IEEE Power Electronics Magazine - December 2022 - 65

BOOSTPFC + LLC
96.0
90.0
92.0
94.0
25
50
75
100 125 150 175 200
Output Power [W]
FIG 6 SmartEgg evaluation board efficiency (red plot) compared with
boost PFC-plus-LLC converter (blue line).
FIG 4 SmartEgg waveforms: input voltage (CH4, green), input current
(CH2, light blue), output voltage (CH1, dark blue), at 230 VAC, 100 W.
Efficiency plots are given in Figure 6 comparing the
evaluation board with a traditional boost PFC-plus-LLC
converter solution, both with a RM12 core for the isolation
transformer. Plots are given for 5 and 20 V outputs
with the light load efficiency improvement with the
SmartEgg circuit particularly evident at 5 V, although it is
better across the range of output power and voltage.
EMI performance of the evaluation board is given in
Figure 7, showing that the claimed size of the board can
include filtering adequate to meet CISPR22 standards,
with a good margin of around 10 dBµV, worst case.
Perhaps the most telling comparison is in the BOM
FIG 5 The SmartEgg evaluation board, a fully functional, high efficiency,
230 W peak ac-dc converter, meeting worldwide EMC and safety
specifications.
programmability. Protection includes over-voltage, overpower,
over-current, over-temperature, and brown-out.
A version of the SmartEgg circuit has been proven with
the " bridgeless " totem-pole PFC input
arrangement for a further increase
in efficiency, but at the cost of some
extra complexity.
Performance Achieved
To gauge the effectiveness of the
SmartEgg design, an evaluation board
has been prepared by Eggtronic which
is a fully functional product with reinforced
safety isolation, meeting worldwide
EMI specifications including IEC
costs. SmartEgg uses just one magnetic component compared
with at least two for the boost PFC-plus-LLC circuit
and requires just half the number of active components.
Voltage and current stresses are comparable among the
switches in the two solutions. This leads to a significant
reduction in component and build costs. This is summarized
in Table 1.
Conclusion
Protection includes
over-voltage, overpower,
over-current,
over-temperature, and
brown-out.
61000-3-2 for mains harmonics emissions with a PF of >0.9
(Figure 5). The board is rated at 150 W continuous for a
power density of 17.6 W/inch3 and 230 W peak for 20 seconds
at 26.4 W/inch3, in a package size of 3.15 × 2.44 × 1.11
inches (80 × 62 × 28.2 mm).
For ac-dc converters up to around the 1 kW level, the
SmartEgg solution offers an improvement in efficiency,
size and costs over the currently popular boost PFC stage
and LLC converter. While the traditional approach typically
requires two separate controllers
with complex design and
interactions, the single EPIC controller
from Eggtronic for the SmartEgg
topology makes the implementation
of a high-performance design easy.
This yields yet more savings in new
product design and development,
derisking the process and improving
time to market.
As in any isolated power conversion
stage, the design of the transformer
and the choice of the switching frequency have an
impact on both the power loss and the EMC performances
of the power converter.
With a particular focus on the design of the power
transformer, two possible approaches can be chosen:
December 2022 z IEEE POWER ELECTRONICS MAGAZINE 65
SMARTEGG
Efficiency [%]
IEEE Power Electronics Magazine - December 2022

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