UNIVERSAL INPUT, 12V/5A ADAPTER EVALUATION BOARD

EVX2001-Y-00B Rev.1.1

www.MonolithicPower.com

5

6/8/2017

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CIRCUIT DESCRIPTION

The EVX2001-Y-00B is a single-stage flyback

converter with All-in-One controller. The input is

universal and output is 12V/5A. The All-in-One

controller integrates primary side and secondary

side in one chip so the opto-coupler and TL431

can be saved.

F1, LX1, LX2, CX1, BD1, RX1 and RX2 compose

the input stage. F1 is the fuse and is used to

protect the component failure or some excessive

short events. LX1, LX2 and CX1 are configured

the EMI filter to suppress conducted EMI. BD1 is

the rectifier bridge to convert AC voltage to DC

voltage.

RX1 and RX2 are the discharging

resistors

to

make

CX1

discharging

time

compliant with safety regulation.

C1 is the filter capacitor. D1, R5, R6, R24 and C2

are configured RCD snubber to suppress voltage

spike of Mosfet.

R12, C3, C5 and D3 are used as Vcc power

supply.

D5, R23 and Q3 are optional OVP circuit. The

OVP threshold can be set by this external circuit.

MPX2001 and its peripheral components are

configured flyback controller circuit. MPX2001

integrates the primary side and secondary side in

one chip so the opto-coupler and TL431 can be

saved.

Q1 is the main switch and R4, R7 and R9 are the

current sensing resistors.

T1 is the transformer to transfer the power from

primary side to secondary side. It is key

component for the whole circuit normal working

with good performance. So it should be designed

carefully.

CY1 is Y capacitor lowering common mode noise

to make sure there is enough EMI margin.

Q2 is secondary synchronous rectifier (SR) and

R15A, R15B and C8 are their snubber to

suppress SR high voltage spike.

C10, C12 and C14 are output capacitors. R18,

C9 and C17 are configured as the compensation

network. R20 and R21 are feedback resistors.

R22 is the output current sensing resistor for the

over current protection.