AP3710M-E1 查看數據表（PDF） - BCD Semiconductor

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AP3710M-E1

LOW POWER PWM CONTROLLER FOR OFF-LINE ADAPTER

BCD Semiconductor 

Data Sheet

LOW POWER PWM CONTROLLER FOR OFF-LINE ADAPTER

Function Description

1. UVLO and Start up Circuit

The AP3710's turn on threshold voltage is 5.6V and its

turn off threshold voltage is 3.65V, so the UVLO

hysteresis voltage is 1.95V, which helps AP3710 to

draw adequate energy to supply VCC terminal during

start-up. Please see Figure 13 for UVLO chart.

VIN

Rectified AC

D6

R2+R3

R5

Q1

APT13003

D6

R8

U3

PC817

Turn off

Turn on

R6

OUT VSEN

+ C4

VA VCC

GND

R7

+

C5

C6

U1

AP3710

AP3710

VO

R13

R14

R16 C7

U2

AZ431

R16

3.65 5.6

VCC: Supply Voltage (V)

Figure 13. 5.6/3.65V UVLO

Threshold of AP3710

The VCC terminal in Figure 3 is used for both bias

supply and feedback control. When AP3710 is

powered on, the start-up current source turns on and it

can not turn off until VCC level increases to its

threshold value and PWM pulse is produced.

Figure 14. The Start-up

Circuit of Typical Application

In start-up section of typical application shown by

Figure 14, the rectified line voltage VIN charges the

capacitor C4 through start-up resistor R2+R3 until Q1

is turned on so OUT terminal can directly drive

external Q1, a MOSFET inside AP3710 is connected

in series with the Q1.

Once the start-up is set up, the auxiliary bias winding

will supply the VCC terminal enough operating

current. The start-up sequence is shown in Figure 15.

Aug. 2008 Rev. 1. 3

Figure 15. Power up Waveforms

BCD Semiconductor Manufacturing Limited

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