AN3233 datasheet(15/35 Pages) STMICROELECTRONICS

15 / 35 page

AN3233

Functional check

Doc ID 17595 Rev 1

15/35

Zero voltage switching

Figure 9

and 10 show details of ZVS operation. Both MOSFETs turn on when current is

flowing through their body diodes and drain-source voltage is zero.

Startup and shutdown

Figure 11

and 12 show the start-up and shut-down sequence of the two converter stages:

The PFC starts first and the LLC only starts after the PFC achieves regulation. In the same

way the PFC stops first and the LLC shuts down as its input voltage falls below the allowed

voltage.

Figure 13

and 14 again show startup and shutdown but highlighting the current flowing

through the resonant tank.

Figure 9.

High-side MOSFET ZV turn-on

at 115 V – 60 Hz – full load

Figure 10.

Low-side MOSFET ZV turn-on

at 115 V – 60 Hz – full load

CH1: HB voltage

CH2: HVG pin voltage

CH1: HB voltage

CH2: HVG pin voltage

CH3: LVG pin voltage

Figure 11.

Converter startup

at 115 Vac full load

Figure 12.

Converter shutdown

at 115 Vac full load

CH1: Half-bridge node

CH2: PFC drain

CH1: Half-bridge node

CH2: PFC drain

CH3: Output voltage

CH4: LINE pin

CH3: Output voltage

CH4: LINE pin

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