Yeunhee Huh

10.4 A hybrid inductor-based flying-capacitor-assisted step-up/step-down DC-DC converter with 96.56% efficiency

The number of mobile device users increases every year. Each mobile device is usually equipped with a Li-ion battery having voltage that varies from a minimum of 2.7V to a maximum of 4.2V. Therefore, as the battery voltage decreases with time, a DC-DC converter is required for a regulated supply lower or higher than the battery voltage. A simple buck converter is not suited for this case, since step-up conversion is not available [1]. Instead, a non-inverting buck-boost converter can be a solution over the entire range of the battery voltage [1–4]. Many research studies related to buck-boost converters operated on Li-ion batteries set the target output voltage at around 3.4V [3,4]. Since Li-ion batteries have a wide plateau from 3.6V to 3.8V and a small energy storage below the plateau, DC-DC converters are generally operated on step-down mode at most of the battery voltage range, as shown in Fig. 10.4.1 top. Notwithstanding, step-up conversion is also required for extracting the energy below the plateau even if it is a small amount in the battery. Therefore, in DC-DC converters, it is critical to maintain high efficiency over the whole range of the battery voltage when it operates on both step-down and step-up modes to prolong the battery usage effectively. However, if the conventional buck-boost topology of Fig. 10.4.1 bottom-left is used for step-up and step-down purposes, there are always two switches (S1 and S3) conducting in the main current path through the inductor. Thus, the switches become large in size to minimize the conduction loss. As the switching loss also increases when the switch size is larger, the efficiency of this structure is usually lower than that of the simple buck (or boost) converter [1]. In this respect, this paper proposes a topology named a flying-capacitor buck-boost (FCBB) converter suitable for such an application by obtaining both step-up and step-down operations with high efficiency throughout the whole range of the battery voltage.

A 10.1” 183-

A high-signal-to-noise ratio (SNR) inductor-free 3-D hover sensor is presented. This paper solved the low-signal component issue, which is the biggest problem in 3-D hover sensing. For this purpose, we propose a power- and cost-effective high-voltage driving technique in the self-capacitance sensing scheme (SCSS) and lateral resolution optimization of a touch panel. In addition, the huge panel offsets in the SCSS from both vertical panel capacitance (CSV) and horizontal panel capacitance (CSH) can effectively be eliminated by exploiting the panel’s natural characteristics, without using other costly resources. Therefore, in the proposed design, the total calibration block is minimized only for parasitic capacitance mismatches. Last, by adopting new driving scheme, two-phase simultaneous sensing is enabled to increase the SNR further. The proposed hover sensing system achieved a 39-dB SNR at a 1-cm hover point under a 240-Hz scan rate condition in noise experiments, while consuming 183

\mu \text{W}

\mu \text{W}

/electrode, 0.73-mm2/sensor High-SNR 3-D Hover Sensor Based on Enhanced Signal Refining and Fine Error Calibrating Techniques

/electrode and 0.73 mm2/sensor, which are the lowest power per electrode performance and the smallest die-area per sensor performance, respectively, in comparison to the state-of-the-art 3-D hover systems.

A 10.1" 56-channel, 183 uW/electrode, 0.73 mm 2 /sensor high SNR 3D hover sensor based on enhanced signal refining and fine error calibrating techniques

This paper presents a high SNR self-capacitance sensing 3D hover sensor that does not use panel offset cancelation blocks. Not only reducing noise components, but increasing the signal components together, this paper achieved a high SNR performance while consuming very low power and die-area. Thanks to the proposed separated structure between driving and sensing circuits of the self-capacitance sensing scheme (SCSS), the signal components are increased without using high-voltage MOS sensing amplifiers which consume big die-area and power and badly degrade SNR. In addition, since a huge panel offset problem in SCSS is solved exploiting the panels natural characteristics, other costly resources are not required. Furthermore, display noise and parasitic capacitance mismatch errors are compressed. We demonstrate a 39dB SNR at a 1cm hover point under 240Hz scan rate condition with noise experiments, while consuming 183uW/electrode and 0.73mm2/sensor, which are the power per electrode and the die-area per sensor, respectively.

5.2 An 8Ω 10W 91%-power-efficiency 0.0023%-THD+N multi-level Class-D audio amplifier with folded PWM

As the portable device market tries to enhance user experience, high-power audio systems with boosted supply voltage have been the main design focus recently. Several past works have addressed issues related to boosted supply voltages [1,2]. Nevertheless, the power stage retained the classical H-bridge structure in the previous works, which resulted in aggravated electromagnetic interference (EMI) from high switching amplitude and poor efficiency due to voltage boosting. The use of multi-level pulse-width modulation (PWM) shown in Fig. 5.2.1 can naturally eliminate the complications caused by high supply voltages. Since the audio signal has a high crest factor, a multi-level Class-D amplifier draws most power directly from a low-voltage battery source, which in turn improves the power efficiency significantly [3]. Spread spectrum techniques prevent energy localization in the power spectral density [2]. Nevertheless, the diffusion of switching harmonics into the nearby frequencies complicates EMI management. However, the multi-level switching scheme suppresses EMI by reducing the switching amplitude without spreading the energy spectrum [4]. In this work, a new folded-PWM (FPWM) architecture implementing a multi-level H-bridge topology is presented.

A reconfigurable SIMO system with 10-output dual-bus DC-DC converter using the load balancing function in group allocator for diversified load condition

This paper presents a reconfigurable SIMO system with 10-output dual-bus DC-DC converter having two buses for heavy and light load outputs, respectively. The converter controls the load condition for each bus to be well balanced. Under diversified load condition, a group allocator assigns each output to the corresponding bus properly depending on its load current. Due to such load balancing function, severe regulation issues which could occur under diversified load condition are resolved with output voltage ripples below 25mV, and over 81% efficiency is achieved under wide range of load (0–300mA).