AN1842 datasheet(4/17 Pages) STMICROELECTRONICS

4 / 17 page

AN1842 APPLICATION NOTE

4/17

Figure 2. Drain voltage & current @115 VAC -

60Hz - full load

Figure 3. Drain voltage & current @230 VAC -

50Hz - full load

The pictures here above show the drain voltage

and current at the nominal input mains voltage

during normal operation at full load. As visible, the

circuit works in CCM both at nominal high and low

mains.

The figure 4 shows the measurement of the drain

peak voltage at full load and maximum input mains

voltage. The measured voltage of 672V, ensures

a reliable operation of the MOSFET with a good

margin against the maximum BVDSS. Even the

maximum rectifiers PIV have been measured dur-

ing the worst operating condition and they are in-

dicated on the right of figure 5. The margin, with

respect to the maximum voltage withstood by each

diode, ensures safe operating conditions for these

devices.

Figure 4. Drain voltage & current @265 VAC -

50Hz - full load

Figure 5. Maximum rectifiers PIV @Vin = 265

VAC - 50 Hz and full load

Here following the most salient controller IC sig-

nals are shown. In both pictures it is possible to

distinguish clean waveforms free of hard spikes or

noise that could affect the controller correct oper-

ation.

CH1:

VQ4 - Drain

CH2:

VPIN8 (Vcc)

CH4:

VR16 (Drain Current)

CH1:

VQ4 - Drain

CH2:

VPIN8 (Vcc)

CH4:

VR16 (Drain Current)

CH1:

VQ4 - Drain

CH2:

VPIN8 (Vcc)

CH4:

VR16 (Drain Current)

CH3:

+5V RECTIFIER: Anode voltage

CH4:

+12V RECTIFIER: Anode voltage

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