DER-94
LCD Monitor Internal Supply
September 12, 2005
11.3 Ripple with 12 V Burst Load
Figure 25 – Burst Load Ripple, 90 VAC, 2 ms / div
Top Trace: 5 V Ripple, 50 mV / div Second Trace:
12 V Ripple, 50 mV / div Third Trace: 12 V Load
Current, 2 A / div Fourth Trace: 5 V Ripple,
Expanded View, 50 mV / div Fifth Trace: 12 V
Ripple, Expanded View, 50 mV / div Bottom Trace:
12 V Load Current, Expanded View, 2 A / div
Figure 26 – Burst Mode Ripple, 90 VAC, 2ms/div
Top Trace: 5 V Ripple, 50 mV / div, Middle Trace:
12 V Ripple, 50 mV / div, Bottom Trace: 12 V Load
Current, 2 A / div
Figure 27 – Burst Mode Ripple, 265 VAC, 2 ms / div
Top Trace: 5 V Ripple, 50 mV / div, Middle Trace:
12 V Ripple, 50 mV / div, Bottom Trace: 12 V Load
Current, 2A/div
The three figures above (Figures 25-27) show the effects of a 12 V burst load on the 5 V
and 12 V output ripple. The 12 V load was switched from 0 A to 2 A using a MOSFET
switch and resistive load. The load switching frequency was ~770 kHz, with a burst of 5
switching cycles repeated at a rate of one burst every 4 milliseconds.
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