AP3304

Document number: DS43559 Rev. 4 - 2

7 of 12

www.diodes.com

October 2021

© Diodes Incorporated

AP3304

Operation Description

The AP3304 realizes Multi-Mode Operation including Burst mode, QR mode and CCM mode, which is specifically designed for off-line AC-DC

power supply used in LCD monitor, notebook adapter and battery charger applications. At medium load, the IC will enter QR mode with frequency

foldback to improve system efficiency and EMI performance. It offers a cost effective solution with a versatile protection function.

Figure 3

Multi-Mode Operation

The switching frequency curve in Figure 3 shows three operation modes.



Burst Mode

At no load and light load, the system will operate at burst mode with fixed switching frequency 23kHz to avoid audible noise. When the FB

voltage is lower than 0.6V, the controller will not provide driving signal and the FB voltage will rise above 0.8V, then the driving signal will

resume. By this control strategy, the system will eliminate a bunch of pulses and the power loss is reduced.



QR Mode

QR is the abbreviation of Quasi-Resonant which means that the power MOSFET is forced to turn on at valleys of VDS. With QR control, the

switching power loss will be reduced by lower voltage stress on MOSFET. The VDS valley is detected by DEM pin through the voltage divider

network of RDEM and RSOVP. In QR mode, the trend of switching frequency is modulated by AP3304.



CCM

When AP3304 operates in QR mode with 1st Valley, switching frequency starts to fall as load increases. If the switching frequency falls to

80kHz,CCM is implemented to achieve high efficiency. Usually at low line voltage, the system will enter CCM at heavy load, while high line

voltage the system may still operate in QR mode with 1st or 2nd valley.

100KHz

80KHz