AN3009 datasheet(7/36 Pages) STMICROELECTRONICS

Part #	AN3009

Description	How to design a transition mode PFC pre-regulator using the L6564

PDF	36 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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7 / 36 page

AN3009

Operating the transition mode PFC (boost topology)

Doc ID 16032 Rev 4

7/36

The resulting inductor current and the timing intervals of the MOSFET are shown in

Figure 3, where it can be observed that, by geometric relationships, the average input

current (the one drawn from the mains) is just one half of the peak inductor current

waveform.

Figure 3.

Inductor current waveform and MOSFET timing

The system operates not exactly on, but very close to, the boundary between continuous

and discontinuous current mode and that is why this system is called a transition mode PFC.

Besides the simplicity and the few external parts required, this system minimizes the

inductor’s size due to the low inductance value needed. On the other hand, the high current

ripple on the inductor involves high RMS current and high noise on the rectified mains bus,

which needs a heavier EMI filter to be rejected. These drawbacks limit the use of the TM

PFC to lower power range applications.

AN3009 Datasheet(PDF) 7 Page - STMicroelectronics