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A new single-stage isolated ac-dc converter, which can achieve a better efficiency and a better power factor, is proposed. It is based on a general forward topology so that it can utilise the transformer more than converters based on flyback topology. In addition, since the capacitive output filter is adopted instead of an inductive type filter, the voltages on the secondary rectifiers can be clamped to the output voltage; meanwhile, the capacitor used in the output filter can be utilised for the resonance with the leakage inductance, and the turn-off loss in the primary main switch and the dissipative loss in the snubber can be reduced. Moreover, since this converter can be operated at the boundary conduction mode, the line input current can be automatically shaped as the waveform of a line voltage and quasi-resonant zero voltage switching can be also obtained. Therefore, it features higher efficiency, lower voltage stress and a smaller-sized transformer than other topologies. A 100 W prototype has been ...

An analysis and design of single-stage, single-switch bi-flyback ac/dc converter is presented. The main flyback stage controls the output power from the link capacitor voltage with Discontinuous Conduction Mode (DCM) or Continuous Conduction Mode (CCM) operation, while an auxiliary flyback stage supplies the power to the output directly from ac line input with DCM operation. This scheme can effectively reduce the voltage stress on the link capacitor and can achieve the power factor correction (PFC) without a dead band at line zero-crossings, which reduces the harmonic distortion in ac line current. Theoretical analysis of the converter is presented and design guidelines to select circuit components are given. The experimental results on a 60 W (15 V, 4 A), 100 kHz ac/dc converter show that maximum link voltage and maximum efficiency are around 415 V and 82%, respectively. The power factor is above 0.96 under universal line input and load conditions.

A new single-stage power factor corrected ac–dc converter for universal line applications is proposed in this paper. This converter has a buck topology as a power factor corrector. The dc bus voltage of the proposed converter is always lower than the peak input voltage at any load condition. Therefore, the problem of high dc bus voltage under the light load condition for the single-stage converter is solved, especially in the case of universal line applications. The design equations are presented for the proposed converter and a design example for a 5V 12A application is presented. The theoretical analysis and experimental results show that the dc bus voltage can be limited within 260V and the line input current harmonics can meet IEC 61000-3-2 Class D requirements at any load conditions for the line input voltages from 90 to 260Vac.

A very simple control approach using a neural network for the robust position control of a permanent magnet synchronous motor (PMSM) is presented. The linear quadratic controller plus feedforward neural network compensator is employed to obtain the robust PMSM system approximately linearized using a field-orientation method for an AC servo. The neural network is trained in on-line phases and a feedforward recall and error back-propagation training compose this neural network. Since the total number of nodes is only eight, this system is realized easily by the general microprocessor. During normal operation, the input–output response is sampled and the weighting value is trained multi-times by an error back-propagation method at each sample period to accommodate the possible variations in the parameters or load torque. The state space analysis is also performed to obtain the state feedback gains systematically. In addition, the robustness is also obtained without affecting overall system response. A floati...

A DSP-based high speed sensorless control for a brushless DC (BLDC) motor using a DC link voltage control scheme is presented. By operating the BLDC motor in a highspeed range, the drive system can have a small size and be light weight at the same output rating. In the existing sensorless control schemes, the PWM technique is generally used as a speed control. However, since the PWM and inverter commutation cannot be performed independently, a significant commutation delay may exist in a high-speed region. On the other hand, using the DC linkvoltage control scheme, the inverter is operatedwiththe squarewave of 120° conduction and the speed control is achieved by regulating the DC link input voltage of the inverter through the chopper. By using this technique, since the voltage control and commutation can be achieved independently, a commutating delay does not exist even in a high speed region. Also, the phase current can have a waveform similar to the rectangular wave and the terminal voltage is more effi...

A new phase-shifted parallel-input/series-output (PISO) dual convertor for high-power and high-output voltage applications is proposed. The new convertor is based on a two-module PISO modular dual convertor operating at a constant duty cycle and employs an auxiliary circuit to control the output voltage with a phase shift between two modules. This convertor shows a high step-up ratio, fast control-to-output dynamics, significantly reduced switch turn-off stress, and high efficiency due to the reduced switch voltage rating. The steady-state operation is analysed and the mathematical models based on this analysis are presented. A comparative analysis with the conventional two-module PISO dual convertor is performed to explore the various features of the proposed convertor. Also, experimental results from a 50 kHz, 800 W, 350 V dc prototype with an input voltage range of 20–32 V dc are presented to confirm the validity of the proposed convertor. The new convertor compares favourably with the conventional PIS...

The single-current sensor technique obtaining three phase currents from only a DC-link current sensor has been applied to reduce the cost and increase the reliability for various voltage-fed PWM inverters; however, in this technique there are some practical problems, such as unreliable detection of phase currents andphase shift. A new method that overcomes these problems by employing the estimation scheme with identified system parameters is proposed. The Space Vector PWM (SVPWM) strategy is modified to generate the switching pattern adequate for the proposed method. To obtain a good detection in spite of parameter uncertainties, system parameters used in the estimation method are identified using a recursive least square method (RLSM). Experimental results show that the proposed scheme not only provides a very good detection method for three phase currents without current sensors, but also identifies system parameters very well. This proposed method is very simple, has a small detection error, and gives ...

An improved digital current control technique of a permanent magnet (PM) synchronous motor with a simple feedforward disturbance compensation scheme is presented. Among the various current control schemes for an inverter-fed PM synchronous motor drive, the predictive control is known to give a superior performance. This scheme, however, requires the full knowledge of machine parameters and operating conditions, and cannot give a satisfactory response under the parameter mismatch. To overcome such a limitation, the disturbances caused by the parameter variations are estimated by using a disturbance observer theory and used for the computation of the reference voltages by a feedforward control. Thus, the steady state control performance can be significantly improved with a relatively simple control algorithm, while retaining the good characteristics of the predictive control. The proposed control scheme is implemented on a PM synchronous motor using the software of DSP TMS320C30 and the effectiveness is verified through the comparative simulations and experiments.

A new current control technique is presented for three-phase PWM inverterfed AC drives. The features of several existing approaches are analyzed and an integral variable structure control (IVSC) is proposed as an effective way of realizing the high-performance current control. The characteristics of the proposed IVSC are investigated and the design method is presented for the AC drives associated with a voltage-fed PWM inverter. By employing the proposed control, a robust control performance against the parameter uncertainties is obtained in both transient and steady states. The proposed control is applied to the three-phase induction motor drives and the performance improvement is well demonstrated through the simulations and experiments.

The mathematical interpretation of a practical sampler which is useful to obtain small signal models for peak and average current mode controls is proposed. Due to difficulties in applying Shannon's sampling theorem to the analysis of sampling effects embedded in the current mode control, several different approaches have been reported. However, these approaches require information about the inductor current in a discrete expression, which restricts the application of the reported methods to peak current mode control. In this paper, mathematical expressions of sampling effects on a current loop to which Shannon's sampling theorem can be directly applied are newly proposed, and are applied to the modelling of peak current mode control. From newly derived models of a practical sampler, models in a discrete time domain and a continuous time domain are obtained. It is expected that the derived models are useful for the control loop design of power supplies. The effectiveness of the derived models are verified...

A DSP-based nonlinear speed control of a permanent magnet synchronous motor (PMSM), which is robust to unknown parameter variations and speed measurement error, is presented. The model reference adaptive system (MRAS)based adaptation mechanisms for the estimation of slowly varying parameters are derived using the MIT rule. For the disturbances or quickly varying parameters, a quasi-linearized and decoupled model including the influence of parameter variations and speed measurement error on the nonlinear speed control of a PMSM is derived. Based on this model, a boundary layer integral sliding mode controller to improve the robustness and performance of a PMSM drive is designed and compared with the conventional controller. To show the validity of the proposed control scheme, simulations and experimental works are carried out and compared with the conventional control scheme.

A novel isolated zero voltage switching (ZVS) PWM power factor correction circuit is proposed. This circuit provides the input power factor correction and direct conversion from AC line to 48VDC bu...

A predictive current control technique for a permanent magnet synchronous motor (PMSM) employing a resonant DC link inverter is proposed to overcome the disadvantage of the current regulated delta modulation (CRDM) control technique. Also, the discrete model of a PM synchronous motor and estimation of back EMF are investigated. Based on this discrete model and estimated back EMF, a predictive current control technique is newly developed. Using the proposed control technique, the minimized current ripple with a small number of switchings can be obtained. Finally, the comparative computer simulation and experimental results are given to show the usefulness of the proposed technique.

An improved method to determine the pulse density modulation (PDM) pattern is proposed for the high-frequency series resonant inverter (SRI) with a loadmatching transformer. A simple discrete-time model of SRI is derived and the constraints given by a load-matching transformer are analysed. Using the model and constraints, the optimal PDM pattern is derived. The output current ripple is much reduced with this method and the transformer saturation problem can also be avoided. The results of a prototype experiment verify that the unwanted spectral component in the output current is effectively decreased by the optimal pattern. It is believed that the proposed technique is useful for practical applications such as the high-frequency power supply of an induction heating system.

An overcurrent protection control technique of a zero current switched (ZCS) series resonant rectifier (SRR) is proposed. With the proposed control technique, the rectifier can be operated safely, and optimum rating devices can be used. By employing a zero current switching operation for all switches, the series resonant rectifier can be operated at high switching frequencies and high power levels. Based on the dynamic model of this rectifier, the characteristics of an internal operation are explored. With the proposed control technique, the unity power factor without an overcurrent and a wide range of output voltage can be obtained.

A new push-pull type quantum series resonant rectifier for the power factor correction is proposed. The proposed single phase rectifier enables the zero-current switching operation of all power devices, allowing the circuit to operate at high switching frequencies and high power levels. A samples data dynamic model for this rectifier is developed and an analysis for the internal operational characteristics is explored. Based on this analysis, a predictive current control technique is investigated and its advantages over the other types of current control techniques are discussed. With the proposed control technique, the unity power factor and greatly reduced line current harmonics can be obtained.

To obtain a stable output voltage from a recently-developed rectification circuit called a quantum boost series resonant rectifier (QBSRR), two control schemes, digital PI (proportional-integral) control and deadbeat control, are derived for a computer-based system. Since the output voltage regulation loop has a sampling time corresponding to the zero crossing point of the AC line voltage, the output voltage can be controlled regardless of the 120 Hz ripple component. By deriving a simple and exact model for the current program loop (open loop) of a QBSRR and using the pole-assignmenl technique, the controller gains can be systematically designed in the digital PI control scheme. The deadbeat control scheme is also developed to maintain fast dynamic performance in the presence of any load variations. In this control scheme, the controller gain is adjusted in accordance with the load information using a load estimation method. Simulation and experimental results are presented to verify the usefuln...

A quantum series resonant inverter (QSRI)is utilized as a DC motor drive. A sampled-data dynamic model including both a QSRI and a DC motor is proposed to obtain an effective analytical tool. Based on this model, an optimal predictive resonant current (OPRC) control technique that minimizes the current error is developed and compared with other types of current control techniques. In respect of the current ripple and offset current, near optimum operational mode patterns can be obtained using the proposed OPRC control technique. The usefulness of an OPRC-controlled QSRI for a DC motor drive with four-quadrant operation is verified by employing motor current and speed controllers in simulation and experiment.

A high frequency and soft-switched AC-to-DC rectifier employing a series-type resonant circuit is proposed to overcome the disadvantages of the conventional peak-rectifying circuit. Using the proposed rectifier, a high power factor and low harmonic currents are obtained in the AC line. Furthermore, several advantages such as high power density and wide output voltage range can also be available. Through simulation and experimental results, the usefulness of the proposed rectifier is verified.

A discrete time domain modelling is presented for the pulse-width modulated series resonant converter (PWM-SRC) with a discontinuous current mode. This nonlinear system is linearized about its equilibrium state to obtain a linear discrete time model for the investigation of small signal performances such as the stability and transient response. The usefulness of this small signal model is verified by dynamic simulation.

A dynamic model and an improved current control technique for a quantum series resonant converter with non-periodic integral cycle mode are proposed to overcome the disadvantages of the integral cycle mode controlled series resonant converter. With the proposed dynamic model, a simple and exact analysis for the internal operational characteristics is newly explored. Based on this analysis, a new improved current control technique is developed and its advantages over other types of current control techniques are discussed. With respect to current ripple and current offset, near optimum operational mode patterns can be obtained using the proposed control technique. Furthermore, fast transient response with negligible overshoot can also be achieved.

A theorem presented by Tran and Sawan (1984), which gives a lower bound for the determinant of the positive definite solution of the discrete algebraic Riccati matrix equation, is shown to be erroneous.