BL8892 Current Mode PWM Power Switch Freq Shuffling GENERAL DESCRIPTION FEATURES BL8892 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 15W range. BL8892 offers complete protection coverage with automatic self-recovery feature including Cycle-by-Cycle current limiting (OCP), over load protection (OLP), VDD over voltage clamp and under voltage lockout (UVLO). Excellent EMI performance is achieved with proprietary frequency shuffling technique together with soft switching control at the totem pole gate drive output. The tone energy at below 30KHZ is minimized in the design and audio noise is eliminated during operation. BL8892 is offered in DIP-8 and DIP-7 package. ■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 ■Fixed 60KHZ 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 Self-Recovery VDD Over Voltage Clamp and Under Voltage Lockout with Hysteresis (UVLO) Line Input Compensated Cycle-by-Cycle Over-current Threshold Setting For Constant Output Power Limiting Over Universal Input Voltage Range Overload Protection (OLP) Over voltage Protection (OVP) ■Pb-Free DIP-8L,DIP-7 APPLICATIONS Offline AC/DC flyback converter for ■Battery Charger ■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 BL8892 www.belling.com.cn -0- V1.0 BL8892 GENERAL INFORMATION Pin Configuration The BL8892 is offered in DIP8 package as shown below. VDDG GND VDD GND FB Drain SENSE Drain Absolute Maximum Ratings Drain Voltage (off state) -0.3V to 600V VDD Voltage -0.3V to 30V VDD-G Input Voltage -0.3V to 30V VDD Clamp Continuous Current 10mA FB Input Voltage -0.3V to 7V SENSE Input Voltage -0.3V to 7V Min/Max Operating Junction Temperature TJ Min/Max Storage Temperature Tstg 0℃ to 125℃ -25℃ to 150℃ Lead Temperature (Soldering,10secs) Ambient Operating Temperature 260℃ -25℃ to 85℃ Thermal Resistance from Junction to case θJC Thermal Resistance from Junction to ambient θJA 15℃/W 75℃/W Note: θJA is measured with the PCB copper area of approximately 1 2 in (Multi-layer). That need connect to exposed pad. TERMINAL ASSIGNMENTS Pin Name I/O GND P Ground VDD-G P Internal Gate Driver Power Supply FB I Feedback input pin. The PWM duty cycle is determined by voltage level into this pin and the current-sense signal at Pin 4. SENSE I Current sense input Drain O HV MOSFET Drain Pin. The Drain pin is connected to the primary lead of the transformer VDD P IC DC power supply Input www.belling.com.cn Description -1- V1.0 BL8892 BLOCK DIAGRAM ELECTRICAL CHARACTERISTICS (TA = 25℃, VDD=VDDG=16V, if not otherwise noted) Symbol Parameter Test Conditions Min Typ. Max Unit 6 20 uA Supply Voltage (VDD) I_start up VDD Start up Current I_op Operation Current UVLO(ON) UVLO(OFF) VDD_Clamp VDD=14.5V,Measure Leakage current into VDD VFB=3V VDD Under Voltage Lockout Enter VDD Under Voltage Lockout Exit VDD Zener Clamp Voltage www.belling.com.cn IDD=10mA -2- 1.60 mA 8.7 9.3 10.7 V 14.8 15.3 16.0 V 30 V V1.0 BL8892 OVP(ON) Over Voltage Protection CS=0V,FB=3VRamp up Threshold VDD until gate clock is off 27.0 28.8 30.0 V 5.8 6.0 6.2 V Feedback Input Section (FB Pin) VFB_Open IFB_Short VTH_0D VTH_PL TD_PL ZFB_IN VFB Open Loop Voltage FB pin short circuit Short FB pin to GND and measure current current Zero Duty Cycle FB Threshold Voltage Power Limiting FB Threshold Voltage Power Limiting FB Debounce Time Input Impedance 0.45 mA 1.3 V 3.7 V 50 ms 4 KΩ 4 ms 270 ns 40 KΩ 120 ns Current Sense Input (Sense Pin) Soft start time T_blanking ZSENSE_IN TD_OC VTH_OC Leading edge blanking time Input Impedance Over Current Detection and Control Delay Internal Current Limiting Threshold Voltage From Over Current occurs till the Gate drive output start to turn off FB=3.3V 0.73 0.78 0.83 V 58 63 68 KHz Oscillator Fosc △f_Temp △f_VDD D_ max F_ Burst Normal Oscillation Frequency Frequency Temperature 5 Stability Frequency Voltage 5 Stability Maximum duty cycle(Note) % FB=3.3V,CS=0V 70 Burst Mode Base 80 % 90 30 Frequency % KHz Power MOSFET Section BV-DSS On Resistance MOSFET Drain-Source 600 Breakdown Voltage Rdson V 4.4 5.9 Ω +4 % Frequency △f_OSC Frequency Modulation -4 range/Base frequency Note: Guaranteed by design. www.belling.com.cn -3- V1.0 BL8892 CHARACTERIZATION PLOTS (The characteristic graphs are normalized at Ta=25℃) www.belling.com.cn -4- V1.0 BL8892 OPERATION DESCRIPTION The BL8892 is a low power off-line SMPS Switcher reduction on the power loss and thus conserves the optimized for off-line flyback converter applications in sub energy. The switching frequency is internally adjusted at 15W power range. The ‘Extended burst mode’ control no load or light load condition. greatly reduces the standby power consumption and help The switch frequency reduces at light/no load condition to the design easily to meet the international power improve the conversion efficiency. At light load or no load conservation requirements. condition, the FB input drop below burst mode threshold level and device enters Burst Mode control. The Gate ● Startup Current and Start up Control drive output switches only when VDD voltage drop below Startup current of BL8892 is designed to be very low so a preset level and FB input is active to output an on state. that VDD could be charged up above UVLO threshold Otherwise the gate drive remains at off state to minimize level and device starts up quickly. A large value startup the switching loss and reduces the standby power resistor can therefore be used to minimize the power loss consumption to the greatest extend. The switching yet achieve a reliable startup in application. For AC/DC frequency control also eliminates the audio noise at any adaptor with universal input range design, a 2.2MΩ, 1/8 W loading conditions. startup resistor could be used together with a VDD Oscillator Operation capacitor to provide a fast startup and yet low power ● dissipation design solution. The switching frequency of BL8892 is internally fixed at 60KHZ. No external frequency setting components are ● Operating Current required for PCB design simplification. The Operating current of BL8892 is low at 1.6mA.Good efficiency is achieved with BL8892 low operating current together with the ‘Extended burst mode’ control features. Current Blanking ● Sensing and Leading Edge Cycle-by-Cycle current limiting is offered in BL8892 ● Soft Start current mode PWM control. The switch current is detected BL8892 features an internal 4ms soft start to soften the by a sense resistor into the sense pin. An internal leading electrical stress occurring in the power supply during edge blanking circuit chops off the sensed voltage spike at startup. It is activated during the power on sequence. As initial internal power MOSFET on state due to snubber soon as VDD reaches UVLO(OFF), the peak current is diode reverse recovery and surge gate current of internal gradually increased from nearly zero to the maximum power MOSFET so that the external RC filtering on sense level of 0.78V. Every restart up is followed by a soft start. input is no longer needed. The current limiting comparator is disabled and cannot turn off the internal power Frequency shuffling for EMI improvement MOSFET during the blanking period. The PWM duty cycle The frequency Shuffling (switching frequency modulation) is determined by the current sense input voltage and the is implemented in BL8892. The oscillation frequency is FB input voltage. ● modulated so that the tone energy is spread out. The Internal Synchronized Slope Compensation spread spectrum minimizes the conduction band EMI and ● therefore eases the system design. Built-in slope compensation circuit adds voltage ramp onto the current sense input voltage for PWM generation. This ● Extended Burst Mode Operation greatly improves the close loop stability at CCM and At light load or zero load condition, most of the power prevents the sub-harmonic oscillation and thus reduces dissipation in a switching mode power supply is from the output ripple voltage. switching loss on the MOSFET, the core loss of the transformer and the loss on the snubber circuit. The Drive magnitude of pow er loss is in proportion to the switching ● frequency. Lower switching frequency leads to the The internal power MOSFET in BL8892 is driven by a www.belling.com.cn -5- V1.0 BL8892 Protection Controls dedicated gate driver for power switch control. Too weak ● the gate drive strength results in higher conduction and Good power supply system reliability is achieved with its switch loss of MOSFET while too strong gate drive results rich protection features including Cycle-by-Cycle current the compromise of EMI. limiting (OCP), Over Load Protection (OLP) and over voltage clamp, Under Voltage Lockout on VDD (UVLO). OPERATION DESCRIPTION With Proprietary technology, the OCP is line voltage A good tradeoff is achieved through the built-in totem pole compensated to achieve constant output power limit over gate design with right output strength and dead time the universal input voltage range. At overload condition control. The low idle loss and good EMI system design is when FB input voltage exceeds power limit threshold easier to achieve with this dedicated control scheme. value for more than TD_PL, control circuit reacts to shut In addition to the gate drive control scheme mentioned, down the switcher. Switcher restarts when VDD voltage the gate drive strength can also be adjusted externally by drop below UVLO limit. VDD is supplied by transformer a resistor connected between VDD and VDDG, the falling auxiliary winding output. It is clamped when VDD is higher edge of the Drain output can be well controlled. It provides than 30V. The output of BL8892 is shut down when VDD great flexibility for system EMI design. drop below UVLO_ON limit and Switcher enters power on start-up sequence. www.belling.com.cn -6- V1.0 BL8892 PACKAGE MECHANICAL DATA 8-Pin Plastic DIP Symbol Dimensions In Millimeters Dimensions In Inches Min Max Min Max A 3.710 4.310 0.148 0.0170 A1 0.510 A2 3.200 3.600 0.126 0.142 B 0.380 0.570 0.015 0.022 B1 0.020 1.524(BSC) 0.060(BSC) C 0.204 0.360 0.008 0.014 D 9.000 9.400 0.3540 0.370 E 6.200 6.600 0.2440 0.260 E1 7.320 7.920 0.288 0.312 e 2.540(BSC) 0.100(BSC) L 3.000 3.600 0.118 0.142 E2 8.400 9.000 0.331 0.354 www.belling.com.cn -7- V1.0 BL8892 7-Pin Plastic DIP www.belling.com.cn -8- V1.0