AN2950 datasheet(11/37 Pages) STMICROELECTRONICS

11 / 37 page

AN2950

Testing the board

Doc ID 15494 Rev 1

11/37

Testing the board

2.1

Typical board waveforms

The drain voltage and current waveforms are reported for the two nominal input voltages

and for the minimum and maximum voltages of the converter’s input operating range.

Figure 7 and Figure 8 show the drain current voltage waveforms at nominal input voltages

(115 VAC and 230 VAC) and maximum load (2 A). Figure 9 and Figure 10 show the same

waveforms for the same load conditions, but with minimum (90 VAC) and maximum

(265 VAC) input voltages.

Figure 11 and Figure 12 show the same waveforms during peak load conditions (3.3 A),

which the converter is able to sustain for approximately 1.9 seconds while still keeping the

output voltage under regulation.

The converter is operated in continuous conduction mode (CCM) at low input voltage during

full load conditions and even at high input voltage during peak load conditions. CCM allows

reducing the value of the root mean square currents, both on the primary side (in the power

switch) and on the secondary side (in the output diode D4 and in the output capacitors C9

and C14), thus reducing the power dissipation and the stress on the power components.

Figure 7.

Drain current and voltage at

maximum load 115 VAC

Figure 8.

Drain current and voltage at

maximum load 230 VAC

Figure 9.

Drain current and voltage at

maximum load 90 VAC

Figure 10.

Drain current and voltage at

maximum load 265 VAC

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