Testing the board

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Doc ID 15282 Rev 1

Figure 20.

3.6

Secondary winding short-circuit protection

The VIPER17L is equipped with an adjustable first level of primary overcurrent limitation that

switches off the power MOSFET if this level is exceeded. This limitation acts cycle-by-cycle

and its main purpose is to limit the maximum deliverable output power. A second level of

primary non-adjustable overcurrent protection is also present, fixed at 600 mA (typical

the device enters into a warning state. At the next cycle, the MOSFET is switched on and if

the second level of overcurrent protection is exceeded again, the device assumes that a

secondary winding short-circuit or a hard saturation of the transformer has occurred, so the

MOSFET is no longer allowed to switch on and the device stops operating. In order to

nd

overcurrent protection activation is not removed, the device switches into auto-restart mode.

This protection was tested on the STEVAL-ISA058V1demonstration board. The secondary

winding of the transformer was shorted in different operating conditions. Figure 21 and

Figure 22

show the behavior of the system during the tests.