Infineon XMC Series - Without Slope Compensation, Fixed-ON-Time (FOT) ZCD Control; Without Slope Compensation, Fixed-OFF-Time (FOFFT) PCC

Introduction to Digital Power Conversion
XMC4000/1000 Family
Modulation
Application Guide 71 V1.0, 2015-01
Figure 54 PCC Stable Area – Considering Slope Response upon Input Voltage +V
IN
Variation
6.5.6 Without Slope Compensation, Fixed-ON-Time (FOT) ZCD Control
There are current mode control loops that do not suffer from parasitic sub-oscillations, such as Fixed-
On-Time (FOT) ZCD (Zero-Crossing-Detection) Mode Control, where the current reflections are
forced in to stability by the Fixed On-Time term.
Figure 55 Modulation – ZCD FOT – Stability Recovered w/o Slope Compensation
6.5.7 Without Slope Compensation, Fixed-OFF-Time (FOFFT) PCC
In Fixed Off-Time (FOFFT) switch mode, with PCC in the feed-back loop, the converter is able to work
even in deep CCM, without sub-harmonic oscillations. No current slope compensation add-on
techniques are required in this control loop because of the stabilization effect by the FOFFT.
Figure 56 Modulation – PCC FOFFT – Stability Recovered w/o Slope Compensation