OB2550MP

OB2550 High Precision CC/CV Primary-Side Controller FEATURES OB2550 is a high performance offline PSR controller for low power AC/DC charger and adapter applications. It operates in primary-side sensing and regulation. Consequently, opto-coupler and TL431 could be eliminated. Proprietary Constant Voltage (CV) and Constant Current (CC) control is integrated as shown in the figure below. In CC control, the current and output power setting can be adjusted externally by the sense resistor Rs at CS pin. In CV control, multi-mode operations are utilized to achieve high performance and high efficiency. In addition, good load regulation is achieved by the built-in cable drop compensation. Device operates in PFM in CC mode as well at large load condition and it operates in PWM with frequency reduction at light/medium load. The chip consumes very low operation current, it can achieve less than 30mW standby power to meet strict standby power standard. OB2550 offers comprehensive protection coverage with auto-recovery features including Cycle-by-Cycle current limiting, VDD over voltage protection, feedback loop open protection, short circuit protection, built-in leading edge blanking, VDD under voltage lockout (UVLO), OTP etc. OB2550 is offered in SOT23-6 package.  Primary-side Sensing and Regulation Without TL431 and Opto-coupler  High Precision Constant Voltage and Current Regulation at Universal AC Input  Multi-mode PWM/PFM operation for efficiency improving  Meet 30mW no load standby power standard  Good dynamic response  Programmable CV and CC Regulation  Built-in Line Voltage and Primary Winding Inductance Compensation  Programmable Cable Drop Compensation  No Need For Control Loop Compensation  Precise Internal Over Temperature Protection  Audio Noise Free Operation  Drive BJT Switch  Built-in Leading Edge Blanking (LEB)  Ultra Low Start-up Current (Typ. 1uA) and Low Operating Current (Typ. 360uA)  Comprehensive Protection Coverage with auto-recovery  VDD Over Voltage Protection  VDD Under Voltage Lockout with Hysteresis (UVLO)  Cycle-by-Cycle Current Limiting  Feedback Loop Open Protection  Output Short Circuit Protection  Over Temperature Protection (OTP) on fid en tia lt o 鼎 威 GENERAL DESCRIPTION APPLICATIONS ht C Low Power AC/DC offline SMPS for  Cell Phone Charger  Digital Cameras Charger  Small Power Adapter  Auxiliary Power for PC, TV etc.  Linear Regulator/RCC Replacement ig Figure.1. Typical CC/CV Curve O n- Br TYPICAL APPLICATION ©On-Bright Electronics Confidential -1- Preliminary datasheet OB_DOC_DS_255003 OB2550 High Precision CC/CV Primary-Side Controller Absolute Maximum Ratings Parameter Value VDD Voltage -0.3 to 30V FB Input Voltage -0.3 to 7V CS Input Voltage -0.3 to 7V ED Input Voltage -0.3 to 24V BD Input Voltage -0.3 to 24V Min/Max Operating Junction -40 to 150 ℃ Temperature TJ Min/Max Storage Temperature -55 to 150 ℃ Tstg Lead Temperature (Soldering, 260 ℃ 10secs) Note: Stresses beyond those listed under “absolute maximum GENERAL INFORMATION 鼎 威 Pin Configuration The pin map is shown as below for SOT23-6. O n- Br ig ht C on fid Package Dissipation Rating Package RθJA (℃/W) SOT23-6 200 Recommended operating condition Symbol Parameter Range VCC VCC Supply Voltage 9 to 22V Operating Ambient TA -20 to 85 ℃ Temperature en tia Ordering Information Part Number Description OB2550MP SOT23-6, Pb-free, T&R lt o 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. ©On-Bright Electronics Confidential -2- Preliminary datasheet OB_DOC_DS_255003 OB2550 High Precision CC/CV Primary-Side Controller I/O 1 FB I 2 3 4 5 6 GND CS ED BD VDD P I O O P Description The voltage feedback from auxiliary winding. Connected to resistor divider from auxiliary winding reflecting output voltage. Ground Power Mosfet source Enable driver. Base drive with current limit for power BJT. Power Supply on fid Pin Name O n- Br ig ht C Pin Num en tia TERMINAL ASSIGNMENTS lt o 鼎 威 Marking Information ©On-Bright Electronics Confidential -3- Preliminary datasheet OB_DOC_DS_255003 OB2550 High Precision CC/CV Primary-Side Controller O n- Br ig ht C on fid en tia lt o 鼎 威 BLOCK DIAGRAM ©On-Bright Electronics Confidential -4- Preliminary datasheet OB_DOC_DS_255003 OB2550 High Precision CC/CV Primary-Side Controller ELECTRICAL CHARACTERISTICS (TA = 25℃, VDD=15V, if not otherwise noted) Symbol Parameter Test Conditions Min Typ Max Unit Supply Voltage (VDD) Section I start-up Start up current I static Static current UVLO(OFF) VDD under voltage lockout exit 18.4 19.4 UVLO(ON) VDD under voltage lockout enter 6.5 7.1 VDD_OVP VDD over voltage protection 26.5 uA 0.65 1.0 mA 20.4 V 7.8 V 29.5 V 26 V 28.0 lt TLEB LEB time Vth_ocp_min Minimum over current threshold Vth_ocp_max Maximum over current threshold Minimum CS threshold Ton_max Maximum Ton Td_oc OCP propagation delay 485 on fid Vcs_mini en tia Current Sense Input Section FB Input Section 威 15 o Max. Operating Voltage 5 鼎 VDD=UVLO_OFF-1V 0.5 500 us 515 mV 555 mV 100 mV 50 us 100 ns Reference voltage for feedback threshold Tpause_min Minimum Toff F_min Minimum frequency 720 800 880 Hz Icomp_cable Maximum cable compensation current 44 48 52 uA 20 30 40 mA ig ht C Vref_fb 2.475 2.50 2.525 2.0 V us BASE Drive Section Base sourcing maximum current Br Is_max Base sourcing pre-off current after 1.5 n- Is_preoff mA Base drive low side on resistor 1.0 2 ohm IED_leak Before startup, ED pin leakage VED=VDD-1V current 0 1 uA 2.85 3.0 3.15 V 150 165 180 ℃ 115 130 145 ℃ O Rdson_l Output Over Voltage Protection V_OVP Output Over voltage threshold On chip Over temperature Section T_otp Over temperature trigger point protection T_otp_rec Over temperature recovery point protection ©On-Bright Electronics Confidential -5- Preliminary datasheet OB_DOC_DS_255003 OB2550 High Precision CC/CV Primary-Side Controller CHARACTERIZATION PLOTS IVdd vs VDD Ivdd_startup vs Temperature 5.5 400 200 0 0 5 10 15 20 5.3 5.1 4.9 威 600 4.7 4.5 -40 25 -10 o UVLO(OFF)(V) 2.46 2.44 -40 -10 20 50 80 lt 19.8 19.6 19.4 19.2 19 -40 110 140 -10 Temperature(℃) 7.08 Br ig 7.06 Icomp_cable(uA) ht C 7.1 7 -10 20 50 80 80 110 140 Icable vs Temperature 50 48 46 44 42 -40 110 140 50 -10 20 50 80 110 140 Temperature(℃) Temperature(℃) O n- -40 20 Temperature(℃) UVLO(ON) vs Temperature UVLO(ON)(V) 110 140 en tia 2.48 on fid Vref_fb(V) 2.5 7.02 80 UVLO(OFF) vs Temperature Vref vs Temperature 20 7.04 50 Temperature(℃) VDD(V) 2.52 20 鼎 Ivdd_startup(uA) IVdd(uA) 800 ©On-Bright Electronics Confidential -6- Preliminary datasheet OB_DOC_DS_255003 OB2550 High Precision CC/CV Primary-Side Controller OPERATION DESCRIPTION OB2550 is a cost effective PSR controller optimized for off-line low power AC/DC applications including battery chargers. It operates in primary side sensing and regulation, thus opto-coupler and TL431 are not required. Proprietary built-in CV and CC control can achieve high precision CC/CV control meeting most charger application requirements. 威 鼎 o (1) The auxiliary voltage reflects the output voltage as shown in Figure.2 and it is given by V AUX  N AUX  (VO  V ) NS (2) Where V indicates the drop voltage of the output Diode. on fid + ht C + VAUX PWM Off ig TON PWM On Br Figure.2. Auxiliary voltage waveform Via a resistor divider connected between the auxiliary winding and FB (pin 1), the auxiliary voltage is sampled at the middle of the de-magnetization and it is hold until the next sampling. The sampled voltage is compared with Vref (2.5V) and the error 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. When the sampled voltage is below Vref and the error amplifier output reaches its minimum, the switching frequency is controlled by the sampled voltage to regulate the output current, thus the constant output current can be achieved. O n-  CC/CV Operation OB2550 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, OB2550 will regulate the output current constant regardless of the output voltage drop. Principle of Operation ©On-Bright Electronics Sampling Instance TDemag  Operating Current The Operating current of OB2550 is as low as 650uA. Good efficiency and 30mW standby power is achieved with the low operating current.  NP  IP NS lt IS  en tia  Fast Start up Control Startup current of OB2550 is designed to be very low so that VDD could be charged up above UVLO threshold and starts up quickly. The startup resister Rstart from the rectified high voltage DC rail supplies current to the base of the NPN transistor Q1. An amplified emitter current charge VDD capacitor through diode D1 from ED pin to VDD pin. Thus, a large value startup resistor can therefore be used to minimize the power loss in application. To support OB2550 proprietary CC/CV control, system needs to be designed in DCM mode for flyback system (Refer to Typical Application Diagram on page1). In the DCM flyback converter, the output voltage can be sensed via the auxiliary winding. During BJT turn-on time, the load current is supplied from the output filter capacitor, Co. The current in the primary winding ramps up. When BJT turns off, the energy stored in the primary winding is transferred to the secondary side such that the current in the secondary winding is Confidential -7- Preliminary datasheet OB_DOC_DS_255003 OB2550 High Precision CC/CV Primary-Side Controller conditions and the operation modes. For flyback operating in DCM, The maximum output power is given by  Adjustable CC point and Output Power In OB2550, the CC point and maximum output power can be externally adjusted by external current sense resistor Rs at CS pin as illustrated in typical application diagram. The larger Rs, the smaller CC point is, and the smaller output power becomes, and vice versa as shown in Figure.3. Po MAX  1 LP FSW I p2 2 (3) Where Lp indicate the inductance of primary winding and Ip is the peak current of primary winding. Refer to the equation 3, the change of the primary winding inductance results in the change of the maximum output power and the constant output current in CC mode. To compensate the change from variations of primary winding inductance, the switching frequency is locked by an internal loop such that the switching frequency is Vo 威 Large Rs FSW  Since TDemag is inversely proportional to the inductance, as a result, the product Lp and fsw is constant, thus the maximum output power and constant current in CC mode will not change as primary winding inductance changes. Up to ±7% variation of the primary winding inductance can be compensated. on fid  On time OCP compensation The variation of max output current in CC mode can be rather large if no compensation is provided. The OCP threshold value is self adjusted higher at higher AC voltage. This OCP threshold slope adjustment helps to compensate the increased output current limit at higher AC voltage. In OB2550, a proprietary OCP compensation block is integrated and no external components are needed. The OCP threshold in OB2550 is a function of the switching ON time. For the ON time less than 3.7us, the OCP threshold changes linearly from 500mV to 555mV. For the ON time larger than 3.7us, the OCP threshold is clamped to 555mV, as shown in Figure 4. (4) en tia Figure.3. Adjustable output power by changing Rs 2TDemag lt Io 1 o 鼎 Small Rs O n- Br ig ht C  Programmable Cable drop Compensation In OB2550, cable drop compensation is implemented to achieve good load regulation. An offset voltage is generated at FB pin by an internal current flowing into the resister divider. The current is proportional to the switching off time, as a result, it is inversely proportional to the output load current, thus the drop due to the cable loss can be compensated. As the load current decreases from full-load to no-load, the offset voltage at FB will increase. It can also be programmed by adjusting the resistance of the divider to compensate the drop for various cable lines used. The percentage of maximum compensation is Icomp _ cable  R110 6 V  100% 2.5 Vout V is load compensation voltage and Vout is output voltage; For example: R1=6.2Kohm, the percentage of maximum compensation is V 47  6200  10 6   100%  11.6% 2.5 Vout Figure.4. On time OCP compensation  Operation switching frequency The switching frequency of OB2550 is adaptively controlled according to the load ©On-Bright Electronics Confidential -8- Preliminary datasheet OB_DOC_DS_255003 OB2550 High Precision CC/CV Primary-Side Controller 35mA). 威  Protection Control Good power supply system reliability is achieved with its rich protection features including Cycle-by-Cycle current limiting (OCP), Output over voltage protection, VDD over voltage protection, short circuit protection, Under Voltage Lockout on VDD (UVLO) and over temperature protection (OTP). VDD is supplied by transformer auxiliary winding output. The output of OB2550 is shut down when VDD drops below UVLO (ON) and the power converter enters power on start-up sequence thereafter. To prevent the circuit being damaged under abnormal conditions, OB2550 provides over thermal protection function. When the die temperature rises above over temperature threshold T_otp, the OB2550 will shut down the gate output and then latch the power supply off. The controller will remains latched until the die temperature drops below the recovery threshold T_otp_rec and the OB2550 will reset at the same time. Current Sensing and Leading Edge Blanking Cycle-by-Cycle current limiting is offered in OB2550. 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 BJT on state so that the external RC filtering on sense input is no longer needed. o lt en tia O n- Br ig ht C on fid  Base Drive The drive is a push pull stage with supply voltage VDD. It provides the driving current for the external power bipolar transistor. The output signal is current limit to Is_max (typical 鼎  ©On-Bright Electronics Confidential -9- Preliminary datasheet OB_DOC_DS_255003 OB2550 High Precision CC/CV Primary-Side Controller ht C on fid en tia lt o 鼎 威 PACKAGE MECHANICAL DATA Dimensions In Millimeters A Max Min Max 1.000 1.450 0.039 0.057 0.000 0.150 0.000 0.006 0.900 1.300 0.035 0.051 b 0.300 0.500 0.012 0.020 c 0.080 0.220 0.003 0.009 D 2.800 3.020 0.110 0.119 E 1.500 1.726 0.059 0.068 E1 2.600 3.000 0.102 0.118 O A2 n- Br A1 Dimensions In Inches Min ig Symbol e 0.950 (BSC) 0.037 (BSC) e1 1.800 2.000 0.071 0.079 L 0.300 0.600 0.012 0.024 θ 0º 8º 0º 8º ©On-Bright Electronics Confidential - 10 - Preliminary datasheet OB_DOC_DS_255003 OB2550 High Precision CC/CV Primary-Side Controller 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. lt o 鼎 威 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 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 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_255003