1、OB2283 High Performance Current Mode PWM Controller GENERAL DESCRIPTION OB2283 is a highly integrated current mode PWM control IC optimized for high performance,low standby power and cost effective offline flyback converter applications.PWM switching frequency at normal operation is internally fixed
2、 and is trimmed to tight range.At no load or light load condition,the IC operates in extended burst mode to minimize switching loss.Lower standby power and higher conversion efficiency is thus achieved.VCC low startup current and low operating current contribute to a reliable power on startup and lo
3、w standby design with OB2283.OB2283 offers comprehensive protection coverage with auto-recovery including Cycle-by-Cycle current limiting(OCP),over load protection(OLP),and VCC under voltage lockout(UVLO).It also provides the protections with latched shut down including over temperature protection(O
4、TP),and over voltage protection(OVP).Excellent EMI performance is achieved with On-Bright proprietary frequency shuffling technique.The tone energy at below 25KHz is minimized in the design and audio noise is eliminated during operation.OB2283 is offered in SOT23-6 package.APPLICATIONS Offline AC/DC
5、 flyback converter for Printer,Storage power supplyPower AdapterFEATURES Power on soft start reducing MOSFET VdsstressFrequency shuffling for EMIExtended burst mode control for improvedefficiency and low standby power designAudio noise free operationPeak load operation with increased frequencyCompre
6、hensive protection coverageoVCC Under Voltage Lockout withhysteresis(UVLO)oVCC Over Voltage Protection(VCC OVP)oCycle-by-cycle over current thresholdsetting for constant output power limitingover universal input voltage rangeoOver Load Protection(OLP)with auto-recoveryoExternal(if NTC resistor is co
7、nnected atPRT pin)or internal Over TemperatureProtection(OTP)with latched shut downoOutput Over Voltage Protection(OutputOVP)with latched shut down,and theOVP triggered voltage can be adjusted bythe resistor connected between auxiliarywinding and PRT pinoOutput diode short protection with auto-recov
8、eryoGND open protection with auto-recoveryTYPICAL APPLICATION EMIFilterAC INDC OutOB2283VCCGNDGATEFB1236CS45 PRTVauxOB2283 High Performance Current Mode PWM Controller GENERAL INFORMATION Pin Configuration PRTVCCFBCSGate123456GNDOrdering Information Part Number Description OB2283MP SOT23-6,Pb-free i
9、n T&R Package Dissipation Rating Package R JA(/W)SOT23-6200Recommended operating condition Symbol Parameter Range VCC VCC Supply Voltage 12 to 28V TA Operating Ambient Temperature-20 to 85 Absolute Maximum Ratings Parameter Value VCC DC Supply Voltage VOVP-1V FB Input Voltage-0.3 to 7VCS Input Volta
10、ge-0.3 to 7VPRT Input Voltage -0.3 to 7VMin/Max Operating Junction Temperature TJ-40 to 150 Min/Max Storage Temperature Tstg-55 to 150 LeadTemperature(Soldering,10secs)260 Note:Stresses beyond those listed under“absolutemaximum ratings”may cause permanent damage to the device.These are stress rating
11、s 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.OB2283 X X High Performance Current Mode PWM Contro
12、ller PackageM:SOT23-6Package Pb-freeP:Pb-freeMarking Information 83YWW.ZZZSY:Year CodeWW:Week Code(01-52)s:Internal codeZZZ:Lot code OB2283 High Performance Current Mode PWM Controller TERMINAL ASSIGNMENTS Pin Name I/O Description VCCP Power SupplyCS I Current sense input Gate O Totem-pole gate driv
13、er output for power MOSFET GNDP GroundPRTI Dual functions pin.Connecting a NTC resistor to ground for OTP detection.Connecting a resistor from Vaux can adjust OVP trigger voltage.If both OTP and OVP are needed,a diode should be connected between PRT pin and the NTC resistor.FBI Feedback input pin.Th
14、e PWM duty cycle is determined by voltage level into this pin and the current-sense signal at Pin CS.OB2283 High Performance Current Mode PWM Controller FUNCTIONAL BLOCK DIAGRAM OLPPWM ComparatorOSCRSQSlope compensationAVDDVocpLEBSoft Driver LogicControlTimerPK/Green/BurstUVLOVref&IrefAVDDInternal b
15、locksOLPOCP ComparatorLatchOVPOVPOVPTemp senseEX OTPEX OVPOTPGND openDiode shortDiode shortDiode shortOB2283 High Performance Current Mode PWM Controller ELECTRICAL CHARACTERISTICS(TA=25,VCC=18V,unless otherwise noted)Symbol Parameter Test Conditions Min Typ MaxUnit Supply Voltage(VDD)Istartup VCC S
16、tart up Current VCC=UVLO(OFF)-1V,measure leakage current into VCC 3 10 uA I_VCC_Operation Operation Current VDD=18V,CS=4V,FB=3.5V,measure I(VCC)2.5 3 mA I_VCC_Burst Burst Current CS=0V,FB=0.5V,measure I(VCC)0.55 0.65mA UVLO(ON)VCC Under Voltage Lockout Enter 7 8 9VUVLO(OFF)VCC Under Voltage Lockout
17、Exit(Recovery)19 21 23VVpull-up Pull-up PMOS active 10 V OVP VCC Over Voltage Protection threshold voltage FB=3V,CS=0V.Slowly ramp VCC,until no gate switching.29 30 31 V Vlatch_release Latch release voltage 5 V Feedback Input Section(FB Pin)VFB_OpenVFB Open Loop Voltage 5.1 V Avcs PWM input gain VFB
18、/VCS3.5 V/V Maximum duty cycle Max duty cycle VCC=18V,VFB=3V,VCS=0V 75 78 81%Vref_green The threshold enter green mode1.85 V Vref_burst_H The threshold exits burst mode1.33 V Vref_burst_L The threshold entersburst mode 1.23 VIFB_Short FB pin short circuit current Short FB pin to GND and measure curr
19、ent 0.3 mA VTH_OLP Open loop protection,FB Threshold Voltage 4.4 VTd_OLP Open loop protection,Debounce Time 15 msZFB_INInput Impedance 16 KohmCurrent Sense Input(CS Pin)SST_CS Soft start time for CS peak 4 ms T_blanking Leading edge blanking time 250 ns Td_OC Over Current Detection and Control Delay
20、 From Over Current Occurs till the Gatedriver output start to turn off 90 ns VTH_OC Internal Current Limiting Threshold Voltage with zero duty cycle 0.43 0.45 0.47VVTH_OC_Clamp OCP CS voltage clamper 0.69 V Vdiode_scp Diode short protection voltage 1.4 V Td_dio Diode short debounce time 8 CyclesOB22
21、83 High Performance Current Mode PWM Controller Vgnd_open GND open protection voltage difference between GND and CS 0.3 VTd_gnd_open GND open protectiondebounce time 20 usTd_OCP Over Current protection debounce Time 60 msPRT pin IRT Output current for external OTP detection 95 100 105uAVOTP Threshol
22、d voltage for externalOTP 0.95 1 1.05VTd_OTP External OTP debounce time 5 CyclesIoutput_ovp Current threshold for adjustable output OVP 70 uATd_output_ovp Output OVP debounce time 5 CyclesIn-chip OTP OTP enter 150 OTP exit 120 Oscillator FOSC Normal Oscillation Frequency VDD=18V,FB=3V,CS=0V 60 65 70
23、 KHz Fosc_PKPeak frequencyVDD=18V,FB=4.5V,CS=0V 142 KHz SST_freq Soft start time of frequency 30 ms f_OSCFrequency jittering+/-6%F_shufflingShuffling frequency 32 Hzf_TempFrequencyTemperatureStability 1%f_VCCFrequency Voltage Stability 1%F_Burst Burst Mode Switch Frequency 25 KHz Gate driver VOL Out
24、put low level VDD=18V,Io=5mA 1VVOH Output high level VCC=18V,Io=20mA 6 VV_clamping Output clamp voltage 12 V T_r Output rising time 1.2V 10.8V CL=1000pF 160 nsT_f Output falling time 10.8V 1.2V CL=1000pF 50 nsOB2283 High Performance Current Mode PWM Controller CHARACTERIZATION PLOTS VDD=18V,TA=25 co
25、ndition applies if not otherwise noted.UVLO_ON vs Temperature77.27.47.67.88-40-10205080110140Temperature()UVLO _O N(V)UVLO_OFF vs Temperature2020.220.420.620.821-40-10205080110140Temperature()UVLO _O FF(V)Fosc vs Temperature606264666870-40-10205080110140Temperature()Fosc(KHz)Ton_comp vs Temperature7
26、7.27.47.67.88-40-10205080110140Temperature()Ton_comp(us)VOTP vs Temperature0.950.970.991.011.031.05-40-10205080110140Temperature()VOTP(V)VTH_OC vs Temperature0.30.360.420.480.540.6-40-10205080110140Temperature()VTH_OC(V)OVP vs Temperature2828.428.829.229.630-40-10205080110140Temperature()OVP(V)IRT v
27、s Temperature8090100110120-40-10205080110140Temperature()IRT(V)OB2283 High Performance Current Mode PWM Controller OPERATION DESCRIPTION OB2283 is a highly integrated current mode PWM control IC optimized for high performance,low standby power and cost effective offline flyback converter application
28、s.The extended burst mode control greatly reduces the standby power consumption and helps the design easier to meet the international power conservation requirements.Startup Current and Start up ControlStartup current of OB2283 is designed to be verylow so that VCC could be charged up aboveUVLO thre
29、shold level and device starts up quickly.A large value startup resistor can therefore beused to minimize the power loss yet achieve areliable startup in application.Operating CurrentThe Operating current of OB2283 is low at 2.5mA(typical).Good efficiency is achieved with OB2283low operation current
30、together with the extendedburst mode control features.Soft StartOB2283 features an internal 4ms(typical)softstart to soften the electrical stress occurring in thepower supply during startup.It is activated duringthe power on sequence.As soon as VCC reachesUVLO(OFF),the CS peak voltage is graduallyin
31、creased from 0.05V to the maximum level.Every restart up is followed by a soft start.Frequency shuffling for EMI improvementThe frequency shuffling(switching frequencymodulation)is implemented in OB2283.Theoscillation frequency is modulated so that the toneenergy is spread out.The spread spectrummin
32、imizes the conduction band EMI and thereforeeases the system design.Extended Burst Mode OperationAt light load or no load condition,most of thepower dissipation in a switching mode powersupply is from switching loss of the MOSFET,thecore loss of the transformer and the loss of thesnubber circuit.The
33、 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.The switching frequency is internally adjusted at no load or light load condition.The switch frequency reduces at light/no load condit
34、ion to improve the conversion efficiency.At light load or no load condition,the FB input drops below Vref_burst_L(the threshold enter burst mode)and device enters Burst Mode control.The Gate drive output switches when FB input rises back to Vref_burst_H(the threshold exit burst mode).Otherwise the g
35、ate drive remains at off state to minimize the switching loss and reduces the standby power consumption to the greatest extend.Oscillator OperationDuring the full load power operation,OB2283operates at a 65KHz(typical)fixed frequency.Theefficiency and system cost is controlled at anoptimal level.A p
36、eak power mode is implementedto supply a peak current output requirement.Inpeak power mode,frequency is increased from65KHz(typical)to 142KHz(typical).At light load levels,OB2283 enters the light loadmode,where the output current is reduced.Theswitching losses are reduced by lowering theswitching fr
37、equency.Current Sensing and Leading EdgeBlankingCycle-by-Cycle current limiting is offered in OB2283 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 MOSF
38、ET on state due to snubber diode reverse recovery and surge gate current of power MOSFET.The current limiting comparator is disabled and cannot turn off the internal power MOSFET during the blanking period.The PWM OB2283 High Performance Current Mode PWM Controller duty cycle is determined by the cu
39、rrent sense input voltage and the FB input voltage.Internal Synchronized Slope CompensationBuilt-in slope compensation circuit adds voltageramp into the current sense input voltage for PWMgeneration.This greatly improves the close loopstability at CCM and prevents the sub-harmonicoscillation and thu
40、s reduces the output ripplevoltage.DriverThe power MOSFET is driven by a dedicated gatedriver for power switch control.Too weak the gatedriver strength results in higher conduction andswitch loss of MOSFET while too strong gatedriver strength results the compromise of EMI.A good tradeoff is achieved
41、 through the built-intotem pole gate design with right output strengthand dead time control.The low idle loss and goodEMI system design is easier to achieve with thisdedicated control scheme.Dual Function of External OTP and OutputOVPOn-Bright proprietary dual function of external OTP and output OVP
42、 provides feasible and accurate detection of external OTP through NTC resistor and output OVP.The dual function is realized through time-division technology as shown in the figure.For external OTP detecttion,when switch control signal S1=“1”,about 20uA(typical)current flows out from PRT pin.When swi
43、tch control signal S0=“1”,about 120uA(typical)current flows out from PRT pin.The PRT pin voltage difference Votp at phase S0 and S1 phase is equal to RT*Iotp.When Votp1V,external OTP latch protection is triggered after 5 Gate cycles debounce.For output OVP detection,when Sovp=“1”,Iovp is equal to Vo
44、/ROVP.If Iovp is larger than 70uA(typical),OVP latch protection is triggered after 5 Gate cycles debounce.By selecting proper Rovp resistance,output OVP level can be programmed.Protection ControlsGood power supply system reliability is achievedwith auto-recovery protection features includingCycle-by
45、-Cycle current limiting(OCP),and UnderVoltage Lockout on VDD(UVLO),and latchedshutdown features including Over TemperatureProtection(OTP),VCC and output Over VoltageProtection(OVP).With On-Bright proprietary technology,the OCP isline voltage compensated to achieve constantoutput power limit over the
46、 universal input voltagerange.At overload condition when FB input voltage exceeds power limit threshold value for more than Td_OLP,control circuit reacts to shut down the converter.It restarts when VDD voltage drops below UVLO limit.For protection with latched shut down mode,control circuit shuts do
47、wn(latch)the power MOSFET when an over temperature condition or over voltage condition is detected until VDD drops below 5V(typical)(Latch release voltage),and the device enters power on restart-up sequence thereafter.At output diode short condition,CS can ramp higher than 1.4V(typical).After 8 cycl
48、es debounce time for CS higher than 1.4V(typical),auto-recover protection is triggered.At GND open condition,the voltage of GND is higher than CS.If GND is greater than CS+0.3V(typical)for more than 20us(typical),auto-recover protection is triggered.Pin Floating and Short ProtectionOB2283 provides P
49、IN floating protection for all thepins and pin short protection for adjacent pins.Inthe cases when a pin is floating or two adjacentpins are shorted,Gate switching is disabled.OB2283 High Performance Current Mode PWM Controller PACKAGE MECHANICAL DATA Dimensions In Millimeters Dimensions In Inches S
50、ymbol Min Max Min Max A 1.000 1.450 0.039 0.057 A1 0.000 0.150 0.000 0.006 A20.9001.3000.0350.051b 0.300 0.500 0.012 0.020 c0.0800.2200.0030.009D 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 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 08
