David Reusch

Understanding the Effect of PCB Layout on Circuit Performance in a High-Frequency Gallium-Nitride-Based Point of Load Converter

The introduction of enhancement-mode gallium-nitride-based power devices such as the eGaN FET offers the potential to achieve higher efficiencies and higher switching frequencies than possible with silicon MOSFETs. With the improvements in switching performance and low parasitic packaging provided by eGaN FETs, the printed circuit board (PCB) layout becomes critical to converter performance. This paper will study the effect of PCB layout parasitic inductance on efficiency and peak device voltage stress for an eGaN FET-based point of load (POL) converter operating at a switching frequency of 1 MHz, an input voltage range of 12-28 V, an output voltage of 1.2 V, and an output current up to 20 A. This paper will also compare the parasitic inductances of conventional PCB layouts and propose an improved PCB design, providing a 40% decrease in parasitic inductance over the best conventional PCB design.

High-Frequency High Power Density 3-D Integrated Gallium-Nitride-Based Point of Load Module Design

The demand for the future power supplies that can achieve higher output currents, smaller sizes, and higher efficiencies cannot be satisfied with the conventional technologies. There are limitations in the switch performance, packaging parasitics, layout parasitics, and thermal management that must be addressed to push for higher frequencies and improved power density. To address these limitations, the utilization of Gallium-Nitride (GaN) transistors, 3-D integrated technique, low-profile magnetic substrates, and ceramic substrates with high thermal conductivity are considered. This paper discusses the characteristics of GaN transistors, including the fundamental differences between the enhancement mode and the depletion mode GaN transistors, gate driving, and the deadtime loss, the effect of parasitics on the performance of high-frequency GaN point-of-load (POLs), the 3-D copackage technique to integrate the active layer with low profile low temperature cofired ceramic magnetic substrate, and the thermal design of a high -density module using advanced substrates. The final demonstrators are three 12-1.2-V conversion POL modules: a single-phase 20 A 900 W/in3 2-MHz converter using enhancement mode GaN transistors, a single-phase10-A 800 W/in3 5-MHz converter, and a two-phase 20-A 1100 W/in3 5-MHz converter using the depletion mode GaN transistors. These converters offer unmatched power density compared to state-of-the-art industry products and research.

Gallium Nitride based 3D integrated non-isolated point of load module

The introduction of Gallium Nitride (GaN) based power devices offers the potential to achieve higher efficiency and higher switching frequencies than possible with Silicon MOSFETs. This paper will discuss the GaN device characteristics, packaging impact on performance, gate driving methods, and the integration possibilities using GaN technology. The final demonstration being an integrated 3D point of load (POL) converter operating at a switching frequency of 2MHz for a 12V to 1.2V buck converter with a full load current of 20A. This 3D converter employs a low profile low temperature co-fired ceramic (LTCC) inductor and can achieve a full load efficiency of 83% and a power density of 750W/in3 which doubles the power density of current integrated POL converters on the market today.

Understanding the effect of PCB layout on circuit performance in a high frequency gallium nitride based point of load converter

The introduction of enhancement mode gallium nitride based power devices such as the eGaN®FET offers the potential to achieve higher efficiencies and higher switching frequencies than possible with Silicon MOSFETs. With the improvements in switching performance and low parasitic packaging provided by eGaN FETs, the PCB layout becomes critical to converter performance. This paper will study the effect of PCB layout parasitic inductance on efficiency and peak device voltage stress for an eGaN FET based point of load (POL) converter operating at a switching frequency of 1 MHz, an input voltage range of 12-28 V, an output voltage of 1.2 V, and an output current up to 20 A. This work will also compare the parasitic inductances of conventional PCB layouts and propose an improved PCB design providing a 40% decrease in parasitic inductance over the best conventional PCB design.

Optimization of a high density gallium nitride based non-isolated point of load module

The demand for future power supplies to achieve higher output currents, smaller size, and higher efficiency cannot be achieved with conventional technologies. There are limitations in the packaging parasitics, thermal management, and layout parasitics that must be addressed to push for higher frequencies and improved power density. To address these limitations, the use of integrated 3D point of load (POL) converters utilizing GaN transistors, low profile magnetic substrates, and ceramic substrates with high thermal conductivity will be considered. This paper will discuss the effect of parasitics on the performance of high frequency GaN POLs, methods to improve the circuit layout of a highly integrated 3D integrated POL module, and the thermal design of a high density module using advanced substrates. The final demonstration is a 900W/in3 12V 2MHz Alumina DBC GaN converter which offers unmatched power density compared to state of the art industry products and research.

Evaluation of Gallium Nitride Transistors in High Frequency Resonant and Soft-Switching DC–DC Converters

The emergence of gallium nitride (GaN)-based power devices offers the potential to achieve higher efficiencies and higher switching frequencies than possible with mature silicon (Si) power MOSFETs. In this paper, we will evaluate the ability of gallium nitride transistors to improve efficiency and output power density in high frequency resonant and soft-switching applications. To experimentally verify the benefits of replacing Si MOSFETs with enhancement mode GaN transistors (eGaNFETs) in a high frequency resonant converter, 48-12 V unregulated isolated bus converter prototypes operating at a switching frequency of 1.2 MHz and an output power of up to 400 W are compared using Si and GaN power devices.

High frequency high power density 3D integrated Gallium Nitride based point of load module

The Gallium Nitride (GaN) transistors offer the capability of high efficiency at high operation frequency. This paper will discuss the characteristics of enhancement mode and depletion mode GaN transistors; the high frequency GaN converter design considerations include gate driving, reducing dead-time loss, minimizing parasitics inductance, and the three dimension (3D) technology to integrate the active layer with low profile low temperature co-fired ceramic (LTCC) magnetic substrate to achieve high power density. The final demonstrations are two 12 V to 1.2 V conversion integrated point of load (POL) modules: a single-phase10A 800 W/in3 5 MHz converter, a two-phase 20 A 1000 W/in3 5 MHz converter using the depletion mode GaN transistors. These converters offer unmatched power density compared to state-of-the-art industry products and research.

Three level buck converter with control and soft startup

The three level buck converter can offer high efficiency and high power density in VR and POL applications. The gains are made possible by adding a flying capacitor that reduces the MOSFET voltage stress by half allowing for the use of low voltage devices, doubles the effective switching frequency, and decreases the inductor size by reducing the volt-second across the inductor. To achieve high efficiency and power density the flying capacitor must be balanced at half of the input voltage and the circuit must be started up without the MOSFETs seeing the full input voltage for protection purposes. This paper provides a new novel control method to balance the flying capacitor with the use of current control and offers a simple startup solution to protect the MOSFETs during start up. Experimental verification shows the efficiency gains and inductance reduction.

Three-level driving method for GaN power transistor in synchronous buck converter

The emerging Gallium-Nitride (GaN) based power transistors offers the potential to achieve higher efficiency and higher switching frequencies than possible with Silicon MOSFETs. This paper will discuss the GaN device characteristics, and based on this, the driving method will be discussed. Then a three-level driving method is proposed to overcome the high reverse conduction loss issue of the GaN power transistor. Finally, a 12V to 1.2V Synchronous Buck converter with a full load current of 20A is built to verify the proposed method. The experimental results show that the proposed method is necessary and effective for efficiency improvement in high switching applications of GaN power transistor.

High frequency bus converter with low loss integrated matrix transformer

The trend in isolated DC/DC converters is increasing output power demands and higher operating frequencies. Improved topologies and semiconductors can allow for lower loss at higher frequencies. A major barrier to further improvement is the transformer design. With high current levels and high frequency effects the transformers can become the major loss component in the circuit. High values of transformer leakage inductance can also greatly degrade the performance of the converter. Matrix transformers offer the ability to reduce winding loss and leakage inductance. This paper will study the impact of increased switching frequencies on transformer size and explore the use of matrix transformers in high current high frequency isolated applications. This paper will also propose an improved integrated matrix transformer design that can decrease core loss and further improve the performance of matrix transformers.