OB2576TCPA

OB2576xT High Performance QR mode Primary-Side Power Switch GENERAL DESCRIPTION FEATURES  Primary-side sensing and regulation operates in QR mode without TL431 and opto-coupler  High precision constant voltage and current regulation at universal AC input  Programmable CV and CC regulation  Integrated power MOSFET  Good dynamic response  Built-in line compensation for tight CC regulation  Built-in fixed cable compensation  Built-in primary winding inductance compensation  Built-in control loop compensation  Built-in leading edge blanking (LEB)  Ultra low start-up current and low operating current  Comprehensive protection coverage with auto-recovery  VDD over voltage protection (VDD OVP)  VDD under voltage lockout with hysteresis (UVLO)  Cycle-by-cycle current limiting  Feedback open loop protection (OLP)  Output short circuit protection (SCP) en tia lt o 坤 兴 OB2576xT is an excellent primary side regulation power switch with CC/CV operation for medium level power AC/DC charger and adapter applications. The device integrates an internal power MOSFET and operates in QR mode to provide high efficiency along with several functions of built-in protections. It removes the need for secondary feedback circuitry to lower the total bill of material cost. Proprietary Constant Voltage (CV) and Constant Current (CC) control is integrated as shown in the figure below. In CV control, the controller changes the mode of operation according to load condition. At full loading, the controller operates in quasi-resonant (QR) mode in the universal line voltage. The primary side regulation power supplies up to high power without the efficiency limitation of DCM or audible noise. In CC control, OB2576xT samples the Vcs peak current and the demagnetization pulse to regulation the output current. The current and output power setting can be adjusted externally by the sense resistor Rs at CS pin. OB2576xT offers comprehensive protection coverage with auto-recovery feature including Cycle-by-Cycle current limiting, VDD OVP, OLP, SCP, OTP etc. OB2576xT consumes less than 75mW input power at no- load condition with high line voltage. OB2576xT is offered in SOP8 package. on fid APPLICATIONS rig ht c Medium level Power AC/DC offline SMPS for  Cell phone charger  Tablet PC  AC/DC adapter  Set-top box power supplies Figure.1. Typical CC/CV Curve O nB TYPICAL APPLICATION ©On-Bright Electronics Confidential -1- Preliminary Datasheet OB_DOC_DS_2576xT00 OB2576xT High Performance QR mode Primary-Side Power Switch GENERAL INFORMATION 8 DRAIN GND 2 7 DRAIN FB 3 6 DRAIN CS 4 5 DRAIN Ordering Information Part Number Description OB2576TCP SOP8, Halogen-free in Tube OB2576TCPA SOP8, Halogen-free in T&R OB2576ATCP SOP8, Halogen-free in Tube OB2576ATCPA SOP8, Halogen-free in T&R OB2576BTCP SOP8, Halogen-free in Tube OB2576BTCPA SOP8, Halogen-free in T&R -40 to 150 ℃ -20 to 85 ℃ -55 to 150 ℃ 260 ℃ en tia lt o 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. Recommended Operating Condition Symbol Parameter Range VDD VDD Supply Voltage 9 to 31V O nB rig ht c on fid Package Dissipation Rating Package RθJA (℃/W) SOP8 85 Marking Information Value -0.3 to 35V -0.3 to 7V -0.3 to Bvdss -0.3 to 7V 坤 VDD 1 Absolute Maximum Ratings Parameter VDD Voltage FB Input Voltage Drain Voltage (off state) CS Input Voltage Min/Max Operating Junction Temperature TJ Operating Ambient Temperature TA Min/Max Storage Temperature Tstg Lead Temperature (Soldering, 10secs) 兴 Pin Configuration YWWZZZ OB2576TCP A S Y:Year Code WW:Week Code(01-52) ZZZ:Lot Code C:SOP8 Package P:Green Package(Halogen-free) A:Character Code S:Internal Code(Optional) ©On-Bright Electronics Confidential -2- Preliminary Datasheet OB_DOC_DS_2576xT00 OB2576xT High Performance QR mode Primary-Side Power Switch TERMINAL ASSIGNMENTS for OB2576xTCP Pin Name I/O Description 1 VDD P Power Supply 2 GND P Ground 3 FB I The voltage feedback from auxiliary winding. Connected to resistor divider from auxiliary winding reflecting output voltage. 4 CS I Current sense input. Connect a sense resistor from this pin to ground. 5,6,7,8 DRAIN O Internal MOSFET DRAIN output O nB rig ht c on fid en tia lt o 坤 兴 Pin Num ©On-Bright Electronics Confidential -3- Preliminary Datasheet OB_DOC_DS_2576xT00 OB2576xT High Performance QR mode Primary-Side Power Switch BLOCK DIAGRAM Vref Demag detect QR & CV foldback multi mode control dem Logic Vcomp sample Vref_CV S EA + Cable compensation CLR LPF Q Vline_os + CC comp dem CC Control LEB CS dem O nB rig ht c SC Filter + S/H Vref_CC GND Gate Drive Q CV comp + on fid Vline_os Line compensation R SET DRAIN o FB Fs_max / Fs_min 兴 OVP & Open loop& Iref 坤 UVLO&AVDD en tia lt VDD Reference ©On-Bright Electronics Confidential -4- Preliminary Datasheet OB_DOC_DS_2576xT00 OB2576xT High Performance QR mode Primary-Side Power Switch ELECTRICAL CHARACTERISTICS (TA = 25℃, VDD=18V, if not otherwise noted) Symbol Parameter Supply Voltage (VDD) Section I start-up Start up current Operating current FB=1V 14.5 6.5 31 15 uA 0.8 1.0 mA 1.5 2.5 mA 16 7 33 17.5 7.5 35 en tia lt on fid 55 ht c rig Unit V V V 525 ns 700 mV 600 mV 2.475 2.5 For OB2576ATCP Maximum cable compensation to For OB2576TCP Vout ratio For OB2576BTCP CC Loop Section Vref_cc CC loop reference Timer Section Fs_max CV QR maximum frequency Fmin Minimum switch frequency Internal OTP Section nB 5 VDD=UVLO_OFF-1V UVLO(OFF) VDD under voltage lockout exit UVLO(ON) VDD under voltage lockout enter VDD_OVP VDD over voltage protection Current Sense Input Section LEB time and OCP propagation TLEB+TD_OC delay Maximum over current Vth_ocp_max threshold@ Low AC voltage Maximum over current Vth_ocp_max threshold@ High AC voltage FB Input Section Reference voltage for feedback Vref_fb threshold V_OVP Output Over voltage threshold Vth_cc_shutdown CC mode shut down threshold CC mode shut down debounce Tdbs_cc_shutdown time ∆cable_max/Vout Max 兴 Iop_s Typ. 坤 Standby current Min o I standy Test Conditions 2.525 V 3.25 1.55 60 V V 65 3 5 7 ms % % % 290 300 310 mV 74 0.27 80 0.3 86 0.33 KHz KHz OTP_int_enter internal OTP enter temperature 150 ℃ OTP_int_exit internal OTP exit temperature 120 ℃ O MOSFET Section BVdss Rdson Mosfet Drain-Source Breakdown Voltage Static drain to source on resistance ©On-Bright Electronics Confidential -5- 620 V 2.2 Ώ Preliminary Datasheet OB_DOC_DS_2576xT00 OB2576xT High Performance QR mode Primary-Side Power Switch O nB rig ht c on fid en tia lt o 坤 兴 CHARACTERIZATION PLOTS ©On-Bright Electronics Confidential -6- Preliminary Datasheet OB_DOC_DS_2576xT00 OB2576xT High Performance QR mode Primary-Side Power Switch OPERATION DESCRIPTION 兴 charging starts in the CC portion of the curve until it is nearly full charged and smoothly switches to operate in CV portion of the curve. The CC portion provides output current limiting. In CV operation, the output voltage is regulated through the primary side control. In CC operation mode, OB2576xT will regulate the output current constant regardless of the output voltage drop. o 坤 Principle of Operation With OB2576xT proprietary CC/CV control, system can be designed in QR/DCM mode for flyback system (Refer to the Typical Application Diagram in page1). In the flyback converter, the output voltage can be sensed via the auxiliary winding. During MOSFET turn-on time, the load current is supplied from the output filter capacitor and the current in the primary winding ramps up. When MOSFET turns off, the energy stored in the primary winding is transferred to the secondary side and the current in the secondary winding is en tia lt OB2576xT is an excellent integrated multi-mode (see Figure 2) PWM power switch optimized for off-line middle power AC/DC applications. It operates in quasi-resonant mode (QR) to provide high efficiency with primary side sensing and regulation thus provides cost effective solution for energy efficient power supplies. At full loading, the IC operates in QR mode in the universal line input voltage. In this way, high efficiency in the universal input range at full loading can be achieved. At normal load condition, it operates in QR mode. To minimize switching loss, the maximum switching frequency in QR mode is internally limited to 80 kHz (typical). When the load goes low, it operates in PFM mode with valley switching for high power conversion efficiency. When the load is very small, the IC switch frequency can be reduced to 0.3kHz to minimize the standby power loss. As a result, high conversion efficiency can be achieved in the whole loading range. IS  NP  IP NS (1) on fid The auxiliary winding voltage reflects the output voltage as shown in Figure.3 and it is given by V AUX  N AUX  (VO  V ) NS (2) ht c Where V indicates the voltage drop of the output Diode. rig Figure 2 Multi-mode operation diagram Proprietary built-in CV and CC control can achieve high precision CC/CV control meeting most charger application requirements. nB Startup Current and Start Up Control Startup current of OB2576xT is designed to be very low so that VDD could be charged up above UVLO threshold level and device starts up quickly. A large value startup resistor can therefore be used to minimize the power loss yet achieve a reliable startup in application. O Figure.3. Auxiliary winding voltage waveform Via a resistor divider connected between the auxiliary winding and FB PIN, the auxiliary voltage is sampled and hold during the demagnetization cycle. The sampling instance is variable according to the demagnetization width. The output voltage can be monitored when the secondary current is small. Thus ∆V can be ignored. The sampled voltage is compared with reference voltage Vref (typical 2.5V) and the difference is amplified. The error amplifier output reflects the load condition and controls the switching off time to regulate the output voltage, thus constant output voltage can Operating Current The Operating current of OB2576xT is as low as around 800uA @ no load mode. Good efficiency and less than 75mW standby power is achieved with the low operating current. CV Mode Operation OB2576xT is designed to produce good CC/CV control characteristic as shown in the Figure. 1. In charger applications, a discharged battery ©On-Bright Electronics Confidential -7- Preliminary Datasheet OB_DOC_DS_2576xT00 OB2576xT High Performance QR mode Primary-Side Power Switch be achieved. CC Mode Operation OB2576xT sample the CS peak and the transformer core demagnetization period to regulate to output current. The primary CS peak is adaptively controlled according to vref_cc and the internal CC comp voltage. Tdemag 1 1 1 Vcs Tdemag (3)  N  I pk   N  Ts Rcs Ts 2 2 Where Ipk is the peak current of primary winding, Tdemag is the transformer core demagnetization period, and Ts, the switch period. Refer to the equation 3, Regulating the Ipk can achieve the constant output current. The constant output current is independent of the primary Ts be modulated equal to vref_cc which is 0.3V. Then Io can be determined by Io  坤 o Vcs Tdemag Figure.5. CC line voltage compensation The CS threshold voltage Vcs is given by 1 Naux Ros (5) Vcs  Vth _ cc    2  Vac  Rup M Np Where Vth_cc threshold determined by internal CC comp voltage, M is the FB current mirror ratio(M=55), Naux/Np is the auxiliary winding to primary winding turns ratio, Vac is the effective voltage of input voltage, Ros is the internal line compensation offset resistor(Ros=1.5kohm) , Rup is the external FB PIN up side resistor. will en tia lt winding inductance. The ratio of 兴 Io  1 1 Vcs Tdemag 1 vref _ cc (4) N   N 2 Rcs Ts 2 Rcs Current Sensing and Leading Edge Blanking Cycle-by-Cycle current limiting is offered in OB2576xT. The switch current is detected by a sense resistor into the CS pin. An internal leading edge blanking circuit chops off the sensed voltage spike at initial power MOSFET on state so that the external RC filtering on sense input is no longer needed. on fid Adjustable CC Point and Output Power In OB2576xT, the CC point and maximum output power can be externally adjusted by external current sense resistor Rs at CS pin as illustrated in the typical application diagram. The larger the Rs is, the smaller CC point is, and the smaller output power becomes, and vice versa as shown in Figure.4. rig ht c Internal Over Temperature Protection with GATE Shutdown The internal OTP circuit of OB2576xT is triggered and only shuts down the internal MOSFET when the chip temperature rises above 150℃, and the internal MOSFET will resume switching after the chip temperature falls below 120℃. nB Protection Control Good power supply system reliability is achieved with its rich protection features including Cycle-by-Cycle current limiting, Output over voltage protection, VDD over voltage protection, short circuit protection, Under Voltage Lockout on VDD. VDD is supplied by transformer auxiliary winding output after startup. The output of OB2576xT is shut down when VDD drops below UVLO (ON) and the power converter enters power on start-up sequence thereafter. Figure.4. Adjustable output power by changing Rs O CC Line Voltage Compensation The variation of maximum output current in CC mode can be rather large at high input voltage (such as 264Vac) if no compensation is provided. The CC threshold value is self adjusted higher at higher AC voltage due to CC propagation delay. In OB2576xT, the AC line voltage information is sampled through detecting FB sourcing current when gate turns on, and the AC line voltage information is added to the CS pin voltage. So the maximum CS threshold voltage Vcs_max in OB2576xT is a function of the CC threshold and AC line voltage information as shown in Figure5. ©On-Bright Electronics CC mode shutdown function In OB2576xT, to prevent the controller operating under abnormal conditions, the minimum output voltage of CC mode is limited to predetermined voltage. The CC output voltage is sampled through FB pin from auxiliary winding at the middle of the de-magnetization. When the FB sampled voltage Confidential -8- Preliminary Datasheet OB_DOC_DS_2576xT00 OB2576xT High Performance QR mode Primary-Side Power Switch is below 1.55V and last 60ms, the controller will shut down. Bypass Capacitor and FB Divider Resistor: The bypass capacitor on VDD and the FB divider resistor should be placed as close as possible to pin out. And the negative node of VDD capacitor and the FB down resistor should be connected directly to the IC GND pin before single point connected to the negative node of the output capacitor. (Blue wire as shows in Fig.6) Ground Path: The GND path of the input power loop and IC controller path should be separated and connected at the negative terminal of input capacitor by single point, such as power sense resistor, the negative of the auxiliary winding and the IC GND. (White region as shows in Fig.7) on fid en tia lt o 坤 兴 PCB Layout Consideration The following rules should be followed in OB2576xT PCB Layout: The Area of Power Loop: The area of the main current loop should be as small as possible to reduce EMI radiation, such as the primary current loop, the snubber circuit and the secondary rectifying loop (Red wire as shows in Fig.6). Drain pin increases the copper area of the drain terminal for heat dissipation (Green region as shows in Fig.7). And the PCB trace must be wide and short for thermal consideration. O nB rig ht c Fig.6 Flyback Schematic with OB2576xT ©On-Bright Electronics Fig.7 Recommend PCB Layout of OB2576xT Confidential -9- Preliminary Datasheet OB_DOC_DS_2576xT00 OB2576xT High Performance QR mode Primary-Side Power Switch O nB A A1 A2 b c D E E1 e L θ Dimensions In Millimeters Min Max 1.350 1.750 0.050 0.250 1.250 1.650 0.310 0.510 0.100 0.250 4.700 5.150 3.800 4.000 5.800 6.200 1.270 (BSC) 0.400 1.270 0º 8º rig Symbol ht c on fid en tia lt o 坤 兴 PACKAGE MECHANICAL DATA ©On-Bright Electronics Confidential - 10 - Dimensions In Inches Min Max 0.053 0.069 0.002 0.010 0.049 0.065 0.012 0.020 0.004 0.010 0.185 0.203 0.150 0.157 0.228 0.244 0.050 (BSC) 0.016 0.050 0º 8º Preliminary Datasheet OB_DOC_DS_2576xT00 OB2576xT High Performance QR mode Primary-Side Power Switch IMPORTANT NOTICE RIGHT TO MAKE CHANGES On-Bright Electronics Corp. reserves the right to make corrections, modifications, enhancements, improvements and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. o 坤 兴 WARRANTY INFORMATION On-Bright Electronics Corp. warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with its standard warranty. Testing and other quality control techniques are used to the extent it deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. On-Bright Electronics Corp. assumes no liability for application assistance or customer product design. Customers are responsible for their products and applications using On-Bright’s components, data sheet and application notes. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. en tia lt LIFE SUPPORT On-Bright Electronics Corp.’s products are not designed to be used as components in devices intended to support or sustain human life. On-bright Electronics Corp. will not be held liable for any damages or claims resulting from the use of its products in medical applications. O nB rig ht c on fid MILITARY On-Bright Electronics Corp.’s products are not designed for use in military applications. On-Bright Electronics Corp. will not be held liable for any damages or claims resulting from the use of its products in military applications. ©On-Bright Electronics Confidential - 11 - Preliminary Datasheet OB_DOC_DS_2576xT00