We design an error feedback controller using the regulator theory for stabilizing a boost converter, subject to disturbances, around a desired equilibrium point. The input voltage to the converter is a constant whose nominal value is known; but its actual value is not known. The difference between the nominal and actual values of the input voltage is modeled as a constant unknown disturbance. In addition, the converter is also subject to a sinusoidal disturbance current. According to the regulator theory, we derive the nonlinear regulator equations for our model of the converter. We show that these equations reduce to an equivalent first order quasilinear PDE without boundary conditions, which nevertheless has a locally unique solution. We solve this PDE via a semi-analytic approach. Finally, following a recently proposed technique for designing minimal order controllers using the solution to the regulator equations, we design an error feedback controller that stabilizes the boost converter. Simulation results demonstrating the efficacy of our approach are presented. A key contribution of this work is the solution of the regulator equations for the boost converter, which provides insights into the nature of such equations.