PL3378 datasheet(6/8 Pages) PMICRO

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Application

Application Notes

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

meeting very strict requirements.

working in 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 at the amplitude of

9.1 Startup & Operating Current

ISpk 

N P

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

power loss in application.

The operating current of PL3378 is also very

low. Together with PFM control features we

IPpk is the current in the primary winding at the

point BJT turns off.

Through coupling between the secondary and

auxiliary winding the output voltage is given by

Vo  Ns



Vaux  V

could get high efficiency especially in light load.

Naux

(2)

9.2 Under Voltage Lockout (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 4.5 V, typically.

9.3 Realization of CC/CV

The CC/CV control is based on the system

Where Vaux is the voltage of the auxiliary winding

and △ V indicates the drop voltage of the output

diode.

PL3378 Datasheet(PDF) 6 Page - Suzhou Juyuan Microelectronics Co., Ltd

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