of DC input, acceptable input range is -0.3V~6V: within 100ns -10V~6V is acceptable, but electrical specifications are not guaranteed during such a short time. FAN7930 — Critical Conduction Mode PFC Controller Absolute Maximum Ratings Thermal Impedance Symbol ΘJA Parameter Min. (3) Thermal Resistance, Junction-to-Ambient 150 Max. Unit °C/W Note: 3. Regarding the test environment and PCB type, please refer to JESD51-2 and JESD51-10. © 2010 Fairchild Semiconductor Corporation FAN7930 • Rev. 1.0.1 www.fairchildsemi.com 4 VCC = 14V, TA = -40°C~+125°C, unless otherwise specified. Symbol Parameter Conditions Min. Typ. Max. Units VCC Section VSTART Start Threshold Voltage VCC Increasing 11 12 13 V VSTOP Stop Threshold Voltage VCC Decreasing 7.5 8.5 9.5 V 3.0 3.5 4.0 V 20 22 HYUVLO UVLO Hysteresis VZ Zener Voltage VOP Recommended Operating Range ICC=20mA 13 24 V 20 V Supply Current Section ISTART Startup Supply Current VCC=VSTART-0.2V 120 190 µA IOP Operating Supply Current Output Not Switching 1.5 3.0 mA IDOP Dynamic Operating Supply Current 50kHZ, CI=1nF 2.5 4.0 mA 90 160 230 µA 2.465 2.500 2.535 V 0.1 10.0 mV IOPDIS Operating Current at Disable VINV=0V Error Amplifier Section VREF1 ΔVREF1 ΔVREF2 Voltage Feedback Input Threshold1 TA=25°C Line Regulation VCC=14V~20V Temperature Stability of VREF1 (4) 20 IEA,BS Input Bias Current VINV=1V~4V IEAS,SR Output Source Current VINV=VREF -0.1V -12 µA IEAS,SK Output Sink Current VINV=VREF +0.1V 12 µA VEAH Output Upper Clamp Voltage VINV=1V, VCS=0V VEAZ Zero Duty Cycle Output Voltage gm Transconductance (4) -0.5 mV 0.5 µA 6.0 6.5 7.0 V 0.9 1.0 1.1 V 90 115 140 µmho 35.5 41.5 47.5 µs 11.2 13.0 14.8 µs 0.7 0.8 0.9 V -1.0 -0.1 1.0 µA 350 500 ns FAN7930 — Critical Conduction Mode PFC Controller Electrical Characteristics Maximum On-Time Section tON,MAX1 Maximum On-Time Programming 1 TA=25°C, VZCD=1V tON,MAX2 Maximum On-Time Programming 2 TA=25°C, IZCD=0.469mA Current-Sense Section VCS ICS,BS tCS,D Current Sense Input Threshold Voltage Limit Input Bias Current VCS=0V~1V Current Sense Delay to Output dV/dt=1V/100ns, from 0V to 5V (4) Continued on the following page… © 2010 Fairchild Semiconductor Corporation FAN7930 • Rev. 1.0.1 www.fairchildsemi.com 5 VCC = 14V, TA = -40°C~+125°C, unless otherwise specified. Symbol Parameter Conditions Min. Typ. Max. Units 1.35 1.50 1.65 V 0.05 0.10 0.15 V 5.5 6.2 7.5 V 0 0.65 1.00 V -1.0 -0.1 1.0 µA Zero-Current Detect Section VZCD HYZCD Input Voltage Threshold (4) (4) Detect Hysteresis VCLAMPH Input High Clamp Voltage IDET=3mA VCLAMPL Input Low Clamp Voltage IDET= -3mA IZCD,BS Input Bias Current VZCD=1V~5V (4) IZCD,SR Source Current Capability TA=25°C -4 mA IZCD,SK Sink Current Capability TA=25°C 10 mA tZCD,D Maximum Delay From ZCD to Output (4) Turn-On dV/dt=-1V/100ns, from 5V to 0V 100 200 ns 9.2 (4) Output Section VOH Output Voltage High IO=-100mA, TA=25°C 11.0 12.8 V VOL Output Voltage Low IO=200mA, TA=25°C 1.0 2.5 V (4) CIN=1nF 50 100 ns (4) CIN=1nF 50 100 ns 13.0 14.5 V 1 V tRISE tFALL Rising Time Falling Time VO,MAX Maximum Output Voltage VCC=20V, IO=100µA VO,UVLO Output Voltage with UVLO Activated VCC=5V, IO=100µA 11.5 FAN7930 — Critical Conduction Mode PFC Controller Electrical Characteristics Restart / Maximum Switching Frequency Limit Section tRST fMAX Restart Timer Delay (4) Maximum Switching Frequency 50 150 300 µs 250 300 350 kHz 2 4 mA 320 500 mV 1 µA RDY Pin IRDY,SK Output Sink Current 1 VRDY,SAT Output Saturation Voltage IRDY,LK IRDY,SK=2mA Output Leakage Current Output High Impedance Soft-Start Timer Section tSS (4) Internal Soft-Soft 3 5 7 ms 2.185 2.240 2.295 V UVLO Section VRDY HYRDY Output Ready Voltage Output Ready Hysteresis 0.600 V Protections VOVP HYOVP VEN HYEN OVP Threshold Voltage TA=25°C 2.620 2.675 2.730 V OVP Hysteresis TA=25°C 0.120 0.175 0.230 V 0.40 0.45 0.50 V 0.050 0.10 0.15 V 125 140 155 °C Enable Threshold Voltage Enable Hysteresis TSD Thermal Shutdown Temperature THYS Hysteresis Temperature of TSD (4) (4) 60 °C Note: 4. These parameters, although guaranteed by design, are not production tested. © 2010 Fairchild Semiconductor Corporation FAN7930 • Rev. 1.0.1 www.fairchildsemi.com 6 Function PFC Ready Pin FAN7530 None FAN7930 FAN7930 Advantages Integrated No External Circuit for PFC Output UVLO Open-Drain Pin has Versatile Uses Reduction of Power Loss and BOM Cost Caused by PFC Out UVLO Circuit Frequency Limit None Integrated AC Absent Detection Integrated Increase System Reliability with AC On-Off Test None Reduce Voltage and Current Stress at Startup No External Resistor is Needed Soft-Start and Overshoot-less None Integrated THD Optimizer External Internal TSD None 140°C with 60°C Hysteresis © 2010 Fairchild Semiconductor Corporation FAN7930 • Rev. 1.0.1 Abnormal CCM Operation Prohibited Abnormal Inductor Current Accumulation can be Prohibited Guarantee Stable Operation at Short Electric Power Failure Eliminate Audible Noise due to Unwanted OVP Triggering Stable and Reliable TSD Operation Converter Temperature Range Limited Range FAN7930 — Critical Conduction Mode PFC Controller Comparison of FAN7530 and FAN7930 www.fairchildsemi.com 7 Figure 4. Voltage Feedback Input Threshold 1 (VREF1) vs. TA Figure 5. Start Threshold Voltage (VSTART) vs. TA Figure 6. Stop Threshold Voltage (VSTOP) vs. TA Figure 7. Startup Supply Current (ISTART) vs. TA Figure 8. Operating Supply Current (IOP) vs. TA Figure 9. Output Upper Clamp Voltage (VEAH) vs. TA © 2010 Fairchild Semiconductor Corporation FAN7930 • Rev. 1.0.1 FAN7930 — Critical Conduction Mode PFC Controller Typical Performance Characteristics www.fairchildsemi.com 8 Figure 10. Zero Duty Cycle Output Voltage (VEAZ) vs. TA Figure 11. Maximum On-Time Program 1 (tON,MAX1) vs. TA Figure 12. Maximum On-Time Program 2 (tON,MAX2) vs. TA Figure 13. Current Sense Input Threshold Voltage Limit (VCS) vs. TA Figure 14. Input High Clamp Voltage (VCLAMPH) vs. TA Figure 15. Input Low Clamp Voltage (VCLAMPL) vs. TA © 2010 Fairchild Semiconductor Corporation FAN7930 • Rev. 1.0.1 FAN7930 — Critical Conduction Mode PFC Controller Typical Performance Characteristics www.fairchildsemi.com 9 Figure 16. Output Voltage High (VOH) vs. TA Figure 17. Output Voltage Low (VOL) vs. TA Figure 18. Restart Timer Delay (tRST) vs. TA Figure 19. Output Ready Voltage (VRDY) vs. TA Figure 20. Output Saturation Voltage (VRDY,SAT) vs. TA Figure 21. OVP Threshold Voltage (VOVP) vs. TA © 2010 Fairchild Semiconductor Corporation FAN7930 • Rev. 1.0.1 FAN7930 — Critical Conduction Mode PFC Controller Typical Performance Characteristics www.fairchildsemi.com 10 1. Startup: Normally, supply voltage (VCC) of a PFC block is fed from the additional power supply, which can be called standby power. Without this standby power, auxiliary winding to detect zero current detection can be used as a supply source. Once the supply voltage of the PFC block exceeds 12V, internal operation is enabled until the voltage drops to 8.5V. If VCC exceeds VZ, 20mA current is sinking from VCC. Figure 23. Circuit Around INV Pin VOUTPFC 413V 390Vdc 390V 349V 256V Figure 22. 70V Startup Circuit 2. INV Block: Scaled-down voltage from the output is the input for the INV pin. Many functions are embedded based on the INV pin: transconductance amplifier, output OVP comparator, disable comparator, and output UVLO comparator. 2.65V 2.50V 2.50V 2.24V 1.64V 0.45V 0.35V VCC 15V For the output voltage control, a transconductance amplifier is used instead of the conventional voltage amplifier. The transconductance amplifier (voltagecontrolled current source) aids the implementation of OVP and disable function. The output current of the amplifier changes according to the voltage difference of the inverting and non-inverting input of the amplifier. To cancel down the line input voltage effect on power factor correction, effective control response of PFC block should be slower than the line frequency and this conflicts with the transient response of controller. Twopole one-zero type compensation may be used to meet both requirements. 2.0V IOUTCOMP Current sourcing Current sourcing Disable I sinking VRDY Voltage is decided by pull-up voltage. OVP Vcc<2V, internal logic is not alive. - RDY pin is floating, so pull up voltage is shown. - Internal signals are unknown. t Figure 24. The OVP comparator shuts down the output drive block when the voltage of the INV pin is higher than 2.675V and there is 0.175V hysteresis. The disable comparator disables the operation when the voltage of the inverting input is lower than 0.35V and there is 100mV hysteresis. An external small-signal MOSFET can be used to disable the IC, as shown in Figure 23. The IC operating current decreases to reduce power consumption if the IC is disabled. Figure 24 is the timing chart of the internal circuit near the INV pin when rated PFC output voltage is assumed at 390VDC and VCC supply voltage is 15V. © 2010 Fairchild Semiconductor Corporation FAN7930 • Rev. 1.0.1 55V VINV FAN7930 — Critical Conduction Mode PFC Controller Applications Information Timing Chart for INV Block 3. RDY Output: When the INV voltage is higher than 2.24V, output UVLO voltage is triggered to high and lasts until the INV voltage is lower than 1.64V. This signal outputs through the RDY pin. RDY pin output is open-drain type, so needs an external pull-up resistor to supply the proper power source. The RDY pin output remains floating until VCC is higher than 2V. www.fairchildsemi.com 11 T VAUX = − AUX ⋅ VAC TIND (1) T VAUX = AUX ⋅ (VPFCOUT − VAC ) TIND (2) including COSS of the MOSFET; an external capacitor at the D-S pin to reduce the voltage rising and falling slope of the MOSFET; a parasitic capacitor at inductor; and so on to improve performance. Resonated voltage is reflected to the auxiliary winding and can be used as detecting zero current of boost inductor and valley position of MOSFET voltage stress. For valley detection, a minor delay by the resistor and capacitor is needed. A capacitor increases the noise immunity at the ZCD pin. If ZCD voltage is higher than 1.5V, an internal ZCD comparator output becomes HIGH and LOW when the ZCD goes below 1.4V. At the falling edge of comparator output, internal logic turns on the MOSFET. where, VAUX is the auxiliary winding voltage, TIND and TAUX are boost inductor turns and auxiliary winding turns respectively, VAC is input voltage for PFC converter and VOUT_PFC is output voltage from the PFC converter. Figure 25. FAN7930 — Critical Conduction Mode PFC Controller 4. Zero-Current Detection: Zero-current detection (ZCD) generates the turn-on signal of the MOSFET when the boost inductor current reaches zero using an auxiliary winding coupled with the inductor. When the power switch turns on, negative voltage is induced at the auxiliary winding due to the opposite winding direction (see equation 1) and positive voltage is induced (see equation 2) when the power switch turns off. Circuit Near ZCD Because auxiliary winding voltage can swing from negative voltage to positive voltage, the internal block in ZCD pin has both positive and negative voltage clamping circuits. When the auxiliary voltage is negative, internal circuit clamps the negative voltage at the ZCD pin around 0.65V by sourcing current to the serial resistor between the ZCD pin and the auxiliary winding. When the auxiliary voltage is higher than 6.5V, current is sinked through a resistor from the auxiliary winding to the ZCD pin. Figure 27. Auxiliary Voltage Threshold When no ZCD signal is available, the PFC controller cannot turn on MOSFET, so the controller checks every switching off time and forces MOSFET turn on when the off time is longer than 150μs. It is called restart timer. Restart timer triggers MOSFET turn on at startup and may be used at the input voltage zero cross period. 150 μs Figure 26. Auxiliary Voltage Depends on MOSFET Switching To check the boost inductor current zero instance, auxiliary winding voltage is used. When boost inductor current becomes zero, there is a resonance between boost inductor and all capacitors at MOSFET drain pin, © 2010 Fairchild Semiconductor Corporation FAN7930 • Rev. 1.0.1 Figure 28. Restart Timer at Startup www.fairchildsemi.com 12 output, turn-on time lengthens to give more inductor turn-on time, and increased inductor current raises the output voltage. This is how PFC negative feedback controller regulates output. The maximum of VCOMP is limited to 6.5V, which dictates the maximum turn-on time, and switching stops when VCOMP is lower than 1.0V. 0.155 V / μs Figure 31. The roles of PFC controller are regulating output voltage and input current shaping to increase power factor. Duty control based on the output voltage should be fast enough to compensate output voltage dip or overshoot. For the power factor, however, the control loop must not react to the fluctuating AC input voltage. These two requirements conflict; therefore, when designing a feedback loop, the feedback loop should be least 10 times slower than AC line frequency. That slow response is made by C1 at compensator. R1 makes gain boost around operation region and C2 attenuates gain at higher frequency. Boost gain by R1 helps raise the response time and improves phase margin. Figure 29. Maximum Switching Frequency Limit Operation 5. Control: The scaled output is compared with the internal reference voltage and sinking or sourcing current is generated from the COMP pin by the transconductance amplifier. The error amplifier output is compared with the internal sawtooth waveform to give proper turn-on time based on the controller. Figure 32. Figure 30. Turn-On Time Determination FAN7930 — Critical Conduction Mode PFC Controller Because the MOSFET turn on depends on the ZCD input, switching frequency may increase to higher than several megahertz due to the miss-triggering or noise on the nearby ZCD pin. If the switching frequency is higher than needed for critical conduction mode (CRM), operation mode shifts to continuous conduction mode (CCM). In CCM, unlike CRM where the boost inductor current is reset to zero at the next switch on; inductor current builds up at every switching cycle and can be raised to very high current, that exceeds the current rating of the power switch or diode. This can seriously damage the power switch and result in burn down. To avoid this, maximum switching frequency limitation is embedded. If ZCD signal is applied again within 3.3μs after the previous rising edge of gate signal, this signal is ignored internally and FAN7930 waits for another ZCD signal. This slightly degrades the power factor performance at light load and high input voltage. Compensators Gain Curve For the transconductance error amplifier side, gain changes based on differential input. When the error is large, gain is large to make the output dip or peak to suppress quickly. When the error is small, low gain is used to improve power factor performance. Control Circuit Unlike a conventional voltage-mode PWM controller, FAN7930 turns on the MOSFET at the falling edge of ZCD signal. On instance is decided by the external signal and the turn-on time lasts until the error amplifier output (VCOMP) and sawtooth waveform meet. When load is heavy, output voltage decreases, scaled output decreases, COMP voltage increases to compensate low © 2010 Fairchild Semiconductor Corporation FAN7930 • Rev. 1.0.1 www.fairchildsemi.com 13 250 μmho 115 μmho Figure 33. Gain Characteristic 6. Soft-Start: When VCC touches VSTART, internal reference voltage is increased like a stair step for 5ms. As a result, VCOMP is also raised gradually and MOSFET turn-on time increases smoothly. This reduces voltage and current stress on the power switch during startup. Figure 35. Figure 34. FAN7930 — Critical Conduction Mode PFC Controller voltage building time at light load. FAN7930 has “overshoot-less” control at startup. During startup, the feedback loop is controlled by an internal proportional gain controller and when the output voltage reaches the rated value, it switches to an external compensator after a transition time of 30ms. In short, an internal proportional gain controller eliminates overshoot at startup and an external conventional compensator takes over successfully afterward. Overshoot-less Startup Control 8. THD Optimization: Total harmonic distortion (THD) is the factor that dictates how closely input current shape matches sinusoidal form. The turn-on time of the PFC controller is almost constant over one AC line period due to the extremely low feedback control response. The turn-off time is decided by the current decrease slope of the boost inductor made by the input voltage and output voltage. Once inductor current becomes zero, resonance between COSS and the boost inductor makes oscillating waveforms at the drain pin and auxiliary winding. By checking the auxiliary winding voltage through the ZCD pin, the controller can check the zero current of boost inductor. At the same time, a minor delay time is inserted to determine the valley position of drain voltage. The input and output voltage difference is at its maximum at the zero cross point of AC input voltage. The current decrease slope is steep near the zero cross region and more negative inductor current flows during a drain voltage valley detection time. Such a negative inductor current cancels down the positive current flows and input current becomes zero, called “zero-cross distortion” in PFC. Soft-Start Sequence 7. “Overshoot-less” Startup: Feedback control speed of PFC is quite slow. Due to the slow response, there is a gap between output voltage and feedback control. That is why over-voltage protection (OVP) is critical at the PFC controller and voltage dip caused by fast load changes from light to heavy is diminished by a bulk capacitor. OVP is easily triggered at startup phase. Operation on and off by OVP at startup may cause audible noise and can increase voltage stress at startup, which is normally higher than in normal operation. This operation is better when soft-start time is very long. However, too long startup time enlarges the output © 2010 Fairchild Semiconductor Corporation FAN7930 • Rev. 1.0.1 www.fairchildsemi.com 14 IINDUCTOR IMOSFET IDIODE VZCD INEGATIVE 1.5V 1.4V 150ns MOSFET gate ON FAN7930 Rev.00 Figure 36. Figure 37. ON t Input and Output Current Near Input Voltage Peak Input and Output Current Near Input Voltage Peak Zero Cross Circuit of THD Optimizer Figure 39. Effect of THD Optimizer By THD optimizer, turn-on time over one AC line period is proportionally changed, depending on input voltage. Near zero cross, lengthened turn-on time improves THD performance. To improve this, lengthened turn-on time near the zero cross region is a well-known technique, though the method may be different from company to company and may be proprietary. FAN7930 emdodies this by sourcing current through the ZCD pin. Auxiliary winding voltage becomes negative when the MOSFET turns on and is proportional to input voltage. The negative clamping circuit of ZCD outputs the current to maintain the ZCD voltage at a fixed value. The sourcing current from the ZCD is directly proportional to the input voltage. Some portion of this current is applied to the internal sawtooth generator together with a fixed-current source. Theoretically, the fixed-current source and the capacitor at sawtooth generator decide the maximum turn-on time when no current is sourcing at ZCD clamp circuit and available turn-on time gets shorter proportional to the ZCD sourcing current. © 2010 Fairchild Semiconductor Corporation FAN7930 • Rev. 1.0.1 Figure 38. FAN7930 — Critical Conduction Mode PFC Controller IIN 9. Input Voltage Absent Detection: To save power loss caused by input voltage sensing resistors and to optimize THD easily, the FAN7930 omits AC input voltage detection. Therefore, no information about AC input is available from the internal controller. In many cases, the VCC of PFC controller is supplied by a independent power source like standby power. In this scheme, some mismatch may exist. For example, when the electric power is suddenly interrupted during two or three AC line periods; VCC is still alive during that time, but output voltage drops because there is no input power source. Consequently, the control loop tries to compensate for the output voltage drop and VCOMP reaches its maximum. This lasts until AC input voltage is www.fairchildsemi.com 15 Figure 41. Operation with Input Voltage Absent Circuit 10. Current Sense: The MOSFET current is sensed using an external sensing resistor for the over-current protection. If the CS pin voltage is higher than 0.8V, the over-current protection comparator generates a protection signal. An internal RC filter of 40kΩ and 8pF is included to filter switching noise. Figure 40. 11. Gate Driver Output: FAN7930 contains a single totem-pole output stage designed for a direct drive of the power MOSFET. The drive output is capable of up to +500/-800mA peak current with a typical rise and fall time of 50ns with 1nF load. The output voltage is clamped to 13V to protect the MOSFET gate even if the VCC voltage is higher than 13V. Operation without Input Voltage Absent Circuit © 2010 Fairchild Semiconductor Corporation FAN7930 • Rev. 1.0.1 FAN7930 — Critical Conduction Mode PFC Controller live again. When AC input voltage is live again, high VCOMP allows high switching current and more stress is put on the MOSFET and diode. To protect against this, FAN7930 internally checks if the input AC voltage exists. If input does not exist, soft-start is reset and waits until AC input is live again. Soft-start manages the turn-on time for smooth operation when it detects AC input is applied again and applies less voltage and current stress on startup. www.fairchildsemi.com 16 PFC block normally handles high switching current and the voltage low energy signal path can be affected by the high energy path. Cautious PCB layout is mandatory for stable operation. 1. 2. 3. 4. 5. The gate drive path should be as short as possible. The closed-loop that starts from the gate driver, MOSFET gate, and MOSFET source to ground of PFC controller is recommended as close as possible. This is also crossing point between power ground and signal ground. Power ground path from the bridge diode to the output bulk capacitor should be short and wide. The sharing position between power ground and signal ground should be only at one position to avoid ground loop noise. Signal path of PFC controller should be short and wide for external components to contact. PFC output voltage sensing resistor is normally high to reduce current consumption. This path can be affected by external noise. To reduce noise possibility at the INV pin, a shorter path for output sensing is recommended. If a shorter path is not possible, place some dividing resistors between PFC output and the INV pin — closer to the INV pin is better. Relative high voltage close to the INV pin can be helpful. ZCD path is recommended close to auxiliary winding from boost inductor and to the ZCD pin. If that is difficult, place a small capacitor (below 50pF) to reduce noise. Switching current sense path should not share with another path to avoid interference. Some additional components may be needed to reduce the noise level applied to the CS pin. © 2010 Fairchild Semiconductor Corporation FAN7930 • Rev. 1.0.1 A stabilizing capacitor for VCC is recommended as close as possible to the VCC and ground pins. If it is difficult, place the SMD capacitor as close to the corresponding pins as possible. Figure 42. FAN7930 — Critical Conduction Mode PFC Controller PCB Layout Guide Recommended PCB Layout www.fairchildsemi.com 17 Application Device Input Voltage Range Rated Output Power Output Voltage (Maximum Current) LCD TV Power Supply FAN7930 90-265VAC 195W 390V (0.5A) Features Average efficiency of 25%, 50%, 75%, and 100% load conditions is higher than 95% at universal input. Power factor at rated load is higher than 0.98 at universal input. Total Harmonic Distortion (THD) at rated load is lower than 15% at universal input. Key Design Notes When auxiliary VCC supply is not available, VCC power can be supplied through Zero Current Detect (ZCD) winding. The power consumption of R103 is quite high, so its power rating needs checking. Because the input bias current of INV pin is almost zero, output voltage sensing resistors (R112~R115) as high as possible. However, too-high resistance makes the node easily affected by noise. Thus values need to strike a balance between power consumption and noise immunity. Quick charge diode (D106) can be eliminated. Without D106, system operation is normal due to the controller’s highly reliable protection features. 1. Schematic Figure 43. © 2010 Fairchild Semiconductor Corporation FAN7930 • Rev. 1.0.1 FAN7930 — Critical Conduction Mode PFC Controller Typical Application Circuit Demonstration Circuit www.fairchildsemi.com 18 Figure 44. Transformer Schematic Diagram of FAN7930 3. Winding Specification Position Bottom Top No Pin (S → F) Wire Turns Winding Method Np 9, 10 → 7, 8 0.1φ×50 49 Solenoid Winding Barrier Tape TOP BOT Ts 1 FAN7930 — Critical Conduction Mode PFC Controller 2. Transformer Insulation: Polyester Tape t = 0.025mm, 3 Layers NAUX 2→4 0.3φ 6 Solenoid Winding Insulation: Polyester Tape t = 0.025mm, 4 Layers 4. Electrical Characteristics Inductance Pin Specification Remark 9, 10 → 7, 8 230μH ± 7% 100kHz, 1V 5. Core & Bobbin 2 Core: EER3124, Samhwa (PL-7) (Ae=97.9mm ) Bobbin: EER3124 © 2010 Fairchild Semiconductor Corporation FAN7930 • Rev. 1.0.1 www.fairchildsemi.com 19 Part # Value Note Part # Resister Value Note Switch R101 1MΩ 1W R102 330kΩ 1/2W R103 10kΩ 1W D101 1N4746 1W, 18V, Zener Diode 30kΩ 1/4W D102 UF4004 1A, 400V Glass Passivated High-Efficiency Rectifier R107 10kΩ 1/4W D103 1N4148 1A, 100V Small-Signal Diode R108 4.7kΩ 1/4W D104 1N4148 1A, 100V Small-Signal Diode R104 R109 R110 47kΩ 10kΩ Q101 1/4W 0.80kΩ 5W R112, 113, 114 3.9kΩ 1/4W R115 75kΩ 1/4W D105 8A, 600V, General-Purpose Rectifier D106 3A, 600V, General-Purpose Rectifier IC101 FAN7930 Capacitor CRM PFC Controller Fuse C101 220nF/275VAC Box Capacitor C102 680nF/275VAC Box Capacitor C103 0.68µF/630V Box Capacitor C104 12nF/50V Ceramic Capacitor C105 100nF/50V SMD (1206) C107 33µF/50V Electrolytic Capacitor C108 220nF/50V Ceramic Capacitor C109 47nF/50V Ceramic Capacitor C110 1nF/50V Ceramic Capacitor C112 47nF/50V Ceramic Capacitor C111 220µF/450V Electrolytic Capacitor C114 2.2nF/450V Box Capacitor C115 2.2nF/450V Box Capacitor © 2010 Fairchild Semiconductor Corporation FAN7930 • Rev. 1.0.1 20A, 600V, SuperFET Diode 1/4W R111 FCPF20N60 FS101 5A/250V NTC TH101 5D-15 FAN7930 — Critical Conduction Mode PFC Controller 6. Bill of Materials Bridge Diode BD101 15A, 600V Line Filter LF101 23mH T1 EER3124 Transformer Ae=97.9mm 2 ZNR ZNR101 10D471 www.fairchildsemi.com 20 FAN7930 — Critical Conduction Mode PFC Controller Physical Dimensions 5.00 4.80 A 0.65 3.81 8 5 B 1.75 6.20 5.80 PIN ONE INDICATOR 4.00 3.80 1 5.60 4 1.27 (0.33) 1.27 0.25 C B A LAND PATTERN RECOMMENDATION SEE DETAIL A 0.25 0.10 1.75 MAX 0.25 0.19 C 0.51 0.33 0.10 C OPTION A - BEVEL EDGE 0.50 x 45° 0.25 R0.10 GAGE PLANE R0.10 OPTION B - NO BEVEL EDGE 0.36 NOTES: UNLESS OTHERWISE SPECIFIED 8° 0° 0.90 0.40 A) THIS PACKAGE CONFORMS TO JEDEC MS-012, VARIATION AA, ISSUE C, B) ALL DIMENSIONS ARE IN MILLIMETERS. C) DIMENSIONS DO NOT INCLUDE MOLD FLASH OR BURRS. D) LANDPATTERN STANDARD: SOIC127P600X175-8M. E) DRAWING FILENAME: M08AREV13 SEATING PLANE (1.04) DETAIL A SCALE: 2:1 Figure 45. 8-Lead Small Outline Package (SOP) Package drawings are provided as a service to customers considering Fairchild components. Drawings may change in any manner without notice. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor representative to verify or obtain the most recent revision. Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions, specifically the warranty therein, which covers Fairchild products. Always visit Fairchild Semiconductor’s online packaging area for the most recent package drawings: http://www.fairchildsemi.com/packaging/. © 2010 Fairchild Semiconductor Corporation FAN7930 • Rev. 1.0.1 www.fairchildsemi.com 21 FAN7930 — Critical Conduction Mode PFC Controller © 2010 Fairchild Semiconductor Corporation FAN7930 • Rev. 1.0.1 www.fairchildsemi.com 22