DI-89
Key Design Points
68
66
64
62
60
58
56
54
•
•
The PI Xls spreadsheet calculates all of the parameters
required to specify and build transformer T1.
Thepowertransformermusthaveatwolayerprimarywinding
to ensure that its intra-winding capacitance is sufficient for
Clampless operation.
•
•
The reflected output voltage (VOR) of this design was kept
< 90 V (74 V) for Clampless operation.
85 VAC
115 VAC
230 VAC
265 VAC
EPA Std
Since this supply has a Clampless drain node, it must be
verified that the maximum drain voltage does not exceed
650 V when the flyback voltage spike occurs.
The primary current ripple-to-peak ratio (KP) factor should
be > 1 (ensures discontinuous conduction mode operation)
to minimize conducted EMI.
•
•
0
0.5
1
1.5
2
2.5
Output Power (W)
The maximum operating flux density (BM) was kept
< 1500 Gauss to eliminate audible.
Figure 3. Harmonized (EPA, CEC) Active-Mode Efficiency vs.
Output Power (25, 50, 75 & 100%).
0.12
0.1
80
70
60
50
40
30
0.08
0.06
0.04
0.02
0
20
-10
0
0
50
100
150
200
250
300
-10
-20
Input Voltage (VAC)
0.15
1
10
30
Figure 2. No-load Input Power Consumption vs. Input Voltage.
Frequency (MHz)
Figure 4. Conducted EMI Scan to EN55022B Limits: Full-Load,
115 VAC, 60 Hz Input, with Artificial Hand.
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Power Integrations reserves the right to make changes to its products at any time to improve reliability or manufacturability. Power Integrations does
not assume any liability arising from the use of any device or circuit described herein. POWER INTEGRATIONS MAKES NO WARRANTY HEREIN AND
SPECIFICALLY DISCLAIMS ALL WARRANTIES INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
PARTICULAR PURPOSE, AND NON-INFRINGEMENT OF THIRD PARTY RIGHTS. The products and applications illustrated herein (transformer construction and
circuits external to the products) may be covered by one or more U.S. and foreign patents or potentially by pending U.S. and foreign patent applications assigned to
Power Integrations. A complete list of Power Integrations' patents may be found at www.powerint.com. Power Integrations grants its customers a license
under certain patent rights as set forth at http://www.powerint.com/ip.htm.
The PI logo, TOPSwitch, TinySwitch, LinkSwitch, DPA-Switch, EcoSmart, Clampless, E-Shield, Filterfuse,
PI Expert and PI FACTS are trademarks of Power Integrations, Inc. Other trademarks are property of their respective companies.
©Copyright 2005, Power Integrations, Inc.
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A
11/05
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