2 Circuit Description

AN2242

8/31

Here follow some waveforms during normal operation at full load:

The pictures above show the drain voltage and current signal on pin #12 at the nominal input

mains voltage during normal operation at full load. The Envelope acquisition of the scope

provides for the possibility to observe the modulation of the two waveforms, due to the mains

input voltage ripple at twice the line frequency.

Figure 5. The drain voltage waveforms and the measurement of the peak voltage at full load

and maximum input mains voltage are shown. The maximum voltage peak in this condition is

524V, which ensures a reliable operation of the power MOSFET with a good margin against the

maximum BVDSS. The operation during the hard-disk spin-up when the SMPS delivers the

peak power to the loads, brings the drain voltage peak at 540Vpk.

Figure 5.

Vin = 265 Vrms - 50Hz

Figure 5. and Figure 6. depict the most salient controller IC signals. In all pictures it is possible

to distinguish clean waveforms free of hard spikes or noise that could affect the controller

Figure 3.

Vin = 115 Vrms - 60Hz

Figure 4.

Vin = 230 Vrms - 50Hz

CH1: DRAIN VOLTAGE

CH1: DRAIN VOLTAGE

CH1: DRAIN VOLTAGE