“With the increasing use of servers and data centers around the world, the need for stable and efficient power supplies to cope with ever-increasing power consumption is growing. Electricity usage has been growing rapidly due to the need for more integrated central processing units, graphics processing units and accelerators to increase the computing speed of servers and data centers. The increase in electricity efficiency has led to the development of power supply units (PSUs) to provide high energy efficiency, fast transient response, high power density and greater power supply capacity.

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Author: MEGHANA MANAVAZHI

With the increasing use of servers and data centers around the world, the need for stable and efficient power supplies to cope with ever-increasing power consumption is growing. Electricity usage has been growing rapidly due to the need for more integrated central processing units, graphics processing units and accelerators to increase the computing speed of servers and data centers. The increase in electricity efficiency has led to the development of power supply units (PSUs) to provide high energy efficiency, fast transient response, high power density and greater power supply capacity.

High energy efficiency

Energy-efficient server PSUs can reduce the cost of operating a data center and its environmental impact by reducing power consumption and maximizing power transfer efficiency from source to load. This capability enables data centers to meet increasingly stringent energy efficiency standards (such as the 80 Plus), achieve above-average titanium-grade energy efficiency across a wide range of loads, and emit less carbon dioxide into the environment.

fast transient response

In server power applications, having fast transient response helps achieve stable and reliable system operation under changing load and input transient conditions. In addition, the system needs to meet the server power OEM’s more stringent transient response specifications: 80% to 100% load jumps between 2.5A/µS and 5A/µS. Figure 1 illustrates these parameters.

Figure 1: Transient Response Parameters

Higher power density and greater power capacity

The power consumption of servers and data centers continues to grow, requiring greater power capacity. Power technologies such as gallium nitride (GaN) enable smaller power supplies by providing greater power capacity in a smaller space. In order to achieve high power density in power systems and reduce the bill of materials for the overall system, it is critical to use real-time microcontrollers (MCUs) to control high switching frequencies.

Overcoming the Design Challenges of Server PSUs

To achieve the above benefits, server PSU manufacturers face several design challenges, such as

• Implement complex power topologies such as totem-pole bridgeless power factor correction and control algorithms, including zero-voltage switching, zero-current switching, synchronous rectification timing, and Inductor-inductor-capacitor resonant DC/DC conversion with hybrid hysteretic control.
• Enable real-time control performance to speed up control loop execution.
• Reduce power consumption while maintaining higher switching frequencies when using wide bandgap power devices such as GaN and Silicon Carbide (SiC).

To meet the ever-increasing demands for power efficiency and power density in server PSU systems, real-time MCUs need to have several key features, such as low-latency signal chains, high pulse-width modulation (PWM) flexibility and resolution, high control loop speed, and high switching frequency. Figure 2 shows an example PSU block diagram.

Figure 2: Typical dual-controller architecture for server power supplies with AC/DC and DC/DC stages

TMS320F280039C C2000 Real-time MCUs provide all of the above features and can also help meet or reduce the design budget of a server PSU. They will continue to improve the integrated real-time signal chain (detection, processing and control) with flexible and innovative capabilities. Figure 3 shows the F28003x family.

Figure 3: F28003x MCUs expand the C2000 real-time MCU portfolio

High-precision detection

The F280039C MCU achieves high energy efficiency and fast transient response for server PSUs through its integrated analog components, including multiple 4MSPS analog-to-digital converters with flexible management of conversion initiation, 11 significant bits and a post-processing block. The MCU also integrates fast analog comparators with optimized power control features such as blanking, delayed triggering, peak current mode control and slope compensation for precise power conversion.

high performance processing

Based on a 32-bit digital signal processor architecture combined with a control law accelerator, the F280039C provides over 240MIPS of real-time performance, with features such as a floating point unit and trigonometric function accelerator for higher power density and high transient response, capable of handling Complex time-critical calculations.

Flexible high-resolution controls

In high-power server PSU systems, achieving greater power supply capacity and maintaining phase-to-phase synchronization is critical, even at high frequencies. The F280039C provides PWM channels with 150ps resolution, features such as valley switching, delayed triggering, dead-time adjustment and global reloading, enabling precise control of complex power topologies and control algorithms. Integrated configurable logic blocks further enhance the flexibility of PWM and seamlessly integrate GaN technology to achieve high power density.

Additional Benefits of C2000 Real-Time MCUs in Server PSU Systems

In addition to the trend of power management and fast real-time control, the F280039C MCU can meet several other hot requirements for server PSUs:

• Online firmware update provides seamless switchover to new firmware without power interruption and minimizes software overhead with multi-bank models with multiple flash options and faster flash bank erase times.

• Communication interface from PMBus to Controller Area Network (CAN) bus (and possibly CAN-FD) for faster speeds, higher data rates and reliable host communication.

• Security through cryptographic features such as the Advanced Encryption Standard, Secure Boot, and Secure JTAG protocols address industry concerns by protecting code and data from external attacks in a more connected world.

Epilogue

The F280039C MCU extends the C2000 MCU platform to provide integrated features that help you achieve advanced real-time control while reducing bill of materials costs. The F28003x MCU family complements wide-bandgap technologies such as GAN and SiC by unlocking their full potential, enabling higher energy efficiency, higher power density, and faster response times. Easy-to-use software accelerates development for server PSU designers.