Analysis of DC-DC Conversion for Energy Harvesting Systems Using a Mixed-Signal Sliding-Mode Controller

Guilar, N.J.; Amirtharajah, Rajeevan; Hurst, P.J.

doi:10.1109/pesc.2007.4342430

Cited by 4 publications

(1 citation statement)

References 23 publications

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“…The upper 3 channels are time interleaved and together create the kz -1 term. Here, k can be varied to change the phase lead provided by the filter, to control the limit cycle frequency of the SM controller and limit its dependence on the duty cycle [5]. Two additional time-interleaved gain-boosting channels generate a proportional term with a differential gain of g. On φ 1 the error signal V e is sampled onto multiple parallel capacitors C g .…”

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An energy-aware multiple-input power supply with charge recovery for energy harvesting applications

Guilar

Amirtharajah

Hurst

et al. 2009

2009 IEEE International Solid-State Circuits Conference - Digest of Technical Papers

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Energy harvesting systems such as self-powered wireless sensor nodes rely on a diverse set of energy sources in their continuously changing environment for power. A highly flexible power supply with multiple sources is needed to deal with large variation in environmental conditions. This paper describes an integrated power management system for use with multiple energy harvesters, which employs energy awareness and charge recycling. Previous multiple-input power management systems only allow energy to be harvested from a single source at a time [1] (typically the source with the largest voltage) thereby wasting the energy from the other energy harvesters. In order to increase the total energy available, the work presented here allows the system to gather and add together voltages from multiple sources at the same time.Figure 17.7.1 shows a simplified block diagram for the proposed power management system. The system has two inputs: an AC input (V vibe ) and a DC input (V solar ). The AC input can be driven by a multiple-electrode piezoelectric transducer for vibrational energy harvesting [2], while the DC input can be connected to photodiodes for solar energy harvesting or to a thermoelectric generator [3]. The system also has two outputs: a high-ripple output (V int ) and a low-ripple output (V out ). The low-ripple output uses an additional stage of regulation, and therefore requires more energy to operate. Since the power supply regulates energy for multiple loads with differing requirements, allowing a precision-efficiency tradeoff is desirable. This tradeoff is accomplished by a sliding mode (SM) DC/DC controller.For the AC/DC converter in Fig. 17.7.1, the rectified voltage from the piezoelectric generator functions not only as the input to a switched-capacitor (SC) boost converter, but also as the control signal V ct into a VCO, which dictates the boost converter's switching frequency f ct . As the piezoelectric disk vibrates, the VCO output frequency varies, and the current drawn from the disk is proportional to its generated voltage V vibe . When the generated voltage from a piezoelectric disk is near zero, the majority of the disk's energy is held in kinetic form. Open circuiting the load seen by the piezoelectric disk during zero crossings allows the disk to retain more of its kinetic energy. Near maximum deflection, the piezoelectric disk exchanges this preserved kinetic energy for increased potential energy, generating a larger peak voltage. The rectified voltage from the vibrational source is then added to the voltage from the solar source by wiring multiple capacitors in series, similar to a SC charge pump.Figure 17.7.2 shows a schematic of the SM DC/DC converter, which employs a charge recycling technique. The controller first samples the error signal V e , filters it, determines the polarity of the filter output, and drives the output transistors (MN and MP) in the opposite direction of the error. The controller converges to a steady-state limit cycle with a constant frequency and duty cycle. In ...

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