An ultra-low voltage charge pump with 83.6% peak voltage conversion efficiency

The Internet of Things (IOT) facilitates communication between humans and objects, driving the advancement of wearable devices and making them more diverse in terms of functionality and style. For instance, smartwatches have evolved from simple timekeeping to capabilities such as sleep monitoring and heart rate measurement. Portable sensing devices may experience battery depletion due to prolonged usage, leading to interruptions in monitoring functions. Therefore, an energy harvesting system is necessary to sustain sensor operation. Since the available energy in environment is extremely weak, a power conversion system is required to boost ultra-low voltage to operational voltage range. As a result, a DC-DC boost converter with high conversion efficiency and extremely low operating voltage is crucial. The DC-DC boost convertor could not appropriate controlled while the input is extremely low. A start-up circuit with an ultra-low operating voltage charge pump is important. This paper presents an ultra-low voltage charge pump with 83.6% peak voltage conversion efficiency. The efficiency of proposed circuit is independent while the stages of charge pump increased when input voltage is as low as 100mV. We reduce reversion loss by biasing gate voltage of charge-transfer switch. The design was implemented by using 180-nm CMOS process.