Two-loop controlled ultra-high frequency DC-DC converter.

摘要

In this research, an ultra-high frequency dynamically adaptive power supply targeted for radio frequency PA's is conceived, designed and simulated with a discrete integrated circuit. The research presented in this thesis can be divided into four major contributions to the power management technology: switching frequency of 100 MHz, delay less than 9 ns with high efficiency, very high bandwidth and reduced size of 9000 mum2.;Communication oriented signals have bandwidth in the range of 3-30 MHz. The switching frequency of the converter should be at least two times that of the signal (Nyquist law) for perfect tracking. In this work, a new control strategy along with custom tailored design at transistor level was proposed and implemented. Each of the above mentioned four contributions are functions of each other. This is an optimization problem with a trade off between efficiency and performance. The design process was carried out in different levels.;The design of synchronous converters for ultra high frequency with high efficiency was carried out by considering a non ideal model which can capture the mechanical and thermal stress. The filter elements influence the operation of the converter in dynamic mode, especially due to the energy transfer operation with respect to the reference signal. To solve energy storage issue a monolithic planar inductor suitable for high frequency with proper Q factor was designed. Any available MOSFET in AMI 0.5 mum technology was not a good candidate due to the resistance and intrinsic capacitance. An equation was derived for maximizing the efficiency of the switches as a function of channel width for a given length of 0.5 mum.;Small signal analysis was carried out and the stability of the system was verified. Analysis leads to the necessity of having a controller for both input and load variations. Two-loop controller was proposed for the system to overcome any transients from the input and load side. A novel controller with inner loop of one cycle controller and an outer loop with a lead compensator was modeled and simulated. Because of the slew rate and bandwidth limitations conventional operational amplifiers resulted in very poor performance. This leads to the development of the controller based on current conveyor and high speed voltage comparator. The proposed current conveyor is the novel one with very high efficiency, excellent bandwidth of 10 GHz and deprived of saturation. A new voltage comparator is proposed for high speed operation.;An integrated circuit for decoupling the gate signal into two non overlapping signals for converter was designed. A driver circuit was incorporated along with the adaptive delay circuit to drive the switches of the synchronous converter with required gate power. Total area occupied by the controler is 6000 mum 2. The outer loop was designed with current conveyors to constitute a PI controller.;The designed controlled converter now operates at desired RF levels, with power consumption being as low as 45% of that of the systems that are currently in use. The controller design has been completed on 0.5 micron technology, using the AMI Semiconductor technology. The entire chip occupied 0.009 mm2 with one third going for the converter part. The layout will be sent for fabrication to MOSIS and testing of the results would follow thereafter. Current outer loop will be replaced by a TYPE-III amplifier which will provide a more robust operation.;Applications of the controlled converter have been discussed with respect to Handheld Wireless Devices and various inputs that can qualify for power management. The chip is so designed that it can accommodate these inputs in order to provide more effective feedback to the system and thus provide power at the threshold level when required, thereby prolonging the battery life. The chip is expected to increase the life of the battery at least 4 times longer than the fixed controlled system or two times compared to the dynamic converter operating with conventional PWM control.