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In this paper, a simple and low-cost open-circuit fault detection and identification method for a pulse-width modulated (PWM) voltage-source inverter (VSI) employing a permanent magnet synchronous motor is proposed. An open-circuit fault of a power switch in the PWM VSI changes the corresponding terminal voltage and introduces the voltage distortions to each phase voltage. The proposed open-circuit fault diagnosis method employs the model reference adaptive system techniques and requires no additional sensors or electrical devices to detect the fault condition and identify the faulty switch. The proposed method has the features of fast diagnosis time, simple structure, and being easily inserted to the existing control algorithms as a subroutine without major modifications. The simulations and experiments are carried out and the results show the effectiveness of the proposed method.

The LLC resonant converter employing a center-tap rectifier can suffer from a high voltage oscillation across rectifier diodes owing to a leakage inductance of a transformer secondary. The amplitude of this voltage oscillation is varied according to design parameters, parasitic components, and operation regions, i.e., below-resonant region and above-resonant region. To reduce the diode voltage stress, this paper analyzes the voltage oscillation mechanism and presents the design consideration.

In this paper, a new cell-to-cell charge equalization converter using a multiwinding transformer is proposed. The proposed scheme achieves the direct cell-to-cell charge transportation by buck-boost and flyback operation. In this operation, the adjacent two cells share either a current path or a tap of multiwinding transformer. Therefore, the number of windings ia cut in half in comparison to the number of batteries, resulting in a small circuit size. To verify the operation of the proposed charge equalization converter, an experiment with a lithium-ion battery stack is performed.

This paper proposes a simple position observer based on the instantaneous power and a tuning procedure for the proposed observer in driving the surface-mounted permanent magnet synchronous motor. In the instantaneous power of a three-phase system, the imaginary and real powers have the information related to the position and velocity. Using the instantaneous power, the difference between real rotor position and estimated rotor position is calculated. For easy design, gain parameters are described as a bandwidth of position observer. The proper bandwidth is expressed in terms of the desired load transient response, system inertia, and permitted acceleration range. Also, the sensitivity of phase resistance and inductance is analyzed. The described mathematical results show the necessity of accurate parameter information. Simulation and experimental results show the validity of the proposed design method and analysis.

Stacking an auxiliary step-up circuit on top of a boost converter is one of the most attractive structures for nonisolated high step-up applications. In this paper, in order to avoid the large input current ripple of coupled-inductor-based circuits, an auxiliary step-up circuit is integrated via an additional transformer and its balancing capacitor. A voltage-doubler is adopted as an auxiliary step-up circuit, which is inherently suitable for high-voltage applications due to its simple structure and low-voltage stress. Moreover, the transformer leakage inductor and the balancing capacitor constitute a resonant tank so that the quasi-resonant operation makes the current sinusoidal. As a result, a reduced switch turn-off loss and reverse recovery of the diode can be expected. The proposed converter is verified with a 24 V input, 160 W - 200 V output prototype.

This paper describes nonisolated high step-up DC-DC converters using zero voltage switching (ZVS) boost integration technique (BIT) and their light-load frequency modulation (LLFM) control. The proposed ZVS BIT integrates a bidirectional boost converter with a series output module as a parallel-input and series-output (PISO) configuration. It provides many advantages such as high device utilization, high step-up capability, power and thermal stress distribution, switch voltage stress clamping, and soft switching capability. As an example of ZVS BIT, a flyback converter with a voltage-doubler rectifier (VDR) as a series output module is presented and analyzed in detail. In addition, to overcome the efficiency degradation at a light load due to the load-dependent soft switching capability of the proposed ZVS BIT, a control method using a frequency modulation (FM) proportional to the load current is proposed. By means of ZVS BIT and LLFM control, the overall conversion efficiency is significantly improved. The experimental results are presented to clarify the proposed schemes.

A transformer magnetizing current offset for a phase-shift full-bridge (PSFB) converter is dealt with in this paper. A model of this current offset is derived and it is presented as a first-order system having a pole at a low frequency when the effects from the parasitic components and the switching transition are considered. A digital offset compensator eliminating this current offset is proposed and designed considering the interference in an output voltage regulation. The performances of the proposed compensator are verified by experiments with a 1.2-kW PSFB converter. The saturation of the transformer is prevented and the efficiency is improved by this compensator.

A new interleaved forward (IF) converter, adopting the series-input series-rectifier (SISR) structure with a common transformer reset circuit (CTRC), is proposed in this paper. The series-input structure distributes the switch voltage stress so that it is suitable for high-input-voltage applications. Moreover, in order to simplify the total circuit, one active-clamp circuit is shared with two forward converters as a CTRC for transformer reset. In addition, the series-rectifier structure with a common output inductor guarantees a fair current balance between the primary modules, while the interleaving technique reduces the output-filter size. All these features make the proposed SISR IF converter promising for high-input-voltage applications with a high efficiency and a simple structure.

Till now, various types of current-fed converters have been developed, and they exhibit good performance in isolated step-up applications. However, they have a common limitation in that the duty cycle must be larger than 0.5 for a proper operation, which guarantees a conducting path for the boost-inductor current. The limited duty cycle causes an inrush current at start-up and it makes it difficult to regulate the output voltage in a light-load condition. Although various auxiliary circuits have been developed that can be solutions for a duty cycle below 0.5, they increase the size and complexity of the total circuit. To relieve these problems, a new two-transformer current-fed (TTCF) converter, which can be operated along a wide duty cycle range with a simple structure, is proposed in this paper. In the TTCF converter, a magnetizing inductor of the transformer acts as a boost inductor, thus no additional boost inductor is needed. Moreover, only one auxiliary diode is employed for operation with a duty cycle below 0.5. Therefore, the proposed converter can be promising for isolated step-up applications with a simple structure.

To obtain a high step-up gain with high efficiency in nonisolated applications, a high step-up technique based on isolated-type converters is introduced in this paper. By stacking the secondary side of an isolated converter in addition to its primary side, a high step-up conversion ratio and a distributed voltage stress can be achieved. Moreover, a careful choice of an isolated converter can provide zero-voltage switching, continuous input current, and reduced reverse recovery on diodes. Based on a conventional voltage-doubler-rectifier boost-integrated half-bridge converter, the derived converter satisfies all these features, which make it suitable for high step-up applications. The operational principle and characteristics of the proposed converter are presented, and verified experimentally with a 135-W, 24-V input, 250-V output prototype converter for a LED driver.

For a nonisolated high step-up converter, the combination of a boost converter with a series output module is investigated in this paper. As a solution to supplement the insufficient step-up ratio and distribute a voltage stress of a classical boost converter, a sepic-integrated boost (SIB) converter, which provides an additional step-up gain with the help of an isolated sepic converter, is proposed. Since the boost converter and the sepic converter share a boost inductor and a switch, its structure is simple. Moreover, the SIB converter needs no current snubber for the diodes, since the transformer leakage inductor alleviates the reverse recovery. The operational principle and characteristics of SIB converter are presented, and verified experimentally with a 200 W, 42 V input, 400 V output prototype converter.

In low-to-medium power applications, an active-clamp forward (ACF) converter is popular for its simple structure and zero-voltage switching (ZVS) capability. However, the high voltage stress on switches can be a burden in high-input-voltage applications. To relieve this, a three-switch ACF (TS-ACF) converter, which employs two main switches for a forward converter and one auxiliary switch for an active-clamp circuit (ACC), is proposed in this paper. With a repositioned ACC, all the switches of TS-ACF converter have relatively low voltage stress compared to the conventional one. In addition, one of the main switches always ensures ZVS during the transformer reset. Consequently, the TS-ACF converter can be promising for high-input-voltage applications with high efficiency.

The flyback converter is one of the most attractive isolated converters in small power applications because of its simple structure. However, it suffers from a high device stress and a large transformer size. To relieve these drawbacks, a high-efficient pulsewidth modulation resonant single-switch isolated converter is proposed. The proposed converter derives the power using the resonance between transformer leakage inductor and secondary capacitor without a large filter inductor. Therefore, the switch turn-off loss and snubber loss are reduced by a sinusoidal-shaped current. Moreover, it has a reduced voltage stress on the secondary diodes without a dissipative snubber and a smaller transformer size. Therefore, it features a simple structure, low cost, and high efficiency. The operational principle and characteristics of the proposed converter are presented and verified experimentally with a 300~400 Vdc input, 70 Vdc/1.5 A output prototype converter.

The single sustaining driver (SSD) for an AC plasma display panel (AC-PDP) can simplify and optimize the circuit part of the PDP; however, it suffers from twice the high voltage stress of switches compared with the conventional sustaining driver. To solve this problem, a new SSD employing a voltage stress reduction technique is proposed. By adjusting the gate timing with the proposed simple structure, the voltage stresses of all devices are effectively ensured at the sustaining voltage.

A new double-ended type zero-voltage switching (ZVS) half-bridge zeta (HBZ) converter employing a double-ended rectifier (DER) is proposed. The proposed DER for the HBZ converter provides a bidirectional powering path in the rectifier. As a result, the improved voltage waveform of the rectifier reduces the output filter size and voltage stresses on rectifier components. Moreover, it offers a wide ZVS range. In addition, to minimize the secondary snubber loss, a simple lossless snubber is adopted. The operational principles and characteristics of the proposed converter are to be analyzed and verified experimentally.

A high-performance and low-cost single-switch current-fed energy recovery circuit (ERC) for an alternating current (ac) plasma display panel (PDF) is proposed. Since it is composed of only one power switch compared with the conventional circuit consisting of four power switches and two large energy recovery capacitors, it features a much simpler structure and lower cost. Furthermore, since all power switches can be switched under soft-switching operation, the proposed circuit has desirable merits such as an increased reliability, and low switching loss. Especially, there are no serious voltage notches across the PDP with the aid of gas discharge current compensation, which can greatly reduce the current stress of all inverter switches, and provide those switches with the turn on timing margin. To confirm the validity of the proposed circuit, its operation and performance were verified on a prototype for 7-in test PDP.

A new cost-effective zero-voltage and zero-current switching (ZVZCS) current-fed energy-recovery display driver for a plasma display panel (PDP) is proposed. It features a simpler structure, less mass, and lower cost of production. Furthermore, since all power switches are turned on or off under zero-voltage or zero-current switching, it has several favorable advantages such as an improved electromagnetic interference (EMI), low switching losses, and reduced burden on the cooling system. Particularly, since the current source built in the inductor can compensate the large gas-discharge current, main inverter switches have the reduced current stress and turn-on timing margin. Therefore, the undesirable voltage notch problem caused by the improperly controlled gate signal can be solved, which enables the panel to light at lower voltage such as 143 V compared with about 165 V of the prior circuit. To confirm the operation, validity, and features of the proposed circuit, experimental results from a prototype built with 6-in test PDP are presented.

This paper presents a zero-voltage switching (ZVS) two-transformer full-bridge (TTFB) pulsewidth modulation (PWM) converter with lossless diode-clamp rectifier for a plasma display panel sustaining power module (PSPM). The TTFB converter has series-connected two transformers which act as an output inductor as well as a main transformer. Although the naturally doubled leakage inductor due to the series-connected two transformers contributes to achieve the ZVS of the lagging leg, it creates a serious voltage ringing across the output rectifier diodes. This results in the heavy voltage stresses across the rectifier diodes. Thus the dissipative snubber circuits are required in spite of the severe power dissipation. To overcome these problems, a new lossless diode-clamp rectifier (LDCR) is employed as the output rectifier, which helps the voltage across rectifier diodes to be clamped at one half the output voltage (Vo/2) or a full output voltage (Vo). Therefore, no dissipative snubber circuits for the rectifier diodes are needed and a high efficiency as well as a low noise output voltage can be realized. In addition, the clamping capacitors of the LDCR can help considerably to reduce the primary circulating current. The operations, analysis, and design consideration of proposed converter are presented. Also, a 425-W, 385-Vdc input, 170-Vdc output prototype is constructed and experimental results show the validity of the proposed converter

A single-stage power factor correction ac/dc converter based on zero voltage switching (ZVS) full bridge topology with two series-connected transformers is proposed in this paper. The proposed converter offers a very wide ZVS range due to the configuration of two series-connected transformers. It features a high efficiency over wide load ranges. Furthermore, it shows the low voltage stress on a dc link capacitor. The proposed converter also gives the high power factor and low input current harmonics complied with IEC 61000-3-2 Class D requirements by integrating a boost stage operated in a discontinuous current mode. The ZVS conditions, large signal modeling, and design procedure are discussed in detail. Experimental results are presented to show the validity of the proposed converter.

A new active clamping zero-voltage switching (ZVS) pulse-width modulation (PWM) current-fed half-bridge converter (CFHB) is proposed in this paper. Its active clamping snubber (ACS) can not only absorb the voltage surge across the turned-off switch, but also achieve the ZVS of all power switches. Moreover, it can be applied to all current-fed power conversion topologies and its operation as well as structure is very simple. Since auxiliary switches in the snubber circuit are switched in a complementary way to main switches, an additional PWM IC is not necessary. In addition, it does not need any clamp winding and auxiliary circuit besides additional two power switches and one capacitor while the conventional current-fed half bridge converter has to be equipped with two clamp windings, two ZVS circuits, and two snubbers. Therefore, it can ensure the higher operating frequency, smaller-sized reactive components, lower cost of production, easier implementation, and higher efficiency. The operational principle, theoretical analysis, and design considerations are presented. To confirm the operation, validity, and features of the proposed circuit, experimental results from a 200-W, 24-200Vdc prototype are presented.

A resonant energy-recovery circuit for a plasma display panel (PDP) employing a gas-discharge current compensation method is proposed. Its main concept is to make the resonant circuit biased by V/sub s/ and 0V instead of V/sub s//2 in charging and discharging the PDP, respectively. This operation helps the PDP to be fully charged and discharged and all main switches turned on under zero-voltage switching. Moreover, since the inductor current can compensate the large gas-discharge current, the current stresses on main power switches can be considerably reduced and all main switches have the turn-on timing margin, which ensures the no voltage drop across the PDP. Therefore, all these features could favorably provide a high energy-recovery capability, more accumulated wall charge, reduced sustaining voltage, and low electromagnetic interference. Therefore, the proposed circuit is expected to be well suited for a hang-on-the-wall PDP TV.

A new phase shift full bridge (PSFB) converter with series-connected two transformers is proposed. The proposed converter shows wide zero voltage switching (ZVS) ranges and no output inductor is needed since each transformer individually acts as an inductor or a transformer during different times of the switching cycle. The operational principle, large signal modeling, and design equations are presented. Experimental results demonstrate that the proposed converter can achieve a significant improvement in the efficiency for a 100W (5 V, 20 A) telecommunication on-board power supply.

A new on-line dead-time compensation method for a permanent magnet (PM) synchronous motor drive is proposed. Using a simple disturbance observer without any additional circuit and off-line experimental measurement, disturbance voltages in the rotor reference dq frame caused by the dead time and nonideal switching characteristics of power devices are estimated in an on-line manner and fed to voltage references in order to compensate the dead-time effects. The proposed method is applied to a PM synchronous motor drive system and implemented by using software of a digital signal processor (DSP) TMS320C31. Simulations and experiments are carried out for this system and the results well demonstrate the effectiveness of the proposed method.

In this paper, a new predictive current controller for a permanent magnet synchronous motor (PMSM) considering delays is presented. In a full digital current control system for a PMSM, there are inevitable delays in calculating and applying the inverter output voltages to the motor terminals. A predictive current controller implemented in a full digital system has serious problems such as the oscillation and large overshoot. A discussion of compensation methods to cope with the nonlinearities of the real system is also presented. The proposed current controller has been analyzed, and the experimental results are shown to prove the feasibility and effectiveness of the proposed predictive current controller using a prototype 750 W PMSM servo drive system.

In this paper, a dead-beat type digital controller has been introduced to overcome the problems of a conventional direct torque controller. The proposed induction motor drive with a digital dead-beat controller shows good transient response and negligible steady-state error even at a low switching frequency, which is needed for high power machines used for transportation. Including the rotor dynamics, the stability condition and steady-state error of the proposed control system have been examined in the z-plane. In addition, the good performance has been verified through the simulation and experiment. The flux and torque controllers have been designed with only stator voltage equations in the stator flux reference frame in order to take advantages of the direct torque control. Therefore, the proposed flux and torque controllers have simple forms and can be easily designed and implemented.

A simple and robust digital current control technique of a permanent magnet (PM) synchronous motor using a time delay control approach is presented. Among the various current control schemes for a voltage source inverter-fed PM synchronous motor drive, the predictive control is known to give a superior performance. This control technique, however, requires the full knowledge of machine parameters and operating conditions, and gives an unsatisfactory response under the parameter mismatch between the motor and controller. To overcome such a limitation, the disturbances caused by the parameter variations are estimated by using a time delay control approach and used for the computation of the reference voltages by a simple feedforward control. Thus, the steady-state control performance can be significantly improved in an extremely simple manner, while retaining the good characteristics of the predictive control such as the good transient response and stable inverter operation. 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.

An integrated zero current switching (ZCS) quasiresonant converter (QRC) for the power factor correction with a single switch is presented in this paper. The power factor correction can be achieved by the discontinuous conduction mode (DCM) operation of an input current. The proposed converter offers good power factor, low level line current harmonics, and tight output regulation. The design equations are suggested and a prototype converter has been designed based on these equations and experimentally investigated. The input current waveform of the prototype shows less than 15% of total harmonic distortion. Also, the efficiency and power factor of about 84% and 0.977, respectively, can be obtained under the rated condition.

A simple source voltage-clamped resonant link (SVCRL) inverter is proposed to clamp the DC-link voltage to the input source voltage and reduce the current rating of a resonant inductor. The current control of a permanent magnet synchronous motor (PMSM) employing a predictive current control technique (PCCT) for the SVCRL, inverter is also investigated to overcome the disadvantage of the current-regulated delta modulation (CRDM) control technique. By employing the PCCT based on the discrete model of a PMSM and estimation of back electromotive force (EMF), 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.

A combined buck and boost push-pull quantum series resonant rectifier (PPQSRR) is newly proposed to achieve power factor correction without start-up inrush current. With the proposed control method and circuitry, a high power factor and wide range of output voltage without an inrush current can be obtained.

A new instantaneous torque-control strategy is presented for high-performance control of a permanent magnet (PM) synchronous motor. In order to deal with the torque pulsating problem of a PM synchronous motor in a low-speed region, new torque estimation and control techniques are proposed. The linkage flux of a PM synchronous motor is estimated using a model reference adaptive system technique, and the developed torque is instantaneously controlled by the proposed torque controller combining a variable structure control (VSC) with a space-vector pulse-width modulation (PWM). The proposed control provides the advantage of reducing the torque pulsation caused by the nonsinusoidal flux distribution. This control strategy is applied to the high-torque PM synchronous motor drive system for direct-drive applications and implemented by using a software of the digital signal processor (DSP) TMS320C30. The simulations and experiments are carried out for this system, and the results demonstrate the effectiveness of the proposed control.

In this paper, a high frequency and soft-switched AC/DC rectifier employing a series-type resonant circuit is proposed to obtain the sinusoidal AC line current. Using the proposed rectifier, the high power factor and low harmonic currents are obtained in the AC line. Furthermore, several advantages such as the high power density and wide output voltage range can also be available. To regulate the output voltage of the proposed circuit, the digital proportional-integral (PI) controller is used whose sampling time corresponds to the zero-crossing point of the AC line voltage. Including this controller, the model for the closed-loop system is developed in order to examine the stability and dynamic characteristics. With this model, the gain of the PI-controller is determined by the pole assignment technique and the closed-loop dynamics is investigated by the root locus plots. A good agreement is made between the simulated and experimental results.

This paper presents a duty cycle generator for an average model of buck converter with current-mode control, which can simultaneously deal with both the continuous conduction mode (CCM) and the discontinuous conduction mode (DCM). First, a duty cycle generator is mathematically derived, considering the transient-state of the current-loop. This technique plays an important role when the operating modes are changed under a considerable amount of step load change. Second, taking advantage of the analog behavioral modeling of PSpice, duty cycle generators for both the time and frequency domain analyses are built into a PSpice file. The accuracy of these models is verified through the computer simulations, which is compared to the actual circuit for the time domain analysis and the small signal model for the frequency analysis.

A new output voltage control technique is proposed to obtain the improved buck-boost operation of the quantum series resonant power converter (QSRC). The new nonlinear dynamic model of QSRC is first derived and the cross-coupled nonlinear term existing in the output voltage dynamics is decoupled by using control methods such as the periodic control of the boosting switch (PCBS) and the resonant current control (RCC). By applying the state-space averaging concept to the decoupled dynamics, two linear large signal averaged models are obtained for PCBS and RCC schemes. Using the proposed technique, the flux imbalance problem of the isolation transformer and the robustness of the output voltage response can be easily considered. This technique can also be widely applicable to the cascade buck-boost power converter, which can be implemented by inserting a boosting switch between the output filter inductor and the ripple capacitor of the forward power converter. The validity of the proposed scheme is confirmed by the computer simulations and the experiments.