Datasheet LTC1922-1 (Analog Devices) - 10

LTC1922-1
U OPERATIO
.and must be considered when specifying the power trans-
State 4 (Power Pulse 2)
former. If ZVS is required over the entire range of loads, a During power pulse 2, current builds up in the primary small commutating inductor is added in series with the winding in the opposite direction as power pulse 1. The primary to aid with the passive leg transition, since the primary current consists of reflected output inductor leakage inductance alone is usually not sufficient and current and current due to the primary magnetizing induc- predictable enough to guarantee ZVS over the full load tance. At the end of State 4, MOSFET MC turns off and an range. active transition, essentially similar to State 2, but oppo- site in direction (high to low) takes place.
State 1.
POWER PULSE 1 VOUT VIN L1 MA MC N:1 LOAD L2 MB MD + MF ME IP ≈ IL01/N + (VIN • TOVL)/LMAG PRIMARY AND SECONDARY SHORTED
State 2.
ACTIVE FREEWHEEL VOUT TRANSITION INTERVAL MA MC MA MC LOAD MB MD MB MD MF ME
State 3.
PASSIVE TRANSITION MA MC MB MD
State 4.
POWER PULSE 2 VOUT MA MC LOAD MB MD + MF ME 1922 F01
Figure 1. ZVS Operation
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