This paper proposes a multimode digitally controlled boost converter with PID autotuning and constant frequency/constant off-time hybrid pulsewidth modulation (PWM) control. Constant off-time PWM control is introduced...
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This paper proposes a multimode digitally controlled boost converter with PID autotuning and constant frequency/constant off-time hybrid pulsewidth modulation (PWM) control. Constant off-time PWM control is introduced in this converter for avoiding the limit cycle oscillation and maintaining a constant dc gain of the control-output transfer function for a high conversion ratio. Discrete-time modeling of constant off-time PWM is given and verified. An autotuning PID compensator based on frequency-response measurement is adopted to compensate the output stage with variable gain and variable corner frequency. PFM is also included in this controller to improve light load efficiency. A new method of automatic PWM/PFM mode switching without current sensing is proposed. Sufficient loop stability margin and optimal efficiency are obtained by using these techniques for a boost converter operating overwide ranges of output voltages, load currents, and external components. Experimental results are shown for an asynchronous boost converter with 2.5-V input voltage, 3-12V, and 1-400 mA output.
This paper presents a low power boost converter for thermoelectric energy harvesting that demonstrates an efficiency that is 15% higher than the state-of-the-art for voltage conversion ratios above 20. This is achieve...
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This paper presents a low power boost converter for thermoelectric energy harvesting that demonstrates an efficiency that is 15% higher than the state-of-the-art for voltage conversion ratios above 20. This is achieved by utilizing a technique allowing synchronous rectification in the discontinuous conduction mode. A low-power method for input voltage monitoring is presented. The low input voltage requirements allow operation from a thermoelectric generator powered by body heat. The converter, fabricated in a 0.13 mu m CMOS process, operates from input voltages ranging from 20 mV to 250 mV while supplying a regulated 1 V output. The converter consumes 1.6 (1.1) mu W of quiescent power, delivers up to 25 (175) mu W of output power, and is 46 (75)% efficient for a 20 mV and 100 mV input, respectively.
This paper presents a low power boost converter for thermoelectric energy harvesting that demonstrates an efficiency that is 15% higher than the state-of-the-art for voltage conversion ratios above 20. This is achieve...
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This paper presents a low power boost converter for thermoelectric energy harvesting that demonstrates an efficiency that is 15% higher than the state-of-the-art for voltage conversion ratios above 20. This is achieved by utilizing a technique allowing synchronous rectification in the discontinuous conduction mode. A low-power method for input voltage monitoring is presented. The low input voltage requirements allow operation from a thermoelectric generator powered by body heat. The converter, fabricated in a 0.13 mu m CMOS process, operates from input voltages ranging from 20 mV to 250 mV while supplying a regulated 1 V output. The converter consumes 1.6 (1.1) mu W of quiescent power, delivers up to 25 (175) mu W of output power, and is 46 (75)% efficient for a 20 mV and 100 mV input, respectively.
In this paper, we describe the investigation of an electrical stimulus pulse parameter for use in a low-power retinal prosthesis. To obtain efficient stimulus pulse parameters, in vitro electrical stimulus experiments...
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In this paper, we describe the investigation of an electrical stimulus pulse parameter for use in a low-power retinal prosthesis. To obtain efficient stimulus pulse parameters, in vitro electrical stimulus experiments with a detached frog retina were performed using a fabricated pulse-frequency modulation (PFM) image sensor as a retinal prosthesis. The evaluated electrical stimulus pulse parameters were pulse duration, pulse amplitude, and the number of pulses. From the experiments, the firing rate of the retinal ganglion cells (retinal ganglion cells;RGCs) was observed to depend on the injection charge in single-pulse stimulation and the injection charge of the first pulse in pulse-train stimulation. In addition, pulse-train stimulation was found to have a RGC firing rate lower than that of single-pulse stimulation at the same injection charge. From power consumption measurements and an in vitro experiment, it was verified that the stimulus pulse of a short-pulse duration is suitable for use in a low-power retinal prosthesis.
The operation of a novel differential pulse-frequency modulator based on the Asynchronous Delta modulation principle is described in this paper. The complete modulator consists of a Voltage Controlled Oscillator (VCO)...
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The operation of a novel differential pulse-frequency modulator based on the Asynchronous Delta modulation principle is described in this paper. The complete modulator consists of a Voltage Controlled Oscillator (VCO) in a feedback configuration and generates an output pulse train whose frequency is proportional to the slope of the input signal. It is shown that the proposed system allows substantially larger input signal amplitudes for linear operation than those permitted by open loop VCO schemes or other voltage-to-frequency converters. In addition, the feedback path provides "locally" a signal that tracks the input, so that the feedback arrangement can be readily used as a demodulator at the receiver end.
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