By Damon Huang and Yosef Zhou, Pulse Electronics
Traditionally, voltage regulation in data centers, storage systems, graphics cards, and personal computing devices relied on multi-phase buck regulators. However, the increasing demands of these applications have exposed the limitations of the traditional approach. That’s where TLVR, Trans Inductor Voltage Regulator comes into play – and magnetic structures play an important role.
TLVR introduces a novel concept by replacing traditional inductors with trans-inductors (1:1 ratio transformers). The result? A reliable and efficient power delivery solution that revolutionizes transient response and voltage regulation. TLVR has garnered widespread adoption in VR14 and related programs, but there’s still much to explore.
Join us as we dive deep into the magnetic structures of TLVR inductors. We examine the challenges they pose, such as mechanical stability, phase-phase isolation voltage, and increased costs. But fear not, as we also discuss potential solutions that pave the way for TLVR to become a widely adopted technology.
Efficiency is a key factor in any power management solution. That’s why we compare the efficiencies of TLVR and traditional VRMs, shedding light on the advantages and considerations of each approach. From core losses to AC winding effects, we analyze the intricacies of TLVR technology and the road ahead for its continued improvement.
Introduction
The Trans-Inductor Voltage Regulator (TLVR) has emerged as a promising topology for powering low-voltage, high-current, multi-phase applications such as data centers, storage systems, graphics cards, and personal computing. These systems require a reliable and efficient power delivery solution that can support processors, memory, and high-current ASICs and FPGAs.
Traditionally, voltage regulator modules (VRMs) have been used to meet these requirements. However, the increasing demands of these applications have led to the limitations of the traditional approach. The TLVR circuit was introduced proposing a novel approach that replaces the traditional inductors with trans-inductors (1:1 ratio transformers). This change dramatically improves transient response and voltage regulation and has been widely adopted in VR14 and related programs.
Despite the significant benefits of the TLVR topology, there has been little investigation of the magnetic components’ actual performance, efficiency, manufacturability, and cost. This paper aims to address this gap by reviewing both the non-TLVR and TLVR topologies and magnetic structures. Additionally, the paper will examine the circuit waveforms and 3D finite element models and provide a detailed analysis of the trade-offs between the two approaches. The analysis will include an efficiency comparison based on simulation results.
Voltage Regulator Module (Non TLVR)
Traditional VRMs commonly used in high-current applications like data centres and FPGAs employ a multi-phase buck regulator. This regulator typically consists of several tightly packed power stages with 5*6mm or 4*6mm, each with an inductor of around 6×12 mm or 6×10 mm size, and a height of 12 mm. The input voltage in these applications is around 12V, while the output voltage can be as low as 1.X V or 0.8 V.
During normal operation, one phase in the multi-phase buck regulator is turned on, while the others remain off, and continue to cycle through. While each phase will have a ripple current like that of a traditional buck converter, the currents into the output are summed, creating an overall smaller ripple. An example of the inductor current waveforms and output current ripple can be seen in Figure 2.
During a transient period, the current per phase can increase rapidly, leading to a drooping in the output voltage before the converter can respond and regulate properly. This increase in load current can be seen in Figure 3.
As the converter is not able to respond to the change in load current until the next phase switches on, the output voltage will temporarily droop, as seen in Figure 4. In sensitive processor circuits, this output voltage droop can become problematic, and novel converter approaches are needed to support more strict transient responses, especially as processor demands continue to increase.
Trans Inductor Voltage Regulator (TLVR)
The TLVR is a novel approach to voltage regulation that maintains the traditional multi-phase buck approach used in VRMs but modifies the inductors by adding an additional 1 turn inner lead, creating a trans-inductor. This modification enables the TLVR to eliminate voltage droop/overshoot during an increase/decrease in current, making it a more efficient voltage regulator.
In a TLVR circuit, all of the newly added secondary windings are placed in a series loop, with an external compensation inductor added to fine-tune the transient response. The schematic for a TLVR circuit is almost identical to the traditional VRM, with the only significant difference being the inclusion of the TLVR inductor. Figure 5 shows the updated schematic of the TLVR circuit.
This article, “Revolutionizing High Current Power Management” continues on the Pulse Electronics website in the Resources/Newsroom section.
About Pulse Electronics, a Yageo company
Pulse continues to expand its portfolio of inductors used to power processors, memory, FPGAs and ASICs in servers, datacenters and storage systems. Several recent product developments are specifically designed for use with the trans-inductor voltage regulator (TLVR) topology. For more information about TLVR products and technology, see www.pulseelectronics.com.
