Introduction: Zero Bias TLVR was a proposed modification of the standard TLVR topology designed to better utilize the TLVR magnetic structure. Comparing Zero Bias TLVR with to other topologies. The solution density and overall system efficiency can be improved with the new design of the Zero Bias TLVR magnetic structure.
Applications: • By relaxing the inductor ISAT requirements for a give application, we have more degrees of freedom in the TLVR inductor design. • TLVR inductance can be kept the same, but inductor size can be reduced, shrinking overall design size; TLVR inductor size can be kept the same, but inductance can be increased, resulting in increased efficiency. • Vertical power delivery requires compact designs which tends to drive switching frequency up. Higher switching frequency favors lower intermediate bus voltages, but as ASIC current increases, lower intermediate bus voltages become challenging to support due to number of 1st stage converters required and PCB IR losses. Zero Bias TLVR helps achieve small size and low switching frequency, which means the intermediate bus voltage can be increased. • Instead of optimizing Zero Bias TLVR inductor design for density, lateral power designs can be optimized for high inductance and increasing efficiency. By reducing ISAT to below 30A, primary inductance can be increased to few hundreds of nH which significantly reducing core and switching losses in the magnetics and power stages. • Traditional TLVR requires a Lc inductor to be placed on the side of the power train, increasing solution size width. Similar layout to traditional TLVR, but because the secondary side is actively driven by a phase, the Lc inductor is now part of the power train. Net result is reduced solution size width.
Summary: This paper introduced the ZB-TLVR operation theory, highlighted the benefits of different applications, and addressed the TLVR secondary winding interconnections DRC power loss. Figure 4 show the experiment setup condition and the new group ZB-TLVR. From the preliminary test results with the collaboration with Cyntec, Renesas, and MPS. ZB-TLVR shows 0.5% (1.3%) improvement at peak efficiency and 0.2% improvement (1%) at full load with 200KHz (400KHz) Fsw reduction. Using group TL, the total width can be improved by 10mm (16.8%) which largely improved power density.
