AN2544 Datasheet, PDF (12/17 Pages) STMicroelectronics – Designing a low cost power supply using

Circuit operation
Figure 10. Burst mode
AN2544
1.8
Short circuit
The VIPer has pulse-by-pulse current limit. When the current ramps up to the current limit,
the pulse is terminated. This is manifested by reducing the output voltage as the current is
increased. The voltage decreases until it falls below the undervoltage shutdown threshold of
9 V, (pin4). During a short circuit the VIPer turns on and off. When the V_dd reaches the
starting voltage, the current is limited by the pulse-by-pulse current limit. The voltage falls to
the undervoltage shutdown point and the cycle repeats itself at a 16% duty cycle. This
reduces the RMS current going through the circuit as seen in Figure 11.
Figure 11. Operation during a short
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