CMOS Implementation of Adaptive Input-Output Linearization Technique for a Boost DC-DC Converter

Linear control techniques have been widely used to control non-isolated nonlinear DC-DC converters. Type-I, type-II and type-III controllers are some of the most widely used linear control techniques. However, when a linear control is used, the plant or the DC-DC converter is linearized around a single operating point. Converters like boost and buck-boost converters are nonlinear in nature and linear controllers do not account for this non-linearity. As a result, if the operating point of the DC-DC converter changes, for efficient control, the controller needs to be redesigned. Therefore, nonlinear controllers are more suited for such DC-DC converters as they account for the non-linearities of the plant at all operating points and need not be redesigned for each of the operating points.

Adaptive input linearization (AIOL) is one such nonlinear control used to control nonlinear converters and this technique has been widely studied in this work. One of the prime reasons for using AIOL is that it works on any plant irrespective of its parameters which make it a universal controller. In this work, an AIOL controller for a boost DC-DC converter is implemented at the schematic level in 0.35µm CMOS technology using Cadence Spectre software. The output voltage range targeted in this work is 1.5V - 2V which is normally the operating voltage for many micro controllers or hand-held devices like the mobile phones. The controller is designed purely using analog components like op-amp differentiators and comparators. The main focus of this work is to improve on transient response during a step change in the input duty cycle and during load transients. The response time is then compared with the results obtained by using a type III linear compensator implemented using the same CMOS technology. Simulation results indicate that using an AIOL controller results in lesser overshoots and undershoots at the output than using a type-III compensator. Also, the load regulation provided by the AIOL controller is found to be the same at all operating points while it was found to vary with operating points with a type-III compensator.