AP3306

Document number: DS42803 Rev. 6 - 2

9 of 13

www.diodes.com

May 2022

© Diodes Incorporated

AP3306

Operation Description (continued)

If Fault Occurs

GATE

Vcc

I_CHG

VST

VCC-UVLO

6V

I CHARGE-L

I CHARGE - H

I CHARGE-FAULT

I CHARGE-H

0mA

0mA

Figure 6. HV to VCCL Charge Current

X-CAP Discharge Function

To attenuate the differential-mode noise for higher power applications, an X-CAP is used before the rectifier bridge. Also present are paralleled

resistors to discharge the X-CAP for safety consideration when the AC line is off. The paralleled resistors have large power dissipation and will

increase standby power. The AP3306 integrates an X-CAP discharge function to replace discharge resistors and decrease the standby power.

This function contains two processes; the first process detects the condition of the AC line through the HV pin, with the detected voltage named VB.

When the system is plugged in, an inner timer of 40ms within the AP3306 begins to work. Meanwhile, a phase-drifted and filtered signal VC is

generated based on VB, compared to VB with VC, as shown in Figure 7.

Whenever signal VC crosses over with signal VB, the inner 40ms timer will reset, representing that the AC line is on. If the system is disconnected

from the AC line, the cross-over signal of VC and VB will disappear and the 40ms timer will continue to count until it reaches 40ms. At this moment,

the second process (discharge process) will come into effect and a 1.7mA discharge current will flow through the HV pin to GND, lasting for 40ms.

After the AC line is off, the first process and the second process will act alternately until the HV pin voltage is discharged below 10V, even when

the VCC voltage is lower than VCC-UVLO.

Vb

Vc

Timer

Reset

IDISCH-X

X-CAP Discharge Current

0mA

40ms

0mA

Figure 7. X-CAP Discharge

Built-In VCC LDO

The AP3306 integrates a VCC LDO circuitry. The LDO regulates the wide-range VCC_IN, which is rectified from auxiliary winding to an acceptable

value. This makes the AP3306 a good choice in wide-range output-voltage applications.