AN3011 datasheet(33/37 Pages) STMICROELECTRONICS

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AN3011

Efficiency

Doc ID 16043 Rev 1

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having a monotonically decay to zero of the output voltage when the converter itself is

unplugged from the mains. A typical situation, in most cases for converters designed for the

European range (230 VAC), could be a converter that when unplugged shuts down due to

the overload protection (due to the low input voltage the converter is not able to supply full

power), but the voltage on the Bulk capacitor is higher than VDRAIN RESTART, so the device

starts again and the output voltage rises again. This situation could be dangerous for some

loads, and in many applications is best avoided.

Figures 37 and 38 show how brown-out protection works in the VIPer27 board when used.

Figure 37

shows the behavior of the board when the input voltage is changed from 90 VAC to

75 VAC with full-load applied. The system stops switching and the output load, no longer

supplied, decays monotonically to zero. Figure 38 shows the system behavior when the

input voltage changes from 75 VAC to 90 VAC.

Figure 37.

Input AC voltage steps from 90 VAC to 65 VAC

Figure 38.

Input voltage steps from 90 VAC to 0 VAC

AN3011 Datasheet(PDF) 33 Page - STMicroelectronics