Spanningsconversie in CMOS met hoge conversieratio voor een efficiënte netgeconnecteerde standby

The focus of this work can be seen as making the bridge between the fields of Solid-State Integrated Circuits (IC) and Power Electronics. Multiple AC-DC and DC-DC power converters are investigated from the IC standpoint, this means a constant effort to realize converters that are fully integrated on a single chip, or have at least a very high level of integration. Moreover, it is of paramount importance to improve power conversion efficiency throughout the transport chain of energy from source (e.g., a battery, the mains) to load (i.e., the application which is the consumer). Creating new converter systems that are very efficient and integrated into chip-scale solutions enable the benefit of longer battery autonomy in portable devices, on top of enabling ever lighter and slimmer devices. In non-mobile applications, less power is required from the mains for the same functionality and consequently this helps to reduce emissions related to electricity generation, such as carbon dioxide, etc. To summarize this work, a few different research targets are introduced: 1) monolithic switched-capacitor DC-DC conversion for granular power delivery on-chip, 2) reduction of standby power in mains-connected devices through the addition of an efficient and compact auxiliary supply to provide power during standby mode, and 3) high-ratio DC-DC voltage conversion in a monolithic context. Modern integrated circuits contain more and more functionality within a single chip. These are also called Systems on Chip and examples of such systems are the Application Processing Unit chips at the heart of today’s smartphones or personal computers. Because these single-chip systems house a large amount of subsystems, it is only logical that they require multiple different supply voltages to power these functions. In the past, most required voltages were generated off-chip on the printed circuit board, in the vicinity of the chip. This approach, however, is becoming less and less viable due the growing number of desired supply voltages and the associated number of interconnection pins to get the power from the off-chip power converters to the on-chip loads. Moreover, there are other negative aspects related to this approach. Therefore, a better approach is to provide the chip with one, or a few, different supply voltages, and use on-chip power converters to further provide the desired supply voltages. This requires less package pins, and enables better regulation of the desired supply voltage, since the feedback loop can now be performed locally on the chip. The goal of this work is to enable the above. To that end, an investigation of suitable fully-integrated DC-DC converters is conducted. Specifically, the realization of a switched-capacitor DC-DC converter in a standard CMOS technology with a high power density was targeted. It is important to implement the converter in a standard CMOS process to enable co-integration with its loading circuits on the same chip. Secondly, a high power conversion density yields a lower chip area requirement to implement the converter. This work investigated circuit techniques to deliver top-notch specifications, given this context. Standby power is caused by mains-connected devices in standby mode. They have a power supply that is optimized for the active mode, where power levels may be very large with respect to the low required power level of standby, a factor 100x or more. It cannot be expected that these converters are efficient both at their nominal power (active mode) and also at light-load (standby mode) condition. Therefore, the power consumption of mains-connected devices is much higher than what it could be. Since standby power on a global scale is associated to about 10% of residential electricity consumption and 1% of CO2 emissions, standby power reduction could help to counter global warming. Therefore, this work aims to build the AC-DC converters that enable such reductions in standby power and prevent the associated emissions. The research toward high-ratio voltage conversion in an integrated context is motivated by the research conclusion, of the previous work on AC-DC converters, that switched-capacitor DC-DC converters are particularly well suited for this task. Monolithic high-ratio DC-DC conversion can, for example, be used to deliver high voltages from a standard Li-ion battery in a very small and light form factor, which is particularly important for robotic insects, where high voltages are required in the drivers that power the wings. Switched-capacitor DC-DC converters do not rely on the duty cycle to set their voltage conversion ratio, as its popular inductive buck converter counterpart does, and can therefore maintain a 50% duty cycle, regardless of the actual voltage conversion ratio. Instead, the conversion ratio is a consequence of the switched-capacitor topology. As such, it is a better candidate for high-ratio voltage conversion than the buck converter, which is this case more affected by efficiency limiting drawbacks, due to its reliance on very low duty cycles in order to obtain high voltage conversion ratios. The research in this work explores, given the system-level choice for the SC DC-DC converter, which topology is expected to yield the best performance, considering the typical context of CMOS integration.Contents Voorwoord i Abstract v Samenvatting vii Contents ix List of abbreviations xv List of symbols xvii 1 Introduction 1 1.1 Standby energy consumption . . . . . . . . . . . . . . . . . . . 2 1.1.1 Origin . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1.2 Quantifying standby power . . . . . . . . . . . . . . . . 2 1.1.3 Future trend . . . . . . . . . . . . . . . . . . . . . . . . 4 1.2 Auxiliary low-power converter for high efficiency in standby . . 4 1.3 Recent evolution of power management circuits . . . . . . . . . 6 1.3.1 From discrete to fully integrated . . . . . . . . . . . . . 6 1.3.2 From centralized to granularized . . . . . . . . . . . . . 9 1.4 Dissertation outline . . . . . . . . . . . . . . . . . . . . . . . . . 10 2 Switched-capacitor DC-DC in bulk CMOS for on-chip power granularization 13 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.2 Topology of a 2:1 step-down switched-capacitor DC-DC converter 15 2.2.1 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.3 Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.3.1 CMOS integration difficulties . . . . . . . . . . . . . . . 20 2.3.2 Flying-Well technique . . . . . . . . . . . . . . . . . . . 20 2.3.3 Intrinsic-Charge-Recycling technique . . . . . . . . . . . 22 2.3.4 Multi-phase time interleaving . . . . . . . . . . . . . . . 31 2.3.5 Avoiding multi-phase time interleaving . . . . . . . . . . 32 2.4 Converter design and optimization . . . . . . . . . . . . . . . . 33 2.5 Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 2.6 Experimental verification . . . . . . . . . . . . . . . . . . . . . 39 2.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 3 Toward monolithic integration of mains interfaces 47 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 3.2 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 3.3 Target functionality and specification . . . . . . . . . . . . . . . 50 3.4 Research challenges . . . . . . . . . . . . . . . . . . . . . . . . . 52 3.5 Bridging the voltage gap . . . . . . . . . . . . . . . . . . . . . . 54 3.5.1 Single-stage approach . . . . . . . . . . . . . . . . . . . 54 3.5.2 Two-stage approach . . . . . . . . . . . . . . . . . . . . 54 3.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 4 A single-stage monolithic mains interface in 0.35 μm CMOS 57 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 4.2 High-input-voltage architectures . . . . . . . . . . . . . . . . . 59 4.3 Proposed system architecture and operation . . . . . . . . . . . 62 4.3.1 Capacitive AC-DC step-down . . . . . . . . . . . . . . . 64 4.3.2 Shunt overvoltage protection and series regulation . . . 64 4.4 Converter model . . . . . . . . . . . . . . . . . . . . . . . . . . 65 4.5 Implementation in CMOS . . . . . . . . . . . . . . . . . . . . . 68 4.5.1 High-voltage passive components . . . . . . . . . . . . . 68 4.5.2 Regulation circuits . . . . . . . . . . . . . . . . . . . . . 70 4.6 Chip measurements . . . . . . . . . . . . . . . . . . . . . . . . . 71 4.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 5 Two-stage approach for compact and efficient low power from the mains 77 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 5.2 Subdivision of the voltage processor . . . . . . . . . . . . . . . 78 5.2.1 Synergy through cascading . . . . . . . . . . . . . . . . 78 5.2.2 Considering the low-power mains-connected context . . 79 5.2.3 Design choice overview . . . . . . . . . . . . . . . . . . . 80 5.2.4 Primary converter . . . . . . . . . . . . . . . . . . . . . 83 5.2.5 Secondary converter: high-efficiency and high-ratio DC- DC voltage conversion . . . . . . . . . . . . . . . . . . . 86 5.2.6 Summary of system considerations from full-system point of view . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 5.3 Searching for switched-capacitor converter topology candidates 89 5.3.1 Topology trends : regularity vs irregularity . . . . . . . 89 5.3.2 Switched-capacitor topology construction . . . . . . . . 91 5.3.3 Switched-capacitor topology survey . . . . . . . . . . . . 93 5.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 6 An 11/1 switched-capacitor DC-DC converter for low power from the mains 97 6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 6.2 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 6.3 System overview and operation . . . . . . . . . . . . . . . . . . 99 6.3.1 Architecture . . . . . . . . . . . . . . . . . . . . . . . . 99 6.3.2 11/1 power plant . . . . . . . . . . . . . . . . . . . . . . 102 6.3.3 Power-switch driver construction and operation . . . . . 103 6.3.4 Auxiliary rail generation . . . . . . . . . . . . . . . . . . 106 6.3.5 Control system . . . . . . . . . . . . . . . . . . . . . . . 107 6.4 Chip implementation and measurements . . . . . . . . . . . . . 110 6.4.1 Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . 112 6.4.2 Load regulation . . . . . . . . . . . . . . . . . . . . . . . 114 6.4.3 Line regulation . . . . . . . . . . . . . . . . . . . . . . . 115 6.4.4 Comparison . . . . . . . . . . . . . . . . . . . . . . . . . 117 6.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 7 Monolithic SC DC-DC toward even higher voltage conversion ratios 121 7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 7.2 Motivation and target . . . . . . . . . . . . . . . . . . . . . . . 123 7.3 Impact of CMOS integration and topology comparison parameters124 7.3.1 Integrated capacitors . . . . . . . . . . . . . . . . . . . . 124 7.3.2 Integrated switches . . . . . . . . . . . . . . . . . . . . . 127 7.3.3 Topology comparison parameters . . . . . . . . . . . . . 128 7.4 Topology comparison . . . . . . . . . . . . . . . . . . . . . . . . 129 7.5 The difference between theory and practice . . . . . . . . . . . 132 7.6 Simulation results for Dickson Star topology . . . . . . . . . . . 134 7.7 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 8 Conclusions and future work 139 8.1 Overview and conclusions . . . . . . . . . . . . . . . . . . . . . 139 8.2 Main contributions . . . . . . . . . . . . . . . . . . . . . . . . . 141 8.3 Future work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 8.3.1 Fundamental concepts . . . . . . . . . . . . . . . . . . . 142 8.3.2 Application concepts . . . . . . . . . . . . . . . . . . . . 144 A Topology survey data 147 Bibliography 159 Biography 169 List of publications 171nrpages: 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