PT6909 Power Factor Correction LED Driver DESCRIPTION PT6909 is a fixed frequency PWM controller IC designed to control high brightness LED driver using a single-stage PFC boost-buck topology. It can achieve a well power factor and a higher dc-bus voltage. This topology allows reducing the filter capacitors and using non-electrolytic capacitors to improve reliability. The PT6909 uses open-loop peak current control technique eliminates a need for loop compensation, limits the input inrush current, and is inherently protected from input under-voltage condition. PT6909 provides a low frequency PWM dimming input that can accept an external control signal with a duty cycle of 0-100% and a frequency of between 100Hz and a few KHz. The PWM dimming capability enables PT6909 phase control solutions that can work with standard TRIAC. FEATURES • • • • • • • • Simple power factor correction Integrated Low start-up current 8V to 12V input range Constant-current driver Programmable fixed frequency operation Input and output current sensing Input current limit Boost circuit over-voltage protection(LED open protection) • Input voltage limitation • Low Input current harmonic distortion • PWM Low-frequency dimming and phase Dimming compatible APPLICATIONS • • • • • LED replacement tube AC/DC LED driver LED Lamp with phase dimmable Street lamps Traffic signals BLOCK DIAGRAM Tel: 886-66296288‧Fax: 886-29174598‧ http://www.princeton.com.tw‧2F, 233-1, Baociao Road, Sindian, Taipei 23145, Taiwan PT6909 TYPICAL APPLICATION Typical 110V/AC 8W LED Tube With PFC Application V1.1 2 April 2010 PT6909 ORDER INFORMATION Valid Part Number PT6909-S Package Type 8 Pins, SOP, 150MIL Top Code PT6909-S PIN CONFIGURATION PIN DESCRIPTION Pin Name CS1 GND GD VIN PWMD OVP CS2 RF V1.1 Description Input or Output Current Sense Ground Drives the Gate of External MOSFET Input Voltage 8V-12V DC Low Frequency PWM Dimming pin, also Enable pin Over Voltage Detection Input or Output Current Sense Oscillator Frequency Setting 3 Pin No. 1 2 3 4 5 6 7 8 April 2010 PT6909 FUNCTION DESCRIPTION POWER TOPOLOGY PT6909 is optimized to drive non-isolated topology, cascading an input PFC boost stage and an output buck converter power stage. This power converter topology offers numerous advantages useful for driving high-brightness LED. These advantages include power factor correction, low harmonic distortion of the input AC line current. The power converter topology also permits reducing the size of a filter capacitor needed, enabling use of non-electrolytic capacitors. The latter advantage greatly improves reliability of the overall solution. PT6909 is a peak current-mode controller that is specifically designed to drive a constant current buck power converter. PT6909 controls two identical current sense comparators for detecting input and output current. One of the comparators regulates the output LED current, while the other is used for sensing the input inductor current. The comparator sensing the input inductor current is mainly responsible for the converter start-up. The control scheme can achieve a low inrush current, also avoid a high input current while the AC input is under-voltage. OVER VOLTAGE DETECTION PT6909 includes output over voltage detection function. The OVP pin is used for sensing the output voltage of boost stage. The PT6909 will latch the GD output at shutdown state when the output voltage reaches OVP threshold voltage. In the typical application circuit, the system will go into hiccup mode if the LED load is open. When the LED load is disconnected, the output voltage rises as the output capacitor C1 starts charging. When the PT6909 detects an over voltage condition and turns off the converter. The PT6909’s power supply VIN drops under UVLO threshold voltage and goes into low current start-up status. The PT6909 restarts and turns on the converter. The system starts another cycle until the LED load is re-connected. INPUT VOLTAGE LIMITATION PT6909 built-in power-supply clamped circuit. In the typical application circuit, when the VIN voltage rises higher than 14V typically, it will be clamped at this level with internal 5mA current sink capability. SETTING INPUT AND OUTPUT CURRENT Two current sense comparators are included in the PT6909. Both comparators have their inverting inputs internally connected to 240mV. The CS1 and CS2 inputs are non-inverting inputs of the comparators. When either the CS1 or CS2 pin voltage rises up 240mV, the GD pulse is terminated. A leading edge blanking delay of 300ns(typ) is added. The GD voltage becomes high again upon receiving the next clock pulse of the oscillator circuit. Referring to the Typical Application Diagram, the CS1 comparator is responsible for regulating output current. The output LED current can be programmed using the following equation: 0.24 1 I LED = − ΔI L1 R CS1 2 Where △IL1 is the peak-to-peak current ripple in L1. The CS2 comparator limits the current in the input inductor L2. Therefore, the PT6909 starts-up in the input current limiting mode. The CS2 voltage sensing must be programmed such that no input current limiting occurs in normal steady-state operation. The L2 current sensing resistor RCS2 can be programmed using the following equation: RCS2 < 0.24 I L2P Where, IL2P is the maximum peak current in L2. V1.1 4 April 2010 PT6909 PWM DIMMING AND TRAIC DIMMING PWM dimming scheme can be implemented by external low frequency PWM signal to the PWMD pin. When the PWMD pin is pulled high, the gate driver is enabled and the circuit operates normally. When the PWMD pin is left open or connected to GND, the gate driver is disabled and the external MOSFET turns off. By using the duty cycle of the PWM control method that can change the working and the closing time, and the light output can be adjusted between zero and the internal set. In addition, the PWM dimming method is limited because the output current cannot be exceeded the internal set. The power topology does not require filter capacitance at the output side of rectifier bridge. Therefore, sampling the phase-controlled voltage waveform of TRAIC connects PT6909’s PWMD pin can realize TRAIC dimming. OSCILLATOR Connecting an external resistor from RF pin to GND programs switching frequency: Fosc = V1.1 2.6 x 1010 R RF 5 April 2010 PT6909 ABSOLUTE MAXIMUM RATINGS Parameter VIN to GND CS1,CS2 to GND GD to GND PWMD to GND OVP to GND RF to GND Operating temperature Storage temperature Symbol Rating -0.3 ~ +16 -0.3 ~ +6 -0.3 ~ +16 -0.3 ~ +16 -0.3 ~ +6 -0.3 ~ +6 -40 ~ +85 -65 ~ +150 Topr Tstg Unit V V V V V V ℃ ℃ ELECTRICAL CHARACTERISTICS (Unless otherwise specified, Ta=25℃) Parameter Input DC supply voltage VIN clamped voltage Current sink capability at VIN Start-up current Symbol VIN VCLP ICLP ISTART VST VHYS VENL VENH REN VCS Conditions DC input voltage PWMD=VIN PWMD=VIN PWMD=GND, VIN rising VIN=12V, PWMD=VIN, VCS1=VCS2=0.5V VIN=12V, PWMD=VIN, VCS1=VCS2=GND VIN rising VIN falling VIN=8~12V VIN=8~12V VPWMD=5V VIN=8~12V VOVP VIN=8~12V Active supply current IINAC Stand-by supply current IINST VIN start voltage VIN under voltage lockout hysteresis Pin PWMD input low voltage Pin PWMD input high voltage Pin PWMD pull-down resistance Current sense threshold voltage Over voltage protection threshold voltage RF voltage Oscillator frequency Maximum oscillator PWM duty cycle Current sense blanking internal GD high output voltage GD low output voltage GD output rise time GD output fall time V1.1 VRF FOSC DMAX TBLANK VGDH VGDL TRISE TFALL VIN=8~12V, RRF =270KΩ RRF=270KΩ RRF=270KΩ, CS1= CS2=GND VCS1=VCS2=0.5V ISource=10mA ISink=10mA CGD=560pF CGD=560pF 6 Min. 8 Typ. 9 14 Max. 12 5 30 Unit V V mA uA 0.56 0.7 mA 0.46 0.6 mA 6.5 0.6 7.0 0.9 7.5 1.2 1.2 2.5 170 220 200 240 230 260 V V V V KΩ mV 1.21 V 1.18 75 1.21 95 200 VIN-0.3 300 1.24 115 100 400 30 30 0.2 50 50 V KHz % ns V V ns ns April 2010 PT6909 PACKAGE INFORMATION 8 PINS, SOP, 150MIL Symbol A A1 A2 b c D E E1 e L θ Millimeter Nom. 1.60 0.15 1.40 4.90 6.00 3.90 1.27BSC 0.60 - Min. 1.35 0.08 1.20 0.33 0.17 4.70 5.80 3.70 0.38 0° Max. 1.77 0.28 1.65 0.51 0.26 5.10 6.20 4.10 1.27 8° Notes: 1. All dimensions are in millimeter 2. Refer to JEDEC MS-012 AA V1.1 7 April 2010 PT6909 IMPORTANT NOTICE Princeton Technology Corporation (PTC) reserves the right to make corrections, modifications, enhancements, improvements, and other changes to its products and to discontinue any product without notice at any time. PTC cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a PTC product. No circuit patent licenses are implied. Princeton Technology Corp. 2F, 233-1, Baociao Road, Sindian, Taipei 23145, Taiwan Tel: 886-2-66296288 Fax: 886-2-29174598 http://www.princeton.com.tw V1.1 8 April 2010