Chattering-Free Event-Trigger Fast Recovery Stable Digital Sliding Mode Control in DC-DC Converters

Sliding mode control (SMC) offers fast transient per-formance and robust disturbance rejection in DC-DC converters by suitably designing a switching surface. In this paper, novel digital SMC architectures are proposed, in which chattering-free sliding motion is achieved using event-triggered sampling and constant on/off-time modulation. Steady-state switching frequency can be programmed by adjusting the constant timing parameter using an in-built all-digital PLL. First-order as well as higher-order switching surfaces can be realized using mixed-signal or fully digital implementation, in which the output voltage is sampled once in a switching cycle. The former requires one ADC and one DAC to keep the fast changing inductor current in the analog domain, whereas only one time-multiplexed ADC is sufficient for the later. Further, a unified discrete-time (DT) framework is proposed to design a DT switching surface and to carry out stability analysis during reaching phase as well as sliding motion. Thereafter, a real-time gain scheduling method is considered, which achieves near time optimal transient recovery in a boost converter using a simple first-order surface. This helps in reducing hardware complexity and resources, thereby making it useful for high frequency implementation. Experimental results of a boost converter are presented to justify the effectiveness of the proposed architectures.