Songsong Nie

Open-Circuit Fault Diagnosis and Fault-Tolerant Strategies for Full-Bridge DC–DC Converters

This paper proposes a four-step open-circuit fault diagnosis and fault-tolerant scheme for isolated phase-shifted full-bridge (PSFB) dc-dc converters to improve the reliability. The fault diagnostic method utilizes the primary voltage of the transformer as the diagnostic criterion, which can be obtained easily by adding an auxiliary winding. When an open-circuit fault occurs in any switch of the PSFB converter, the proposed fault detection method can generate an indication of the abnormal state and trigger an active-phase-shifted in the control system. Under the APS state, it is very easy to locate the exact position of faulty switch because the voltage waveform of the primary winding heavily depends on the location of the faulty switch. After locating the position of the faulty switch, the PSFB converter is reconfigured into an asymmetrical half-bridge (AHB) converter by turning ON the normal switch in the faulty leg and adding a redundant winding to the secondary side. Therefore, the rebuilt AHB converter can keep the output voltage constant under a reduced power rating after the open-circuit fault. The operational principle, design consideration, and implementation are discussed in this paper. The experimental results are given to verify the validity of theoretical analysis. The proposed strategies outperform the traditional schemes in terms of cost, reliability, and power density.

Monitoring and Diagnosis for the DC–DC Converter Using the Magnetic Near Field Waveform

A new diagnostic method for the dc-dc converter, which utilizes the magnetic near field as the diagnostic criterion, is proposed in this paper. The magnetic near field of the converter is captured using a loop magnetic near field probe. The frequency information in the measured waveform is extracted by the fast Fourier transfer; the interested low-order harmonic components are classified by the neural network while the interested high-order harmonic components are evaluated using the simple mathematical method. Finally, by compromising the results of the two parts, the detailed diagnostic conclusions are obtained. In this paper, the methodologies of the measurement and diagnosis are clearly described; then, the proposed method is used to monitor and diagnose the buck and phase shift full bridge converters. The experimental results are presented to show the validity of the analysis. Since the two chosen examples include most of the potential situations, the proposed method can be generalized and applied to many other types of converters.

Fault Diagnosis of PWM DC–DC Converters Based on Magnetic Component Voltages Equation

Switch fault diagnosis is an important design aspect for pulse width modulation (PWM) dc-dc power converters. It can prevent power converters from further damage, and also make preparations for remedial actions. In this paper, a fast switch fault diagnostic method is proposed for PWM dc-dc converters operating in continuous conduction mode. The proposed method utilizes the magnetic component (inductor or transformer) voltage for fault diagnosis. Based on the real-time voltage measurement and switch gate-driver signals, characteristics of switch open-circuit faults and short-circuit faults are rapidly extracted, and thus, switch faults can be quickly detected. The magnetic component voltage can be measured by an auxiliary winding in the magnetic core, and gate-driver signals can be easily got from the control circuit. Moreover, the fault detection can be implemented by a low-cost logical hardware circuit, and this circuit can be integrated into the control circuit. The fault diagnosis principle, design considerations, and implementation are discussed in this paper. Experiments are conducted to verify the theoretical analysis.

Switch Short-Circuit Fault Diagnosis and Remedial Strategy for Full-Bridge DC–DC Converters

Switch fault diagnosis and remedial actions are an important design aspect for isolated full-bridge dc-dc converters, and they can highly improve reliability of the whole system. In this paper, a fast switch short-circuit fault (SCF) diagnostic method is proposed for the phase-shifted full-bridge (PSFB) converter. The dc-link current and transformer primary voltage are treated as diagnosis criteria. Based on the combination of real-time criteria and switch gate-driver signals, the switch SCF can be identified rapidly, and thus further damage can be avoided. Besides, a remedial action for the faulty PSFB converter is introduced to keep the continuity of the system. The converter under fault can be reconfigured into an asymmetrical half-bridge converter. Moreover, a boost unit, including a switch and a diode, is inserted into between the output rectifier and filter capacitor to compensate the output voltage. The operational principle, design considerations, and implementation are discussed in this paper. Experimental results are shown to verify the validity of theoretical analysis.

The Multiple-Output DC–DC Converter With Shared ZCS Lagging Leg

A multiple-output dc-dc converter with shared zero-current-switching (ZCS) lagging leg is presented in this paper. In this proposed converter, each output is regulated by the phase shifted between the independent leading legs and the shared lagging leg. The switches in the leading legs process the individual output power and work in zero-voltage switching (ZVS), which are suitable for utilizing the MOSFETs; the switches in the shared lagging leg process the total output power and work in ZCS, which especially suit for using the insulated gate bipolar transistor. The ZVS of the leading legs is easy to achieve and the ZCS of the lagging leg is independent of the loads. Therefore, the proposed converter has compact structure, fully regulation abilities, adapted soft-switching modes, and simple modulation schemes. Moreover, the new outputs can be conveniently obtained by using the uniform algorithm. In this paper, the derivation of the proposed converter is presented; the proposed shared ZCS lagging leg converter with dual output is analyzed, and the analysis is further extended to the general multiple-output situation; the state variation of the proposed converter is also surveyed; finally, a three-output prototype with 200-240 V input, 24 V/5 A, 15 V/15 A, and 12 V/10 A outputs is built, and the analysis is verified by the experimental results.

A DSP-based diagnostic system for DC-DC converters using the shape of voltage across the magnetic components

A new diagnostic method for the dc-dc converters is proposed in this paper. The shape of voltage across the magnetic component is used as the diagnostic criterion. The Fast Fourier Transform (FFT) is utilized to extract the features of the waveform and the neural network (NN) is applied to realize the state classification. The voltage sensor is needless because the required voltage signatures can be obtained easily by adding a winding in the magnetic component, or fixing a magnetic near field probe near the magnetic component. The diagnostic system is isolated from the power stage naturally; all the A/D conversion, FFT and NN are realized in a single DSP chip TMS320F2812; using the inner A/D channels of the DSP, up to sixteen dc-dc converters can be monitored synchronously. For the illustrative purpose, the diagnostic process of one A/D channel will be described in this paper and the phase shift full bridge (PSFB) converter is chosen as the diagnostic object. Based on the discussion, the proposed method can be easily extended to the other types of dc-dc converters.

State monitoring and fault diagnosis of the PWM converter using the magnetic field near the inductor components

This paper proposes a new fault diagnostic method for the PWM converter. A loop magnetic near field probe is used to detect the magnetic field near the inductor components in the PWM converters, and the measured waveform is utilized as the diagnostic criterion. The features of the waveform are extracted by the Fast Fourier Transform, and the interested low and high order harmonic components are used to classify the states of the converters. The low order harmonic components are classified by the Back Propagation Neural Network and the high order harmonic components are classified by the simple mathematical method. Finally, by compromising both the two results, the detailed diagnostic conclusions are obtained.

Fault diagnosis of a single-phase inverter using the magnetic field waveform near the output inductor

A low-cost diagnostic method for the single-phase inverter is proposed in this paper. A low-cost fabricated loop magnetic filed probe is used to detect the magnetic field near the output inductor of the inverter; the measured waveform is utilized as the diagnostic criterion, and is processed by the simple peak detector and comparators. With the proposed circuit, the open-circuit faults of the inverter can be diagnosed during the soft-start period. The voltage sensor is needless; the circuit is isolated from the power stage naturally and the diagnostic system is low-cost but effectual. The waveform analysis, diagnostic circuit design and the experimental results are presented in this paper.

The multiple-output DC-DC converter with the shared leg chain

A new multiple-output DC-DC converter with the shared leg chain is proposed in this paper. Two full bridge converters and one resonant half bridge converter are combined together by sharing two of their legs. The first leg works as the leading leg of the first output; the second leg works as both the lagging leg of the first output and the leading leg of the second output; and the third leg acts as not only the lagging leg of the second output but also the half-bridge leg of the third output. Only three legs are required but two full bridge and one half bridge converters are structured. The first and second outputs are regulated by the phase shift modulations, and the third output is regulated by the pulse frequency modulation. All the outputs are fully regulated, and all the switches can achieve zero-voltage-switching (ZVS) easily. The derivation, operational principle and ZVS analysis are presented in this paper, and a 280∼300V input, 15V/10A, 36V/10A and 24V/5A prototype is built to verify the analysis and design.