The rapid expansion of cloud services has significantly advanced data centers, networks, and telecommunications equipment. The number of Internet of Things (IoT) devices connected via IP addresses now surpasses the global human population. These developments have placed immense pressure on servers, storage systems, and network switches that manage growing volumes of data and video traffic, pushing infrastructure equipment to its performance limits. For power supply design engineers, the key challenge is to deliver efficient power and effective heat dissipation while minimizing energy consumption.
Engineers must balance power footprint and thermal management when working with modern processors, ASICs, and FPGAs. This paper explores the evolution of multiphase converter architectures and compares various control schemes. It introduces a new family of multiphase controllers featuring integrated current control, enabling precise cycle-by-cycle current balancing and faster transient response with zero latency in phase current tracking.
Multiphase technology has evolved to meet the demands of IoT applications. As terminal systems become more powerful, so does the need for higher processing capabilities. High-end CPUs, digital ASICs, and network processors are central to this growth, powering servers, storage, and networking equipment distributed across the network. These devices share similar power profiles, requiring high output currents—often ranging from 100A to 400A or more—depending on their complexity.
While the industry has adapted by integrating lower power states into digital loads, allowing them to consume less power when idle and peak when needed, this approach still poses challenges. Engineers must ensure that the power supply can handle over 200A of full load current and react to load steps exceeding 100A in under one microsecond, maintaining tight voltage regulation.
A common solution for end systems is the use of multiphase DC/DC buck converters, typically converting 12V to around 1V. Distributing the load across multiple phases allows for better efficiency, smaller size, and lower cost compared to single-stage solutions. This method mirrors the multi-core CPU approach, where workloads are divided among cores. Figure 1 shows a multiphase solution using 150 phases to deliver 150A to a CPU.
Figure 1: Multiphase solution with four phases
Choosing the right control scheme is crucial for optimizing power delivery. The trend in end systems favors stronger performance, compact designs, and improved power management. This translates to higher switching frequencies and lower input voltages with higher currents, which places greater demands on the control loop. The main challenge in multiphase controllers is ensuring even current distribution across all phases, both under steady-state and transient conditions.
Failure to maintain balanced phase currents can lead to thermal imbalances and oversized inductors, contradicting the goal of efficient multiphase design. A reliable control loop must monitor phase current and output voltage without delay or sampling lag.
Intersil has introduced an innovative solution using digital control technology to overcome these challenges. By implementing an integrated current control loop, the controller achieves cycle-by-cycle current balancing and fast transient response. Instead of relying on traditional voltage control methods, the Intersil controller generates a noise-free, accurate current signal through direct measurement of parameters like voltage and inductance.
This approach enables the controller to generate a detailed current waveform, as shown in Figure 2, and compensate for errors caused by aging, temperature changes, or inductive saturation. The digital loop also controls internal delays, eliminating the need for additional components.
Figure 2: Inductor current waveform
The block diagram in Figure 3 illustrates how digital signal processing enhances system response. Voltage loop compensation uses adjustable PID coefficients, and AC current feedback improves transient performance. An adjustable filter and threshold allow dynamic load changes to be injected directly into the loop, resulting in a faster response proportional to the load step.
Figure 3: Block diagram of the control loop
Integrated current control offers significant advantages, including cycle-by-cycle current balancing and fast transient response. With accurate phase current monitoring, the system remains stable under continuous load variations, ensuring even current distribution. Combined with zero-delay current feedback, this allows the device to respond quickly to load changes, reducing the need for large output capacitance.
Even for high-current CPUs, an "all ceramic" output capacitor solution can be used. Zero-delay, full-bandwidth digital current waveforms enable precise voltage positioning, mimicking the load distribution curve and avoiding the traditional analog RC attenuation seen in conventional systems. Figure 4 demonstrates the device’s ability to meet load transient requirements without a load line, stabilizing the output voltage effectively.
Figure 4: Transient response of the 90A load step
The integrated current control loop helps power modern high-current loads such as CPUs, FPGAs, and ASICs. Accurate phase current control ensures minimal output capacitance and avoids oversized inductors, making it ideal for high-performance applications.
In conclusion, the multiphase control architecture has entered the digital era, offering powerful solutions for powering modern high-current loads. The revolutionary integrated current control scheme provides excellent transient response and phase balance, along with numerous other benefits. One key advantage is the ability to adjust, control, and monitor settings through software, simplifying loop design and tuning via tools like the PowerNavigator GUI. This flexibility allows engineers to debug systems efficiently, understand power supply conditions in real time, and compensate for noise through adjustable filters and software control—without the need for board redesign.
About the author
Chance Dunlap is the Director of Infrastructure Power at Intersil, a subsidiary of Renesas Electronics. With 17 years of experience in the power electronics industry, he has worked in applications, business development, and marketing, focusing on digital power supplies and isolated power controllers. He holds six patents, has authored several technical papers, and has presented at numerous symposia and conferences. Chance earned a BSEE from Purdue University and an MBA from the University of Arizona.
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