Infineon XMC Series - Fast Average Current Mode PCC

Introduction to Digital Power Conversion
XMC4000/1000 Family
Modulation
Application Guide 65 V1.0, 2015-01
6.5.2 Fast Average Current Mode PCC
The steady state duty-cycle-to-output CCM Average Current through the inductor (L) is a DC current
on half the ∆I
L
ripple height.
∆I
L
= DTV
L
/ L where:
V
L
= V
IN
- V
OUT
or = -V
OUT
toggling across the inductor
D = duty-cycle.
To maintain a fixed ACC level, the peak current must align to V
IN
variations.
Steady State ACC PCC Transfer Function with or without Peak Current Slope Compensation
There are 2 examples in the next figure. The example at the top demonstrates the necessity of an
aligning Peak Current that follows the input voltage variations (e.g. from V
IN1
to V
IN2
), in order to keep
the average current unchanged. On a short term basis this cannot be performed by software, only in
the long-term control loop.
The bottom example demonstrates the advantage of Slope Compensation. A steady state duty-cycle-
to-output maintained CCM inductor average current on



∆I
L
ripple range, independent of the input
voltage, on a short term basis, without CPU, due to an inherent loop.
Figure 49 ACC PCC Transfer Function – without or with Peak Current Slope Compensation