Introduction to Digital Power Conversion
XMC4000/1000 Family
PWM Generation
Application Guide 42 V1.0, 2015-01
4.14 Half-Bridge LLC Control - Synchronous Rectification using CCU4
A single CCU4 CAPCOM unit is capable of driving an entire LLC converter with synchronous rectifier.
Dead-time insertions are implemented in all switch commutations.
The MOSFETs in the rectifier stage offer lower voltage drop than diodes do for high currents. The
control paths to Q
3
,Q
4
assume isolation.
Figure 31 PFM – Using Half-Bridge LLC – Synchronous Rectification
LLC Control by Matrix-Interaction Paths in the Timer Cell Pair Setup with CC40/41 and CC42/43
All four timers work in single-shot mode. The CC40/41 timer pair interacts by alternating start requests
on a period match. However the timer CC42 is acting as a slave to the timer CC40: It will start the
CC42 on a compare match. This relationship and action is the same from timer CC41 to timer CC43.
LLC Control by Frequency, Dead-Time Delays and PWM Tuning
Frequency is changed by simultaneous period register updates by hardware (via shadow transfer
requests from the software). Dead-Times are controlled individually by compare registers.
Power transfer tuning can be accomplished by add-on control of compare registers, or by shortening
the CC42/43 single-shots.
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