A high-resolution hybrid randomized modulation scheme for switched-mode DC-DC converters

Abstract

Switched-mode dc-dc converters are routinely employed in the power supply section of low-power electronic systems, such as biomedical implants, to convert a supply voltage from one voltage level to another voltage level. The switched-mode dc-dc converter employs a modulator to modulate the output pulses. In Pulse Width Modulation (PWM)-based digital modulators, an N-bit counter is employed to generate 2N possible pulse widths, where the value of N is relatively small (≤10). As a consequence of small N, the output has limited resolution that may cause steady-state limit cycles in closed-loop converters [1]. The limit cycles translate to harmonic distortion in the output power spectrum. The impetus is, therefore, to improve the output resolution without increasing N that would otherwise increase the clock frequency and power dissipation of the counter, and without causing harmonic distortion or limit cycles.