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ZVS Self-Driven 12V VRM

In conventional high frequency 12V input voltage regulators (VR), the extreme duty cycle impairs the VR's efficiency and imposes obstacles for the transient response. Moreover, large gate driver loss and body diode conduction loss raise crucial challenges to its gate driver implementation. A novel self-driven DC/DC converter for non-isolated 12V VR is proposed (U.S Patent 6,859,372). ZVS of all the MOSFETs is achieved to reduce the switching loss. By adding a transformer, the proposed topology extends its duty cycle so that both the switching loss and body diode reverse recovery loss are further reduced. This innovative self-driven concept eliminates the need for synchronous rectifier drivers which saves cost and driver loss. In addition, self-driven scheme reduces the body diode conduction loss. Although the control FET's conduction loss and the transformer loss are two limitation factors, the benefits we get override these impacts. The prototype is a 1U 1MHz VRM for server applications, and it has 88% overall efficiency at 1.3V/100A output.
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