Esam H. Ismail

Integrated high quality rectifier-regulators

A family of AC-to-DC converters which integrate the functions of low harmonic rectification, low frequency energy storage, and wide bandwidth output voltage control into a single converter containing one, two, or four active switches is presented. These converters utilize a discontinuous conduction mode input inductor, an internal energy storage capacitor, and transformer secondary circuits which resemble the bridge, forward, flyback, or Cuk DC-DC converters. A large-signal equivalent circuit model for this family which uses the loss-free resistor concept is presented. Design strategies and experimental results are given. High performance regulation with satisfactory line current harmonics is demonstrated with conventional duty ratio control. Further improvements in line current are possible by simultaneous duty ratio and switching frequency control.<<ETX>>

Bridgeless SEPIC Rectifier With Unity Power Factor and Reduced Conduction Losses

In this paper, a new bridgeless single-phase AC-DC converter with an automatic power factor correction (PFC) is proposed. The proposed rectifier is based on the single-ended primary inductance converter (SEPIC) topology and it utilizes a bidirectional switch and two fast diodes. The absence of an input diode bridge and the presence of only one diode in the flowing-current path during each switching cycle result in less conduction loss and improved thermal management compared to existing PFC rectifiers. Other advantages include simple control circuitry, reduced switch voltage stress, and low electromagnetic-interference noise. Performance comparison between the proposed and the conventional SEPIC PFC rectifier is performed. Simulation and experimental results are presented to demonstrate the feasibility of the proposed technique.

New Bridgeless DCM Sepic and Cuk PFC Rectifiers With Low Conduction and Switching Losses

New bridgeless single-phase ac-dc power factor correction (PFC) rectifiers based on Sepic and Cuk topologies are proposed. The absence of an input diode bridge and the presence of only two semiconductor switches in the current flowing path during each switching cycle result in less conduction losses and improved thermal management compared to the conventional Sepic and Cuk PFC converters. The proposed topologies are designed to work in discontinuous conduction mode (DCM) to achieve almost unity power factor in a simple and effective manner. The DCM operation gives additional advantages such as zero-current turn-on in the power switches, zero-current turn-off in the output diode and reduces the complexity of the control circuitry. The proposed rectifiers are theoretically investigated. Performance comparisons between the proposed and conventional Sepic PFC rectifiers are performed. Simulation and experimental results are provided for a design example of a 65-W/48-V at 100- Vrms line voltage to evaluate the performance of the proposed PFC rectifier.

A single transistor three phase resonant switch for high quality rectification

Three new classes of low-cost 3 phi AC-DC high-power-factor/low-harmonic controlled rectifiers are derived from parent DC-DC power converter topologies containing boost-type inputs, buck-type inputs, and quasi-resonant zero-current-switch (ZCS) buck-type inputs. With a single active switch in addition to the diode bridge rectifier, the converters are capable of drawing a high-quality input-current waveform naturally at nearly unity power factor. Thus a simple 3 phi AC-DC high power factor rectifier is obtained. Simulation and experimental results are supplied to demonstrate the validity of the concept.<<ETX>>

New Efficient Bridgeless Cuk Rectifiers for PFC Applications

Three new bridgeless single-phase ac-dc power factor correction (PFC) rectifiers based on Cuk topology are proposed. The absence of an input diode bridge and the presence of only two semiconductor switches in the current flowing path during each interval of the switching cycle result in less conduction losses and an improved thermal management compared to the conventional Cuk PFC rectifier. The proposed topologies are designed to work in discontinuous conduction mode (DCM) to achieve almost a unity power factor and low total harmonic distortion of the input current. The DCM operation gives additional advantages such as zero-current turn-ON in the power switches, zero-current turn-OFF in the output diode, and simple control circuitry. Performance comparisons between the proposed and conventional Cuk PFC rectifiers are performed based on circuit simulations. Experimental results for a 150 W/48 Vdc at 100 Vrms line voltage to evaluate the performance of the proposed bridgeless PFC rectifiers are provided.

High Conversion Ratio DC–DC Converters With Reduced Switch Stress

In this paper, a new class of single-switch nonisolated high step-up DC-DC converters with simple topologies is proposed. The proposed topologies utilize a hybrid switched capacitor technique for providing a high voltage gain without extreme switch duty cycle and yet enabling the use of a lower voltage and RDS-ON MOSFET switch so as to reduce cost, switch conduction and turn-on losses. Other advantages of the proposed topologies include: continuous input/output current, simple structure and control. The principle of operation in continuous conduction mode and discontinuous inductor current mode are analyzed. Experimental results obtained on a 45-W prototype are also presented.

Buck–Boost-Type Unity Power Factor Rectifier With Extended Voltage Conversion Ratio

A buck-boost-type unity power factor rectifier is proposed in this paper. The main advantage of the proposed rectifier over the conventional buck-boost type is that it can perform input power factor correction (PFC) over a wider voltage conversion range. With a single switch, a fast well-regulated output voltage is achieved with a zero-current switch at turn-on. Moreover, the switch voltage stress is independent of converter load variation. The proposed converter is well suited for universal offline PFC applications for a low power range (<150 W ). The feasibility of the converter is confirmed with results obtained from a computer simulation and from an experimental prototype.

Integrated Buck–Boost–Quadratic Buck PFC Rectifier for Universal Input Applications

This paper presents a new single-stage single-switch (S4) high power factor correction (PFC) ac/dc converter suitable for low-power applications (¿150 W) with a universal input voltage range (90-265 Vrms). The proposed topology integrates a buck-boost input current shaper with a quadratic buck converter. As a result, the proposed converter can operate with larger duty cycles compared to the exiting S4 topologies; hence, making them suitable for high-frequency nonisolated applications. Additional features are gained when both the input PFC buck-boost cell and the quadratic buck cell operate in discontinuous conduction mode (DCM). These features include low semiconductor voltage stress, zero-current switch at turn-on, and simple control with a fast well-regulated output voltage. A detailed circuit analysis is performed to derive the design equations. The feasibility of the converter is confirmed with results obtained from a computer simulation and an experimental prototype.

An Improved Topology of SEPIC Converter With Reduced Output Voltage Ripple

An improved version of a single-ended primary inductor converter (SEPIC) is presented. The converter consists of a conventional SEPIC converter plus an additional high-frequency transformer and diode to maintain a freewheeling mode of the DC inductor currents during the switch on state. The voltage conversion ratio characteristics and semiconductor device voltage and current stresses are characterized. The main advantages of this converter are the continuous output current, smaller output voltage ripple, and lower semiconductors current stress compared with the conventional SEPIC converter. The design and simulation of the concept is verified by an experiment with a 48-V input and 12-V/3.75-A output converter.

A new bridgeless PFC Sepic and Cuk rectifiers with low conduction and switching losses

New bridgeless single phase ac-dc power factor correction (PFC) rectifiers based on Sepic and Cuk topologies are proposed. The absence of an input diode bridge and the presence of only two semiconductor switches in the current flowing path during each switching cycle results in less conduction losses and improved thermal management compared to the conventional Sepic and Cuk PFC converters. The proposed topologies are designed to work in discontinuous conduction mode (DCM) to achieve almost unity power factor in a simple and effective manner. The DCM operation gives additional advantages such as: zero-current turn-on in the power switches, zero-current turn-off in the output diode, and reduces the complexity of the control circuitry. The proposed rectifiers are investigated theoretically. Performance comparisons between the proposed and conventional Sepic PFC rectifiers are performed. Simulation and experimental results are provided for a design example of a 65W/48V at 100 Vrms line voltage to evaluate the performance of the proposed PFC rectifier.