Metal rectifier

Abstract: This paper first presents a hybrid-switching step-down dc-dc converter, and then, by introducing transformer isolation, a novel hybrid-switching phase-shift full-bridge dc-dc converter is derived for electric vehicle battery chargers. The proposed converter provides wide zero-voltage-switching range in the leading-leg switches, achieves zero-current-switching for lagging-leg switches, and uses a hybrid-switching method to avoid freewheeling circulating losses in the primary side. Because the resonant capacitor voltage of the hybrid-switching circuit is applied between the bridge rectifier and the output inductor for the duration of the freewheeling intervals, a smaller sized output inductor can be utilized. With the current rectifier diode of the hybrid-switching circuit providing a clamping path, the voltage overshoots that arise during the turn-off of the rectifier diodes are eliminated and the voltage stress of bridge rectifier is clamped to the minimal achievable value, which is equal to secondary-reflected input voltage of the transformer. The inductive energy stored in the output inductor and the capacitive energy stored in the resonant capacitor of the hybrid-switching circuit are transferred to the output simultaneously during the freewheeling intervals with only one diode in series in the current path, achieving more effective and efficient energy transfer. The effectiveness of the proposed converter was experimentally verified using a 3.6-kW prototype circuit designed for electric vehicle onboard chargers. Experimental results of the hardware prototype show that the converter achieves a peak efficiency of 98.1% and high system efficiencies over wide output voltage and power ranges.

Abstract: A synchronous rectifier for use with a clamped-mode power converter uses in one embodiment a hybrid rectifier with a MOSFET rectifying device active in one first cyclic interval of the conduction/nonconduction sequence of the power switch and a second rectifying device embodied in one illustrative embodiment as a low voltage bipolar diode rectifying device active during an alternative interval to the first conduction/nonconduction interval. The gate drive to the MOSFET device is continuous at a constant level for substantially all of the second interval which enhances efficiency of the rectifier. The bipolar rectifier device may also be embodied as a MOSFET device. The subject rectifier may be used in both forward and flyback power converters.

Abstract: A resonant synchronous rectifier which combines the fast switching of Schottky diodes with low conduction drop of MOSFET devices is discussed. The MOSFET devices are driven in a resonant fashion by the power circuit, resulting in partial recovery of the energy stored in the parasitic capacitances. Power loss in the resonant synchronous rectifier is determined as a function of various devices parameters and switching frequency. Contributions of conduction losses, gate-drive switching losses, and losses due to current circulating in the parasitic capacitances are discussed. The analysis indicates that, at megahertz range switching frequencies, a resonant synchronous rectifier has a significantly higher efficiency than either a PWM (pulse width modulation) synchronous rectifier or a Schottky diode rectifier. >

Abstract: A novel AlGaN/GaN-on-Si rectifier with a gated ohmic anode has been proposed to reduce the turn-on voltage without breakdown-voltage degradation. The combination of an ohmic anode and a recessed Schottky gate is responsible for the low turn-on voltage and thus increases the forward current. In comparison with conventional Schottky diodes, the forward current at 1.5 V was increased by 2 to 3 times, whereas no breakdown-voltage degradation was observed. The proposed rectifier with an anode-to-cathode distance of 18 μm exhibited a turn-on voltage of 0.37 V, a forward current density of 92 mA/mm at 1.5 V, and a breakdown voltage of 1440 V.