Characterization of fast relaxation by oxide-trapped charges under BTI stress on 64 nm HfSiON/SiO2 MOSFETs

For HfSiON/SiO2 n-type and p-type MOSFETs with a channel length L = 64 nm, the fast relaxation effect of oxide-trapped charges Q(ox) during interrupt for bias temperature instability (BTI) degradation measurement were investigated, and a model that compensated for this effect to predict lifetime t(L) was proposed. Experimental results show that the fast relaxation of Qox during threshold-voltage V-th measurement rapidly saturates within 1 s and is exponentially increasing for gate stress voltage V-g,V-str and exponentially decreasing for measurement duration t(m) but does not affect the BTI degradation mechanism. Using the V-g,V-str and t(m) dependence of Q(ox's) fast relaxation under BTI stress, t(L) prediction model was proposed to compensate the recovery effect by V-th measurement from BTI degradation measured in slow measurement (SM) condition with t(m) > 1 mu s. The proposed model increases the precision of the estimate of t(L) by considering the recovery effect of Qox even in SM. (C) 2020 The Japan Society of Applied Physics11Nsciescopu

Quasi-Resonant Passive Snubber for Improving Power Conversion Efficiency of a DC-DC Step-Down Converter

A quasi-resonant passive snubber for the conventional dc-dc step-down converter is proposed. The snubber uses six passive components to achieve a zero-current turn-ON and zero-voltage turn-OFF of the switch, and to suppress the reverse recovery current of diode. At input voltage of 200 V, output voltage of 100 V, output power of 300 W, and switching frequency of 190 kHz, the snubber increased the power conversion efficiency eta(e) by 2.8% and stabilized the temperature of MOSFET switch at similar to 68 degrees C. The snubber worked well for both MOSFET and insulated gate bipolar transistor (IGBT) switches without increasing the voltage stress. These experimental results show that the proposed snubber is very helpful for improving eta(e) of a dc-dc step-down converter that operates at a high frequency.11Nsciescopu

Reduction of input voltage/current ripples of boost half-bridge DC-DC converter for photovoltaic micro-inverter

This paper describes a boost half-bridge DC-DC converter for photovoltaic system that reduces the input voltage and current ripples by using a 1:1 transformer and an auxiliary capacitor. The 1:1 transformer replaces the boost inductor in a previous boost half-bridge converter. The auxiliary capacitor is connected serially to the secondary coil of the 1:1 transformer, and resonates with the leakage inductance of the 1:1 transformer. The input voltage and current ripples are reduced by setting the switching frequency equal to the resonance frequency between the auxiliary capacitor and the leakage inductance, and by coupling the resonance current to the primary coil of the 1:1 transformer. The proposed converter had input voltage ripple less than 0.2 V-p.p, input current ripple less than 0.81 A(p.p), 5, and power-conversion efficiency higher than 94.5% when the converter was operated at input voltage of 30-50 V, output voltage of 400 V, output power of 30-300 W, and switching frequency of 46 kHz. These experimental results show that the proposed converter is well suited for photovoltaic micro-inverter applications that require a small input capacitor, low input voltage, high input current, high output voltage, and high power-conversion efficiency.11Nsciescopu

Wireless Battery Charging Circuit Using Load Estimation without Wireless Communication

A wireless battery charging circuit is proposed, along with a new load estimation method. The proposed estimation method can predict the load resistance, mutual inductance, output voltage, and output current without any wireless communication between the transmitter and receiver sides. Unlike other estimation methods that sense the high-frequency AC voltage and current of the transmitter coil, the proposed method only requires the DC output value of the peak current detection circuit at the transmitter coil. The proposed wireless power transfer (WPT) circuit uses the estimated parameters, and accurately controls the output current and voltage by adjusting the switching phase difference of the transmitter side. The WPT prototype circuit using a new load estimation method was tested under various coil alignment and load conditions. Finally, the circuit was operated in a constant current and constant voltage modes to charge a 48-V battery pack. These results show that the proposed WPT circuit that uses the new load estimation method is well suited for charging a battery pack

Modularized Design of Active Charge Equalizer for Li-Ion Battery Pack

A modularized design of an active charge equalizer and a charge equalization algorithm for a Li-ion battery pack are proposed in this paper. The equalizer consists of one module-balancing circuit andM cell-balancing circuits, where M is the number of modules in the battery pack. Each balancing circuit uses an inductor that is placed in a bridge of four bidirectional switches and works as an energy carrier, and uses a cell/module access network that enables energy transfer from one cell/module to another cell or module. The charge equalization between modules can be performed simultaneously with that between cells, so the proposed circuit can significantly reduce the time required to equalize the charges of all cells in the battery pack. The proposed circuit was tested under various charging/discharging conditions for a battery pack composed of four serially connected modules, with four serially connected cells permodule. Experimental results show that the proposed circuit and algorithm comprise a good solution to balance a Li-ion battery pack.11Nsciescopu

Active Balancing of Li-ion Battery Cells Using Transformer as Energy Carrier

A circuit for balancing Li-ion battery cells is proposed. This circuit requires one small transformer and N + 3 bilateral switches to equalize the charging states of N serially connected battery cells. The transformer works as an energy carrier, and the switches select two unbalanced cells that require an energy transfer from one to the other cell. The circuit was tested for a 12-cell Li-ion battery under static, cyclic, and dynamic charging/discharging conditions. Under static condition, the power-transfer efficiency was measured as 80.4% at a balancing power of 0.78 W; two 4400-mA·h battery cells at a state of charge (SOC) = 70 and 80% were equalized after 78 min. The results of cyclic and dynamic charging/discharging conditions show that the circuit is appropriate for balancing the Li-ion battery cells for vehicles and energy storage systems.11206sciescopu