AN2929 datasheet(9/32 Pages) STMICROELECTRONICS

9 / 32 page

AN2929

Testing the board

Doc ID 15333 Rev 2

9/32

Testing the board

2.1

Typical board waveforms

Drain voltage and current waveforms were captured for the two nominal input voltages and

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

Figure 5 and Figure 6 show the drain current and the drain voltage waveforms at the

nominal input voltages of 115 VAC and 230 VAC when the load is the maximum (2.4 A).

Figure 7 and Figure 8 show the same waveforms for the same load condition, but for the

minimum (90 VAC) and the maximum (265 VAC) input voltages.

The converter is designed to operate in continuous conduction mode (in full-load condition)

at low line. CCM (continuous conduction mode) allows reducing the root mean square

current values at the primary side in the power switch inside the VIPER27LN and at the

secondary side in the output diode (D4) and in the output capacitors (C9 and C14).

Reducing RMS currents means reducing the power dissipation (mainly in the VIPER27LN)

and the stress on these components.

Figure 5.

Drain current and voltage at

full load 115 VAC

Figure 6.

Drain current and voltage at

full load 230 VAC

Figure 7.

Drain current and voltage at

full load 90 VAC

Figure 8.

Drain current and voltage at

full load 265 VAC

AN2929 Datasheet(PDF) 9 Page - STMicroelectronics