Integrated Cold Start of a Boost Converter at 57 mV Using Cross-Coupled Complementary Charge Pumps and Ultra-Low-Voltage Ring Oscillator

• Published in: IEEE journal of solid-state circuits 2019-10, Vol.54 (10), p.2867-2878
• Main Authors: Bose, Soumya, Anand, Tejasvi, Johnston, Matthew L.
• Format: Article
• Language: English
• Subjects: Charge pump; Charge pumps; Charge transfer; Circuits; Clocks; CMOS; Cold; Cold starts; Converters; dc–dc converter; Electric potential; Energy harvesting; integrated cold start; Multiplication; ring oscillator; Ring oscillators; Switches; System-on-chip; Thermal energy; thermoelectric energy harvesting; Threshold voltage; Voltage; Voltage multipliers
• ISSN: 0018-9200; 1558-173X
• DOI: 10.1109/JSSC.2019.2930911

This paper demonstrates an on-chip electrical cold-start technique to achieve low-voltage and fast start-up of a boost converter for autonomous thermal energy harvesting from human body heat. An improved charge transfer through high gate-boosted switches by means of cross-coupled complementary charge pumps enables voltage multiplication of the low input voltage during cold start. The start-up voltage multiplier operates with an on-chip clock generated by an ultra-low-voltage ring oscillator. The proposed cold-start scheme implemented in a general-purpose 0.18-μm CMOS process assists an inductive boost converter to start operation with a minimum input voltage of 57 mV in 135 ms while consuming only 90 nJ of energy from the harvesting source, without using additional sources of energy or additional off-chip components.