Alexander Abramovitz

A resonant DC-DC transformer

The characteristics of a push-pull parallel resonant converter (PPRC) when operated as a DC-DC transformer were investigated theoretically and experimentally. In the DC-DC transformer region, the voltage transfer ratio of the PPRC was found to be practically constant and independent of the input voltage and load. In this mode, all the switching elements operate in the zero voltage switching (ZVS) condition. Another important feature of the proposed DC-DC transformer is the ability to drive it by an arbitrary switching frequency, provided that the latter is lower than the self-oscillating frequency. This permits the synchronization of the converter to a master clock. The analytical expressions for voltage and current stresses, as well as the other key parameters derived, are applied to develop design guidelines for the DC-DC transformer. The proposed topology was tested experimentally on a 100-W unit which was run in the 200-kHz frequency region. >

A Resonant DC–DC Transformer With Zero Current Ripple

The paper presents a resonant converter topology capable of providing zero ripple conditions (ZRC) at either its input or output current. The basic properties of the proposed topology are discussed in detail. The remarkable symmetry and the proportional voltages of the circuit allow it to maintain ripple-less current independent of the load or switching frequency. Theoretical predictions are well supported by simulation and experimental results

Investigation of an alternative APFC control with no sensing of line voltage based on a triangular modulation carrier

An alternative control method for a boost active power factor corrector (APFC) operating in continuous conduction mode is presented, analyzed and verified by simulation and experiments. The proposed APFC scheme employs average current control to shape the input current. The power level is adjusted by modulating the amplitude of a triangular carrier as a function of the outer loop error signal. The proposed APFC does not require neither line voltage sensing nor an input voltage reference circuitry. The theoretical predictions are well supported by simulation and experimental results. The experimental results demonstrate some improved performance at low power levels as compared to other methods of APFC without sensing of input voltage.

A novel self-oscillating synchronously-rectified DC-DC converter

A self-oscillating synchronously rectified DC-DC converter (SOSYRC) is proposed and examined analytically and experimentally. The converter is composed of an autonomous high-frequency push-pull oscillator, a synchronous pulsewidth modulated (PWM) controller/driver, a synchronous rectifier, and an output filter. The synchronous controller is built around a conventional PWM controller. Its function is to maintain zero voltage switching (ZVS) and to pass integer number of cycles of the main frequency to prevent saturation of the push-pull transformer due to unbalanced operation. The main features of the SOSYRC are: operation under ZVS conditions, sinusoidal voltage waveforms, and the ability to independently control multiple outputs. Another important feature is the fact that only a fraction of the resonant current passes through the switches. Simulation and experimental results were found to be in good agreement with the model developed for the proposed SOSYRC.<<ETX>>

A resonant power factor conditioner

The applicability of a current-fed push-pull parallel-resonance power converter to power factor conditioning was investigated theoretically and experimentally. The experimental switching frequency was in the range 300-860 kHz. The basic features of soft switching, inherent high power factor and simple control, make the proposed approach a viable design alternative for power input stages.<<ETX>>

Current spectra translation in single phase rectifiers: implications to active power factor corrections

This study examines the input and output current spectra translation of a line-commutated single-phase full wave rectifier. Analytical expressions for the spectra translation of the current harmonics are derived. The proposed method is then used to quantify the contribution of a current-loop with finite bandwidth to the overall THD budget in average current mode APFC systems. The proposed theory is supported by computer simulation.

Performance evaluation of MagAmp regulated isolated AC-DC converter with high PF

This paper evaluates the performance of magnetic amplifier regulator in isolated off-line power supplies with power factor correction stage. Simplified controller circuitry is suggested and analyzed. Experimental results are reported.