Yao-Ching Hsieh

A Zero-Voltage-Switched Three-Phase Interleaved Buck Converter

ABSTRACT This paper proposes a three-phase interleaved buck converter which is composed of three identical paralleled buck converters. The proposed solution has three shunt inductors connected between each other of three basic buck conversion units. With the help of the shunt inductors, the MOSFET parasitic capacitances will resonate to achieve zero-voltage-switching. Furthermore, the decreasing rate of the current through the free-wheeling diodes is limited, and therefore, their reverse-recovery losses can be minimised. The active power switches are controlled by interleaved pulse-width modulation signals to reduce the input and output current ripples. Therefore, the filtering capacitances on the input and output sides can be reduced. The power efficiency is measured to be as high as 98% in experiment with a prototype circuit.

A new digital control strategy of boost PFC at high-line light-load condition

The power factor correction (PFC) converter is commonly used in many applications nowadays. For high power applications, boost PFC converter operated in continuous conduction mode is usually employed. However, at high-line light-load condition, the converter operates in discontinuous conduction mode. This leads to erroneous input current sampling which results in low power factor (PF) and high total harmonic distortion (THD). Moreover, the effect of EMI filter capacitor causes the displacement between the input current and input voltage. This paper proposes a digital control method to improve PF and reduce THD by using the current sample correction algorithm, duty ratio feed forward for current controller and EMI filter capacitance current injection algorithm. The increase of PF and reduction of THD are demonstrated by experiments on a 400W boost PFC converter.

A DSP-based differential boost inverter with maximum power point tracking

This paper presents a DSP-based differential boost inverter (DBI) with maximum power point tracking (MPPT) for photovoltaic (PV) applications. In a conventional DC/AC MPPT system, power of photovoltaic is delivered into two stages, they are DC/DC boost converter and buck type DC/AC inverter. A DC link capacitor appears between these two stages. Furthermore the system has higher complexity and costly than that of DC/AC MPPT system with a single stage boost inverter. Here, a single stage differential boost inverter is implemented. Since it can produce a sinusoidal output voltage higher than its DC voltage input, it is not only able to reduce the stage number of DC/AC MPPT system but also able to eliminate the DC link capacitor. The MPPT method employed in this study is P&O method. This technique is widely used due to its easy implementation, and unimportant extreme weather change consideration. To implement this technique, a digital signal processor (DSP) was used. In this paper, a review of DBI and MPPT implementation are presented. Finally a 400 W laboratory prototype has been built. The result shows that the P&O MPPT method has been successfully implemented for various PV power and it can reach 95% maximum MPPT accuracy. In addition, the DBI is able to produce a sinusoidal output voltage at the various PV power conditions.

Study on LCC-C Wireless Power Transfer

This paper presents the study and analysis of the LCC-C Wireless Power Transfer (WPT). The study aims to understand the characteristic and behavior of the proposed resonant compensation under various variables such as the load, frequency, and coupling coefficient. This study can be used as a consideration for the selection of the compensation network for a specific purpose of WPT. To verify the theoretical analysis, numerical simulation has been performed for 3kW LCC-C WPT. It has been done for variable load and variable coupling coefficient. The results show that the maximum efficiency of the proposed WPT can achieve 94.9% at 53.3Ω output load (3kW output power) with k=0.3. The results suggest the important of the switching frequency selection for optimum operation.

High-Efficiency Wireless Power Transfer System for Electric Vehicle Applications

In this brief, a high-efficiency wireless power transfer (WPT) system for electric vehicle charging application is studied and implemented. Series–series resonant topology with RF feedback design is adopted as the WPT dc–dc stage due to the advantages of circuit simplicity, easy analysis, and control. A 500-W laboratory prototype is built and tested to verify the feasibility of the proposed design. According to the experimental results, high wall-to-battery efficiency and unity power factor can be achieved over an air gap of 15 cm and maximum sliding distance of 10 cm under various power conditions and universal input voltage from 90VAC to 264VAC.

High power density and high efficiency inverter with ripple decoupler circuit

By reducing the inductance of the inductor, the reverse current will enable the ZVS turn on of the switches. GaN device can achieve this lossless turn off with much smaller capacitor in parallel, and does so faster, therefore GaN device will be used.

High step-up forward-flyback converter with parallel output

A high efficiency, low profile and high step-up dc-dc converter is proposed for low dc voltage renewable energy system. Generally, the power source such as photovoltaic array and the fuel cell stack have low voltage output because of that a high voltage step-up converter is required to boost the voltage much higher than the voltage level for front-end application. The efficiency and voltage gain of conventional dc-dc converter are limit due to the parasitic components. In order to solve the above mentioned problem, the proposed converter is based on active-clamp technique and the converter is the combination of a forward converter and a flyback converter. Multiple secondary windings can be employed for low profile design and help to reduce high transformer copper loss and high output rectifiers conduction losses. The proposed converter is confirmed with experiments on 250-W prototype and the maximum efficiency of ±94% was measured at full load.

Constant voltage and constant current control implementation for electric vehicles (evs) wireless charger

This paper presents the implementation of Constant Voltage (CV) and Constant Current (CC) control for a wireless charger system. A battery charging system needs these control modes to ensure the safety of the battery and the effectiveness of the charging system. Here, the wireless charger system does not employ any post-regulator stage to control the output voltage and output current of the charger. But, it uses a variable frequency control incorporated with a conventional PI control. As a result, the size and the weight of the system are reduced. This paper discusses the brief review of the SS-WPT, control strategy and implementation of the CV and CC control. Experimental hardware with 2kW output power has been performed and tested. The results show that the proposed CV and CC control method works well with the system.

An interleaved buck converter with asymmetric phase-shift control

Abstract This paper proposes a new control algorithm to operate an interleaved buck converter with an extended step-down ratio. The algorithm is to asymmetrically phase-shift the turn-on periods of the two active switches, i.e. partially overlapping the turn-on intervals. Therefore, one of the active switches can benefit from zero-voltage-switching (ZVS). This improves the power efficiency of a hard-switched interleaved buck converter. In addition, the output voltage is regulated by adjusting the duty ratio, instead of varying the switching frequency. In this paper, a 120 W prototype with input voltage ranging from 54 to 84 V and output voltage of 24 V is designed and implemented. According to the experimental results, the highest efficiency is up to 96%.

Wide-range dimmable LED lighting based on QL-SEPIC converter

ABSTRACT This paper proposes quadratic-like single-ended primary inductance converter (SEPIC) converter, a DC/DC converter suitable for wide-input voltage range. This circuit can be gated at higher duty ratio compared with conventional SEPIC converter, while the voltage conversion ratio is low. This feature is beneficial for high-input voltage because it prevents the controller from falling into extremely low duty ratio limitation. A prototype circuit is implemented with Pulse-Width-Modulation (PWM) control to drive the Light emitting diode (LED) strings for demonstration of the circuit application. Recent studies have advocated LEDs as efficient and durable technology for lighting applications. A stabilized output converter is required to regulate the current flowing through the LED lamp. The dimming control of the LED light output is implemented by the controller. This converter can be powered from either a 24-Vdc battery or from the universal AC input voltage (up to 360 Vdc). Such a wide-input voltage application can be found in emergency lighting in which the light is possibly powered either from battery or AC input voltages. Experimental results prove the feasibility of the circuit topology and theoretical analysis.