AN2929

Testing the board

Doc ID 15333 Rev 2

23/32

Figure 23.

In Figure 23 when the board was working in full-load condition with an input voltage of

a high drain current. After two switching cycles, the system stops and continuous running

with high currents in the primary as well as in the secondary windings and through the

power section of the VIPER27LN is avoided. Figure 24 shows the situation when a

permanent short-circuit is applied on the secondary windings. Most of the time the power

section of the VIPER27LN is off, eliminating any risk of overheating.

Figure 24.

Operating with secondary winding shorted - restart mode

Ch4 = IDRAIN

Test condition:

Full load before

short

Ch3 = VDD

Test condition

Secondary winding

shorted