Ultra-low Voltage Circuit Techniques for Energy Harvesting

Preface
Contents
Chapter 1: Introduction to Ultra-Low-Voltage Energy Harvesting
	1.1 Introduction
	1.2 Common Methods for Low-Power Energy Harvesting
		1.2.1 Thermal Energy Harvesting
			1.2.1.1 Harvesting Thermal Energy from the Human Body
		1.2.2 Photovoltaic Energy Harvesting
		1.2.3 Vibrational Energy Harvesting
		1.2.4 Radiofrequency Energy Harvesting
	1.3 Ultra-low-voltage Energy-Harvesting Applications
	1.4 Ultra-low-voltage Energy-Harvesting Converters
		1.4.1 Switched-Capacitor Converters
		1.4.2 Switched-Inductor Converters
			1.4.2.1 On-Chip Startup Mechanisms
			1.4.2.2 Off-Chip Startup Mechanisms
	1.5 MOS Transistor Modeling for Ultra-Low-Voltage Design
		1.5.1 DC Model of the MOS Transistor
		1.5.2 Low-Frequency Small-Signal Model of the MOS Transistor
		1.5.3 Medium-Frequency Small-Signal Model of the MOS Transistor
		1.5.4 Diode-Connected MOS Transistors
	1.6 Transistor Selection and Characterization
		1.6.1 Extraction of the Main MOSFET Parameters
		1.6.2 Comparison Between Zero-VT and Standard Transistors Operating as Diodes
	References
Chapter 2: Ultra-Low-Voltage Oscillators
	2.1 Introduction to Ultra-Low-Voltage Oscillators for Energy Harvesting
	2.2 The Cross-Coupled LC Oscillator
		2.2.1 Analysis of the Cross-Coupled LC Oscillator
			2.2.1.1 Oscillation Frequency of the Cross-Coupled Oscillator
			2.2.1.2 Minimum Supply Voltage for Oscillation Startup of the Cross-Coupled Oscillator
		2.2.2 Cross-Coupled Oscillator Design and Experimental Results
			2.2.2.1 Design of a Fully Integrated Cross-Coupled Oscillator
	2.3 The Enhanced-Swing Cross-Coupled Oscillator
		2.3.1 Analysis of the Enhanced-Swing Cross-Coupled Oscillator
			2.3.1.1 Oscillation Frequency of the Enhanced-Swing Cross-Coupled Oscillator
			2.3.1.2 Enhanced-Swing Cross-Coupled Oscillator Minimum Supply Voltage for Oscillation Startup
			2.3.1.3 The Effect of the Load on the Oscillating Frequency and Minimum Transistor Gain
		2.3.2 Enhanced-Swing Cross-Coupled Oscillator Design and Experimental Results
			2.3.2.1 Design of an Enhanced-Swing Cross-Coupled Oscillator Using Off-the-Shelf Components
			2.3.2.2 Design of a Fully Integrated Enhanced-Swing Cross-Coupled Oscillator
	2.4 The Ultra-low-Voltage Enhanced-Swing Colpitts Oscillator
		2.4.1 Analysis of the Enhanced-Swing Colpitts Oscillator
			2.4.1.1 Oscillation Frequency of the Enhanced-Swing Colpitts Oscillator
			2.4.1.2 Minimum Transistor Gain for Oscillation Startup
			2.4.1.3 Minimum Supply Voltage for Oscillation Startup
		2.4.2 Enhanced-Swing Colpitts Ocillator Design and Experimental Results
			2.4.2.1 Design of an Enhanced-Swing Colpitts Oscillator with Off-the-Shelf Components
			2.4.2.2 Design of a Fully Integrated Enhanced-Swing Colpitts Oscillator
	2.5 Comparison Between the Circuits
	References
Chapter 3: Rectifier Analysis for Ultra-Low-Voltage Operation
	3.1 Introduction to Ultra-Low-Voltage Rectifiers
		3.1.1 The Basic Half-Wave Rectifier
			3.1.1.1 The Ripple of the Half-Wave Rectifier
	3.2 The Dickson Charge Pump
		3.2.1 Analysis of the Dickson Charge Pump
		3.2.2 Dickson Charge Pump Power Conversion Efficiency
		3.2.3 Dickson Charge Pump Input Resistance
	3.3 The Voltage Multiplier
		3.3.1 Power Conversion Efficiency of the Voltage Multiplier
		3.3.2 The Voltage Multiplier Input Resistance
		3.3.3 Analysis of the Full-Wave Voltage Multiplier
	3.4 The Equivalence Between Square and Sine-Wave Signals
	Appendix: Dickson Charge-Pump Diode Power Losses
	References
Chapter 4: Rectifier Design
	4.1 Introduction to Application-Oriented Rectifier Design
	4.2 DC-DC Converter Prototypes
		4.2.1 Off-the-Shelf Converter Prototype
		4.2.2 A Wire-Bonded Converter Prototype
		4.2.3 A Fully Integrated Prototype
	4.3 Design Methodology for Cold Starters
		4.3.1 Selecting the Oscillator
		4.3.2 Cold-Starter Design
	4.4 Design Methodology for RF Energy Harvesters
		4.4.1 Matching-Network Gain
		4.4.2 Design Optimization
			4.4.2.1 Maximizing Sensitivity
			4.4.2.2 Maximizing the Output Voltage and Efficiency
	References
Chapter 5: Analysis of the Inductive Boost Converter for Ultra-Low-Voltage Operation
	5.1 Introduction to Inductive Boost Converters
	5.2 The Converter Conduction Mode
	5.3 The Ideal Boost Converter in Discontinuous Conduction Mode
	5.4 The Ideal Gain Factor
	5.5 Efficiency in Energy-Harvesting Boost Converters
	5.6 Extraction Efficiency of Ultra-Low-Voltage Boost Converters
		5.6.1 Harvesting from Known Available Power
			5.6.1.1 Insertion of an Input Capacitor
		5.6.2 Maximum Power Point Tracking
			5.6.2.1 Converter Input Impedance
			5.6.2.2 Controlling the Converter Input Voltage
	5.7 Conversion Efficiency
		5.7.1 Conduction Losses
		5.7.2 Leakage Losses
		5.7.3 Dynamic Losses
		5.7.4 Losses in the Control Block
		5.7.5 Maximizing the Conversion Efficiency
			5.7.5.1 Switches Sizing
			5.7.5.2 Switching Frequency and Duty Cycle
		5.7.6 Zero-Current Switching Schemes
	5.8 Output Capacitor and Ripple
	5.9 Input Capacitor and Ripple
	References
Chapter 6: Ultra-Low-Voltage Boost Converter for Energy-Harvesting Applications
	6.1 Introduction
	6.2 Converter Architecture
	6.3 VDD Buildup
		6.3.1 Phase A
		6.3.2 Phase B
		6.3.3 Phase C
	6.4 Control Circuit
		6.4.1 Voltage Reference
		6.4.2 Sensing Circuit
		6.4.3 Hysteretic Comparators
		6.4.4 Negative Voltage Generator
		6.4.5 Clock Source
		6.4.6 Zero-Current Switching
			6.4.6.1 Operation Principle
			6.4.6.2 The Measurement Delay and tSP
			6.4.6.3 Analytical Determination of tSP0
			6.4.6.4 Pulse Scaling
	6.5 Cold Starter
	6.6 Experimental Results
		6.6.1 Startup
		6.6.2 VDD Buildup
		6.6.3 Zero-Current Switching
		6.6.4 Clock Frequency
		6.6.5 Efficiency
	References
Index