AN4026 datasheet(20/40 Pages) STMICROELECTRONICS

20 / 40 page

Functional check

AN4026

20/40

Doc ID 022603 Rev 1

operating frequency of the half bridge, set by the resistor R34 in series to the optocoupler, is

103 kHz.

4.2

Startup

The waveforms relevant to the adapter startup at 90 Vac and full load have been captured in

Figure 19. The output voltage reaches the nominal value 600 ms after plug-in. The L6563H,

HV PFC controller, has an embedded high-voltage startup charging the VCC capacitor by a

constant current, ensuring a constant wake-up time. Comparing Figure 19 with Figure 20

relevant to a startup at 265 Vac and no load, the output voltage rises at the nominal level in

the same time. In both conditions the output voltage has no overshoot and the rise is

monotonic.

In Figure 21 the salient waveforms in the resonant tank during startup of the LLC are

reported. In Figure 22 the detail of waveforms at the beginning of operation shows that the

resonant circuit is working correctly in zero voltage switching operation from the initial

Figure 17.

Pout = 250 mW operation

Figure 18.

Pout = 250 mW operation - detail

CH1: HB voltage

CH3: STBY

CH2: LVG

CH4: V.out (AC coupl.)

CH1: HB voltage

CH3: STBY

CH2: LVG

CH4: res. tank current

Figure 19.

Startup at 90 Vac - full load

Figure 20.

Startup at 265 Vac - no load

CH1: HB voltage

CH3: +19 Vout

CH2: GD L6563H

CH4: VCC L6563H

CH1: HB voltage

CH3: +19 Vout

CH2: GD L6563H

CH4: VCC L6563H

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