HVLED001 Datasheet, PDF (20/27 Pages) STMicroelectronics – 800 V high voltage start-up

Application information
HVLED001
The internal small signal model of the PSR E/A is obtained considering the voltage gain
(G_V = 73 dB) and the gain bandwidth product (GBWP = 1 MHz) and is illustrated in
Figure 10.
Figure 10. PSR E/A small signal model
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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.
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.
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.
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