AN3290 datasheet(20/34 Pages) STMICROELECTRONICS

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Protection features

AN3290

20/34

Doc ID 18038 Rev 1

Protection features

The ALTAIR04-900 has several protection features that considerably increase end-product

safety and reliability: auxiliary winding disconnection (or brownout) detection, shorted

secondary rectifier detection, and transformer saturation protection.

Moreover, using the primary CC loop it is possible to set the maximum deliverable output

current without any secondary extra component, therefore providing a best-in-class

protection against overload and short-circuit.

In the following paragraphs all protections are tested and the results are presented.

5.1

Overload and short-circuit protection

The CC mode circuitry is able to regulate the maximum deliverable output current also when

the output is shorted with good precision.

This means that during short-circuit protection, the output voltage is close to zero, while the

output current is fixed to a constant value close to the maximum operative output current,

resulting in an extremely safe mode of operation, with no overcurrent stress on the

secondary components.

At the same time, the overload also coincides with the maximum operative output current.

Figures 22 and 23 show the drain voltage and the output current waveforms at different input

voltage values and output 1 shorted.

Figure 22.

Short-circuit mode: 13 V shorted at 115 VAC

AN3290 Datasheet(PDF) 20 Page - STMicroelectronics