AN3339 datasheet(21/44 Pages) STMICROELECTRONICS

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AN3339

Functional check

Doc ID 18449 Rev 2

21/44

Figure 35 shows the waveforms during startup at 115 Vac and full load. Note the sequence

of the two stages: the PFC starts and its output voltage increases from the mains rectified

voltage to its nominal value. In the meantime, the L6599A is kept inactive by the LINE pin

(#7) until the PFC voltage reaches the set threshold. Then, the resonant starts operating

and the output voltage reaches the nominal level. Output voltage achieves the nominal value

150 ms after power-on signal.

Figure 36 shows the waveforms at shutdown. Opening the on/off signal, both L6564 and

L6599A are no longer supplied. Output voltage drops to 0 V 40 ms after power off signal.

Figure 37 shows details of waveforms at startup. Note that the resonant current at turn-on

has some oscillations due to the charging of the resonant elements. Anyhow, current zero-

crossing always lags the HB commutations and consequently the MOSFETs are soft-

switched.

Figure 33.

12 V and 24 V rectifier PIV

Figure 34.

130 V rectifier PIV

CH3: D9-A anode

CH1: D4-A anode

CH2: D4-B anode

CH4: D9-B anode

CH3: D26 rev. voltage

CH1: D27 rev. voltage

CH2: D25 rev. voltage

CH4: D24 rev. voltage

Figure 35.

Startup at full load and 115 Vac by

on/off signal

Figure 36.

Shut down at full load and 115 Vac

by on/off signal

CH3: +12 V o/p voltage

CH1: HB voltage

CH2: PFC drain

CH4: on/off

CH3: +12 V o/p voltage

CH1: HB voltage

CH2: PFC drain

CH4: on/off

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