Neeraj Keskar

Self-stabilizing, integrated, hysteretic boost DC-DC converter

In portable, battery-powered applications, integration of switching DC-DC converters is crucial to reap maximum benefits in size, cost, and design ease. The frequency compensation circuit, whose design varies with off-chip, passive filter (L-C) components, forms a critical hurdle to obtaining a fully integrated solution. Surveying state-of-the-art control techniques in literature, hysteretic control in buck converters, which in a single loop, controls inductor current ripple indirectly while regulating the output voltage, is observed to be the simplest, fastest, and needing no compensation circuit, thus being best suitable for integration. However, the technique is not readily applied to boost converters. This paper proposes a novel technique to harness voltage-mode hysteretic control in boost converters by controlling inductor current and output voltage through separate loops. The proposed circuit designed for V/sub IN/=1.2 V (nom), V/sub out/=3.3 V /spl plusmn/5%, I/sub out/=0.1 to 1 A shows excellent voltage regulation and transient response (/spl plusmn/150 mV), without the use of any compensation circuit.

SiP integration of intelligent, adaptive, self-sustaining power management solutions for portable applications

Power management is an essential component of any electrical system, and nowadays a limiting factor in the miniaturization of portable electronic devices. Not only are the battery and power components difficult to integrate but their performance requirements in mobile environments are more stringent. And although point-of-load (PoL) regulation techniques and monolithic controllers are industry standards today, more integration is indispensable. To address these issues, system-in-package (SiP) self-renewable energy source and storage devices are proposed alongside an array of circuit techniques designed to circumvent the shortcomings of such a miniaturized environment, like smart load-sharing schemes, customizable and self-adaptive PoL regulators, active inductor and capacitor multipliers, and robust self-calibrating and self-stabilizing dc-dc converters. On their own, each seeks to push the limits of integration while maintaining and many times improving performance. As a whole, they promise the birth of a new generation of ICs

A Fast, Sigma–Delta

Power supplies in portable electronics must adapt to their highly integrated environments and, more intrinsically, respond quickly to fast load dumps. However, frequency compensation must cater to the worst case design LC combination, be it because of tolerance and/or variable design targets, limiting speed and regulation performance to the worst-case scenario, even under best case conditions. Sigma-delta (SigmaDelta) control, which addresses this issue in buck converters, has not been able to concurrently achieve both high speed and wide LC compliance in boost converters. This paper presents a dual-loop SigmaDelta boost converter whose prototype (5 plusmn5% V, 1A) was 20% faster and at least nine times more LC compliant than its leading current-mode PWM counterpart, and this without a compensation circuit. Light load efficiency, intrinsic for battery life, was also better (2% higher at 0.5 W, 600 kHz) because of lower switching losses. The tradeoffs for these benefits were higher output ripple voltage (5 V plusmn1.7%) and lower high load efficiency (less than 1.9% lower at 5 W, 300 kHz).

(\Sigma \Delta)

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 (/spl Sigma//spl Delta/) 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 paths bandwidth, which is a requirement for stability. This paper proposes a switching boost converter with a high bandwidth, bypass, /spl Sigma//spl Delta/ path that yields fast transient response (up to 50 % /spl Delta//spl Sigma/ 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 (/spl plusmn/ 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.

Boost DC–DC Converter Tolerant to Wide LC Filter Variations

Portable electronic devices not only require switching DC-DC converters to be compact and integrated but also compliant to wide off-chip LC filter variations, which are subject to manufacturing tolerances, temporal and thermal parameter drifts, and more often than not, application-driven constraints. While optimal LC compliance has been demonstrated in ΣΔ buck converters, little has been done in boosting applications. This paper presents an asynchronous ΣΔ boost converter and describes how LC variations affect stability, steady-state error, and switching frequency, and how a frequency-dependent gain mitigates these effects. Simulations show the circuit is stable for 1-30μH inductances and 15-350μF output capacitances, its steady-state error is less than 1%, and its switching frequency varies 15% less (over load and line variations) than in conventional ΣΔ converters.