VIPER28

Operation descriptions

Doc ID 15028 Rev 5

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7.11

Burst-mode operation at no load or very light load

When the load decrease the feedback loop reacts lowering the feedback pin voltage. If it

switched on. After the MOSFET stops, as a result of the feedback reaction to the energy

reported on

Table 8 and Figure 26 shows this behavior. Systems alternates period of time

where power MOSFET is switching to period of time where power MOSFET is not switching;

this device working mode is the burst mode. The power delivered to output during switching

periods exceeds the load power demands; the excess of power is balanced from not

switching period where no power is processed. The advantage of burst mode operation is

an average switching frequency much lower then the normal operation working frequency,

up to some hundred of hertz, minimizing all frequency related losses. During the burst-mode

Figure 26.

Burst mode timing diagram, light load management

time

time

time

Burst Mode