Product Specification SG6203 Synchronous Rectifier Controller for Flyback Converter FEATURES DESCRIPTION The SG6203 is designed to control and drive the synchronous rectifier for the flyback converter. The synchronous signal of the primary switch is obtained by a single diode connected between the transformer secondary winding and the SG6203. Using the SG6203, no additional transformer winding is required and the circuit complexity can be minimized. Low operation current (1.7mA) One resistor for timing setting Internal automatic tracking for optimum dead time No reverse energy flow at light load Best suited for primary green-mode PWM IC Wide supply voltage range from 6V to 20V Built-in 18V Zener diode Optional current sensing: - Current shunt - RC network for better efficiency APPLICATIONS Flyback converters, such as: Power adaptors Open-frame SMPS The power unit can be properly operated under discontinuous conduction mode (DCM) or continuous conduction mode (CCM). Problems such as “shoot-through” or “cross conduction” in CCM and energy-reverse from the secondary to the primary in DCM are prevented by the SG6203 design. TYPICAL APPLICATION © System General Corp. Version 1.0.1 (IAO33.0010.B1) -1- www.sg.com.tw • www.fairchildsemi.com September 24, 2007 Product Specification SG6203 Synchronous Rectifier Controller for Flyback Converter MARKING DIAGRAMS PIN CONFIGURATION T: D=DIP, S=SOP P : Z=Lead Free + ROHS Compatible XXXXXXXX: Wafer Lot Y: Year; WW: Week V: Assembly Location SG6203TP XXXXXXXXYWWV VCC IN+ Output IN- GND RT VZ DET ORDERING INFORMATION Part Number Pb-Free Package SG6203SZ 8-Pin SOP SG6203DZ 8-Pin DIP PIN DESCRIPTIONS Pin Name Function 1 Vcc Supply voltage of gate driver and control circuits. 2 Output Totem-pole output to drive the synchronous power MOSFET. When the voltage on DET pin falls below 1.4V from above 2.1V, the synchronous MSOFET is turned on. To prevent the reversed energy flow, this pin is disabled once the voltage on IN+ pin is lower than that of IN- pin or the internal one-shot timer is terminated. 3 GND The power ground and signal ground. A 0.1µF decoupling capacitor placed between VCC and GND is recommended. 4 VZ Built-in 18V Zener diode. When the flyback output voltage is higher than 18V, this pin can be used to provide a stable 18V to VCC pin. If the flyback output voltage is lower than 18V, this pin can be left open and the output voltage connected directly to VCC pin. DET Connecting a diode from this pin to the transformer secondary winding provides on/off information of the primary switch. Low DET level indicates the secondary rectifier is conducted, therefore the synchronous MOSFET should be turned on. DET stays high when the primary switch is conducting or secondary rectifier turns off and the synchronous MOSFET should be turned off. RT Current reference. Connecting a resistor from this pin to ground can program the internal current reference IRT. Three internal current sources, which are IIN+, IIN-, and IDET, are then mirrored from IRT. IRT determines the duration of the internal one-shot signal, then the maximum on-time of the synchronous MOSFET is obtained by subtracting the on-time of the primary switch from the one-shot signal duration. If the resistor is too small, the synchronous MOSFET may be turned off even when the secondary rectifier is still conducting, which decreases the system efficiency. However, if the resistor is too large, the output is shut off immediately once DET gets high. In SG6203, an internal phase-locked-loop (PLL) modulates the duration of the internal one-shot signal to maintain a suitable dead time between the primary switch and the synchronous MOSFET. IN- The inverting input of the current sense comparator. In discontinuous conduction mode, the secondary rectifier turns off before the next switching cycle of the primary switch. Once the secondary rectifier is off, the synchronous MOSFET must be turned off to prevent the reversed energy flow. A resistor connected between IN+ and IN- can used to develop the zero current crossing signal of the secondary rectifier. Once the voltage on IN+ is lower than IN-, the output is pulled low. IN+ The non-inverting input of the current sense comparator. In discontinuous conduction mode, the secondary rectifier turns off before the next switching cycle of the primary switch. Once the secondary rectifier is off, the synchronous MOSFET must be turned off to prevent the reversed energy flow. A resistor connected between IN+ and IN- can used to develop the zero current crossing signal of the secondary rectifier. Once the voltage on IN+ is lower than IN-, the output is pulled low. 5 6 7 8 © System General Corp. Version 1.0.1 (IAO33.0010.B1) -2- www.sg.com.tw • www.fairchildsemi.com September 24, 2007 Product Specification Synchronous Rectifier Controller for Flyback Converter SG6203 BLOCK DIAGRAM © System General Corp. Version 1.0.1 (IAO33.0010.B1) -3- www.sg.com.tw • www.fairchildsemi.com September 24, 2007 Product Specification SG6203 Synchronous Rectifier Controller for Flyback Converter ABSOLUTE MAXIMUM RATINGS Symbol Parameter Value Unit VCC DC Supply Voltage* 25 V IOUT Gate Output Current 500 mA VH DET, OUT, VZ -0.3 to 25.0 V VL RT, IN+, IN- -0.3 to 7.0 V PD Power Dissipation Rθ JA Thermal Resistance (Junction-to-Air) SOP8 400 DIP8 800 SOP8 208.4 DIP8 82.5 mW °C/W TJ Operating Junction Temperature 150 °C TSTG Storage Temperature Range -65 to +150 °C TL Lead Temperature (Soldering, 10 Seconds) 300 °C ESD Electrostatic Discharge Capability, Human Body Model 2.0 KV Electrostatic Discharge Capability, Machine Model 200 V * All voltage values, except differential voltages, are given with respect to GND pin. * Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. RECOMMENDED OPERATING CONDITIONS Symbol Parameter Value Unit VCC DC Supply Voltage <20 V TA Operating Ambient Temperature -30~85 °C RT Pulse Width of the One-shot Signal 12~36 KΩ ELECTRICAL CHARACTERISTICS VCC=12V; RT=24KΩ ; TA=25°C, unless otherwise noted. Timing Control Section Symbol Parameter VRT Voltage on RT Pin TRT Pulse Width of the One-shot Signal △ TRT Adjustable Range of the Pulse Width Compared to TRT TDEAD Timing Margin Between Output Turn-off (Output Falling) and Next Switching Cycle Start (DET Rising) © System General Corp. Version 1.0.1 (IAO33.0010.B1) Test Condition Min. Typ. Max. Unit 1.14 1.20 1.26 V RT=12KΩ 6.5 7.5 8.5 µs RT=24KΩ 13 15 17 µs RT=36KΩ 19.5 22.5 25.5 µs +40 +60 +80 % 1000 ns RT=12KΩ ; RT=24KΩ ; RT=36KΩ 200 -4- www.sg.com.tw • www.fairchildsemi.com September 24, 2007 Product Specification SG6203 Synchronous Rectifier Controller for Flyback Converter Synchronous Detection Section Symbol Parameter Test Condition VTH Threshold Voltage to Enable One-shot Signal VTL Threshold Voltage to Enable Output IN+ - IN- > 5mV IDET Current Output from DET Pin RT=24KΩ TD_LOW Debounce Time from DET Low to Enable Output Min. Typ. Max. Unit 1.9 2.1 2.3 V 1.2 1.4 1.6 V 250 300 µA 300 ns Max. Unit 10 mV 150 Current Detection Section Symbol Parameter Test Condition Min. Typ. VOFFSET Offset Voltage IIN+ Current Output from IN+ RT=24KΩ 90 100 110 µA IIN- Current Output from IN- RT=24KΩ 90 100 110 µA IIN+ - IIN- Differential Current of IN+ and IN- 12KΩ < RT < 36KΩ 1.5 µA TP Propagation Delay (OUTPUT from Low to High) DET< VTL, IN+ - IN- > 5mV PSRR Power Supply Rejection Ratio 65 dB CMRR Common Mode Rejection Ratio 65 dB CMRR-f Common Mode Rejection Ratio at 70KHz 32 dB 200 ns Zener Section Symbol Parameter Test Condition Min. Typ. Max. Unit VZ Zener Voltage IVZ=0.1 ~ 3mA 18 19 20 V Test Condition Min. Typ. Max. Unit VCC=12V, ISOURCE=50mA 11.2 VCC=6V, ISOURCE=30mA 3.5 Output Section Symbol Parameter VOH Output Voltage High V V VCC=12V, ISINK=50mA 1 V VCC=6V, ISINK=30mA 1.2 V VOL Output Voltage Low Tr Rising Time TA=25°C; CL=5nF, VCC=12V 150 175 ns Tf Falling Time TA=25°C; CL=5nF, VCC=12V 150 175 ns Typ. Max. Unit 20 V 1.7 4.0 mA 6.0 6.3 V VCC Section Symbol Parameter VOP Continuously Operating Voltage ICC_OP Operating Current VTH(ON) Start Threshold VTH(OFF) Minimum Operating Voltage © System General Corp. Version 1.0.1 (IAO33.0010.B1) Test Condition Min. VDD=12V, Output=open, DET=50KHz, IN-=IN+=open, RT=12KΩ 4.8 -5- 5.1 V www.sg.com.tw • www.fairchildsemi.com September 24, 2007 Product Specification SG6203 Synchronous Rectifier Controller for Flyback Converter TYPICAL CHARACTERISTICS Pulse width of the one-shot signal (TRT) vs Temperature 6.5 16.0 6.4 15.9 6.3 15.8 6.2 15.7 6.1 TRT(uS) VTH(ON) (V) Start Threshold (VTH(ON)) vs Temperature 6.0 5.9 15.6 15.5 15.4 5.8 15.3 5.7 15.2 5.6 15.1 5.5 -40 -25 -10 5 20 35 50 65 80 95 110 -40 125 -25 -10 5 Minimum Operating Voltage (VTH(OFF)) vs Temperature 50 65 80 95 110 125 350.0 5.80 300.0 5.75 5.70 250.0 5.65 TD_LOW (nS) VTH(OFF) (V) 35 Debounce time form DET low to enable the output (TD_LOW ) vs Temperature 5.85 5.60 5.55 5.50 200.0 150.0 100.0 5.45 50.0 5.40 5.35 0.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 -40 -25 -10 5 Temperature (℃) 20 35 50 65 80 95 110 125 Temperature (℃) Threshold voltage to enable an one shot signal (VTH) vs Temperature Operating Current (ICC_OP) vs Temperature 1.842 2.0 1.8 1.840 1.6 1.4 1.838 1.2 1.836 VTH(V) ICC_OP(mA) 20 Temperature (℃) Temperature (℃) 1.0 0.8 0.6 1.834 1.832 0.4 1.830 0.2 1.828 0.0 -40 -25 -10 5 20 35 50 65 80 95 110 -40 125 Temperature (℃) © System General Corp. Version 1.0.1 (IAO33.0010.B1) -25 -10 5 20 35 50 65 80 95 110 125 Temperature (℃) -6- www.sg.com.tw • www.fairchildsemi.com September 24, 2007 Product Specification Synchronous Rectifier Controller for Flyback Converter SG6203 Threshold voltage to enable the output (VTL) vs Temperature 1.56 1.54 VTL(V) 1.52 1.50 1.48 1.46 1.44 1.42 -40 -25 -10 5 20 35 50 65 80 95 110 125 Temperature (℃) © System General Corp. Version 1.0.1 (IAO33.0010.B1) -7- www.sg.com.tw • www.fairchildsemi.com September 24, 2007 Product Specification SG6203 Synchronous Rectifier Controller for Flyback Converter OPERATION DESCRIPTION Synchronization The DET pin provides on/off information of the primary switch. As shown in the following reference circuits, one diode connected between the DET pin and the secondary winding of the transformer is used to get this information. Low DET voltage level indicates the secondary rectifier is conducted; therefore, the synchronous MOSFET should be turned on. The voltage on DET pin stays high when the primary switch is conducting and the synchronous MOSFET should be turned off. This innovative feature requires no auxiliary winding and the circuit complexity is greatly reduced. Anticipation and Phase Lock Loop A resistor from the RT pin to ground is used to determine the internal current source reference. When the primary switch is turned on with DET high, an internal one-shot timer outputs high for a duration proportional to the RT resistor. The duration of this one-shot signal can be expressed as: TRT = 15 × R T (KΩ ) (µs) 24 shut off immediately once DET gets high. In SG6203, an internal phase locked loop modulates the duration of the internal one-shot signal to maintain a suitable dead time between the primary switch and the synchronous MOSFET. The duration of the one-shot signal can be extended 80% compared with the original value decided by RT resistor. Current Sense In discontinuous conduction mode, the secondary rectifier turns off before the next switching cycle of the primary switch. Once the secondary rectifier is off, the synchronous MOSFET must be turned off to prevent the reverse energy flow. Therefore, a zero current crossing detector is needed when the converter is operated under DCM. The SG6203 provides two configurations to achieve this: output capacitor ESR method (reference Circuit-A) and current-sensing resistor method (reference Circuit-B). When the secondary rectifier is turned off, the voltage on IN+ is lower than that of IN-. Once this happens, the driving signal for the synchronous MOSFET is turned off. (1) Under-Voltage Lockout (UVLO) Primary Switch PWM One-Shot Signal T The SG6203 has an internal UVLO circuit with hysteresis. The IC is turned on if VCC is higher than 6V. Once turned on, SG6203 is turned off if VCC is lower than 5.1V. When the flyback output voltage is higher than 18V, the VZ pin can be used to provide a stable 18V to VCC pin. Output The on-time of the synchronous MOSFET is obtained by subtracting the on-time of the primary switch from the one-shot signal duration. If the resistor is too small, the synchronous MOSFET may be turned off when the secondary rectifier is still conducting, which decreases system efficiency. If the resistor is too large, the output is © System General Corp. Version 1.0.1 (IAO33.0010.B1) -8- www.sg.com.tw • www.fairchildsemi.com September 24, 2007 Product Specification SG6203 Synchronous Rectifier Controller for Flyback Converter REFERENCE CIRCUIT-A BOM Ref Des Part Number Description C2 0.1µF C5 22pF D1 FR102 100V/1A D2 SB1100 100V/1A D3 1N4148 100V/0.2A Q1 PSMN015-110P 110V/75A; 15mΩ R1 2.2KΩ R2 22Ω R3 47KΩ R4 1.8KΩ R5 2KΩ R6 0 R7 16.2KΩ © System General Corp. Version 1.0.1 (IAO33.0010.B1) -9- www.sg.com.tw • www.fairchildsemi.com September 24, 2007 Product Specification Synchronous Rectifier Controller for Flyback Converter SG6203 REFERENCE CIRCUIT-B © System General Corp. Version 1.0.1 (IAO33.0010.B1) - 10 - www.sg.com.tw • www.fairchildsemi.com September 24, 2007 Product Specification SG6203 Synchronous Rectifier Controller for Flyback Converter PACKAGE INFORMATION 8 PINS-SOP(S) 8 C 5 H E F 1 4 b e D Θ A1 L A Dimensions Symbol Millimeter Min. Typ. Max. Inch Min. A A1 b c D E e F H L θ˚ 1.346 0.101 1.752 0.254 0.053 0.004 0.406 0.203 4.648 3.810 1.016 5.791 0.406 0° © System General Corp. Version 1.0.1 (IAO33.0010.B1) 1.270 0.381X45° Typ. Max. 0.069 0.010 0.016 0.008 4.978 3.987 1.524 0.183 0.150 0.040 6.197 1.270 8° 0.228 0.016 0° - 11 - 0.050 0.015X45° 0.196 0.157 0.060 0.244 0.050 8° www.sg.com.tw • www.fairchildsemi.com September 24, 2007 Product Specification SG6203 Synchronous Rectifier Controller for Flyback Converter 8PINS–DIP(D) D Θ¢X 5 E1 8 e B E A A1 A2 4 1 L b1 b e Dimension Symbol A A1 A2 b b1 D E E1 e L eB θ° Millimeter Min. 0.381 3.175 9.017 6.223 2.921 8.509 0° © System General Corp. Version 1.0.1 (IAO33.0010.B1) Inch Min. Typ. Max. 5.334 3.302 1.524 0.457 9.271 7.620 6.350 2.540 3.302 9.017 7° 3.429 0.015 0.125 10.160 0.355 6.477 0.245 3.810 9.525 15° 0.115 0.335 0° - 12 - Typ. Max. 0.210 0.130 0.060 0.018 0.365 0.300 0.250 0.100 0.130 0.355 7° 0.135 0.400 0.255 0.150 0.375 15° www.sg.com.tw • www.fairchildsemi.com September 24, 2007 Product Specification Synchronous Rectifier Controller for Flyback Converter © System General Corp. Version 1.0.1 (IAO33.0010.B1) - 13 - SG6203 www.sg.com.tw • www.fairchildsemi.com September 24, 2007