Datasheet

RAMP/CS
VREF
UCC28250
C
S
R
S
CT
1:n
Transformer Primary
Side Current
BLANK
OUTA OUTB
UCC28250
SLUSA29C –APRIL 2010– REVISED JULY 2011 www.ti.com
Peak Current Mode Control
For peak current mode control, RAMP/CS pin is connected directly with the current signal generated from a
current transformer. The current signal must be compatible with the input range of the COMP pin. External slope
compensation is required to prevent sub-harmonic oscillation and to maintain flux-balance. The slope
compensation can be implemented by using OUTA and OUTB to charge external capacitors and use the voltage
follower to add into the sensed the current signal, as shown in Figure 43. Follow the peak current mode control
theory to select compensation slope or refer to “Modeling, Analysis and Compensation of the Current-Mode
Converter”, (TI Literature Number SLUA101).
Figure 43. UCC28250 Set Up for Peak Current Mode Control
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