ACT36X datasheet(8/22 Pages) ACTIVE-SEMI

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PSR

PSR TM

Active

High Efficiency AC/DC Primary Switching Solutions

ACT365 5V/2100MA CHARGER

Operation and Application

Figure 1 is the schematic of an offline charger

using ACT365 to provide output power of

5V2100mA. This circuit is a typical flyback power

supply which includes the AC rectified circuit

(BD1,C1, C2),power drive circuit (BD pin, Q1),

secondary rectified circuit (D8, C5,C6) and the IC

control circuit. ACT365SH is a Primary Side

Regulator (PSR) so that the power supply unit

can regulate current and voltage without Opto-

coupler. Pin 6 and Pin 2,4,7 are the VDD and

ground pins to provide power for the IC. Pin 8 is

the base drive for the NPN transistor. Pin 1 is the

switching pin. Pin 5 is the feedback pin that

senses the output current and output voltage. Pin

3 is the peak current sense pin. Resistance of

R10 determines the output DC cord compensa-

tion percentage. This circuit can be used as uni-

versal

charger

for

Cell

Phones,

PDAs,

MP3,Portable Media Players, Shaver, DSCs, and

Other Portable Devices and Appliances.

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 R9 in

the schematic. Fsw is the switching frequency,

which design value is 75kHz. η 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 R5, R6 as

shown in formula (2).

Np/Ns/Naux (110/8/18) 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 2100mA 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

ACT365SH

150mW

10.5W

EPC17

Flyback

Figure 1:

Schematic of Charger

L=40.0mm

W=28.1mm

H=22.1mm

(1)

(2)

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