AN1376 APPLICATION NOTE

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12 SHORT CIRCUIT PROTECTION @ LOW LOAD

After the full load tests some checks on the short circuit protection with reduced loads have

been done.

@Half Load

At Vin = 115Vac: shorting each output by the active load the over current protection works

correctly, providing for the hic-cup working mode, except for the 5V which is protected by the

current limiting of the linear regulator.

At Vin = 220Vac: the circuit behaves like at 115V.

@Reduced Load - 1

At Vin = 115Vac: shorting the 3.3V, 7V, 12V and 35V it provides for the hic-cup working mode

of the circuit.

At Vin = 220Vac: the behaviour is the same.

@Reduced Load - 2

Both at 115V and 220V the circuit is still protected against short circuits on all the outputs

13 SHORT CIRCUIT PROTECTION @ NO LOAD

Even in this abnormal condition, with the output connector unplugged, a short on the outputs

provides for the same results of the previous tests, both at 115Vac or at 220 Vac.

Figure 22. 3.3V OUTPUT: SHORT @NO LOAD

35V

12V

7V

5V

3.3V

15mA

0.25 A

0.35A

0.55A

1A

35V

12V

7V

5V

3.3V

15mA

0.5 A

0A

0A

1A

35V

12V

7V

5V

3.3V

15mA

0.4 A

0A

0A

0A

CH1:

DRAIN VOLTAGE

CH1:

DRAIN VOLTAGE

CH2:

CH2:

CH3:

3.3V OUTPUT

CH4:

3.3V OUTPUT