DC-DC converter utilizing hysteretic current-mode control for low-voltage microprocessor systems with power management

A DC-DC converter with high efficiency and good voltage regulation is required for battery-operated microprocessor systems. To fully utilize battery energy, microprocessors use power management to reduce power dissipation. Microprocessors require good voltage regulation for reliable operation and long life, necessitating a DC-DC converter between the battery and microprocessor. A synchronous buck converter is chosen as the DC-DC converter.; It is shown that for high efficiency at light load, the DC-DC converter should operate in the discontinuous conduction mode to provide charge pulses at varying frequencies as needed for output voltage regulation. For high efficiency at heavy load, the DC-DC converter can be operated in the continuous conduction mode to reduce output voltage ripple and possibly improve efficiency.; A modified hysteretic current-mode control technique is proposed and shown to provide good voltage regulation at light load and heavy load and also when transitioning between different load levels. Steady-state operating conditions are determined and small-signal discrete-time and averaged continuous-time models are developed to analyze the dynamic behavior of the synchronous buck converter with the proposed control method. These models use piecewise-linear approximations for the system waveforms. Analysis is compared with measured results.