Texas Instruments UCC25640EVM-020, User Manual, Page: 15 / 40

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Performance Data and Typical Characteristic Curves
15 SLUUBX3B – June 2019 – Revised November 2019
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UCC25640EVM-020 Evaluation Module
9 Performance Data and Typical Characteristic Curves
9.1 UCC25640EVM-020 Standalone Standby and Light Load Power
Table 4 lists the total standby and light load power measurement for the standalone EVM. The average
input power is measured over a two minute interval.
Table 4. Standalone Standby Power
I
OUT
(mA) V
OUT
(V) P
OUT
(mW) V
IN
(V) I
IN
(mA) P
IN
(mW)
0 9.740 0.000 389.826 0.115 44.666
10 9.739 97.392 389.823 0.393 153.093
20 9.739 194.772 389.820 0.672 261.815
50 9.739 486.925 389.814 1.514 590.186
100 9.738 973.820 389.807 2.914 1135.799
9.2 PFC Boost Front End Standby Power
9.2.1 Overview
UCC256404 includes a high voltage startup feature. This feature enables the controller to be powered by
a wide AC input, eliminating the need for an external supply to power both the PFC and LLC. When AC
power is applied to UCC256404, a JFET initially charges the VCC capacitor to provide the energy needed
to start the PFC and LLC power system. Once running, power for the PFC and LLC controllers is derived
from a bias winding on the LLC transformer.
Figure 7 illustrates the described startup sequence.
UCC256403 does not include the high voltage startup feature and requires an external power supply as
described in
Section 5.3 .
Figure 7. PFC LLC Startup Sequence