Abbas A. Fardoun

A Family of Single-Switch PWM Converters With High Step-Up Conversion Ratio

A new family of a single-switch three-diode dc-dc pulsewidth-modulated (PWM) converters operating at constant frequency and constant duty cycle is presented in this paper. The proposed converters are different from the conventional dc-dc step-up converters, and they posses higher voltage gain with small output voltage ripples. Other advantages of the proposed converters include lower voltage stress on the semiconductor devices, simple structure, and control. Moreover, the reduced voltage stress on the diodes allows using Schottky diodes for alleviating the reverse-recovery current problem, as well as decreasing the switching and conduction losses. The principle of operation, theoretical analysis, and experimental results of one prototype rated 40 W and operating at 94 kHz are provided in this paper to verify the performance of this new family of converters.

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.

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.

Ultra Step-Up DC–DC Converter With Reduced Switch Stress

In this paper, a new single-switch nonisolated dc-dc converter with high voltage transfer gain and reduced semiconductor voltage stress is proposed. The proposed topology utilizes a hybrid switched-capacitor technique for providing a high voltage gain without an 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. In addition, the low voltage stress across the diodes allows the use of Schottky rectifiers for alleviating the reverse-recovery current problem, leading to a further reduction in the switching, and conduction losses. The principle of operation and a comparison with other high step-up topologies are presented. Two extensions of the proposed converter are also introduced and discussed. Simulation and experimental results are also presented to demonstrate the effectiveness of the proposed scheme.

Reduction of EMI through switching frequency dithering

In this paper, a method is presented to reduce electro-magnetic emissions in AC drives. This method is applicable to many AC drives. It is proposed to dither the switching frequency of the power devices of the inverter in a pseudo-random way to spread out the emitted radio- frequency (RF) energy over larger frequency range. The proposed method requires only software changes. Practical constraints to implement the frequency dithering approach are discussed. Simulation & measurements shows an improvement of more than 10 dB. The proposed method also converts certain spikes at integer harmonics of the switching frequency from narrow band to broadband noise.

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.

Reduction of EMI in AC Drives Through Dithering Within Limited Switching Frequency Range

In this paper, a method is presented to reduce electromagnetic (EM) emissions in AC drives. This method is applicable to many AC drives. It is proposed to dither the switching frequency of the power devices of an inverter in a pseudorandom way to spread out the emitted RF energy over a larger frequency range. The proposed method requires only software changes. Practical constraints to implement the frequency dithering approach are discussed. Simulation and measurement results show an improvement of more than 10 dB. The proposed method also converts specific spikes in the long-wave range from narrowband to broadband noise, which results in less stringent EM emission requirements for many applications.

A comparison between three proposed bridgeless Cuk rectifiers and conventional topology for power factor correction

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 switching cycle result in less conduction losses and an improved thermal management compared to the conventional Cuk PFC converter. The proposed topologies are designed to work in discontinuous conduction mode (DCM) to achieve almost unity power factor and low total harmonic distortion (THD) of 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 reduces the complexity of the control circuitry. Performance comparisons between the proposed and conventional Cuk PFC rectifiers are performed based on circuit simulation. Experimental results for a 150W/48Vdc at 100 Vrms line voltage to evaluate the performance of the proposed bridgeless PFC rectifier are provided.

Bridgeless PFC-Modified SEPIC Rectifier With Extended Gain for Universal Input Voltage Applications

In this paper, a new single-phase ac-dc PFC bridgeless rectifier with multiplier stage to improve the efficiency at low input voltage and reduce the switch-voltage stress is introduced. The absence of an input rectifier bridge in the proposed rectifier 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 full bridge topology. Lower switch voltage stress allows utilizing a MOSFET with lower RDS-on. The proposed topology is designed to operate in discontinuous conduction mode (DCM) to achieve almost a unity power factor and low total harmonic distortion (THD) of the input current. The DCM operation gives additional advantages such as zero-current turn-on in the power switches and simple control circuitry. The proposed topology is compared with modified full-bridge SEPIC rectifier in terms of efficiency, THD, and power factor. Detailed converter analysis, small signal model, and closed-loop analysis are presented. Experimental results for a 200 W/400 Vdc at universal line voltage range to evaluate the performance of the proposed bridgeless PFC rectifiers are detailed.