-50mV

-150mV

90%TSR(N-1)

TSR(N)

90%TSR(N)

TSR(N+1)

ISR

VDS

VGATE

t

t

t

16

UCC24612

SLUSCM5A – AUGUST 2017 – REVISED FEBRUARY 2018

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Feature Description (continued)

Figure 18. Forced Proportional Gate-Drive for Deep CCM Operation

For Flyback converters, the SR current starts from its maximum amplitude and keeps reducing. Proportional gate

drive is only enabled at the later part of the SR current conduction period. However, for other topologies such as

LLC or Active Clamp Flyback, the SR current starts from lower amplitude and then increases to a higher

amplitude. To prevent the proportional gate drive from being enabled at the beginning of the conduction period,

proportional drive is disabled for the first 50% of the SR conduction time, based on the previous cycle SR

conduction time. In this way, the proportional drive is always enabled on the current falling slope and minimizes

impact on the conduction loss.