OB2535CPA

OB2535 High Precision CC/CV Primary-Side PWM Power Switch GENERAL DESCRIPTION FEATURES OB2535 is a high performance offline PWM Power switch 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. OB2535 offers power on soft start control and protection coverage with auto-recovery features including Cycle-by-Cycle current limiting, VDD OVP, VDD clamp and UVLO. Excellent EMI performance is achieved with On-Bright proprietary frequency shuffling technique. High precision constant voltage (CV) and constant current (CC) can be achieved by OB2535.  ±5% Constant Voltage Regulation at Universal AC input  High Precision Constant Current Regulation at Universal AC input  Primary-side Sensing and Regulation Without TL431 and Opto-coupler  Programmable CV and CC Regulation  Adjustable Constant Current and Output Power Setting  Built-in Secondary Constant Current Control with Primary Side Feedback  Built-in Adaptive Current Peak Regulation  Built-in Primary winding inductance compensation  Programmable Cable drop Compensation  Power on Soft-start  Built-in Leading Edge Blanking (LEB)  Cycle-by-Cycle Current Limiting  VDD Under Voltage Lockout with Hysteresis (UVLO)  VDD OVP  VDD Clamp APPLICATIONS . 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 OB2535 is offered in SOP8 package. Fig.1. Typical CC/CV Curve TYPICAL APPLICATION ©On-Bright Electronics Confidential -1- Datasheet OB_DOC_DS_2535A2 OB2535 High Precision CC/CV Primary-Side PWM Power Switch Package Dissipation Rating Package RθJA (℃/W) SOP8 90 Note: Drain Pin Connected 100mm2 PCB copper clad. GENERAL INFORMATION Pin Configuration The pin map is shown as below for SOP8. VDD 1 8 GND COMP 2 7 GND INV 3 6 DRAIN CS 4 5 DRAIN Absolute Maximum Ratings Parameter Drain Voltage (off state) VDD Voltage VDD Zener Clamp Continuous Current COMP Voltage CS Input Voltage INV Input Voltage Max Operating Junction Temperature TJ Min/Max Storage Temperature Tstg Lead Temperature (Soldering, 10secs) Ordering Information Part Number Description OB2535CP SOP8, Pb-free, Tube OB2535CPA SOP8, Pb-free, T&R ©On-Bright Electronics Value -0.3V to Bvdss -0.3 to VDD_clamp 10 mA -0.3 to 7V -0.3 to 7V -0.3 to 7V -40 to 150 oC -55 to 150 oC 260 oC 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. Confidential -2- Datasheet OB_DOC_DS_2535A2 OB2535 High Precision CC/CV Primary-Side PWM Power Switch Marking Information TERMINAL ASSIGNMENTS Pin Num 1 2 Pin Name VDD COMP I/O P I 3 INV I 4 CS I 5/6 DRAIN O 7/8 GND P Description Power Supply Loop Compensation for CV Stability The voltage feedback from auxiliary winding. Connected to resistor divider from auxiliary winding reflecting output voltage. PWM duty cycle is determined by EA output and current sense signal at pin 4. Current sense input HV MOSFET Drain Pin. The Drain pin is connected to the primary lead of the transformer Ground OUTPUT POWER TABLE Product OB2535 230VAC±15% Adapter1 6W 85-264VAC Adapter1 5W Notes: 1. Maximum practical continuous power in an Adapter design with sufficient drain pattern as a heat sink, at 50℃ ambient. Higher output power is possible with extra added heat sink or air circulation to reduce thermal resistance. ©On-Bright Electronics Confidential -3- Datasheet OB_DOC_DS_2535A2 OB2535 High Precision CC/CV Primary-Side PWM Power Switch BLOCK DIAGRAM ©On-Bright Electronics Confidential -4- Datasheet OB_DOC_DS_2535A2 OB2535 High Precision CC/CV Primary-Side PWM Power Switch ELECTRICAL CHARACTERISTICS (TA = 25OC, VDD=VDDG=16V, if not otherwise noted) Symbol Parameter Test Conditions Min Typ Max Unit 5 20 uA - 2 3 mA Supply Voltage (VDD) Section I DD ST Standby Current VDD=13V I DD op Operation Current Operation supply current INV=2V, CS=0V, VDD=VDDG=18V UVLO(ON) VDD Under Voltage Lockout VDD falling Enter 8.2 9.0 10.5 V UVLO(OFF) VDD Under Voltage Lockout VDD rising Exit 13.5 14.8 16.0 V VDD_clamp Maximum voltage IDD=10mA 27 28.5 30 V OVP Over voltage Threshold protection Ramp VDD until gate shut down 26 27.5 29 V VDD operation Current Sense Input Section TLEB LEB time 625 Vth_oc Over current threshold Td_oc OCP Propagation delay ZSENSE_IN Input Impedance T_ss Soft start time 880 910 ns 940 110 mV ns 50 Kohm 17 ms Frequency Section Freq_MaxNote 1 IC Maximum frequency Freq_Nom System Nominal frequency 55 switch Freq_startup △f/Freq INV=0V, Comp=5V Frequency shuffling range 60 65 KHz 50 KHz 14 KHz +/-6 % Error Amplifier section Vref_EA Reference voltage for EA Gain DC gain of EA I_COMP_MAX Max. Cable compensation current 1.97 INV=2V, Comp=0V 2 2.03 V 60 dB 37.5 uA Power MOSFET Section BVdss MOSFET Drain-Source Breakdown Voltage Rdson On Resistance 600 Static, Id=0.4A V 12 15 Ώ Note: 1. Freq_Max indicates IC internal maximum clock frequency. In system application, the maximum operation frequency of 50Khz nominal occurs at maximum output power or the transition point from CV to CC. ©On-Bright Electronics Confidential -5- Datasheet OB_DOC_DS_2535A2 OB2535 High Precision CC/CV Primary-Side PWM Power Switch CHARACTERIZATION PLOTS UVLO(OFF)(V) vs Temperature(℃) UVLO(OFF)(V) UVLO(ON)(V) UVLO(ON)(V) vs Temperature(℃) 10.5 10.0 9.5 9.0 8.5 8.0 7.5 -10 20 50 80 Temperature( ℃) 110 -40 -10 50 80 20 Temperature(℃) 110 Istartup(uA) vs Temperature(℃) Freq_Max(KHz) vs Temperature(℃) 70.0 Istartup(uA) Freq_Max(KHz) -40 16.00 15.50 15.00 14.50 14.00 13.50 13.00 65.0 60.0 55.0 50.0 3.0 2.5 2.0 1.5 1.0 -40 -10 20 50 80 Temperature(℃) -40 110 -10 80 20 50 Temperature(℃) 110 Rdson(ohm) vs Temperature(℃) Rdson(ohm) 40.0 30.0 20.0 z 10.0 0.0 25 50 75 100 125 Temperature(℃) ©On-Bright Electronics 150 Confidential -6- Datasheet OB_DOC_DS_2535A2 OB2535 High Precision CC/CV Primary-Side PWM Power Switch OPERATION DESCRIPTION OB2535 is a cost effective PWM power switch optimized for off-line low power AC/DC applications including battery chargers and adapters. 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 adapter and charger application requirements. from the output filter capacitor Co. The current in the primary winding ramps up. When MOSFET turns off, the primary current transfers to the secondary at the amplitude of IS  （1） The auxiliary voltage reflects the output voltage as shown in fig.2 and it is given by V AUX   Startup Current and Start up Control Startup current of OB2535 is designed to be very low so that VDD could be charged up above UVLO threshold and starts up quickly. A large value startup resistor can therefore be used to minimize the power loss in application. N AUX  (VO  V ) NS (2) Where V indicates the drop voltage of the output Diode. Sampling Instance  Operating Current The Operating current of OB2535 is as low as 2.5mA. Good efficiency is achieved with the low operating current together with ‘Muti-mode’ control features. VAUX PWM Off  Soft Start OB2535 features an internal soft start to minimize the component electrical over-stress during power on startup. As soon as VDD reaches UVLO (OFF), the control algorithm will ramp peak current voltage threshold gradually from nearly zero to normal setting of 0.90V. Every restart is a soft start.  CC/CV Operation OB2535 is designed to produce good CC/CV control characteristic as shown in the Fig. 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. In an AC/DC adapter, the normal operation occurs only on the 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, OB2535 will regulate the output current constant regardless of the output voltage drop. TDemag TON PWM On Fig.2. Auxiliary voltage waveform Via a resistor divider connected between the auxiliary winding and INV (pin 3), the auxiliary voltage is sampled at the end of the demagnetization and it is hold until the next sampling. The sampled voltage is compared with Vref (2.0V) and the error is amplified. The error amplifier output COMP reflects the load condition and controls the PWM switching frequency to regulate the output voltage, thus constant output voltage can be achieved. When sampled voltage is below Vref and the error amplifier output COMP reaches its maximum, the switching frequency is controlled by the sampled voltage thus the output voltage to regulate the output current, thus the constant output current can be achieved.  Principle of Operation To support OB2535 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 MOSFET turn-on time, the load current is supplied ©On-Bright Electronics NP  IP NS  Adjustable CC point and Output Power In OB2535, the CC point and maximumoutput power can be externally adjusted by external current sense resistor Rs at CS pin as illustrated in Typical Application Diagram. The output power is adjusted through CC point change. The larger Confidential -7- Datasheet OB_DOC_DS_2535A2 OB2535 High Precision CC/CV Primary-Side PWM Power Switch Rs, the smaller CC point is, and the smaller output power becomes, and vice versa as shown in Fig.3.  Gate Drive The internal power MOSFET in OB2535 is driven by a dedicated gate driver for power switch control. Too weak the gate drive strength results in higher conduction and switch loss of MOSFET while too strong gate drive compromises EMI. A good tradeoff is achieved through the built-in totem pole gate design with right output strength control. Fig.3 Adjustable output power by changing Rs  Operation switching frequency The switching frequency of OB2535 is adaptively controlled according to the load conditions and the operation modes. No external frequency setting components are required. The operation switching frequency at maximum output power is set to 60K Hz internally. For flyback operating in DCM, The maximum output power is given by Po MAX  1 LP FSW I p2 2  Programmable Cable drop Compensation In OB2535, cable drop compensation is implemented to achieve good load regulation. An offset voltage is generated at INV by an internal current flowing into the resister divider. The current is inversely proportional to the voltage across pin COMP, 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 noload, the offset voltage at INV will increase. It can also be programmed by adjusting the resistance of the divider to compensate the drop for various cable lines used. (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 FSW  1 2TDemag Current Sensing and Leading Edge Blanking Cycle-by-Cycle current limiting is offered in OB2535 current mode PWM control. 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 internal power MOSFET on state so that the external RC filtering on sense input is no longer needed. The PWM duty cycle is determined by the current sense input voltage and the EA output voltage.   Protection Control Good power supply system reliability is achieved with its rich protection features including Cycle-byCycle current limiting (OCP), VDD clamp, Power on Soft Start, and Under Voltage Lockout on VDD (UVLO). VDD is supplied by transformer auxiliary winding output. The output of OB2535 is shut down when VDD drops below UVLO (ON) limit and Switcher enters power on start-up sequence thereafter. (4) 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 ± 10% variation of the primary winding inductance can be compensated.  Frequency shuffling for EMI improvement The frequency shuffling (switching frequency modulation) is implemented in OB2535. The oscillation frequency is modulated so that the tone energy is spread out. The spread spectrum minimizes the conduction band EMI and therefore eases the system design. ©On-Bright Electronics Confidential -8- Datasheet OB_DOC_DS_2535A2 OB2535 High Precision CC/CV Primary-Side PWM Power Switch PACKAGE MECHANICAL DATA Symbol A A1 A2 b c D E E1 e L θ ©On-Bright Electronics Dimensions In Millimeters Min Max 1.350 0.050 1.250 0.310 0.100 4.700 3.800 5.800 1.750 0.250 1.650 0.510 0.250 5.150 4.000 6.200 1.270 (BSC) 0.400 1.270 0º 8º Confidential -9- Dimensions In Inches Min Max 0.053 0.002 0.049 0.012 0.004 0.185 0.150 0.228 0.069 0.010 0.065 0.020 0.010 0.203 0.157 0.244 0.050 (BSC) 0.016 0.050 0º 8º Datasheet OB_DOC_DS_2535A2 OB2535 High Precision CC/CV Primary-Side PWM 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. 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. 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. 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 - 10 - Datasheet OB_DOC_DS_2535A2