Key Technologies Of Low Voltage Low Power Power Management In Portable Medical Electronic Devices

With the development of modern integrated circuit technology, the cost of electronic devices has been cutting down and the system integration level has been constantly improved. This has become a strong impetus to the development and popularization of portable medical electronic equipment. However, the power management system design also faces many critical challenges as people require more power performance for environment-&-application-specific systems. Designing a long-lifetime stable working battery powered system and accommodating the system to new energy technology batteries which provides very low voltage would be important for these days’ engineers.In view of this, this paper focuses on several critical issues in developing low-power high efficient power management systems in portable medical electronic devices. The main contents and innovations include:1. The development of new energy technologies and portable medical devices has broken the bottleneck of portable medical electronic equipment technology. However the output voltage of solar cells and thermal batteries is too low. In this regard, this thesis proposed an ultra-low voltage DC-DC conversion technology to realize a boost converter which is powered by a sub-threshold voltage source and is able to boost the input voltage into a usable output voltage level. The boost converter obtains the start-up energy with the help of an on-chip ring-oscillator and a multi-stage charge pump. A voltage detector is designed with optimized power consumption and area. An open-loop COT controller is used to simplify the control circuit. The system is verified by simulation and experimentation.2. Overall power consumption of the power management system is particularly important in the portable medical electronic equipment applications where total power consumption is very low. This thesis proposed a COT controller based on a critical conduction mode to reduce the complexity and power consumption of the controller while maintaining its performance. A power stage model is used to seek a best tradeoff between chip area, power consumption and efficiency. The specially designed sub-threshold voltage reference circuit and hysteretic voltage comparator help to control total power cost. The system is verified by simulation and experimentation.3. Charge pumps are known for their small size and low cost and low EMI because of its non-inductor nature. This thesis proposed a variable frequency control technology with feedback for charge pumps to achieve high efficiency and low output voltage ripple. An detailed model for the charge pump power stage is given to guide the system design. The simulation and testing results showed that the new control technique have a great advantage compared to conventional charge pump control schemes.