Switch node QBd is valley switching and node QDd has achieved ZVS. Please refer to Figure 7-13 and Figure 7-14. It is not uncommon for switch node QDd to obtain ZVS before QBd. This is because during the QDd switch node voltage transition, the reflected output current provides immediate energy for the LC tank at the switch node. Where at the QBd switch node transition the primary has been shorted out by the high-side or low-side FETs in the H bridge. This transition is dependent on the energy stored in LS and LLK to provide energy for the LC tank at switch node QBd making it take longer to achieve ZVS.

VIN = 390V

IOUT = 5A

Figure 7-11 Full-Bridge Gate Drives and Primary Switch Nodes (QB_d and QD_d)

VIN = 390V

IOUT = 10A

Figure 7-13 Full-Bridge Gate Drives and Switch Nodes (QB_g QB_d)

VIN = 390V

IOUT = 5A

Figure 7-12 Full-Bridge Gate Drives and Primary Switch Nodes (QD_g QD_d)

VIN = 390V

IOUT = 10A

Figure 7-14 Full-Bridge Gate Drives and Switch Nodes (QD_g QD_d)

VIN = 390V

IOUT = 25A

Figure 7-15 Full-Bridge Gate Drives and Switch Nodes (QB_g QB_d)

VIN = 390V

IOUT = 25A

Figure 7-16 Full-Bridge Gate Drives and Switch Nodes (QD_g QD_d)

When the converter is running at 25A, both switch nodes are operating into zero voltage switching (ZVS). It is also worth mentioning that there is no evidence of the gate miller plateau during gate driver switching. This is because the voltage across the drains and sources of FETs QA through QD transitioned earlier.

VIN = 390V

IOUT = 50A

Figure 7-17 Full-Bridge Gate Drives and Switch Nodes (QB_g QB_d)

VIN = 390V	IOUT = 50A
ZVS maintained from 50% to 100% output power

Figure 7-18 Full-Bridge Gate Drives and Switch Nodes (QD_g QD_d)