A high bandwidth, bypass, transient-mode sigma-delta DC-DC switching boost regulator with wide LC compliance

DC-DC switching regulators are critical building blocks in electronic systems and integrating them on chip affords numerous savings in system size, cost, and design complexity. A key portion of these regulators is the frequency compensation circuit and, because of its dependence to the passive LC filter parameters in the power stage, it resists integration. This hindrance to system-on-chip (SoC) integration can be overcome by adopting a sliding-mode control scheme, which, in implementing a variation of a sigma-delta (ΣΔ) converter, gives stable operation for a wide range of LC filter values, without the need for a frequency compensation circuit. However, sliding-mode boost DC-DC converters designed to tolerate wide LC variations exhibit a slow transient response because the bandwidth of the feedback circuit is necessarily low, significantly lower than the main power path´s bandwidth, which is a requirement for stability. This paper proposes a switching boost converter with a high bandwidth, bypass, ΣΔ path that yields fast transient response (up to 50 % ΔΣ reduction)-limited only by slew-rate conditions. The proposed converter achieves this fast response without a degradation in LC filter compliance, steady-state voltage ripple (± 0.2 %), or efficiency. In effect, the presented strategy decouples the conflicting design requirements of high relative stability and fast transient response without requiring compensation circuits and therefore offering integrated, user-friendly solutions.