A Study of All-Digital Control for Switched Mode Power Supply Using PDM Pulses with ΔΣ Modulator

Switched Mode Power Supply (SMPS) is widely used as highly efficient stabilized power supply circuit. Triangular wave comparison PWM (TWC-PWM) control is commonly used in the way to regulate voltage. However, TWC-PWM is composed of analog circuits, and it needs to be re-designed if the manufacturing processes of ICs are changed. Furthermore, the accuracy of output voltage degrades because of the non-linearity of analog circuits. In this paper, we propose the SMPS using the Pulse Density Modulation (PDM) control with ΔΣ modulator. It is possible to be composed the ΔΣ modulator by only logic circuits, therefore re-design is not need. Limit cycle oscillation occurs when DC is input to ΔΣ modulator. But it can be suppressed adding AC dither. Dither decreases accuracy of output voltage. But it can be removed by interleaving and pseudo differentiating ΔΣ modulator. We propose improving process portability and accuracy of output voltage by applying digital control. Furthermore, we propose spreading focused spectrum using ΔΣ modulator.