RS2322 High Accurate non-isolated Buck-Boost LED Driver with Active PFC DESCRIPTION The RS2322 integrates active power factor correction and works in quasi resonance mode in order to reduce the MOSFET switching losses. The multi-protection features of RS2322 greatly enhance the system reliability and safety. The RS2322 features over voltage protection, short circuit protection, cycle-by-cycle current limit, VDD UVLO and auto-restart over-temperature protection. The driver output voltage is clamped at maximal 19V to protect the external power MOSFET. The RS2322 is especially designed for non-isolated LED driver. The building in perfect current compensation function ensures the accurate output current. RS2322 has very less external components because of high integrated and simple topology. Thanks to novel power supply, RS2322 need not use transformer and it could simplify PCB design. PROTECTION FEATURES • • • • • • • • • • VDD 25V over-voltage protection Gate 19V clamped voltage Building in hysteresis OTP (150℃) Cycle-by-cycle current limiting Inductor anti-saturation ZCD pin short to GND ZCD pin open CS pin open LED open protection LED+ and LED- short protection FEATURES • High efficiency (Reach 90%) • Active Power Factor Correction (>0.9) • High precision output current regulation (-3%~+3%) when universal AC input voltage (85VAC~265VAC) • Lowest cost and very less component count solution • Non-Isolated Buck-Boost application • Need not transformer to simplify design • Accurate Constant Current Output • Quasi Resonance Mode for High Efficiency • Support no electrolytic capacitor • Programmable output current setting • Tight tolerances and negligible temperature variation • Frequency jittering dramatically reduces EMI, minimizes EMI filter cost • Building in current compensation • Building in 450nS LEB time for CS pin • Audio noise free operation • SOP-8 Pb free package APPLICATIONS • • • • Cell phone charger Small power adaptor LED lamp Industrial controls Tel: 886-66296288‧Fax: 886-29174598‧ http://www.princeton.com.tw‧2F, No.233-1, Baociao Rd., Sindian Dist., New Taipei City 23145, Taiwan RS2322 BLOCK DIAGRAM APPLICATION CIRCUIT Note: Diode D1 must be ultra-fast diode. V1.0 2 January 2013 RS2322 ORDER INFORMATION Device RS2322 Y Z Device Code Y is package & Pin Assignments designator : S : SOP-8 Z is Lead Free designator : P: Commercial Standard, Lead (Pb) Free and Phosphorous (P) Free Package G: Green (Halogen Free with Commercial Standard) PIN CONFIGURATION PIN DESCRIPTION Pin Name COMP GND CS DRV VDD ZCD TM NC V1.0 Description Loop Compensation pin. Connect a compensation network to stabilize the LED driver. Reference GND. Current sense pin, a resistor sense the MOSFET current. Drive external power MOSFET. Power Supply. Zero current detection pin. A negative going edge triggers the turn on signal of the external MOSFET. Over-voltage conditions are detected through ZCD. If ZCD voltage is higher than the over-voltage-protection (OVP) threshold after a blanking time 600ns, the over-voltage condition is detected. Inside test pin. No connect 3 Pin No. 1 2 3 4 5 6 7 8 January 2013 RS2322 FUNCTION DESCRIPTION CIRCUIT OPERATION The RS2322 is a high performance LED driver with single stage power factor correction and Buck-boost structure constant current control. Active Power Factor Correction (PFC) is included to eliminate the unwanted harmonic noise injected onto the AC line. The advanced techniques provide accurate constant current control. Quasi Resonance operation mode improves efficiency by reducing the MOSFET switching losses. POWER FACTOR CORRECTION RS2322 is designed with quasi-resonance and constant on time TON to achieve high power factor under normal operation. The peak current and average current of inductor will be shaped as AC input sinusoid too and then high power factor can be achieved. Figure 1 AC line voltage and Peak current QUASI RESONANCE MODE (QRM) During the external power MOSFET on time (TON), the rectified input voltage is applied across inductor (Lm) from zero to the peak value (IPK). When the external power MOSFET turns off, the energy stored in the inductor forces the Freewheeling diode to be turn-on, and the current of the inductor begins to decrease linearly from the peak value to zero. When the current decreases to zero, the parasitic resonant of inductor and all the parasitic capacitance makes the power MOSFET drain-source voltage decrease, this decreasing is also reflected on the inductor which is shown in figure 2. V1.0 4 January 2013 RS2322 Figure 2 The zero-current detector in ZCD pin generates the turn on signal of the external MOSFET when the ZCD voltage is lower than 0.25V and ensures the MOSFET turn on at a valley voltage (see figure 3). Figure 3 As a result, there are MOSFET had very small switch turn-on losses and eliminate Freewheeling diode reverse recover losses. It ensures high efficiency and low EMI noise. V1.0 5 January 2013 RS2322 STARTUP PROCEDURE An UVLO comparator is implemented in RS2322 to detect the voltage on VDD pin. It would assure the supply voltage enough to turn on the PWM controller and further to driver the power MOSFET. As shown figure 4, a hysteresis is built in to prevent the shutdown from the voltage dip during startup. The turn on and turn off threshold level are set at 15.7V and 10V, respectively. Figure 4 REAL CURRENT CONTROL The perfect detection and compensation control method allows the RS2322 to accurately control the output LED current, the output LED mean current can be calculated as: V ILED R CS RCS --- The sensing resistor connected between the MOSFET source and GND MINIMAL OFF TIME The RS2322 operates with variable switching frequency. The frequency is changing with the input instantaneous line voltage. To limit the maximum frequency and get a good EMI performance, RS2322 employs an internal minimum off time limiter 3.5µs and maximum frequency control below 125 KHz, then external MOSFET will turn on at next valley which shows as figure5. V1.0 6 January 2013 RS2322 MAXIMUM OFF TIME The RS2322 integrates a maximum off time limitation when the MOSFET is turned off, if ZCD fails to send out next turn on signal after 30µs, RS2322 will automatically send out a turn on signal which can avoid unnecessary shut down caused by ZCD missing detection. Figure 5 LEADING EDGE BLANKING FOR ZCD PIN When the power MOSFET is turned off, a damping voltage spike will occur at ZCD pin due to parasitic capacitance and leak inductor of transformer. An internal leading edge blanking is introduced to filter this noise also. Figure 6 shows the leading edge blanking of ZCD pin Figure 6 V1.0 7 January 2013 RS2322 LEADING EDGE BLANKING FOR CS PIN In order to avoid the premature termination of the switching pulse due to the parasitic capacitance discharging at MOSFET turning on, an internal leading edge blanking (LEB) unit is employed between the CS pin and the current comparator input. During the blanking time, the path, CS pin to the current comparator input, is blocked, below figure 6 shows the leading edge blanking. Figure 6 OUTPUT OVER VOLTAGE PROTECTION Output over voltage protection can prevent the components from damage in the over voltage condition. The positive plateau of ZCD pin voltage is proportional to the output voltage. Once the ZCD pin voltage is higher than 3.2V, the OVP signal will be triggered and latched after three cycles, the gate driver will be turned off and the IC works at quiescent mode, the VDD voltage dropped below the VDDOFF which will make the IC shut down and the system restarts again. The output OVP setting point can be calculated as: R ZCD R ZCD VOUT_OVP 3.2 R ZCD VOUT_OVP……Output over voltage protection value RZCD1 ……The resistor connected between auxiliary winding of transformer and ZCD pin RZCD2……The resistor connected between GND and ZCD pin Figure 7：LED open loop protection V1.0 8 January 2013 RS2322 To avoid the incorrect OVP signal by the oscillation spike after the switch turns off, the OVP sampling has a TOVPS blanking period, typical 0.6us, shown in figure 8 VZCD Sample Here t 0 TOVPS Figure 8 OUTPUT SHORT PROTECTION The RS2322 will detect high voltage of ZCD waveform, which is noted as ZCD shown in figure 9. When the output short circuit happens, the high voltage is almost zero. Once ZCD voltage falls below 0.8V and lasts for about 9mS, the GATE output will shut down and restart after UVLO. The output SCP setting point can be calculated as:. VOUT_SCP 0.8 R ZCD R ZCD R ZCD Figure 9 V1.0 9 January 2013 RS2322 ABSOLUTE MAXIMUM RATINGS Parameter Supply Voltage Pin Voltage DRV Pin Voltage VDD OVP Maximal Enter Current Input Voltage to CS Pin Input Voltage to ZCD Pin Input Voltage to COMP Pin Power Dissipation ESD Capability, HBM Model ESD Capability, Machine Model Junction Temperature Storage Temperature Range Lead Temperature(Soldering, 20sec) Symbol VDD VDRV IOVP VCS VZCD VCOMP PD Range 30 30 10 -0.3 ~ 6 -0.3 ~ 6 -0.3 ~ 6 500 4000 400 125 -40~150 260 ESD TJ TSTG TLEAD Unit V V mA V V V mW V V °C °C °C Note: Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, 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-rated conditions for extended periods may affect device reliability ELECTRICAL CHARACTERISTICS (Unless stated otherwise, TA=25°C and VDD=15V) Parameter Supply Voltage (VDD) Section VDD Turn On Threshold VDD Turn Off Threshold VDD Over Voltage Protection Startup Current Operating Current of VDD Oscillator Section Maximal Frequency Maximal Turn On Time Maximal Turn Off Time Symbol VDDON VDDOFF VDDOVP IST IOP Test Conditions Min. Typ. Max. Unit 14.0 8.5 24.0 - 15.7 10.0 25.0 2.0 18.0 10.5 27.0 25 - V V V mA mA - 125 17 30 - KHz μS μS - - 3.5 - μS - - 0.8 3.2 9.0 600 - V V mS nS - - 275 8 8 - mV μA μA VDD = VDDON - 0.3V CDRV=1.5nF FMAX TMAX ON TMAX_OFF - Minimum Turn Off Time TMIN_OFF ZCD Section ZCD Voltage When Output Short to GND Protection VZCD SCP ZCD Voltage When Output Over Voltage Protection VZCD OVP Delay Time When Output Short to GND Protection TZCD SCP ZCD Pin Leading-Edge Blanking Time TZCD LEB COMP Section Reference Voltage for OTA Input VREF COMP Maximal Sink Current ICOMPH COMP Maximal Source Current ICOMPL CS Section CS Pin Leading-Edge Blanking Time TCS_LEB - - 450 - nS Maximal PEAK Voltage VCS_PEAK - - 0.8 - V DRV Section Rise Time of Driver TR CDRV=1.0nF 50 100 200 nS Fall Time of Driver TF CDRV=1.0nF 30 50 100 nS 16 - 19 V DRV Clamped Voltage VDRV-MAX - OTP Section OTP Protection Temp. TOTPP - 150 - °C OTP Release Temp. TOTPR - 125 - °C V1.0 10 January 2013 RS2322 PACKAGE INFORMATION 8-PIN, SOP Symbol A A1 A2 b c e D E E1 L θ Millimeter Nom. 1.27 BSC. - Min. 1.35 0.10 1.25 0.31 0.17 4.80 5.80 3.80 0.40 0° Max. 1.75 0.25 1.65 0.51 0.25 5.00 6.20 4.00 1.27 8° Notes: 1. Refer to JEDEC MS-012 AA. 2. All dimensions are in millimeter. V1.0 11 January 2013 RS2322 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 Dist., New Taipei City 23145, Taiwan Tel: 886-2-66296288 Fax: 886-2-29174598 http://www.princeton.com.tw V1.0 12 January 2013