12 \ VISHAY An Automotive Grade Above
Figure 4: Simplified schematic of the main DC/DC converter stage (Source: Vishay)
In the main DC/DC section of the charger (Figure 3 and Figure
4), the Vishay SQW61N65EF MOSFETs (M1-M4 and M5-M8 in
Figure 4) are configured in H-bridges across the positive DC
link stage (M1-M4) and the negative DC link stage (M5-M8 in
Figure 4). The two stages are symmetrical, and each form an
LLC resonant converter that switches from 150kHz to 250kHz.
Each stage utilizes two transformers to minimize the size and
profile compared to a single transformer implementation. The
two stages work independently, but in the case of a difference in
the respective output voltages, they shut down simultaneously to
Figure 3:
The 22kW OBC main
DC/DC converter stage
(Source: Vishay)
" As the trend toward fast-charging systems
continues, the power demanded from OBC has
been steadily increasing from 5.5kW to 11kW,
and now up to 22kW."
