RS2332 High-Voltage Start-Up Primary Side LED Controller with Active PFC DESCRIPTION The RS2332 integrates 600V ultra high voltage startup circuit reduces the total power consumption to provide a high efficiency solution for lighting applications and it is a single-power stage, isolated, primary-side-control offline LED lighting controller that achieves high power factor in a single SOP-8 package. The proprietary real-current control method can control the LED current accurately from the primary side information. It can significantly simplify the LED lighting system design by eliminating the secondary side feedback components and the opto-coupler. The RS2332 integrates active power factor correction and works in quasi resonance mode in order to reduce the MOSFET switching losses. The multi-protection features of RS2332 greatly enhance the system reliability and safety. The RS2332 features over voltage protection, short circuit protection, cycle-by-cycle current limit, VCC UVLO and auto-restart over-temperature protection. The driver output voltage is clamped at maximal 18V to protect the external power MOSFET. FEATURES • • • • • • • • • • • Very less components Build-in 600V start-up circuit Real current control without secondary feedback Accurate constant current output Active power factor correction (>0.9) Quasi resonance mode for high efficiency Under voltage lockout (UVLO) Programmable input AC voltage compensation Leading edge blanking on CS/ZCD pin Available in an SOP-8 package Protection features - Building in hysteresis OTP - VCC over voltage protection - Clamped Gate output voltage to maximal 18V - Cycle by cycle current limiting on CS - Secondary peak current protection on CS pin - Output short to GND protection - Output programmable over voltage protection APPLICATIONS • Low Power AC/DC offline SMPS for: - Solid state lighting - Industrial and commercial lighting BLOCK DIAGRAM Tel: 886-66296288‧Fax: 886-29174598‧ http://www.princeton.com.tw‧2F, No. 233-1, Baociao Rd., Sindian Dist., New Taipei City 23145, Taiwan RS2332 APPLICATION CIRCUIT ORDER INFORMATION Device RS2332 Y Z V1.1 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) 2 August 2013 RS2332 PIN CONFIGURATION PIN DESCRIPTION Pin Name COMP GND CS GATE VCC ZCD NC HV V1.1 Description Loop Compensation pin. Connect a compensation network to stabilize the LED driver and achieve an accurate LED driver current. Reference GND of IC Current sense pin. The MOSFET current is sensed via a resistor. If the voltage in this pin is higher than the current limit threshold 1.0V after some blanking time in the turn-on interval, the gate signal will be turned off. Gate drive output pin. The totem pole output stage is able to drive high power MOSFET with a peak current of 0.5A source capability and 0.8A sink capability. The high level voltage of this pin is clamped to 19V to avoid excessive gate drive voltage. Power supply. Zero current detection pin. A negative going edge triggers the turn on signal of the external MOSFET. Connect this pin through a resistor divider from the auxiliary winding to GND. Over-voltage conditions is detected through ZCD. If ZCD voltage is higher than the over-voltage-protection (OVP) threshold after a blanking time 1μs, the over-voltage condition is detected. No connect High voltage startup switch instead of resistor 3 Pin No. 1 2 3 4 5 6 7 8 August 2013 RS2332 FUNCTION DESCRIPTION CIRCUIT OPERATION The RS2332 is a high performance LED driver with single stage power factor correction and primary side constant current control. Active Power Factor Correction (PFC) is included to eliminate the unwanted harmonic noise injected onto the AC line. The advanced primary side regulation techniques provide accurate constant current control. Quasi Resonance operation mode improves efficiency by reducing the MOSFET switching losses. The HV startup circuit is build inside for further power saving. POWER FACTOR CORRECTION RS2332 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 transformer 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 the primary side inductor (Lm) and the primary current increases linearly from zero to the peak value (IPK). When the external power MOSFET turns off, the energy stored in the inductor forces the secondary side 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 auxiliary winding which is shown in figure 2. V1.1 4 August 2013 RS2332 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 0.2V and ensures the MOSFET turn on at a valley voltage (see Figure 3). Figure 3 As a result, there are very small primary switch turn-on losses and no secondary diode reverse recover losses. It ensures high efficiency and low EMI noise. V1.1 5 August 2013 RS2332 STARTUP PROCEDURE For the startup, refer figure 4, the HV pin is connected to line input or bulk capacitor. Typically the start-up current drawn from HV pin is about 1.5mA and can charge up the VCC hold capacitor. When the VCC voltage reaches VCCON, the start-up current is switched off. At this moment, the VCC capacitor should keep the VCC before the auxiliary winding of the main transformer to provide the operating current. Refer figure4, the 6V hysteresis voltage is implemented to prevent shutdown from a voltage dip during start-up. Figure 4. Startup procedure PRIMARY SIDE CONSTANT CURRENT CONTROL The proprietary current control method allows the RS2332 to accurately control the secondary side LED current from the primary side information. The output LED mean current can be calculated approximately as: 0.25 N P I LED = × 2RCS N S Where ILED is the secondary output current of LED, NP is number of turns of primary winding and NS is number of turns of the secondary winding. MINIMAL OFF TIME The RS2332 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, RS2332 employs an internal minimum off time limiter, 3.5μs and then external MOSFET will turn on at next valley which shows as figure 5. Figure 5 V1.1 6 August 2013 RS2332 MAXIMUM OFF TIME The RS2332 integrates a maximum off time limitation when the MOSFET is turned off, if ZCD fails to send out next turn on signal after 30μs, RS2332 will automatically send out a turn on signal which can avoid unnecessary shut down caused by ZCD missing detection. 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. Blanking time for ZCD pin Leading Edge blanking for CS pin and Cycle by Cycle Current Limit .The current limit circuit senses primary current by CS pin. When this current exceeds the internal threshold, the GATE output is turned off for the remainder of that cycle. A leading edge blanking circuit inhibits the current limit comparator for a short time (TLEB) after the power MOSFET is turned on. The TLEB has been set so that current spikes caused by capacitance and rectifier reverse recovery will not cause error current limit trigger. Figure 7. Leading edge blanking for CS OUTPUT OVER VOLTAGE PROTECTION Output over voltage protection can prevent the components from damage in the over voltage condition. The positive plateau of auxiliary winding voltage is proportional to the output voltage. The OVP uses the auxiliary winding voltage instead of directly monitoring the output voltage. Once the ZCD pin voltage is higher than 3.6V, the OVP signal will be triggered and latched, the gate driver will be turned off and the IC work at quiescent mode, the VCC voltage dropped below the UVLO which will make the IC shut down and the system restarts again. V1.1 7 August 2013 RS2332 The output OVP setting point can be calculated as: NS R + R ZCD 2 VOUT _ OVP ≈ 3.6 × × ZCD1 N AUX R ZCD2 VOUT_OVP : Output over voltage protection value NAUX : The auxiliary winding turns NS : The secondary winding turns RZCD1 : The resistor connected between auxiliary winding of transformer and ZCD pin RZCD2 : The resistor connected between GND and ZCD pin Figure 8 To avoid the incorrect OVP signal by the oscillation spike after the switch turns off, the OVP sampling has a TOVPS blanking period, typical 1μs, shown in figure 9. Figure 9 V1.1 8 August 2013 RS2332 OUTPUT SHORT CIRCUIT PROTECTION The RS2332 will detect high voltage of ZCD waveform, which is noted as ZCD shown in figure 10. When the output short circuit happens, the high voltage of auxiliary winding voltage is almost zero. Once ZCD voltage falls below 1.2V and lasts for about 9ms, the GATE output will shut down and restart after UVLO. Figure 10. Output short to GND protection OVER TEMPERATURE PROTECTION (OTP) The OTP shutdown circuitry senses the die temperature. The threshold is set at 150℃ typical with a 25℃ hysteresis. When the die temperature rises above this threshold (150℃), GATE output is shut down and remains turning off until the die temperature falls by 25℃, at which point it is re-enabled. VCC OVER VOLTAGE PROTECTION RS2332 provides an over voltage protection circuit for VCC pin to prevent damage due to over voltage conditions. When the voltage of VCC pin exceeds 25V due to abnormal conditions, GATE output will be turned off. FAULT PROTECTION There are several default protections which are integrated in the RS2332 to prevent the IC from being damaged such as ZCD pin open or short, CS pin floating. GATE DRIVER AND CLAMPED The Gate output is a totem pole circuit designed to drive external power MOSFET. A clamp design provides a clamping Gate output at maximal 18V to protect the external power MOSFET from damaging. V1.1 9 August 2013 RS2332 ABSOLUTE MAXIMUM RATINGS Parameter Input voltage to HV pin Maximum supply voltage on VCC pin Input voltage to ZCD pin Input voltage to CS pin Input voltage to COMP pin HBM model Machine model Maximum operating junction temperature Storage temperature range Symbol VHV VVCC VZCD VCS VCOMP Ratings -0.3 ~ 600 28.0 -0.3 ~ 6.0 -0.3 ~ 6.0 -0.3 ~ 6.0 >2000 >200 125 -40 ~ +150 ESD Capability TMAX TSTG Unit V V V V V V V ℃ ℃ 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 (TA=25℃, VDD=15V, if not otherwise noted) Parameter HV Pin Charge VCC current from HV pin when startup VCC Pin Turn-on threshold voltage Turn-off threshold voltage VCC over voltage protection Operating current ZCD Pin ZCD voltage when output short to GND protection ZCD voltage when output over voltage protection Delay time when output short to GND protection COMP pin Reference voltage for OTA input COMP maximal sink current COMP maximal source current CS Pin Cycle by cycle current limited on CS Secondary current protection on CS Leading-edge blanking time QR-Oscillator PWM minimal off time PWM maximum off time GATE Drive Output (GATE Pin) Rise time Fall time Gate clamp voltage Over Temperature Protection Over temperature lockout Over temperature resume V1.1 Symbol Test Condition Min. Typ. Max. Unit IHV_CHARGE HV=40V, VCC=0V - 0.82 - mA - 16.5 10 25 - V V V - 2 - mA VZCD_SCP - 1.0 - V VZCD_OVP - 3.6 - V TZCD_SCP - 9.0 - ms VREF ICOMP1 ICOMP2 - 0.25 29 7.5 - V μA μA VCS1 VCS2 TBLANK 350 1.2 1.8 450 550 V V ns TOFF MIN TOFF MAX - 18 30 - μs μs 16.5 100 50 18 ns ns V - 145 125 - ℃ ℃ VCCON VCCOFF VCCOVP ISS TR TF VGCLAMP OTPH OTPL 10 Gate=1nF ZCD=2.0V & CS=0V CL=1nF CL=1nF August 2013 RS2332 PACKAGE INFORMATION 8-PIN, SOP Symbol A A1 A2 b c e D E E1 L θ Millimeter Nom. 1.60 0.15 1.40 1.27 BSC. 4.90 6.00 3.90 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. Refer to JEDEC MS-012 AA. 2. All dimensions are in millimeter. V1.1 11 August 2013 RS2332 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 V1.1 12 August 2013