DCM analysis and modeling of half-bridge converters with current-doubler rectifier

This paper presents a unified analysis of half-bridge converters with current-doubler rectifier using an averaged circuit model. The model is applicable for both symmetrical and asymmetrical control. Different approaches to integrating the transformer with the inductors are discussed and their equivalent circuit models for use with the averaged converter model are developed. In addition, an inductor loop formed by the transformer and the two filter inductors is identified, and its effects on converter operation and control design are discussed. Numerical simulation and experimental results from a prototype converter are also reported.

Deadtimes are required to avoid simultaneous conduction of high-side and low-side power transistors in half-bridge power converters. During these secure times, free-wheeling current flow generates extra power losses. Very short deadtimes are desired but they cannot be safely set in conventional isolated power converters because of a digital input propagation delay mismatch. A specific deadtime management is introduced in this paper to ensure proper operation of a high-voltage synchronous power converter. A controller integrated in each isolated gate driver secures synchronous switching by detecting the opposite switch turn-off before turn-on. With such a selfswitching technique, very short but safe nonoverlap times can be set. A gate driver has been implemented in a 0.35 μm 20-V CMOS process. The monolithically integrated controller consumes only 140 μA and 0.22 mm2 of silicon area. The proposed local deadtime management has been validated in two synchronous buck converters without external free-wheeling diodes: a 500-W 250-V to 55-V converter based on SiC JFETs and a 30-W 45-V to 10-V converter based on eGaN FETs. In either case, the proposed controller allows a higher efficiency from 10% of the rated load with resulting deadtimes as short as 15 ns.

A novel control method used in the half-bridge single-state power converter is presented in this paper. This proposed control scheme is to enlarge load regulation range in discontinuous conduction mode (DCM), while the new duty pattern will be derived to perform the variable-frequency control. Compared to the conventional control methods, the proposed duty cycle pattern within a switching period is directly proportional to the absolute value of instantaneous source voltage and the output can be regulated by varying the switching frequency using digital signal processor (DSP) control wherein TMS320F2812 manufactured by TI is utilized. Compared to conventional control methods, the proposed is simpler to upgrade the power factor and efficiency. Experimental results show good conformation with the theoretical analysis.

This paper presents an improved current-doubler rectifier (CDR) circuit and its implementation with integrated magnetics for high efficiency, high power-density DC/DC converter applications. Compared to previously published integrated magnetics for CDR circuits, the proposed design significantly increases the equivalent filtering inductance resulting in lower voltage and current ripple and higher efficiency, especially under fight load. Operation of the integrated magnetics is explained, along with an equivalent circuit model suitable for steady state and dynamic response analysis. Experimental results from two 100 W, 3.3 V output half-bridge prototype converters are presented to validate the concept and the analysis.

Under-resonant operation of an ideal multi-resonant series-parallel power converter (MRSPC) with a capacitive output filter is modeled in this paper. This operation allows zero current switching (ZCS), which is convenient for bipolar devices. The capacitive output filtering reduces the recovery effect of the rectifier diodes and is suitable for high output voltage applications. A closed-form solution is found for this power converter, based on state space analysis using energy concepts. This approach simplifies the mathematical operations and gives better physical insight of the system variables. Based on the model, the steady-state characteristics of this power converter are derived by a simulation program, which are discussed and compared with the series resonant half-bridge power converter (SRHC). The optimum power converter parameters are found for given design requirements using computerized optimization routines. Several design examples are presented and compared with SRHC. The validity of the model is verified by SPICE simulations.

This papar proposes which the Dual Active Bridge (DAB) converter changes between Full Bridge (FB) converter's operation and Half Bridge (HB) converter's operation on the secondary side of the high frequency transformer depending on the output power. With the HB converter operation's, the iron loss of the transformer becomes small because the secondary voltage of the transformer becomes half compared to the FB converter's operation. In addition, Zero Voltage Switching (ZVS) is achieved at the light load. Therefore, the proposed circuit can obtain the high efficiency for the wide load by the changing the HB and the FB converter's operation depending on the output power. In this paper, the changing point between the HB and the FB converter is derived using the loss calculation. The validity of the proposed circuit is verified by 800-W prototype. From the experimental results, it is confirmed that the proposed circuit has the two local maximum efficiencies which are 92.9% and 93.4% at the light load and the heavy load using the proposed circuit.

The objective of this study was to develop recommendations for an optimal design of piezoelectric transformer (PT) AC/DC converters. The paper presents a comprehensive comparison of the two commonly used rectifier topologies in a PT based power converters: current doubler and voltage doubler rectifiers. The advantages and disadvantages of the two rectifiers were investigated and the range of their applications with respect to output current, voltage, power capability, load resistance etc.-was delineated. Generic parameters are proposed and used to derive normalized and closed form equations that can help choosing a PT for a given set of requirements. Simulation and experimental results were found to be in a good agreement with the derivation of the theoretical analysis.

A new multiple-coupled inductor (MCI) is proposed for good cross regulation among low output voltages, high power density, and reduced converter volume. Moreover, a current doubler rectifier and a self-driven synchronous rectifier are presented to achieve high efficiency. The structure of the MCI is composed of four windings on a common core, and has the properties of a current doubler and good cross regulation. A dc-dc half-bridge converter using the proposed MCI is analyzed and designed for 40-W low output voltages (3.3, 4.5 V). This converter is very suitable for high current and low voltage applications. It is shown via experimental results that efficiency of over 90% and cross regulation of about 5% are achieved

The conventional half-bridge converter for a dc/dc stage in wide-output-voltage and constant-output-current applications such as LED drivers is limited in achieving high efficiency because it is difficult to be designed optimally. To overcome this limitation, an integrated asymmetrical half-bridge zeta converter is proposed for high efficiency in the overall output voltage range. The proposed converter can be simply implemented by replacing a snubber diode with a switch. The proposed converter operates similar to the asymmetrical half-bridge converter by turning off the switch in the low-output-voltage region, which enables it to have a small dc-offset current in the transformer. In the high-output-voltage region, the proposed converter operates similar to the half-bridge zeta converter by turning on the switch, which has small transformer core loss. Therefore, the proposed converter can achieve high efficiency over the entire output voltage range compared with the conventional converters. The validity of the proposed converter is confirmed by experimental results from a prototype with 400-V input and 90-180-W/3-A output.

An improved half-bridge type ZVS-PWM DC-DC power converter which uses a saturable reactor-assisted soft-switching technique is presented in this paper. The power converter with a high-frequency transformer link has many advantages such as lower switching and conduction losses, load operation in wide range, constant frequency operation and minimized EMI. Its operating principle is illustrated and its steady-state circuit analysis is carried out. In order to demonstrate the remarkable effectiveness of the converter characteristics, feasible experiments are carried out with a 150 W-200 kHz prototype.

A previously reported (Campos-Canton and Espinosa-Perez, 1999) control law that solves the output voltage control problem for a single-phase voltage-source UPS inverter is experimentally evaluated. The adaptive nonlinear controller was developed considering a half-bridge DC-AC power converter connected to a (linear) resistance load. The evaluation procedure considers the following topics: verification of the stability and convergence theoretical properties, evaluation of the dynamic practical response, disturbance (load change) rejection capability, behavior under low size (and then cost) passive elements and (relative) low switching frequency. It is shown that the controller under study satisfies in a remarkable way all the above evaluation criteria.

An improved half-bridge type ZVS-PWM DC-DC power converter which uses a saturable reactor-assisted soft-switching technique is presented in this paper. The power converter with a high-frequency forward and flyback hybrid transformer link has many advantages such as lower switching and conduction losses, load operation in a wide range, constant frequency operation and minimized EMI. Its operating principle is illustrated and its steady-state circuit analysis are carried out. In order to demonstrate the remarkable effectiveness of the converter characteristics, feasible experiments are actually carried out with a 150 W-200 kHz prototype converter using power MOSFETs.

This paper presents a new current-doubler rectifier for application on buck derived DC-DC converters, such as, push-pull, half-bridge, full-bridge, dual-bridge, NPC three-level, and others. This new proposal, named as Three-State Rectifier (TSR), is generated using the three- state switching cell. The proposed rectifier is similar to the Center Tapped Rectifier (CTR), and to the current-doubler rectifier named Interleaving Rectifier (IR). The new rectifier circuit is an alternative to substitute the previous rectifiers topologies, operating with rectifier diodes only, or with synchronized switches depending on the output voltage rating. Advantages of such a new proposal are: the current through the components of the converter are less pulsated which reflects in the conduction losses reduction and the current in the secondary winding of the transformer reaches maximum half of the output average current. The disadvantage of the proposed converter is that the sizes of the autotransformer and the inductor, both equals, are 20% higher than the sizes of the inductors of the IR rectifier. In order to verify the theoretical analysis and compare its performance with similar ones proposed in literature, experimental results consisting of relevant waveforms and curves from a full-bridge phase-shift control DC-DC converter with TSR rectifier and IR rectifier are presented, for a 1.5 kW output power prototype, an input voltage of 400 V and output voltage of 60 V.

An improved multiple-input bidirectional dc-dc converter for application in a fuel cell system is presented in this paper. The converter interconnects a fuel cell, supercapacitor, and load by a combination of a dc-link and magnetic-coupling. Some novel control methods for the proposed multiple-input converter are developed. An easy-to-implement variable hysteresis band control is proposed to achieve zero-voltage switching (ZVS) for the supercapacitor side half-bridge without auxiliary devices. Furthermore, in order to handle the wide variation of the fuel cell voltage while keeping ZVS, an asymmetrical wave control method is introduced. In this way, ZVS is achievable over the entire operating range. Simulation and experimental results that verify the effectiveness of the control methods are presented

This paper presents a concept of smart charging station using bidirectional half bridge converter for an electric vehicle. This battery charging station is useful for charging applications along with harmonics and reactive power compensation in a distribution system. A filter which is adaptive to the supply voltage frequency is used for the estimation of the 50 Hz component of load current. Due to additional features of vehicle charger, associated with the power quality improvement, there will be a drastic reduction in the current drawn from utility to meet the same load demand. The charging station presented in this paper is termed as smart with several function. The proposed smart charger is able to improve power quality of residential loads or other loads, not only during charging/discharging of the vehicle battery, but also in the absence of the vehicle. The Simulink model is developed with MATLAB software and its simulation results are presented. The level of current distortion during charging and and discharging mode is recorded 1.6 % and 2.4 % respectively with unity supply power factor during experiments. The performance of converter is evaluated during charging modes both in constant current (CC) and constant voltage (CV) modes.