ACT36X datasheet(4/22 Pages) ACTIVE-SEMI

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PSR

PSR TM

Active

High Efficiency AC/DC Primary Switching Solutions

ACT361 5V/1000MA CHARGER

Operation and Application

Figure 1 is the schematic of an offline charger

using ACT361 to provide output power of

5V1000mA. This circuit is a typical flyback power

supply which includes the AC rectified circuit (D1-

D4,C1, L1, L2, C2),power drive circuit (BD pin,

Q1), secondary rectified circuit (D7, C6) and the

IC control circuit. ACT361 is a Primary Side

Regulator (PSR) so that the power supply unit

can regulate current and voltage without Opto-

coupler. Pin 4 and Pin 2 are the VDD and ground

pins to provide power for the IC. Pin 3 is the base

drive for the NPN transistor. Pin 1 is the switching

pin. Pin 5 is the feedback pin that senses the out-

put current and output voltage. Pin 6 is the peak

current sense pin. Resistance of R7 determines

the output DC cord compensation percentage.

This circuit can be used as universal charger for

Cell Phones, PDAs, MP3,Portable Media Play-

ers, DSCs, and Other Portable Devices and Ap-

pliances.

Key Component Selection

The maximum output current is decided by for-

mula(1).

Lp is the transformer inductance value, Rcs is the

current sense resistor, which is shown as R4 in

the schematic. Fsw is the switching frequency,

which design value is 45kHz. ŋ is the overall sys-

tem efficiency, which value is approximately

equal to 70%. Voutcc is the output voltage, which

setting is through the flyback voltage of auxiliary

winding and the feedback resistor R8, R9 as

shown in formula (2).

Np/Ns/Naux (140/10/14) must be designed cor-

rectly to ensure it operates in DCM in all condi-

tions. A design value Voutcc equal to 5V and

Ioutcc_min equal to 1000mA are used to do the

design. Ns and Naux are number of turns of sec-

ondary and auxiliary of the transformer. VSEC_R

is the forward voltage drop of the output rectifier

diode at approximately 0.1A bias. The peak cur-

rent limit is set by (0.396×0.9)/Rcs.

)

(

)

396

(

OUTCC

SEC

AUX

REF

OUTCC

)

(

−

Input Voltage

Device

Standby Power

Output Voltage

Power output

Transformer

Topology

85-264VAC

ACT361

150mW

EE16

Flyback

Figure 1:

Schematic of Charger

L=51.0mm

W=31.1mm

H=14.2mm

(2)

(1)

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