Forward Power Converter Research Articles

A new partially isolated hybrid output of multiport multilevel converter for photovoltaic based power supplies

Multiport converters (MPCs), which can have multiple inputs and multiple output (MIMO) ports, have been suggested to integrate a variety of sources (including storage facilities) with diversified loads, thereby guaranteeing both an effective utilization of sources and the uninterruptible supply to loads. MPCs transfer the power between those sources and (active/passive) loads concurrently/independently. The attractive features of MPCs include minimal component count, higher power conversion efficiency, haste response, higher power density, and hence better sizing, combined control point, and bidirectional and soft switching abilities. MPCs are the perfect solution in applications where complex energy distribution prevails, such as renewable energy systems (RES), hybrid electric vehicle (HEV) systems, DC power distribution systems, etc. This paper proposes a hybrid output multiport multilevel converter (HOMPMLC), which is a unique, partially isolated breed of MPC. The HOMPMLC is the multiple input and dual output (MIDO) converter, which can deliver twosome outputs (both AC and DC) from several DC sources. In the HOMPMLC, a new multilevel inverter (MLI) topology, Single stage multilevel DC-link multilevel inverter (SSMLDCMLI), is involved to synthesize a high quality AC output, which utilizes five switches for the seven level improved quality AC output, and the DC output port is accomplished with the help of a forward power converter. The working of the HOMPMLC is studied for a solar photovoltaic system in the MATLAB®Simulink R2016a simulation platform as well as in an experimental investigation involving 4 panels (Schüco MPE-340-AL-01; each 340 Watts).

Isolated battery charger with multi‐level rectifier

This paper presents an isolated battery charger which is configured by a seven-level AC-DC power converter and an isolated DC-DC power converter. The seven-level AC-DC power converter is composed of a diode rectifier and a three-port DC-DC power converter. The three-port DC-DC power converter generates a four-level voltage at the DC bus of the diode rectifier by controlling its power electronic switches. Accordingly, the voltage at the AC input terminals of the diode rectifier is an AC voltage with seven levels, and the input current is sinusoidal and in phase with the utility voltage to perform unity power factor. The inductance of the filter inductor and the capacity of the EMI filter can be reduced due to the seven-level AC voltage at the input AC terminals of the seven-level AC-DC power converter. The isolated DC-DC power converter is a two-level forward power converter to regulate the voltages of the three-port DC-DC power converter and generate an isolated output power to charge the battery set. A prototype is developed and tested to verify the performance of the isolated battery charger. The experimental results show the isolated battery charger performs as expected.

Single‐phase multi‐level AC–DC power conversion interface

This study proposes a single-phase multi-level AC–DC power conversion interface that is composed of a power factor correction stage and a buck power conversion stage. The power factor correction stage is configured using two power factor correctors (PFCs) connected in cascade. Only the power electronic switch in one of the PFCs is switched in high-frequency pulse-width modulation to generate a five-level voltage at the input AC terminals of the power factor correction stage. The input current of the power factor correction stage is controlled to be sinusoidal and in phase with the utility voltage. Accordingly, the voltage stress and switching loss are improved because the change in voltage in each switching operation is reduced. The filter inductance and the electromagnetic interference are also reduced. The buck power conversion stage integrates a buck power converter and a forward power converter that combines the output voltages of the two PFCs in a stable DC voltage that supplies the load. The controllers for the buck power converter and the forward power converter are integrated to simplify the controller for the buck power conversion stage. A hardware prototype is developed to verify the performance of the proposed single-phase AC–DC power conversion interface.

Hybrid Forward and Backward Threshold-Compensated RF-DC Power Converter for RF Energy Harvesting

This paper presents a hybrid forward and backward threshold voltage compensated radio-frequency to direct current (RF-to-DC) power conversion circuit for RF energy harvesting applications. The proposed circuit uses standard p-channel metal-oxide semiconductor transistors in all the stages except for the first few stages to allow individual body biasing eliminating the need for triple-well technology in the previously reported forward compensation schemes. Two different RF-DC power conversion circuits, one optimized to provide high power conversion efficiency (PCE) and the other to produce a large output DC voltage harvested from extremely low input power levels, are designed and fabricated in IBM's 0.13 μm complementary metal-oxide-semiconductor technology. The first circuit exhibits a measured maximum PCE of 22.6% at -16.8 dBm (20.9 μW) and produces 1 V across a 1 MΩ load from a remarkably low input power level of -21.6 dBm (6.9 μW) while the latter circuit produces 2.8 V across a 1 MΩ load from a peak-to-peak input voltage of 170 mV achieving a voltage multiplication ratio of 17. Also, design strategies are developed to enhance the output DC voltage and to optimize the PCE of threshold voltage compensated voltage multiplier.

Flyback Versus Forward Switching Power Supply Topologies For Unipolar Pulsed-Power Applications

We discuss and compare modified flyback and forward switching power converter topologies in applications needing repetitive high-voltage (HV) low duty-cycle rectangular unipolar pulses. The output filters of these two converter topologies are removed, and the needed low duty-cycle operation is used advantageously to generate several kilovolts of pulses using only low-voltage seriesless semiconductors. The two circuits proposed are based on step-up transformers with a constant flux reset clamp that uses the low duty cycle required to reduce the voltage stress on all semiconductor switches. Prototypes were assembled using < 1-kV semiconductor switches to obtain -5-kV output pulses with 5-mus pulsewidth and 10-kHz pulse frequency. Experimental results are presented and discussed. The forward topology was found to be a better choice to deliver HV low duty-cycle unipolar rectangular pulses, and it was tested in a plasma load.

A Saturable Transformer Based Approach to Drive a Synchronous Rectifier

This paper presents a new and an improved approach for driving a synchronous rectifier (SR) in a switching power converter. This approach consists to use a saturable transformer (ST) in series with a synchronous rectifier to detect the synchronous rectifier transition at turn off. The saturable transformer generates a very narrow signal (100 ns to 200 ns) at turn OFF when the current in the synchronous rectifier reaches zero. This signal will be used by the gate drive circuit to drive the synchronous rectifier at turn off. The saturable transformer approach presented in this paper is topology independent and it can be applied to any power converter. In addition, it offers the possibility of parallel connection of power converters without the risk of power sinking. The two-switch forward power converter with two synchronous rectifiers has been implemented to test the functionality of the synchronous rectifier driving method. In this experimental prototype, the input voltage is equal to 100 V the output voltage is equal to 9 V and the output load is 20 A. At the 180 Watts output load, the minimum measured efficiency was 93 % at 9 V.

Two-switch forward soft-switching PWM DC-DC powerconverter

A novel prototype is presented of a two-switch forward soft-switching PWM DC-DC power converter with reduced switching and conduction power losses, which can operate under two soft commutations of zero voltage and zero current of full bridge circuit topology.

Single-switch two-output flyback-forward converter operation

A double power converter with fully independent regulated outputs is introduced. The proposed topology results from magnetic integration of flyback and forward power converters. The derived converter shares a single power switch having a single magnetic component. Also, only one standard pulsewidth modulation (PWM) integrated modulator is needed in order to keep independent closed-loop control of both output voltages. The double regulation may be sustained over a wide spread of current loads. Boundaries of full regulation and experimental results are presented.

Analysis and evaluation of interleaving techniques in forward converters

Analysis, design and evaluation of different interleaving techniques for the forward power converter are presented. Specifically, the performance of the one-choke interleaving approach is compared with the two-choke interleaving approach. The results of the analysis are verified experimentally on two 5 V/20 A interleaved DC/DC power converters. The analysis, design and evaluation results can be extended to any number of interleaved power converters.

Development of an integrated CAD tool for switching power supply design with EMC performance evaluation

A computer-aided tool for the design of switching power supplies integrating a layout editor, autorouter, component library builder and EMI simulator is presented. The software takes on a modular approach and develops the printed circuit board (PCB) layout with emphasis on electromagnetic compatibility (EMC). The prediction of interference level is achieved by SPICE simulation with suitable model assignments of EMI sources, components, and PCB tracks. An offline forward power converter is built and measured to verify the simulated result. Finally, a performance index is introduced to act as an indicator for the EMC performance of a given PCB layout.

Unity power factor ZVS AC-to-DC converters with an active filter

Unity power factor zero-voltage-switched (ZVS) AC-to-DC power converters with an active filter are proposed. The line voltage is supplied to AC-to-DC power converters through a rectifier circuit with an input filter, to reduce high-frequency ripple components. The line current is almost synchronized to the line voltage, due to the low impedance of the input filter. Forward ZVS multiresonant power converters (ZVS-MRCs) are utilized for high-frequency operation and lossless switching. An active filter is introduced to minimize the twice line-frequency ripple component of the output voltage without large-size passive filters. Experimental results show that the proposed scheme gives good steady-state performances of the AC-to-DC power converters.

Forward converter regulator using controlled transformer

A new control scheme is proposed for a forward power converter regulator using a controlled transformer. Pulse width modulation (PWM) control is used to reset the control core of the controlled transformer. As a result, a low-cost ferrite core can be used for the controlled transformer to achieve good regulation and high efficiency. Overall efficiency of 82-86% is achieved in a 200 kHz, 500 W, 5 V output regulator. A PWM-controlled transformer regulator is particularly suited for high-output-current and/or high-output-voltage postregulator applications.

Small-signal modeling of multiple-output forward converters with current-mode control

A small-signal model of current-mode multiple-output feedback forward power converter has been developed. Based on the model, control performances are analytically expressed, and a compensation scheme is proposed. Comparison of such control with other control schemes is also discussed.

Decoupled output voltage control of quantum series resonant converter for improved buck-boost operation

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.

Small-signal analysis and design of weighted voltage control for a multiple-output forward converter

The small-signal model for a multiple-output forward power converter with weighted voltage control is derived. The effects of the weighting factors on the small-signal behavior are investigated. In addition, the small-signal characteristics of weighted voltage control are compared with the characteristics of a multiple-output power converter with coupled output-filter inductors. Finally, the effects of weighted voltage control on the small-signal characteristics of the converter with coupled inductors are examined. Based on the analysis, the design procedure for loop compensation is presented. The small-signal model and the design procedure are verified on an experimental two-output forward power converter.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A novel self-excited forward DC-DC converter with zero-voltage-switched resonant transitions using a saturable core

A novel self-excited forward DC-DC power converter is proposed. The turn-on and turn-off of the switch are zero-voltage-switching with resonant transition. A saturable core is used to achieve the self-excitation and the zero-voltage-switched resonant transition. The voltage waveform across the switch is trapezoidal with sinusoidal transitions, and the current waveform flowing through the switch is quasisquare. The switching losses, the conduction losses and the stresses of the switch are significantly reduced in the proposed power converter. The output voltage is determined by the ON duty ratio of the switch as in a PWM converter. Two methods to modulate the ON duty ratio are proposed. Both methods results in variable-frequency operation. Experiments on two 5 V, 20 A DC-DC power converters show good performance. >

Evaluation of synchronous-rectification efficiency improvement limits in forward converters

Design trade-offs for different implementations of the forward power converter with synchronous rectifiers are presented, and effects of the synchronous rectifier driving method on the conversion efficiency are evaluated. Specifically, the merits and limitations of the RCD-clamp and active-clamp reset approaches for a power converter with self-driven synchronous rectifiers are discussed. Estimates of the upper limits of the efficiency improvements of the discussed synchronous rectification approaches relative to the Schottky diode implementation are derived. Finally, experimental comparisons of efficiencies for an offline, 3.3 V/20 A forward power converter power stage are presented and compared with the theoretically estimated ones.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>