Design Of Boost DC-DC Controller Based On On-Chip Filter Current Sensing Technique

With the rapid development of information technology and rapid growth of consumer electronics market, smaller and more efficient switching power supplies have been widely applied. And the performance of power supply modules will directly influences the overall power consumption, reliability and cost of a electronic system. Therefore, the key specs of a switching power supply such as efficiency, stability, dynamic performence, integration level, etc., have become the focus on which the researchers pay attentions.Boost DC-DC converters are usually applied to portable devices, wireless communication systems as well as LED, OLED, CCD drivers, etc., where high performance and efficiency are required. Considering that the performance of switching power supply is mainly determined from its control method and corresponding design scheme, this thesis chose a peak current mode control scheme for proposed boost DC-DC system in order to gain fast input and output response.Different from traditional voltage control mode, a current-sensing element is needed for current control mode to monitor current. In general, as a simple solution, a series resistor placed at the power path is used to sever as it. Unfortunately, the resistor will cusume additional power which could be considerable especially while load current is large. To avoided this power cunsumption, a novel current-sensing method based on filter was adopted.The key of this current-sensing method is the matching design of the filter, which depends upon whether the exact values of the inductance and its effective serie resistor are learnt, which challenges the realization of on-chip current-sensing. In this thesis, an on-chip self-calibration system was introduced to ensure the on-chip gm-C filter match with the external LR network.Another challenge is that by filter-based current sensing method,it is necessary for filter to detect the voltage across the inductor. Since the voltage has a wide variable range and high frequency, design of active filter and related system that is matched to it become the key issue. Here a gm-C filter with beyond rail input voltage range was proposed, which results in high speed and wide input voltage range. Beside, it is independent to the control system of converter so as to symlify the design. As a result, the current sensing block could be used as a true IP. It is not only fully qualified for Boost topology, but also suitable for different inductor current sensing system including Buck and Buck-Boost converter.The circuits and system are designed and accomplished in 1.5μm BCD technology. It is simulated in Candence Specter S enviroment. The simulation results showed that all the circuits and system work well and the expected specifications were successfully achieved.