Fully Integrated High-Voltage DC-DC and AC-DC Conversion

Table of Contents

1. Frontmatter

2. Chapter 1. Introduction

   Tuur Van Daele, Filip Tavernier

   Abstract

   High-voltage power sources surround us, yet emerging low-power applications call for low supply voltages. This chapter explores the origins of this substantial voltage gap and discusses why current solutions rely on multiple external components to bridge it. It motivates the need for complete integration and examines the potential of switched-capacitor converters to achieve this goal.

3. Chapter 2. Fundamentals of Fully Integrated Switched-Capacitor Converters

   Tuur Van Daele, Filip Tavernier

   Abstract

   The preceding chapter proposed the switched-capacitor converter (SCC) as a solution for fully integrating a high-voltage converter in the milliwatt power range. Before exploring SCCs at 400 V DC input voltage, this chapter delves into the fundamentals of fully integrated switched-capacitor DC-DC converters.

   Initially, it elucidates the operational principle underlying an SCC. This is followed by an analysis encompassing the equivalent model of the SCC and its losses, while also examining the trade-off in relation to power density. Concluding the chapter, control strategies are examined to manage load and line variations.

4. Chapter 3. Fully Integrating a High-Voltage DC-DC Converter

   Tuur Van Daele, Filip Tavernier

   Abstract

   Chapter 1 motivated the suitability of switched-capacitor converters (SCCs) for achieving a high input voltage (\({\sim }400\,\mathrm {V}\)) and complete integration within the milliwatt power range. Therefore, in Chap. 2, the fundamentals of SCCs were elucidated. However, state-of-the-art fully integrated SCCs are confined to a maximum input voltage of 42 V. This chapter targets to push this maximum input voltage to 400 V DC. The proposed topology overcomes the key challenges associated with the increasing input voltage, which include diminished component quality and heightened parasitic losses.

   This chapter starts by elaborating on the specifications and discussing the shortcomings of state-of-the-art approaches. The following part examines the key challenges at high input voltages and proposes a topology to tackle these challenges. Subsequently, the implementation details are covered, including the customization of high-voltage capacitors and drivers, as well as an improved control circuit. Finally, Sect. 3.6 presents the measurement results and compares them with the state of the art.

5. Chapter 4. Gearboxing a Fully Integrated High-Voltage DC-DC Converter

   Tuur Van Daele, Filip Tavernier

   Abstract

   The previous chapter developed a fully integrated high-voltage switched-capacitor converter (SCC) with a DC input voltage. This chapter, along with the subsequent one, targets an AC input voltage, thereby unlocking additional applications powered by the ubiquitous AC mains. While facilitating an AC input voltage, the other specifications of Sect. 3.1 such as complete integration and high power density persist.

   In prior fully integrated AC-DC converters, the AC-DC stage not only rectifies the AC input but also performs the down-conversion. They employ a capacitive divider, leveraging the suitability of capacitors for integration. However, the combination of the low AC mains frequency (50 or 60 Hz) and the low capacitance density on-chip results in a high input impedance. This high impedance prevents the flow of large currents, ultimately restricting the power density to values \({\leq }{1.6}\,\mu \mathrm {W/mm}^{2}\).

   To overcome the dependence on the mains frequency, this chapter investigates a fully integrated DC-DC stage following the AC-DC stage to perform the down-conversion. The ability to independently set the switching frequency of the DC-DC converter, irrespective of the AC mains, enables higher power densities. This approach requires a DC-DC converter handling the slowly varying rectified AC input, spanning from 0 to 325 V (assuming the European mains). The DC-DC converter introduced in the previous chapter is incompatible with this input range due to its fixed ideal voltage conversion ratio (iVCR). In response, this chapter extends the high-voltage SCC from the preceding chapter into a multi-ratio (or gearbox) converter, as a first step toward AC-DC conversion.

   The chapter starts by explaining why a wide-input-range DC-DC converter can handle a rectified AC input voltage. The following part shows that state-of-the-art fully integrated DC-DC converters cannot handle the input voltages required for the AC-DC application and delves into the specific challenges. To address these challenges, a high-voltage multi-ratio DC-DC topology is proposed. Subsequently, the implementation details are presented, covering the high-voltage driver design and high-voltage input sensing. Finally, this chapter shows the measurement results obtained from the prototype and compares them with state-of-the-art solutions.

6. Chapter 5. Fully Integrated AC-DC Converter for High Power Density

   Tuur Van Daele, Filip Tavernier

   Abstract

   The preceding chapter introduced a fully integrated DC-DC converter featuring a 31–325 V DC input range. This chapter extends this DC-DC converter into a fully integrated AC-DC converter with a high power density. While the DC-DC converter covers a broad range of mains-rectified AC inputs, it cannot bridge the zero-crossing. Addressing this challenge mandates a sizeable buffer capacitor, imposing constraints on both integration and power density. Consequently, this chapter searches for topology techniques to minimize the size of the buffer capacitor.

   This chapter commences by discussing state-of-the-art AC-DC converters and their limitations. It subsequently delves into the challenges entailed in the complete integration of an AC-DC converter and proposes a topology to overcome these obstacles. Section 5.4 details the implementation of this topology, encompassing the control, buffer capacitor, and drivers. To conclude, this chapter demonstrates the measurement results obtained from a prototype and compares them with state-of-the-art approaches.

7. Chapter 6. Conclusion

   Tuur Van Daele, Filip Tavernier

   Abstract

   This chapter provides an overview of the work. It begins with the need for fully integrated converters capable of handling high DC and AC input voltages. It then summarizes techniques discussed to advance switched-capacitor converters to meet these requirements.

8. Backmatter