A 12V-to-0.9V active-clamp forward converter power block with planar transformer, standing slab inductor and direct edge solder to motherboard

DC-to-DC power supplies for CPUs or GPUs are critical components on the motherboard of modern computer systems. Converting an intermediate bus voltage (e.g. 12 V) to the core voltage (∼0.9 V) of CPUs or GPUs must be efficient, compact and cost effective. This paper proposes an active-clamp forward converter (ACFC) power block to supply core voltage on a motherboard. The ACFC power block can be individually tested prior to assembly and vertically soldered onto the motherboard to save motherboard area. A low loss, compact planar transformer is designed into the ACFC power block PCB. A custom, standing slab inductor not only provides high inductance and high saturation current but also helps to mechanically support the power block. A one-piece copper winding connects the transformer to the inductor, thereby reducing the DC loss in the current path. Experimental results show a peak efficiency of 90.4% with a 12 V input and 0.9 V output for an output current of 25 A.

[1]  Bor-Ren Lin,et al.  Analysis, design, and implementation of an active clamp forward converter with synchronous rectifier , 2006, IEEE Transactions on Circuits and Systems I: Regular Papers.

[2]  F. D. Tan.  The forward converter: from the classic to the contemporary , 2002, APEC. Seventeenth Annual IEEE Applied Power Electronics Conference and Exposition (Cat. No.02CH37335).

[3]  S.S. Ang,et al.  Digital control of a voltage-mode synchronous buck converter , 2006, IEEE Transactions on Power Electronics.

[4]  Qing Lu,et al.  Model and design of PCB parallel winding for planar transformer , 2003 .

[5]  Michael A. E. Andersen,et al.  Optimal Design and Tradeoff Analysis of Planar Transformer in High-Power DC–DC Converters , 2012, IEEE Transactions on Industrial Electronics.

[6]  Kazunori Watanabe,et al.  A 0.6 V Input CCM/DCM Operating Digital Buck Converter in 40 nm CMOS , 2014, IEEE Journal of Solid-State Circuits.

[7]  Rik W. De Doncker,et al.  Unified Control Strategy Covering CCM and DCM for a Synchronous Buck Converter , 2007, APEC 07 - Twenty-Second Annual IEEE Applied Power Electronics Conference and Exposition.

[8]  F. C. Lee,et al.  Design consideration of the active-clamp forward converter with current mode control during large-signal transient , 2003 .

[9]  Sung-Sae Lee,et al.  High-Efficiency Active-Clamp Forward Converter With Transient Current Build-Up (TCB) ZVS Technique , 2007, IEEE Transactions on Industrial Electronics.

[10]  Peng Xu,et al.  Comparison of three topology candidates for 12 V VRM , 2001, APEC 2001. Sixteenth Annual IEEE Applied Power Electronics Conference and Exposition (Cat. No.01CH37181).

[11]  Bernhard Wicht,et al.  A 10 MHz, 48-to-5V synchronous converter with dead time enabled 125 ps resolution zero-voltage switching , 2016, 2016 IEEE Applied Power Electronics Conference and Exposition (APEC).