Tsong Shing Lee

Inductive Power Transfer Systems for PT-Based Ozone-Driven Circuit With Flexible Capacity Operation and Frequency-Tracking Mechanism

This paper presents inductive power transfer (IPT) systems for a piezoelectric transformer (PT) based ozone-driven circuit with flexible capacity operation and frequency-tracking mechanism. The proposed system consists of an IPT circuit as the front stage along with an ozone-driven circuit as the back stage. Considering that the ozone generator system was often used under high-humidity and particle-polluted environment, the study hence proposes a contactless power source such that the oxidization and rustiness can be better avoided. Next, by taking the system expansion into consideration, this paper proposes multiple modular parallel PTs in order to increase the output capacity of the designated circuit. This is further followed by a frequency-tracking control developed to promote power delivery efficiency. To confirm this proposed method, the developed system has been realized with hardware circuit validation. Experimental results demonstrate that the proposed system not only delivers the power effectively, but also ensures balanced output current of each PT, thereby facilitating the approach for the ozone-driven applications.

Application of Piezoelectric-Transformer-Based Resonant Circuits for AC LED Lighting-Driven Systems With Frequency-Tracking Techniques

This paper proposes an application of piezoelectric transformer (PT) based inverters for alternating current (ac) light-emitting diode (LED) lighting-driven systems with a new resonant topology and frequency-tracking technique. This proposed architecture comprises a full-bridge phase-shift inverter with a PT-based C-L-C series resonant circuit, piezoelectric ceramic transformers, and a microwinding resonant transformer to extend the range of operation frequency, hence achieving a two-terminal alternating voltage to drive ac LED arrays while stabilizing the resonant characteristics. In this system design, a frequency-tracking mechanism is also integrated into the field-programmable gate array controller to improve operation efficiency. Since only the secondary current of the resonant transformer is required for the controller, the circuit implementation is simple and additional sensor devices can be largely saved. Moreover, by considering that the frequency-gain characteristics of PTs may be affected due to temperature changes; the controller is designed to adjust the operation frequency swiftly in order to restrict the temperature effect. This proposed method has been verified on modular ac LED lighting systems. Test results confirm the feasibility of the method for lighting system applications.

Method of feedback detection for loosely coupled inductive power transfer system with frequency-tracking mechanism

This paper proposes a feedback signal detection method and frequency-tracking control approach for inductive power transfer (IPT) systems. The power delivery efficiency is increased by utilizing a resonance compensation circuit and frequency-tracking control. Yet, it was observed that the resonance characteristics of IPT systems are easily influenced by load impedance and coil gap, hence frequency-tracking control is integrated into the microprocessor control unit (MCU) controller such that the operation frequency can be closely locked with the primary current phase. In the circuit design, a voltage across RDS(on) of the power MOSFET is utilized to compensate the resonance features of IPT system, by which the system delivery efficiency and zero-voltage switching can be both achieved. This proposed system has been tested under several scenarios. Test results help confirm the feasibility of IPT module for the application that is investigated.

Enhancing Luminance of CCFL-Based Lighting Systems Using Low-Frequency Driving Techniques

This paper proposes the luminance enhancement with low-frequency driving techniques for cold cathode fluorescent lamp (FL) (CCFL)-based lighting systems. The driver architecture features a full-bridge phase-shift inverter with a resonant tank and a three-winding step-up transformer to reduce leakage current, remove parasitic capacitance, enhance optical efficiency, balance and increase lamp uniformity, and achieve two-terminal high-voltage low-frequency driving of CCFLs. The low-frequency control of the driving technique is implemented in a field-programmable gate array controller to achieve luminance enhancement. The control strategy starts igniting the lamp with a high frequency and then reduces to low frequency in order to facilitate the linear increment of lamp brightness. Through the employment of this proposed approach, since the primary current of the transformers is only required, the circuit implementation can be completed with ease. Experimental results show that the proposed technique and control strategy help enhance luminance efficiency and reduce leakage current, demonstrating the practicality for the application considered.

Application of hybrid-loop control approach to inverter design with piezoelectric transducers

A hybrid-loop control approach applied to inverter circuit design with piezoelectric transducers is proposed in this paper. This approach was motivated because the transducer is easily affected by the temperature effect and damping pressure, causing the mechanical frequency drift and unstable current variation. In view of these demerits, a hybrid-loop control mechanism is suggested to achieve both phase-tracking and constant-current control such that both operation frequency and vibration strength can be well controlled while maintaining a stable mechanical frequency. Moreover, by embedding this hybrid control concept into microprocessor controller units without adding any further sensors devices, the design cost is found to be meanwhile reduced. To validate the feasibility of this approach, the method has been validated through mathematical analysis and hardware realization. Test results confirm the performance improvement of the approach for piezoelectric transducer applications.

Design of wireless power transfer for dynamic power transmission with position-detection mechanism

This paper presents a wireless power transfer design with pick-up device position detection for dynamic power transmission. Since the fixed-point inductive charging is short of providing the power to the moving equipment, the paper is hence motivated to sense the pick-up device, by which the power and flux can be better regulated, meanwhile benefiting the efficiency and maintaining the voltage profile. As for the control strategy made in this study, the voltage of transmission coil is served as the feedback signal, with which the dynamic protection is reached while the modular platform organized by inductive coils are well accomplished. To validate the effectiveness of this method, the prototype is tested to dynamically deliver the power at 5 cm gap. Test results indicate that the power of each transmission coil can be effectively adjusted, where an 82.55% efficiency of the system can be expected. This method owns a high potential of extending to industrial applications when the dynamic power delivery is considered.

Enhancement of Plasma-Driven System With Piezoelectric Transformer-Based Feedback Control Approaches and a Contactless Power Source

This paper proposes a plasma-driven system with piezoelectric transformer-based feedback control approaches along with a contactless power source. The research is motivated because many plasma-driven circuits employed the bulky components as resonant circuit and current feedback sensors. Hence, this study proposes to utilize one piezoelectric ceramic transformer to serve for both resonance tank and feedback devices in order to achieve low cost and design simplification. Moreover, since the plasma discharge often suffers the problem of high humidity and particle-polluted environment, a contactless power transfer circuit integrated with a high-frequency coil is developed as the power source, by which the electrode damage can be better prevented. To reach a better discharge quality and own a higher flexibility of regulating power, the study also completes a constant-power control mechanism and a phase-locked loop control. Both software simulations and hardware realization have been accomplished. Analysis results and experimental outcome help validate the practicality of the proposed approach.

Design of a PT-based resonant inverter for ozone generation with flexible capacity operations

This paper proposes a piezoelectric transformer based on a resonant inverter that allows varying-capacity for ozone generation. The drawback of a piezoelectric transformer (PT) lies in its limited ability to transfer power, rendering it unable to provide sufficient current. Therefore, this study proposes a resonance topology with multiple modular parallel PTs using a PT-equivalent circuit derivation, and analyzes the resulting resonance curve characteristics. The proposed resonance topology can flexibly expand the output capacity, and stabilize the resonance characteristics and mechanical frequency. These results show that the proposed device is better suited to controller design. In addition, the study embeds an asymmetrical pulse width modulation (APWM) control concept into the microprocessor control unit such that the operating power of the ozone generator can be well regulated. This method has been realized with hardware circuit verification. Results demonstrate that the proposed inverter effectively drives the ozone generator system, regulates the operation power, and achieves the zero-voltage switching. The proposed design also ensures that the output current of each PT is evenly balanced, thereby facilitating the flexible capacity operations of the approach for industrial applications.

Contactless energy-transfer system design for lithium iron phosphate battery-charging circuits

This paper proposes a contactless energy-transfer system (CETS) for lithium iron phosphate battery-charging circuits. In the study, the design flow of contactless transformers and compensated circuit are investigated through the analysis of their impedance-matching and resonant features, by which the appropriate inductive coils can be optimally determined such that power transmission efficiency can be increased. Moreover, an algorithm of charging strategy is integrated into the microcontroller chip to facilitate the charging process. From theoretical analysis and hardware realization, they help support the proposed approach applied for the performance improvement of lithium iron phosphate battery-charging applications.

Enhancement of piezoelectric transformer-based LED lighting system with tracking mechanism

This paper proposes a new resonant circuit enhanced with a new tracking control approach for a piezoelectric transformer-based LED lighting system. In this method, the LED driver architecture features full bridge phase shift converter with C-L-C series-resonant circuit along with the piezoelectric transformer. Then, the concept of tracking control is well designated into the FPGA controller such that a higher efficiency of operation can be better reached. Besides, since only the secondary current of resonant transformer is needed for the controller, it helps facilitate the circuit implementation. From experimental results, they solidify the feasibility of this method for modular LED lighting applications.