OB2358AP

OB2358 Current Mode PWM Power Switch OB2358 combines a dedicated current mode PWM controller with a high voltage power MOSFET. It is optimized for high performance, low standby power, and cost effective off-line flyback converter applications in sub 27W range. OB2358 offers complete protection coverage with automatic self-recovery feature including Cycle-byCycle current limiting (OCP), over load protection (OLP), VDD over voltage clamp and under voltage lockout (UVLO). Excellent EMI performance is achieved with On-Bright proprietary frequency shuffling technique together with soft switching control at the totem pole gate drive output. The tone energy at below 20KHZ is minimized in the design and audio noise is eliminated during operation. OB2358 is offered in DIP8 package. FEATURES ■ ■ ■ Fixed 50KHZ Switching Frequency Internal Synchronized Slope Compensation ■ Low VDD Startup Current and Low Operating Current ■ Leading Edge Blanking on Current Sense Input ■ Good Protection Coverage With Auto SelfRecovery o VDD Over Voltage Clamp and Under Voltage Lockout with Hysteresis (UVLO) o On-Bright Proprietary Line Input Compensated Cycle-by-Cycle Over-current Threshold Setting For Constant Output Power Limiting Over Universal Input Voltage Range. o Overload Protection (OLP). o Over voltage Protection(OVP) ■ GENERAL DESCRIPTION ■ Freq Shuffling Power on Soft Start Reducing MOSFET Vds Stress Frequency shuffling for EMI Extended Burst Mode Control For Improved Efficiency and Minimum Standby Power Design Audio Noise Free Operation ■ APPLICATIONS Offline AC/DC flyback converter for ■ AC/DC adaptor ■ PDA power supplies ■ Digital Cameras and Camcorder Adaptor ■ VCR, SVR, STB, DVD&DVCD Player SMPS ■ Set-Top Box Power ■ Auxiliary Power Supply for PC and Server ■ Open-frame SMPS TYPICAL APPLICATION 406442781 Output Power Table Product OB2358 Notes: 1. 230VAC±15% Open Frame1 27W 85-265VAC Open Frame1 16W Maximum practical continuous power in an open frame design with sufficient drain pattern as a heat sink, at 50℃ ambient. ©On-Bright Electronics On-Bright Confidential to Microbridge -1- OB_DOC_DS_5800 OB2358 Current Mode PWM Power Switch Freq Shuffling Package Dissipation Rating RθJA (℃/W) Package DIP8 75 Note: Drain Pin Connected to 100mm2 PCB copper clad. GENERAL INFORMATION Pin Configuration The OB2358 is offered in DIP8 package as shown below. Absolute Maximum Ratings Parameter Value Drain Voltage (off state) -0.3V to BVdss VDD Voltage -0.3V to 30 V VDD-G Input Voltage -0.3V to 30 V VDD Clamp Continuous 10mA Current FB Input Voltage -0.3 to 7V Sense Input Voltage -0.3 to 7V Min/Max Operating Junction -20 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 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. Ordering Information Part Number Description OB2358AP DIP8, Pb-free Marking Information ©On-Bright Electronics -2- Confidential OB_DOC_DS_5800 OB2358 Current Mode PWM Power Switch Freq Shuffling TERMINAL ASSIGNMENTS Pin Name GND FB I/O P I VDD-G SENSE VDD Drain P I P O Description Ground Feedback input pin. The PWM duty cycle is determined by voltage level into this pin and the current-sense signal at Pin 4. Internal Gate Driver Power Supply Current sense input IC DC power supply Input HV MOSFET Drain Pin. The Drain pin is connected to the primary lead of the transformer BLOCK DIAGRAM ©On-Bright Electronics -3- Confidential OB_DOC_DS_5800 OB2358 Current Mode PWM Power Switch Freq Shuffling ELECTRICAL CHARACTERISTICS (TA = 25℃, VDD=16V, if not otherwise noted) Symbol Parameter Supply Voltage (VDD) Istartup VDD Start up Current I_VDD_Operation Operation Current UVLO(ON) VDD Under Voltage Lockout Enter UVLO(OFF) VDD Under Voltage Lockout Exit (Recovery) OVP(ON) Over voltage protection voltage VDD_Clamp VDD Zener Clamp Voltage Feedback Input Section(FB Pin) VFB_Open VFB Open Loop Voltage IFB_Short FB pin short circuit current VTH_0D Zero Duty Cycle FB Threshold Voltage VTH_PL Power Limiting FB Threshold Voltage TD_PL Power limiting Debounce Time ZFB_IN Input Impedance Current Sense Input(Sense Pin) Soft start time T_blanking Leading edge blanking time ZSENSE_IN Input Impedance TD_OC Over Current Detection and Control Delay VTH_OC Internal Current Limiting Threshold Voltage Oscillator FOSC △f_Temp Test Conditions Min Typ Max Unit 5 20 uA 8.7 1.6 9.7 10.7 mA V 14.6 15.8 17.0 V 27.0 28.5 30.0 V VDD =14.5V,Measure Leakage current into VDD VFB=3V CS=0V,FB=3V Ramp up VDD until gate clock is off IDD = 10 mA 30 5.4 Short FB pin to GND and measure current From Over Current Occurs till the Gatedrive output start to turn off FB=3.3V Normal Oscillation Frequency Frequency Temperature Stability 5.7 -4- 6.0 V 1.45 mA 0.8 V 3.7 V 50 mSec 4 Kohm 4 270 ms ns 40 120 Kohm nSec 0.72 0.77 0.82 V 45 50 55 KHZ 5 ©On-Bright Electronics V % Confidential OB_DOC_DS_5800 OB2358 Current Mode PWM Power Switch △f_VDD D_max F_Burst Frequency Voltage Stability Maximum duty cycle Burst Mode Base Frequency 5 FB=3.3V, CS =0V 70 80 % 90 22 Mosfet Section BVdss MOSFET DrainSource Breakdown Voltage Rdson Static, Id=1.0A Frequency Shuffling Frequency ∆f_OSC Modulation range /Base frequency V 4.4 ©On-Bright Electronics -5- % KHZ 600 -4 Freq Shuffling 5.5 Ώ 4 % Confidential OB_DOC_DS_5800 OB2358 Current Mode PWM Power Switch Freq Shuffling CHARACTERIZATION PLOTS (The characteristic graphs are normalized at Ta=25℃) UVLO(OFF)(V) UVLO(ON)(V) UVLO(ON)(V) vs Temperature(C) 10.00 9.80 9.60 9.40 9.20 9.00 -40 -10 20 50 80 Temperature(C) 110 15.9 15.8 15.7 15.6 15.5 15.4 15.3 -40 UVLO(OFF)(V)VS Temp(C) -10 1.2 4.0 1.0 3.5 0.8 Ivdd(m A ) Istartup(uA) 110 Ivdd vs Vdd Istartup(uA) vs Temperature(C) 3.0 0.6 2.5 0.4 2.0 0.2 -40 -10 20 50 80 Temperature(C) 0.0 110 0 5 10 15 20 25 30 Vdd(V) Vth_OC(V)vs duty(%) Fosc(KHz) vs Temperature(C) 1.10 52.0 1.00 51.0 Fosc(KHz) Vth_OC(V) 20 50 80 Temperature(C) 0.90 0.80 0.70 50.0 49.0 48.0 0 15 30 45 60 75 Duty(%) -40 -10 20 50 80 Temperature(C) 110 MOSFET Rdson vs Temperature Rdson(ohm) 10 8 6 4 2 0 25 50 75 100 Temperature(℃) 125 150 ©On-Bright Electronics -6- Confidential OB_DOC_DS_5800 OB2358 Current Mode PWM Power Switch Freq Shuffling OPERATION DESCRIPTION The OB2358 is a low power off-line SMPS Switcher optimized for off-line flyback converter applications in sub 27W power range. The ‘Extended burst mode’ control greatly reduces the standby power consumption and helps the design easily to meet the international power conservation requirements. • Startup Current and Start up Control Startup current of OB2358 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. For AC/DC adaptor with universal input range design, a 2 MΩ, 1/8 W startup resistor could be used together with a VDD capacitor to provide a fast startup and yet low power dissipation design solution. • Operating Current The Operating current of OB2358 is low at 2mA. Good efficiency is achieved with OB2358 low operating current together with the ‘Extended burst mode’ control features. • Soft Start OB2358 features an internal 4ms soft start to soften the electrical stress occurring in the power supply during startup. It is activated during the power on sequence. As soon as VDD reaches UVLO(OFF), the peak current is gradually increased from nearly zero to the maximum level of 0.77V. Every restart up is followed by a soft start. • Frequency shuffling for EMI improvement The frequency Shuffling (switching frequency modulation) is implemented in OB2358. 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. • Extended Burst Mode Operation At light load or zero load condition, most of the power dissipation in a switching mode power supply is from switching loss on the MOSFET, the core loss of the transformer and the loss on the snubber circuit. The magnitude of power loss is in proportion to the switching frequency. Lower switching frequency leads to the reduction on the power loss and thus conserves the energy. ©On-Bright Electronics -7- The switching frequency is internally adjusted at no load or light load condition. The switch frequency reduces at light/no load condition to improve the conversion efficiency. At light load or no load condition, the FB input drops below burst mode threshold level and device enters Burst Mode control. The Gate drive output switches only when VDD voltage drops below a preset level and FB input is active to output an on state. Otherwise the gate drive remains at off state to minimize the switching loss and reduces the standby power consumption to the greatest extend. The switching frequency control also eliminates the audio noise at any loading conditions. • Oscillator Operation The switching frequency of OB2358 is internally fixed at 50KHZ. No external frequency setting components are required for PCB design simplification. • Current Sensing and Leading Edge Blanking Cycle-by-Cycle current limiting is offered in OB2358 current mode PWM control. The switch current is detected by a sense resistor into the sense pin. An internal leading edge blanking circuit chops off the sensed voltage spike at initial internal power MOSFET on state due to snubber diode reverse recovery and surge gate current of internal power MOSFET so that the external RC filtering on sense input is no longer needed. The current limiting comparator is disabled and cannot turn off the internal power MOSFET during the blanking period. The PWM duty cycle is determined by the current sense input voltage and the FB input voltage. • Internal Synchronized Slope Compensation Built-in slope compensation circuit adds voltage ramp onto the current sense input voltage for PWM generation. This greatly improves the close loop stability at CCM and prevents the sub-harmonic oscillation and thus reduces the output ripple voltage. • Drive The internal power MOSFET in OB2358 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 results the compromise of EMI. Confidential OB_DOC_DS_5800 OB2358 Current Mode PWM Power Switch A good tradeoff is achieved through the built-in totem pole gate design with right output strength and dead time control. The low idle loss and good EMI system design is easier to achieve with this dedicated control scheme. In addition to the gate drive control scheme mentioned, the gate drive strength can also be adjusted externally by a resistor connected between VDD and VDDG, the falling edge of the Drain output can be well controlled. It provides great flexibility for system EMI design. • Protection Controls Good power supply system reliability is achieved with its rich protection features including Cycle-by- ©On-Bright Electronics -8- Freq Shuffling Cycle current limiting (OCP), Over Load Protection (OLP) and over voltage clamp, Under Voltage Lockout on VDD (UVLO). With On-Bright Proprietary technology, the OCP is line voltage compensated to achieve constant output power limit over the universal input voltage range. At overload condition when FB input voltage exceeds power limit threshold value for more than TD_PL, control circuit reacts to shut down the switcher. Switcher restarts when VDD voltage drops below UVLO limit. VDD is supplied by transformer auxiliary winding output. It is clamped when VDD is higher than 30V. The output of OB2358 is shut down when VDD drops below UVLO_ON limit and Switcher enters power on start-up sequence thereafter. Confidential OB_DOC_DS_5800 OB2358 Current Mode PWM Power Switch Freq Shuffling PACKAGE MECHANICAL DATA 8-Pin Plastic DIP Symbol A A1 A2 B B1 C D E E1 e L E2 Dimensions In Millimeters Min Max 3.710 4.310 0.500 3.200 3.600 0.350 0.650 1.524 (BSC) 0.204 0.360 9.000 9.500 6.200 6.600 7.320 7.920 2.540 (BSC) 3.000 3.600 8.200 9.000 ©On-Bright Electronics Dimensions In Inches Min Max 0.146 0.170 0.020 0.126 0.142 0.014 0.026 0.060 (BSC) 0.008 0.014 0.354 0.374 0.244 0.260 0.288 0.312 0.100 (BSC) 0.118 0.142 0.323 0.354 On-Bright Confidential to Microbridge -9- OB_DOC_DS_5800