SLUA159 Datasheet, PDF (19/28 Pages) Texas Instruments – Zero Voltage Switching Resonant Power Conversion

APPLICATION NOTE
Fig. 24 - Conversion Freq. vs. Line & Load
6. Analyze the results.
The resonant component values, range of
conversion frequencies, peak voltage and
current ratings seem well within the practical
limits of existing components and technology.
7. Finalize the circuit specifics and details
based on the information obtained above.
U-138
A. Output Filter Section: Select L, and CO
for operation at the lowest conversion
frequency and designed ripple current.
B. Heatsink Requirements: An estimate of
the worst case power dissipation of the
power switch and output catch diode can be
made over line and load ranges.
C. Control Circuit: The UC3861-64 series of
controllers will be examined and pro-
grammed per the design requirements.
Programming the Control Circuit
One-shot= Accommodating Off-time Varia-
tions. The switch off-time varies with line and
load by == ± 35% in this design example using
ideal components. Accounting for initial toler-
ances and temperature effects results in an
much wider excursion. For all practical purpos-
es, a true fixed off-time technique will not
work.
Incorporated into the UC3861 family of ZVS
controllers is the ability to modulate this off-
Fig. 25 -- The UC3861-64 ZVS Controllers -- Block Diagram
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