LLC converter has the benefits of ZVS capability of switches over the full load range. The switching frequency of LLC can be pushed to MHz to increase power density. Conventionally, the magnetic inductance is treated as a constant current source during dead time, which discharges the output capacitance of primary switch to achieve ZVS. However, this view is not suitable for MHz condition, in that the magnetizing current can no longer be regarded as constant over the whole dead time. This paper investigates the detailed operating modes during dead time of LLC converter operating at neighboring resonant frequency. And a new ZVS parameter boundary is proposed. A 1-MHz half-bridge LLC prototype is built to verify the theoretical analysis.