PL3378C

Accurate CC/CV Primary Side

PWM Power Switch

Product Description
Key Features
PL3378C is a high efficiency Primary Side Regulator and • Built-in Integrated Power BJT
highly integrated PWM Power Switch for AC/DC power • Accurate Constant Current
supply applications. It simplifies conventional CC/CV Regulation at Universal AC input
charger/adaptor designs by eliminating the opto-coupler • Eliminates Opto-coupler and all
and secondary control circuitry. Constant output voltage Secondary CC/CV Control Circuitry
and current regulation is realized as shown in the Fig.1 • Built-in Line Compensation for
below. Tighter CC/CV Regulation
Multi-mode operations are utilized to achieve low standby • Built-in Compensation for
power, high efficiency and audio & noise free. PL3378C Transformer Inductance
operates in PFM mode at large load condition, with the Tolerances
load becomes medium or light, the chip operates in Green • Adjustable Output Cable
mode to achieve high efficiency. Compensation
• Adaptive Multi-mode PFM
PL3378C also offers rich protection features including Control for Improving Efficiency
Cycle-by-Cycle peak current limiting, UVLO, OTP, load • Low Start-up Current
OVP, and VDD over voltage. • Built-in Leading Edge Blanking
(LEB)
• Cycle-by-Cycle Current Limiting
• VDD Under Voltage Lockout and
VDD over voltage protection
• Built-in Short Circuit Protection and
Output Overvoltage Protection
• Over temperature protection

Applications
Fig.1. Typical CC/CV Curve
AC/DC power supply applications
Pin Configuration • Cell Phone Charger
• Small Power Adaptor/Charger
• LED Driver
• Standby Supply for Consumer
Electronics

PL3378C

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 Datasheet PL3378C

1 Overview

green-mode function assists the power supply

PL3378C is a high efficiency Primary Side meeting the power conservation requirement.
Regulator and highly integrated PWM Power
Switch for AC/DC power supply applications. It A complete set of integrated protection
simplifies conventional CC/CV charger/adaptor functions allows PL3378C to protect against all
designs by eliminating the opto-coupler and fault conditions including Cycle-by-Cycle peak
secondary control circuitry. Constant output current limiting, VDD UVLO, and VDD_Clamp.
voltage and current regulation is realized The switch continues attempting start-up until
the fault condition is removed.
Multi-mode operations are utilized to achieve
low standby power, high efficiency and audio & PL3378C is offered in SOP7 package.
noise free. PL3378C operates in PFM mode at
large load condition, with the load becomes
medium or light, the chip operates in Green
mode to achieve high efficiency. This

2 Features

 Built-in Integrated Power BJT  Adaptive Multi-mode PFM Control for

 Accurate Constant Current Regulation at Improving Efficiency
Universal AC input  Low Start-up Current
 Eliminates Opto-coupler and all Secondary  Built-in Short Circuit Protection
CC/CV Control Circuitry  Built-in open Circuit Protection
 Built-in Line Compensation for Tighter  LEB
CC/CV Regulation  OCP
 Built-in Compensation for Transformer  VDD_OVP
Inductance Tolerances  UVLO
 Output Cable Compensation  OTP

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 Datasheet PL3378C

3 Pin Diagrams

The pin map is shown as below for SOP7

PL3378C

4 Pin Description

Pin Description
VDD IC power supply.
FB Through two dividing resistors connecting to the bias winding, this pin could get
the information of output to realize the CC/CV regulation.
CS This pin could detect the primary current by the voltage of sensing resistor
connected from CS to GND.
C HV BJT collector Pin. This pin is connected to the primary lead of the transformer.

E HV BJT emitter Pin.

GND IC ground.

5 Absolute Maximum Ratings

Absolute maximum ratings are the parameter values or ranges which can cause permanent
damage and affect device reliability if exceeded.
Parameter Symbol Value Units
DC Supply Voltage Range(pin1) VDD -0.3 to VDD clamp V
CS Input(pin4) CS -0.3 to 5 V
FB Input(pin3) FB -0.3 to 5 V
Maximum Junction Temperature Tjmax 150 ℃
Storage Temperature Tsto -55 to 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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Datasheet PL3378C

6 Recommended Operating Conditions

Parameter data Unit

Operating Ambient Temperature -40 ~ 105 ℃

Typical switching frequency @ full load 65 kHz

7 Block Diagram

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8 Electrical Characteristics

(VDD =21V, TA = 25℃, unless otherwise specified)

Parameter Symbol Test Conditions Min Typ Max Unit
Supply Voltage (VDD) Section
VDD start current IDD_st VDD=UVLO_OFF-1V 5 20 uA
Operation current Idd_static Light load 0.6 1 mA
VDD under voltage lockout
UVLO_OFF VDD rise 12 15 18 v
OFF
VDD under voltage lockout
UVLO_ON VDD_fall 3.5 4.5 5.5 v
ON
VDD over voltage VDD_ OVP 27 v
Current sense Section
Turn on LEB Time TLEB 500 ns
Over Current Threshold Vocp 550 mV
OCP propagation delay Td_oc 100 ns
FB Section
Reference for feedback
Vref_EA 2.44 2.5 2.56 V
threshold
Minimum off time Toff_min 2 us
Minimum frequency Fosc_min 80 Hz
Maximum cable
Icable_max 60 uA
compensation current
Output over voltage threshold Vfb_ovp 3 V
Over Temperature Protection (OTP)
Protection trigger point T_otp 151 ℃
Protection recovery point T_otp_rec 139 ℃
PL3378C(SOP7) Power BJT
Collector-emitter breakdown
Vceo Ic=10mA 400 V
voltage
Collector-base breakdown
Vcbo Ic=1mA 700 V
voltage

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9 Application

Application Notes working in DCM.

PL3378C provides a very effective solution for In the DCM fly-back converter, the output
low power adaptor/charger applications. The voltage can be sensed via the auxiliary winding.
innovative CV and CC control can remove the During MOSFET turn-on time, the current in the
need for secondary feedback circuitry while primary winding ramps up. When MOSFET
achieving excellent CC/CV performance and turns off, the primary current transfers to the
meeting very strict requirements. secondary at the amplitude of
NP
I Spk   I Ppk
9.1 Startup & Operating Current NS (1)
PL3378C has very slight startup current , thus
IPpk is the current in the primary winding at the
the larger value startup resistor and smaller
VDD capacitor can be used to minimize the point BJT turns off.
power loss in application.
Through coupling between the secondary and
The operating current of PL3378C is also very auxiliary winding the output voltage is given by
low. Together with PFM control features we Ns  Vaux
Vo   V
could get high efficiency especially in light load. Naux (2)
Where Vaux is the voltage of the auxiliary winding
9.2 Under Voltage Lockout (UVLO) and △ V indicates the drop voltage of the output
An UVLO detector is implemented in it to detect diode.
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 15 V and
4.5 V, typically.

9.3 Realization of CC/CV

The CC/CV control is based on the system
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 Datasheet PL3378C

Fig.2. Voltage of Auxiliary-winding Waveform locked by an internal loop such that the
switching frequency is
Via a resistor divider connected between the fsw = 4/(7*Tdemag) (4)
auxiliary winding and FB, the auxiliary voltage Where Tdemag is the discharge time of
is sampled based on the internal timing control. inductance. Since Tdemag is inversely
Through the built-in error amplifier the sampled proportional to the inductance, the error of
voltage could be regulated at a preset level, current in CC mode and max output power
thus constant output voltage can be achieved. caused by the variation of inductance will be
eliminated.
During the CC mode of operation PL3378C will
regulate the output current at a constant level 9.6 Adjustable Cable Drop
regardless of the output voltage, while avoiding Compensation
continuous conduction mode. Built-in cable drop compensation is used to get
better load regulation.
9.4 Adjustable CC Point and Output Without compensation of cable drop, the
Power voltage at the end of the cable between no load
In application of AC/DC power supply and full load will not be the same caused by
application, we could change the Rs to get cable drop. To get better load regulation, an
different CC points and the maximum output offset voltage is generated at FB pin by an
power only using one model .The larger Rs, the internal current flowing into the resister divider.
smaller CC point is, and the smaller output The current is proportional to the switching off
power becomes. time, as a result, it is inversely proportional to
the output load current, thus the drop due to the
9.5 Switching Frequency and Lm cable loss can be compensated.
Tolerance Compensation In different applications using different cables,
The system load condition and the operation we could adjust the resistance of the divider
mode decide the switching frequency of connected to the FB pin. The larger impedance
PL3378C.The maximum switching frequency is of the cable, the larger divider will be used.
set by system design. In DCM assuming the
efficiency to 100%, the output power is given by 9.7 Protection Control
1 PL3378C has built-in rich protection
Po  LmfswI Ppk
2
 Vo  IO
2 (3) features including Cycle-by-Cycle Current
Where Lm indicates the inductance of the Limiting, VDD over voltage, Under Voltage
primary winding and IPpk is the peak current of Lockout on VDD, Output OVP and OTP
the primary winding. Protection.
Refer to the equation 3, the change of Lm
PL3378C is shut down when VDD drops below
results in the change of Po and the constant
the UVLO (ON) limit ,and the power converter
output current in the CC mode. The tolerance of
enters the power on start-up sequence
Lm will make CC worse in mass production. To
thereafter.
smooth it away, the switching frequency is

10 Packaging Information

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 Datasheet PL3378C

SOP7 Packaging

11 Important Notice

POWERLINK reserves the right to make changes or corrections to its products at any time without
notice. Customers should verify the datasheets are current and complete before placing orders.

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