Application information

HVLED001

20/27

DocID027333 Rev 1

The internal small signal model of the PSR E/A is obtained considering the voltage gain

Figure 10.

Figure 10. PSR E/A small signal model

7.2.5

Burst-mode operation

As soon as the FB pin drops below Vbm, the burst-mode operating mode is entered. The

switching activity is temporarily interrupted until the FB voltage returns above the Vbm

value. An internal hysteresis improves the noise rejection of this feature. The FB biasing

current follows the same rules as in the normal operation; therefore the burst-mode

operation is either defined by the secondary side error amplifier when an optocoupler is

used or by the internal error amplifier if the PSR operation is on.

An internal biasing mean prevents the FB voltage to drop below disabling thresholds during

the inactive state.

7.3

Gate driver

The output stage, connected to VCC potential and capable of the 300 mA source and the

600 mA sink current, is suitable to drive high current MOSFETs. The resulting managed

power can be greater than 150 W.

7.4

IC supply management

The IC's voltage supply is managed by the UVLO circuitry together with the high voltage

start-up unit and reference generators. These logics define also supply currents during

different operating conditions.