AN1539 STMicroelectronics, AN1539 Datasheet - Page 9

• Manufacturer Part Number: AN1539
• Description: VIPOWER: LOW COST UNIVERSAL INPUT SMPS FOR DIGITAL SET-TOP BOX BASED ON VIPER50
• Manufacturer: STMicroelectronics

AN1539 - APPLICATION NOTE
Figure 4: PCB layout (not in scale)
The board has been developed on a 135X75 Cu single side 70mm FR-4 frame.
2. LAYOUT RECOMMENDATION
Since EMI issues are strongly related to layout, a basic rule has to be taken into account in high current
path routing, i.e. the current loop area has to be minimized.
If a heatsink is used it has to be connected to ground too, in order to reduce common mode emissions
since it is close to the floating drain tab.
One more consideration has to be done regarding the control ground connection: in fact in order to avoid
any noise interference on VIPer logic pin the control ground has to be separated from power ground. This
results in a dedicated track for ground connection of C3, C4, C6, C9 and IC2 collector.
3. EXPERIMENTAL RESULTS
3.1 PERFORMANCE AND TYPICAL WAVEFORMS
In this section the performances of the power supply in terms of voltage regulation, power consumption
as well as typical waveforms are given.
In Table 4 and 5 the main experimental results are listed. The converter features an excellent voltage
regulation as the input voltage changes, with low power consumption at no load and efficiency 70%
higher at full load. In Figure 5 and 6 the drain voltage V
at 110V
and 220V
at no-load and full load
DS
ac
ac
is shown, respectively. In Figure 7 V
during the first cycles at start up is shown: the voltage never goes
DS
higher than 600V, below the breakdown voltage. Start up transient is shown in Figure 8 at 110V
and
ac
220V
respectively. Thanks to the internal current generator, that provides constant 2mA current, the
ac
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