Interleaved Buck and Dual Forward Converter
Original Publication Date: 2001-Oct-27
Included in the Prior Art Database: 2003-Jun-12
The combination of existing industry solutions for current uPs implemented with the dual forward soft switching converter will provide the high efficiency, high current, and fast di/dt (transient response) required by next generation microprocessors. Since next uPs require higher current up to 100-300A, higher efficiency, and very fast transient response (di/dt) up to 300A/uS, there is a need of new DC/DC topology to meet these requirements. The next N-way processors for mid-range and high-end systems will require a +48V distributed architecture for better efficiency when the +12V input from the AC/DC power supply will no longer be feasible for high power. When the DC bus is either +48V or higher, the isolation between the input and output of the DC/DC converters have to be achieved in order to meet the safety regulations. This topology combines the advantages of current non-patented industry multiphase topology with IBM patent pending dual soft switching forward topology to solve all the above described problems. The existing industry multiphase (interleaved) topology provides the advantages of high efficiency, better thermal, fast di/dt, and small form factor but it does not provide the isolation between primary and secondary of the converter. By combining the multiphase topology with dual soft switching forward converter, the converter will not only solve all the next generation microprocessors power converter requirements, but will also provide the isolation required by safety such as UL and CSA. The output voltage is regulated by the front end multiphase which can be scaled in as many phases as it requires to provide the output current. The main power stage consists of a push pull converter that switches at a fix duty cycle. The power stage switches are operated in Zero-Current-Switching at turn-on, so the efficiency will be higher than conventional hard switching or present non-isolated multiphase VRM techniques. The Zero-Current-Switching is achieved by two coupling capacitors connected between reset winding of the first transformer L4, and the drain of the second switch (Q6) and Vs between reset winding of the second transformer, L6, and the drain of the first switch (Q5). The output needs very small output inductors since the current flow through the output on both half cycle, so this will result in fast di/dt. Note: the multiphase can be located in the primary or secondary side of the converter.