CPES Developed Self-Driven ZVS VRM (2003)
In conventional high frequency 12-V 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 12-V 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. The prototype below is a 1U 1-MHz VRM for server applications, and it has 88% overall efficiency at 1.3-V/100-A output, which is about 5% efficiency higher than conventional practices.