The Design And Research Of Low-voltage High-efficiency Key Circuits In Modern Portable Electronic Devices

As the development of modern integrated circuit technology, the portable consumer electronics like mobile phones, digital players, portable medical equipment are developing rapidly, which brings great attention to the design of low-voltage high efficiency integrated circuits (IC). It is not only due to the technology development to nanometer scale, but also because of the lowering trend of power supply voltage. It will be favorable to prolong the effective working time of battery-powered equipments as well as for energy saving and environmental protecting. Since the analog circuits are still widely applied to power supply system and other key modules in modern electronic systems including the portable devices, the low-voltage design of analog circuits faces more challenges than that of the digital ones due to their different working modes.In view of these, this dissertation focused on the research on low voltage high efficiency design of the power supply system for portable devices and other common modules. Meanwhile, the dissertation gives attention to the prospect of developing trend in related fields. The main contents and innovation include:1. The breakthrough in new energy research makes micro fuel cell become most promising energy source for future portable devices to solve the limited-energy-density bottleneck of the lithium battery. However, the issue is that its output voltage is too low to adapt to applications in these circuitries. To solve this problem, a novel low-voltage startup module is put forward, which employs a dynamic substrate biasing technique to implement sub-threshold operation of boost converters. Moreover, its process independence reduces the fabrication cost. In order to improve its coordination with boost converter, a three-stage control method together with a power supply switching module is put forward, which features the different control strategies for power supplying in different stages of the controller. In addition, to solve the issue that the fuel cell may fail to support supplying load and charging battery simultaneously due to its low power density while the lithium-ion battery charging is necessary during the operation of device. Thus, a dynamic power allocation method based on single-inductor dual-output topology is put forward. This method can limit the input power as well as suppress cross modulation. And a constant-current/constant voltage charging algorithm is also embedded.2. The voltage reference is almost necessary for all electronic system. To come up with a design of voltage reference with low supply voltage is one of technical difficulties in analog circuit design. This dissertation puts forward a novel circuit design of low voltage reference based on sub-threshold operation. To improve its integration and compatibility further, a full-CMOS structure is proposed, which has excellent process compatibility with logic process as well as very low power consumption. The reference can be widely applied to micro-power electronic applications such as implantable probe.3. As to the back light source, the main energy dissipation component in portable devices, this dissertation proposes an adaptive-output-voltage-adjusting scheme to improve the efficiency of the system. This scheme is based on the combination of step-down switch converter and linear current regulator, which can adapt to the LED parameters and working temperature variations, and set the operating point of the switch converter automatically. By eliminating the device screening, it saves the cost and time.All the proposed low-voltage low-power design schemes and prototypes have been tapped-out and tested. Results verified the feasibility of the designs.