PL3378

PL3378 PMICRO | Alldatasheet

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Technical content

V1.2 © 2019 1 PL3378 AccurateCC/CVPrimarySide PWMPowerSwitch ProductDescription PL3378 is a high efficiency Primary Side Regulator and highly integrated PWM Power Switch for AC/DC power supply applications. It simplifies conventional CC/CV charger/adaptor designs by eliminating the opto-coupler and secondary control circuitry. Constant output voltage and current regulation is realized as shown in the Fig.1 below. Multi-mode operations are utilized to achieve low standby power, high efficiency and audio & noise free. PL3378 operates in PFM mode at large load condition, with the load becomes medium or light, the chip operates in Green mode toachieve highefficiency. PL3378 also offers rich protection features including Cycle-by-Cycle peak current limiting, UVLO, OTP, load OVP,andVDDovervoltage. Fig.1.TypicalCC/CVCurve PinConfiguration PL3378 KeyFeatures

• Built-in IntegratedPower BJT
• Accurate ConstantCurrent Regulation atUniversalACinput
• Eliminates Opto-couplerandall Secondary CC/CVControlCircuitry
• Built-in LineCompensationfor TighterCC/CVRegulation
• Built-in Compensationfor TransformerInductance Tolerances
• Adjustable OutputCable Compensation
• Adaptive Multi-mode PFM ControlforImprovingEfficiency
• LowStart-up Current
• Built-in LeadingEdgeBlanking (LEB)
• Cycle-by-CycleCurrentLimiting
• VDDUnder VoltageLockoutand VDDovervoltageprotection
• Built-in ShortCircuitProtectionand OutputOvervoltageProtection
• Overtemperatureprotection

Applications

AC/DCpower supplyapplications

• CellPhoneCharger
• SmallPowerAdaptor/Charger
• LEDDriver
• StandbySupply forConsumer Electronics

V1.2 © 2019 2 Datasheet PL3378

1 Overview

PL3378 is a high efficiency Primary Side Regulator and highly integrated PWM Power Switch for AC/DC power supply applications. It simplifies conventional CC/CV charger/adaptor designs by eliminating the opto-coupler and secondary control circuitry. Constant output voltageandcurrentregulationis realized Multi-mode operations are utilized to achieve low standby power, high efficiency and audio & noise free. PL3378 operates in PFM mode at large load condition, with the load becomes medium or light, the chip operates in Green mode toachieve highefficiency. This green-mode function assists the power supply meetingthe power conservationrequirement. A complete set of integrated protection functions allows PL3378 to protect against all fault conditions including Cycle-by-Cycle peak current limiting, VDD UVLO, and VDD_Clamp. The switch continues attempting start-up until thefaultcondition isremoved. PL3378is offered inSOP7 package.

2 Features

 Built-inIntegrated Power BJT  AccurateConstantCurrent Regulationat UniversalAC input  Eliminates Opto-couplerand allSecondary CC/CVControl Circuitry  Built-inLine Compensation forTighter CC/CV Regulation  Built-inCompensation forTransformer Inductance Tolerances  OutputCable Compensation  AdaptiveMulti-modePFM Control for Improving Efficiency  LowStart-up Current  Built-inShort Circuit Protection  Built-inopen Circuit Protection  LEB  OCP  VDD_OVP  UVLO  OTP

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3 PinDiagrams

ThepinmapisshownasbelowforSOP7 PL3378

4 PinDescription

VDD ICpowersupply. FB Throughtwo dividing resistorsconnecting tothe bias winding,this pin couldget the information ofoutput torealize the CC/CVregulation. CS Thispincould detecttheprimary currentby the voltageof sensingresistor connectedfromCStoGND. C HVBJTcollectorPin.This pinisconnectedtotheprimaryleadofthetransformer. E HVBJTcollectorPin. GND ICground.

5 AbsoluteMaximumRatings

Absolute maximum ratings are the parameter values or ranges which can cause permanent damageandaffectdevicereliabilityifexceeded. Parameter Symbol Value Units DCSupply VoltageRange(pin1) VDD -0.3 toVDDclamp V CSInput(pin4) CS -0.3 to5 V FBInput(pin3) FB -0.3 to5 V MaximumJunctionTemperature Tjmax 150 ℃ StorageTemperature Tsto -55to 150 ℃ Lead Temperature(Soldering,10secs) Tlea 260 ℃ Note: These are stress ratings only. Stress beyond these limits may cause permanent damage to the device. Functional operation of the device at these or any conditions beyond those indicated under Recommended Operating Conditions is not implied. Exposure to absolute maximum rated conditions for extended periods of time may affect device reliability.

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6 RecommendedOperatingConditions

OperatingAmbientTemperature -40~105 ℃ Typicalswitchingfrequency@fullload 65 kHz

7 BlockDiagram

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8 ElectricalCharacteristics

(VDD=21V,TA =25℃,unlessotherwisespecified) Parameter Symbol TestConditions Min Typ Max Unit Supply Voltage(VDD)Section VDDstartcurrent IDD_st VDD=UVLO_OFF-1V 5 20 uA Operationcurrent Idd_static Lightload 0.6 1 mA VDDundervoltagelockout OFF UVLO_OFF VDDrise 14 17.5 21 v VDDundervoltagelockout ON UVLO_ON VDD_fall 3.5 4.5 5.5 v VDDovervoltage VDD_ OVP 27 v CurrentsenseSection Turnon LEBTime TLEB 500 ns OverCurrentThreshold Vocp 550 mV OCPpropagationdelay Td_oc 100 ns FBSection Reference for feedback threshold Vref_EA 2.46 2.5 2.54 V Minimumofftime Toff_min 2 us Minimumfrequency Fosc_min 80 Hz Maximumcable compensation current Icable_max 44 uA Outputovervoltage threshold Vfb_ovp 3 V OverTemperature Protection (OTP) Protectiontriggerpoint T_otp 151 ℃ Protectionrecovery point T_otp_rec 139 ℃ PL3378(SOP7)PowerBJT Collector-emitterbreakdown voltage Vceo Ic=10mA 400 V Collector-base breakdown voltage Vcbo Ic=1mA 700 V

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9 Application

PL3378 provides a very effective solution for low power adaptor/charger applications. The innovative CV and CC control can remove the need for secondary feedback circuitry while achieving excellent CC/CV performance and meetingvery strictrequirements. workingin DCM. In the DCM fly-back converter, the output voltage can be sensed via the auxiliary winding. During MOSFET turn-on time, the current in the primary winding ramps up. When MOSFET turns off, the primary current transfers to the secondary attheamplitude of 9.1Startup&OperatingCurrent ISpk  NP N S  IPpk (1) PL3378 has very slight startup current , thus the larger value startup resistor and smaller VDD capacitor can be used to minimize the powerlossinapplication. The operating current of PL3378 is also very low.Together with PFM controlfeatureswe IPpk isthe currentinthe primarywindingat the pointBJTturns off. Through coupling between the secondary and auxiliary winding the outputvoltage isgiven by Vo Ns Vaux V couldgethigh efficiencyespeciallyin lightload. Naux (2) 9.2UnderVoltageLockout(UVLO) An UVLO detector is implemented in it to detect the voltage on the VDD pin. It would assure the supply voltage enough to turn on the PWM controller and further to drive the power BJT. a hysteresis is built in to prevent the shutdown from the voltage dip during startup. The turn-on and turn-off threshold level are set at 17.5 V and 4.5V,typically. 9.3RealizationofCC/CV TheCC/CVcontrolisbased on the system Where Vaux is the voltage of the auxiliary winding and △ V indicates the drop voltage of the output diode.

V1.2 © 2019 7 Fig.2. Voltage of Auxiliary-winding Waveform Via a resistor divider connected between the auxiliary winding and FB, the auxiliary voltage is sampled based on the internal timing control. Through the built-in error amplifier the sampled voltage could be regulated at a preset level, thusconstantoutput voltagecan beachieved. During the CC mode of operation PL3378 will regulate the output current at a constant level regardless of the output voltage, while avoiding continuousconduction mode.

9.4 Adjustable CC Point and Output

In application of AC/DC power supply application, we could change the Rs to get different CC points and the maximum output power only using one model .The larger Rs, the smaller CC point is, and the smaller output powerbecomes.

9.5 Switching Frequency and Lm

The system load condition and the operation mode decide the switching frequency of PL3378.The maximum switching frequency is set by system design. In DCM assuming the efficiencyto 100%,the output poweris givenby smooth it away, the switching frequency is locked by an internal loop such that the switching frequencyis fsw= 4/(7*Tdemag) (4) Where Tdemag is the discharge time of inductance. Since Tdemag is inversely proportional to the inductance, the error of current in CC mode and max output power caused by the variation of inductance will be eliminated. 9.6Adjustable Cable Drop Compensation Built-in cable drop compensation is used to get betterloadregulation. Without compensation of cable drop, the voltage at the end of the cable between no load and full load will not be the same caused by cable drop. To get better 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 cablelosscanbe compensated. In different applications using different cables, we could adjust the resistance of the divider connected to the FB pin. The larger impedance ofthe cable,the largerdividerwillbe used. Po 1 LmfswI 2 Ppk VoIO (3) 9.7ProtectionControl PL3378has built-inrichprotection features Where Lm indicates the inductance of the primary winding and IPpk is the peak current of theprimarywinding. Refer to the equation 3, the change of Lm results in the change of Po and the constant output current in the CC mode. The toleranceof LmwillmakeCCworse inmassproduction. To including Cycle-by-Cycle Current Limiting, VDD over voltage, Under Voltage Lockout on VDD, OutputOVPand OTPProtection. PL3378 is shut down when VDD drops below the UVLO (ON) limit ,and the power converter enters the power on start-up sequence thereafter.

10 PackagingInformation

V1.2 © 2019 8 SOP7Packaging

11 ImportantNotice

POWERLINKreserves the righttomake changes orcorrections toits products atany timewithout notice.Customersshouldverifythe datasheets arecurrentandcomplete beforeplacing orders.