OB2578TAP

OB2578T High Performance CCM/QR Mode Primary-Side Power Switch GENERAL DESCRIPTION FEATURES  Primary-side sensing and regulation operates in CCM/QR mode without TL431 and opto-coupler  High precision constant voltage and current regulation at universal AC input  Fixed frequency (65kHz) CCM mode operation with low line voltage at full load  Integrated 4A MOSFET  Quasi-resonant operation for high efficiency in high line voltage  Programmable CV and CC regulation  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) fid en tia lt o 炜 烨 丰 OB2578T is an excellent primary side regulation power switch with CC/CV operation for medium level power AC/DC charger and adapter applications. The device operates in CCM/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 line voltage and load condition. At full loading, the controller operates in fixed frequency CCM in low line voltage and quasi-resonant (QR) mode in high line voltage. The primary side regulation power supplies up to high power without the efficiency limitation of DCM or audible noise. In CC control, OB2578T samples the primary-side average 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. OB2578T offers comprehensive protection coverage with auto-recovery feature including Cycle-by-Cycle current limiting, VDD OVP, OLP, SCP, OTP etc. OB2578T consumes less than 75mW input power at no-load condition with high line voltage. OB2578T is offered in SOP8 and DIP8 package. APPLICATIONS co n Vo Medium level Power AC/DC offline SMPS for  Cell phone charger  Tablet PC  AC/DC adapter  Set-top box power supplies ht ±5% Io ig I CC Br Figure.1. Typical CC/CV Curve TYPICAL APPLICATION O n- VO ~ AC NS + C O+ + NP + N AUX VDD DRAIN GND DRAIN FB DRAIN CS DRAIN OB2578T ©On-Bright Electronics Confidential -1- Preliminary Datasheet OB_DOC_DS_2578T01 OB2578T High Performance CCM/QR Mode Primary-Side Power Switch GENERAL INFORMATION Pin Configuration The OB2578T is offered in SOP8 and DIP8 package, shown as below. DRAIN GND 2 7 DRAIN FB 3 6 DRAIN CS 4 5 DRAIN 丰 8 烨 1 炜 VDD Absolute Maximum Ratings Parameter Value Drain Voltage (off state) -0.3V to Bvdss VDD Voltage -0.3 to 35V FB Input Voltage -0.3 to 7V CS Input Voltage -0.3 to 7V Min/Max Operating Junction -40 to 150 ℃ Temperature TJ Operating Ambient -20 to 85 ℃ Temperature TA Min/Max Storage -55 to 150 ℃ Temperature Tstg Lead Temperature 260 ℃ (Soldering, 10secs) Note: Stresses beyond those listed under “absolute maximum Ordering Information Part Number Description SOP8, Halogen-free in Tube OB2578TCP OB2578TCPA SOP8, Halogen-free in T&R OB2578TAP DIP8, Halogen-free in Tube o fid en tia lt RθJC (℃/W) 25 17 co n Package Dissipation Rating Package RθJA (℃/W) SOP-8 85 DIP8 70 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. ht OB2578T 90Vac~264Vac Input OB2578TCP 20W OB2578TAP 24W Recommended Operating Condition Symbol Parameter Range VDD VDD Supply Voltage 9 to 29V X X X Package Green Package Packing C:SOP8 A:DIP8 P:Halogen-free Blank :Tube A: Tape/Reel O n- Br ig High Performance CCM/QR mode Primary-Side Power Switch Output Power Table Product ©On-Bright Electronics Confidential -2- Preliminary Datasheet OB_DOC_DS_2578T01 OB2578T High Performance CCM/QR Mode Primary-Side Power Switch Marking Information 烨 炜 o Y:Year Code WW:Week Code(01-52) ZZZ:Lot Code P:Halogen-free Package S:Internal Code(Optional) 丰 YWWZZZ OB2578T Ps fid en tia lt TERMINAL ASSIGNMENTS 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. 5~8 DRAIN I Drain of power MOS. Connected to input line voltage O n- Br ig ht co n Pin Num ©On-Bright Electronics Confidential -3- Preliminary Datasheet OB_DOC_DS_2578T01 OB2578T High Performance CCM/QR Mode Primary-Side Power Switch BLOCK DIAGRAM Vref Reference OVP & Open loop Logic Vcomp EA + R CL R LPF Q Vline_os CV comp + CC comp + fid en tia lt Slope compensation dem CC Control S/H LEB Vref_CC SC Filter CS dem O n- Br ig ht co n GND Gate Drive Q + Cable compensation Vline_os Line compensation SET S 丰 CCM/QR & CV foldback multimode control dem sample Vref_ CV Drain Fs_max / Fs_min 烨 Demag detect FB Iref 炜 UVLO&AVDD o VDD ©On-Bright Electronics Confidential -4- Preliminary Datasheet OB_DOC_DS_2578T01 OB2578T High Performance CCM/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 5 15 uA 0.8 1.0 mA VDD=UVLO_OFF-1V FB=1V, floating pin 14.5 6.5 31 co n fid en tia lt UVLO(OFF) VDD under voltage lockout exit UVLO(ON) VDD under voltage lockout enter VDD_OVP VDD over voltage protection Current Sense Input Section TLEB+TD_OC LEB time and OCP propagation Vth_ocp_max Maximum over current threshold 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 Maximum cable compensation to Vout ratio@Ifb﹥1.02mA ∆cable_max/Vout Maximum cable compensation to Vout ratio@Ifb＜1.0mA GATE 2.475 55 Ifb=Vac*1.414* （Naux/Np）/Rup Recommended value Vac=165Vac @Ifb=1.0mA 1.5 2.5 mA 16 7 33 17.5 7.5 35 V V V 520 650 ns mV 2.5 2.525 V 3.25 1.55 V V 60 65 ms 2 % 4 190 200 210 mV 60 0.27 65 0.3 70 0.33 kHz kHz ig ht CC Loop Section Vref_cc CC loop reference Timer Section Fs_ccm CV CCM fix frequency Fmin Minimum switch frequency Internal OTP Section Unit 丰 Operating current Max 烨 Iop_s Typ. 炜 Standby current Min o I standy Test Conditions internal OTP enter temperature 150 ℃ OTP_int_exit internal OTP exit temperature 120 ℃ Br OTP_int_enter MOSFET Section n- Vds_maxNote O Rdson Mosfet drain-source spike voltage capability Static drain to source on resistance 650 V 2.2 Ώ Note: MOSFET minimum drain to source breakdown voltage is 620V,Voltage spike at not higher than 650V is allowed under the condition that A) Voltage spike duty cycle does NOT exceed 3% B) Voltage spike pulse width does NOT exceed 200ns. ©On-Bright Electronics Confidential -5- Preliminary Datasheet OB_DOC_DS_2578T01 OB2578T High Performance CCM/QR Mode Primary-Side Power Switch CHARACTERIZATION PLOTS UVLO_ON(V) vs Temperature 17.00 8.00 16.60 7.60 16.20 15.80 15.40 15.00 7.20 6.80 6.40 6.00 -10 20 50 80 110 140 -40 -10 2.560 2.520 o 35.20 Vref_CV(V) 2.600 fid en tia lt OVP_VCC(V) 110 140 Vref_fb(V) vs Temperature 36.00 32.80 80 Temperature(℃) VDD_OVP(V) vs Temperature 33.60 50 炜 Temperature(℃) 34.40 20 烨 -40 丰 UVLO_ON(V) UVLO_OFF(V) UVLO_OFF(V) vs Temperature 2.480 2.440 32.00 2.400 -40 -10 20 50 80 110 140 -40 20 50 80 110 140 Temperature(℃) O n- Br ig ht co n Temperature(℃) -10 ©On-Bright Electronics Confidential -6- Preliminary Datasheet OB_DOC_DS_2578T01 OB2578T High Performance CCM/QR Mode Primary-Side Power Switch OPERATION DESCRIPTION 炜 烨 丰 CV Mode Operation OB2578T is designed to produce good CC/CV control characteristic as shown in the Figure. 1. In charger applications, a discharged battery 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, OB2578T will regulate the output current constant regardless of the output voltage drop. o Principle of Operation With OB2578T proprietary CC/CV control, system can be designed in CCM/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 fid en tia lt OB2578T is an excellent integrated multi-mode (see Figure 2) PWM controller optimized for off-line middle power AC/DC applications. It operates in continuous conduction mode (CCM) and 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 fixed frequency (65KHz) CCM mode in the low line input voltage and it operates in QR mode in high 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. Pulse frequency modulation (PFM) mode Frequency IS  80KHz co n ht 22KHz 300Hz Vth3 V AUX  N AUX  (VO  V ) NS Sampling Instance FB 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. Br VAUX PWM Off n- Startup Current and Start Up Control Startup current of OB2578T 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 TDemag TON PWM On 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 Operating Current The Operating current of OB2578T is as low as around 800uA @ no load mode. Good efficiency and less than 75mW standby power is achieved with the low operating current. ©On-Bright Electronics (2) Where V indicates the voltage drop of the output Diode. Fix Frequency CCM Mode ig Vth1 Vth2 (1) The auxiliary winding voltage reflects the output voltage as shown in Figure.3 and it is given by QR mode 65KHz NP  IP NS Confidential -7- Preliminary Datasheet OB_DOC_DS_2578T01 OB2578T High Performance CCM/QR Mode Primary-Side Power Switch small. Thus ∆V can be ignored. The sampled voltage is compared with reference voltage Vref_fb (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 be achieved. + FB Rdw CS RS GND 烨 _ Idw DRAIN Figure.5. CC line voltage compensation (3) 炜 * VDD Ifb CC Mode Operation OB2578T samples the average CS and the transformer core demagnetization period to regulate the output current. The primary average CS is adaptively controlled according to vref_cc and the internal CC comp voltage. Io N AUX 丰 Rup Iup Where Vref_cc (typical 0.2V) is the reference voltage of CC Loop, Nps is the turn ratio of primary side to secondary side of the transformer. Rs is the value of the sense resistor. Refer to the equation 3, regulating the vref_cc can achieve the constant output current. The constant output current is independent of the primary winding inductance. fid en tia lt o The CS threshold voltage Vcs is given by 1 Naux Ros (5) Vcs  Vth _ cc    2  Vac  M Np Rup Where Vth_cc a threshold determined by internal CC comp voltage, M is the FB current mirror ratio (M=430), 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 upside resistor. Adjustable CC Point and Output Power In OB2578T, 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. co n Current Sensing and Leading Edge Blanking Cycle-by-Cycle current limiting is offered in OB2578T. The switch current is detected by a sense resistor connected to 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. Vo Br ig ht Large Rs Internal Over-Temperature Protection with GATE Shutdown The internal OTP circuit of OB2578T 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℃. Small Rs Io 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 OB2578T is shut down when VDD drops below UVLO (ON) and the power converter enters power on start-up sequence thereafter. n- 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 OB2578T, 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 OB2578T is a function of the CC threshold and AC line voltage information as shown in Figure 5. ©On-Bright Electronics CC mode shutdown function In OB2578T, to prevent the controller operating Confidential -8- Preliminary Datasheet OB_DOC_DS_2578T01 OB2578T High Performance CCM/QR Mode Primary-Side Power Switch 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 is below 1.55V and last 60ms, the controller will shut down. rectifying loop (Red wire as shows in Fig.6). 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. 炜 烨 丰 PCB Layout Consideration The following rules should be followed in OB2578T 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 o NP ~ AC + CO fid en tia lt NS VO + + + NAUX VDD Drain GND Drain FB Drain CS Drain OB2578T co n RS O n- Br ig ht Fig.6 Fly-back Schematic with OB2578T Fig.7 Recommend PCB Layout of OB2578T ©On-Bright Electronics Confidential -9- Preliminary Datasheet OB_DOC_DS_2578T01 OB2578T High Performance CCM/QR Mode Primary-Side Power Switch ig ht co n fid en tia lt o 炜 烨 丰 PACKAGE MECHANICAL DATA Symbol O n- Br A A1 A2 b c D E E1 e L θ ©On-Bright Electronics Dimensions In Millimeters Min Max 1.350 1.750 0.050 0.250 1.250 1.650 0.310 0.510 0.170 0.250 4.700 5.150 3.800 4.000 5.800 6.200 1.270 (BSC) 0.400 1.270 0º 8º Confidential - 10 - Dimensions In Inches Min Max 0.053 0.069 0.002 0.010 0.049 0.065 0.012 0.020 0.006 0.010 0.185 0.203 0.150 0.157 0.228 0.244 0.05 (BSC) 0.016 0.050 0º 8º Preliminary Datasheet OB_DOC_DS_2578T01 OB2578T High Performance CCM/QR Mode Primary-Side Power Switch O n- Br A A1 A2 B B1 C D E E1 e L E2 Dimensions In Millimeters Min Max 3.710 5.334 0.381 2.921 4.953 0.350 0.650 1.524 (BSC) 0.200 0.360 9.000 10.160 6.096 7.112 7.320 8.255 2.540 (BSC) 2.921 3.810 7.620 10.920 ig Symbol ht co n fid en tia lt o 炜 烨 丰 PACKAGE MECHANICAL DATA ©On-Bright Electronics Confidential - 11 - Dimensions In Inches Min Max 0.146 0.210 0.015 0.115 0.195 0.014 0.026 0.06 (BSC) 0.008 0.014 0.354 0.400 0.240 0.280 0.288 0.325 0.1 (BSC) 0.115 0.150 0.300 0.430 Preliminary Datasheet OB_DOC_DS_2578T01 OB2578T High Performance CCM/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. 炜 烨 丰 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. fid en tia lt o 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 n- Br ig ht co n 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 - 12 - Preliminary Datasheet OB_DOC_DS_2578T01