Chia Ling Wei

Design of an Average-Current-Mode Noninverting Buck–Boost DC–DC Converter With Reduced Switching and Conduction Losses

With the rapid growth of battery-powered portable electronics, an efficient power management solution is necessary for extending battery life. Generally, basic switching regulators, such as buck and boost converters, may not be capable of using the entire battery output voltage range (e.g., 2.5-4.7 V for Li-ion batteries) to provide a fixed output voltage (e.g., 3.3 V). In this paper, an average-current-mode noninverting buck-boost dc-dc converter is proposed. It is not only able to use the full output voltage range of a Li-ion battery, but it also features high power efficiency and excellent noise immunity. The die area of this chip is 2.14 × 1.92 mm2, fabricated by using TSMC 0.35 μm 2P4M 3.3 V/5 V mixed-signal polycide process. The input voltage of the converter may range from 2.3 to 5 V with its output voltage set to 3.3 V, and its switching frequency is 500 kHz. Moreover, it can provide up to 400-mA load current, and the maximal measured efficiency is 92.01%.

Nonlinear conductance-volume relationship for murine conductance catheter measurement system

The conductance catheter system is a tool to determine instantaneous left ventricular volume in vivo by converting measured conductance to volume. The currently adopted conductance-to-volume conversion equation was proposed by Baan, and the accuracy of this equation is limited by the assumption of a linear conductance-volume relationship. The electric field generated by a conductance catheter is nonuniform, which results in a nonlinear relationship between conductance and volume. This paper investigates this nonlinear relationship and proposes a new nonlinear conductance-to-volume conversion equation. The proposed nonlinear equation uses a single empirically determined calibration coefficient, derived from independently measured stroke volume. In vitro experiments and numerical model simulations were performed to verify and validate the proposed equation.

Volume Catheter Parallel Conductance Varies Between End-Systole and End-Diastole

In order for the conductance catheter system to accurately measure instantaneous cardiac blood volume, it is necessary to determine and remove the contribution from parallel myocardial tissue. In previous studies, the myocardium has been treated as either purely resistive or purely capacitive when developing methods to estimate the myocardial contribution. We propose that both the capacitive and the resistive properties of the myocardium are substantial, and neither should be ignored. Hence, the measured result should be labeled admittance rather than conductance. We have measured the admittance (magnitude and phase angle) of the left ventricle in the mouse, and have shown that it is measurable and increases with frequency. Further, this more accurate technique suggests that the myocardial contribution to measured admittance varies between end-systole and end-diastole, contrary to previous literature. We have tested these hypotheses both with numerical finite-element models for a mouse left ventricle constructed from magnetic resonance imaging images, and with in vivo admittance measurements in the murine left ventricle. Finally, we propose a new method to determine the instantaneous myocardial contribution to the measured left ventricular admittance that does not require saline injection or other intervention to calibrate.

Design of a Switched-Capacitor DC-DC Converter With a Wide Input Voltage Range

A triple-mode step-up/step-down switched-capacitor DC-DC converter is proposed, and it can work with a wide input voltage range. There are three operational modes in the proposed converter: triple-step-up, double-step-up, and step-down modes. A built-in clock generator was designed to generate a constant switching frequency, independent of the input voltage. The proposed circuit was implemented by a 0.35-μm CMOS mixed-signal 2P4M 3.3/5 V polycide process with a die area of 1.56×1.47 mm2. The output voltage is fixed at 3.3 V, while the input voltage range is 1.8-5 V. The maximal load current for a 1.8-V input voltage is 10 mA, while it increases to 30 mA when the input voltage is larger than 3 V.

A Novel MEMS Respiratory Flow Sensor

A novel CMOS-process-compatible MEMS sensor for monitoring respiration is presented. This resistive flow sensor was manufactured by the TSMC 0.35 ¿m CMOS/MEMS mixed-signal 2P4M polycide process. The sensor was demonstrated to be sensitive enough to detect the respiratory flow rate, and the relationship between flow rate and sensed voltage is quite linear. If one can integrate the sensor with its sensing circuit into a single chip, the cost of a pneumotach system can be greatly reduced. Moreover, the proposed sensor is useful in both invasive and noninvasive applications.

Adaptive Peak-Inductor-Current-Controlled PFM Boost Converter With a Near-Threshold Startup Voltage and High Efficiency

A high-efficiency boost dc-dc converter with adaptive peak-inductor-current (APIC) control method is proposed. Besides, a novel two-step startup procedure is also proposed and applied on the boost converter. The proposed integrated boost converter was fabricated by using a 0.18-μm 1P6M mixed-signal process with a die area of 0.96 mm × 0.75 mm, and it is meant to be used with low-power, low-voltage green energy sources and batteries, such as fuel cells, solar cells, and nickel-metal hydride batteries. Hence, the power efficiency, minimal startup voltage, and minimal input voltage are the most important design considerations. The output voltage of the proposed converter is set to 1.8V, and the measured power efficiency is up to 90.6%, occurring when the input voltage is 1.3 V, the output voltage is 1.8 V, and the load current is 50 mA. According to the measured results, the proposed converter can start up successfully with a 0.43-V input voltage. Then, the input voltage can be further lowered to 0.22 V after startup. Moreover, both the efficiency and the output voltage ripple are improved with the proposed APIC method. Furthermore, a two-step startup procedure, which does not require any extra startup assist circuit, is proposed.

An integrated step-down DC-DC converter with low output voltage ripple

An integrated low-output-ripple step-down DC-DC converter, which cascades a Buck converter with a low-dropout regulator (LDO), is presented. The output of the Buck converter can be used to supply digital circuits, while the LDO output is used to power analog circuits. The designed Buck converter can adaptively and automatically switch between the pulse-width modulation (PWM) and pulse-frequency modulation (PFM) to improve the conversion efficiency over the whole load current range. The chip was implemented by TSMC 0.35µm 2P4M polycide CMOS process. The measured maximal load current of the Buck converter was 280 mA, and the measured LDO maximal load current was 100 mA.

A Versatile Step-Up/Step-Down Switched-Capacitor-Based DC-DC Converter

For battery-powered electronic products, one way to extend battery life is to use a versatile step-up/step-down DC-DC converter. A new versatile step-up/step-down switched-capacitor-based converter structure is proposed, and its efficiency is analyzed. In the step-down case, the efficiency is the same as, or even better than the efficiency of linear regulators.

Wide-Range Filter-Based Sinusoidal Wave Synthesizer for Electrochemical Impedance Spectroscopy Measurements

A filter-based wide-range programmable sinusoidal wave synthesizer for electrochemical impedance spectroscopy measurement is proposed. The adopted filter is implemented with switched-capacitor circuits, so its corner frequency is accurate and adjustable by changing its switching frequency. The proposed sine wave synthesizer is implemented by using a 0.35 μm 2P4M 3.3 V mixed-signal polycide process. According to the measured results, the output frequency of the proposed synthesizer is 40 mHz-40 kHz . The measured total harmonic distortion is 0.073% at 10 Hz and 0.075% at 10 kHz, both of which are better than that of a typical function generator.A filter-based wide-range programmable sinusoidal wave synthesizer for electrochemical impedance spectroscopy measurement is proposed. The adopted filter is implemented with switched-capacitor circuits, so its corner frequency is accurate and adjustable by changing its switching frequency. The proposed sine wave synthesizer is implemented by using a 0.35 μm 2P4M 3.3 V mixed-signal polycide process. According to the measured results, the output frequency of the proposed synthesizer is 40 mHz-40 kHz . The measured total harmonic distortion is 0.073% at 10 Hz and 0.075% at 10 kHz, both of which are better than that of a typical function generator.

Calibration Capacity of the Conductance-to-Volume Conversion Equations for the Mouse Conductance Catheter Measurement System

The conductance catheter system is used to measure instantaneous ventricular conductance, and real-time ventricular volume is then determined by converting the measured conductance to volume. Two conductance-to-volume conversion equations for the conductance catheter system have been proposed: Baans linear equation and Weis nonlinear equation. In fact, the accuracy of this volume estimation method is limited by several factors, such as the catheter position deviation. The effects of the mouse catheter position deviations on the volume-conductance relationships are investigated with cylindrical finite-element models and mouse left ventricular models. The accuracy and calibration capacity of the two conversion equations for estimating volume are evaluated and compared. According to the comparison results, the performance of the nonlinear conversion equation is better.