Energy Efficiency

(Thrust leader: Ali Niknejad, UC Berkeley)

Figure 4. The research tasks include multi-stage DC-DC converters pushing the boundaries of efficiency in high conversion ratio (24V-to-1V) applications (Top left, H. Lee, UT Dallas) and 3D packaged vertically integrated two-stage series DC-DC and switched-capacitor converters (Top right, H.-P. Le, UCSD). Increasingly the focus of the research is at the intersection of power, energy, and AI/ML applications. Edge processing requires orders-of-magnitude reduction in inference AI power/energy consumption (Middle left, Bottom left and middle, M. Seok, Columbia University). This thrust also includes efforts on Switching-Mode Active EMI filtering using GaN transistors (Middle right, A. Hanson, UT Austin) and techniques to improve the transient response to higher loads for SIMO converters (Bottom right, C. Huang, Iowa State U.)

 

The TxACE Energy and Efficiency thrust encompasses cross-cutting research tackling energy efficiency in electronic systems, spanning from advanced power management, all the way to the emerging fields of low power machine learning/AI for edge computing and applications to IoT sensor nodes. The power management research forms the foundation of the center and tackles important issues of efficiency in complex system applications, for example in digital multi-core systems that use single inductor multiple output (SIMO) DC-DC converters, addressing modeling and simulation and optimization of performance (transient response, EMI, security) using non-linear computational control, mixed- signal techniques, machine learning and AI, and adaptive algorithms and design automation. This thrust investigates non-conventional hybrid architectures and integration strategies for applications in computing, large-ratio conversion from 48V down to 1V and below, and battery charging applications. Many of the solutions employ mixed-signal techniques, exploiting advanced CMOS digital nodes alongside GaN power devices, and utilize novel scaling-friendly analog architectures to improve the control and expand the flexibility of the overall system.

Energy Efficiency Thrust

Category Accomplishment
Energy Efficiency (Circuits) Active EMI filtering with feedback is used to reduce the volume burden of additional passive filtering by a factor of 20. This approach uses a switch-mode amplifier operating at 30+ MHz with GaN devices with a fractional-order filter to achieve high loop gain over a limited bandwidth. Experimental results with this approach demonstrated 40-60 dB of current attenuation at the first several harmonics, which reduces the volume burden of additional passive filtering. This circuit incurred a 0.4% efficiency penalty on a 120W prototype boost converter, even with 66% ripple ratio. (2810.068, A. Hanson, UT Austin)
Energy Efficiency (Circuits) Most traditional SIMO (single inductor multiple output) converters operate with fixed time multiplexing ordering to handle the multiple outputs with linear PWM control, which limits response to a large and fast load transient. Two non-linear and non-ordered control strategies that overcome these are demonstrated. The first chip prototype demonstrates a total load transient of 2A/ns, which is significantly larger and faster than that of traditional SIMO converters. The peak efficiency of 96.1% is also higher than the state-of-the-art. The second prototype achieves 96.1% efficiency and a transient speed of 2.1A/ns and a maximum current capacity of 2.2A. (2810.079, C. Huang, Iowa State University)
Energy Efficiency (Circuits) Power management circuitry such as DC-DC converters are often designed for the rarely occurring worst-case scenarios that increase their cost. Instead, the circuits are monitored in real time and the circuit parameters are adjusted to enable reliable operation. For example, the system periodically monitors three converter operational parameters: ambient temperature, switching frequency, and load current. Using these, an online algorithm estimates the remaining useful life of each capacitor and the converter in real time. A 24V-to-1V DC-DC converter incorporating these concepts was fabricated. The converter achieves a peak power efficiency of 93.89% at 405-mA load current, an efficiency improvement of up to 34.74% compared to the baseline design. (2810.065, M. Seok, Columbia University)