ABSTRACT
Piezoelectric ceramic actuators utilize an inverse piezoelectric effect to generate high-frequency vibration energy and are widely used in ultrasonic energy conversion circuits. This paper presents a novel drive circuit with input-current shaping (ICS) and soft-switching features which consists of a front AC-DC full-wave bridge rectifier and a rear DC-AC circuit combining a stacked boost converter and a half-bridge resonant inverter for driving a piezoelectric ceramic actuator. To enable ICS functionality in the proposed drive circuit, the inductor of the stacked boost converter sub-circuit is designed to operate in boundary-conduction mode (BCM). In order to allow the two power switches in the proposed drive circuit to achieve zero-voltage switching (ZVS) characteristics, the resonant circuit of the half-bridge resonant inverter sub-circuit is designed as an inductive load. In this paper, a prototype drive circuit for providing piezoelectric ceramic actuators was successfully implemented. Experimental results tested at 110 V input utility voltage show that high power factor (PF > 0.97), low input current total harmonic distortion (THD < 16%), and ZVS characteristics of the power switch were achieved in the prototype drive circuit.
ABSTRACT
Conventional photovoltaic (PV) grid-connected systems consist of a boost converter cascaded with an inverter, resulting in poor efficiency due to performing energy processing twice. Many pseudo DC-link inverters with single energy processing have been proposed to improve system efficiency and simplify circuits. However, their output voltage gain is limited by the non-ideal characteristics of the power diode, making them difficult to apply in high-output voltage applications. This paper proposes combining a boost converter with magnetic coupling and a full-bridge unfolding circuit to develop an inverter featuring high voltage-gain and high efficiency. According to the desired instantaneous output voltage, the high-gain boost converter and the full-bridge unfolding circuit are sequentially and respectively controlled by SPWM. A sinusoidal output voltage can be generated by performing energy processing only once, effectively improving the conversion efficiency. Magnetic coupling is adopted to increase the voltage gain of step-up, and the step-down function is realized by the full-bridge unfolding circuit to reduce conduction loss. Finally, a 500 W prototype was fabricated for the proposed high-gain inverter. The experimental results were used to verify the correctness of the theoretical analysis and the feasibility of the circuit structure.
ABSTRACT
A novel interleaved DC-DC buck converter is proposed to drive high-brightness light-emitting diodes (LEDs). The circuit configuration mainly consists of two buck converters, which are connected in parallel and use interleaved operation. Through interleaved operation, the power capability of the converter is doubled. Traditionally, two individual inductors are used in the two buck converters. The difference between conventional parallel-operated buck converters using two energy storage inductors and the proposed circuit is that the proposed circuit uses two small inductors and a coupled inductor that replace the two inductors of the buck converters. In this way, both buck converters can be designed to operate in discontinuous-current mode (DCM), even if the magnetizing inductance of the coupled inductor is large. Therefore, the freewheeling diodes can achieve zero-current switching off (ZCS). Applying the principle of conservation of magnetic flux, the magnetizing current is converted between the two windings of the coupled inductor. Because nearly constant magnetizing current continuously flows into the output, the output voltage ripple can be effectively reduced without the use of large-value electrolytic capacitors. In addition, each winding current can drop from positive to negative, and this reverse current can discharge the parasitic capacitor of the active switch to zero volts. In this way, the active switches can operate at zero-voltage switching on (ZVS), leading to low switching losses. A 180 W prototype LED driver was built and tested. Our experimental results show satisfactory performance.
ABSTRACT
PWM (pulse-width modulation) voltage source inverters are used in a wide range of AC power systems where the output voltage must be controlled to follow a sinusoidal reference waveform. In order to achieve precision and fast-tracking control, restrictive sliding mode control (RSMC) provides a fast system state convergence time. However, the RSMC still suffers from the chattering problem, which leads to high harmonic distortion and slow response of the inverter output state. Furthermore, the load of the inverter may be severe load changing and the control parameters become difficult to adjust, worsening the adaptability to achieve the desired control of the inverter output. In this paper, a robust optimal control design comprised of an enhanced restrictive sliding mode control (ERSMC) and density particle swarm optimization (DPSO) algorithm is proposed, and then applied to PWM voltage source inverters. The ERSMC not only has finite time convergence but also provides chatter elimination. The DPSO is highly adaptable for acquiring the control parameters of the ERSMC and finding the best solution in the global domain. The proposed controller is realized for the actual PWM voltage source inverter controlled by a TI DSP-based development platform, so that the inverter output voltage has fast dynamic response and satisfactory steady-state behavior despite high load changing and non-linear disturbances.
ABSTRACT
This paper proposes a novel and cost-effective drive circuit for supplying a piezoelectric ceramic actuator, which combines a dual boost AC-DC converter with a coupled inductor and a half-bridge resonant DC-AC inverter into a single-stage architecture with power-factor-correction (PFC) and soft-switching characteristics. The coupled inductor of the dual boost AC-DC converter sub-circuit is designed to work in discontinuous conduction mode (DCM), so the PFC function can be realized in the proposed drive circuit. The resonant tank of the half-bridge resonant inverter sub-circuit is designed as an inductive load, so that the two power switches in the presented drive circuit can achieve zero-voltage switching (ZVS) characteristics. A 50 W-rated prototype drive circuit providing a piezoelectric ceramic actuator has been successfully implemented in this paper. From the experimental results at 110 V input utility-line voltage, the drive circuit has the characteristics of high power factor and low input current total-harmonic-distortion factor, and two power switches have ZVS characteristics. Therefore, satisfactory outcomes from measured results prove the function of the proposed drive circuit.
