Recently, the bi-directional dc-dc converter has been focused on because of the huge demand for diversification of power supply network including battery. The dual active bridge (DAB) dc-dc converter is one of the most popular circuits for bi-directional applications because of its simple structure. However, power efficiency at light load is the intrinsic problem of a bi-directional DAB DC-DC converter. In this paper, the simple solution with digital operation for the problem is proposed and experiments are performed with 1kW system. This method can reduce a switching surge without other circuits such as snubber and improve power efficiency at light load. Therefore it can reduce loss of switching surge and, improve power efficiency. From the results, 37% maximum power efficiency improvement at light load is confirmed. Furthermore, this method is capable of control in the conventional method in the heavy load range. Consequently, it is possible to reduce the switching surge and realize high power efficiency in a wide load range.

́ A Single LED is very small, and their luminance is related to the amount of driving current. Sufficient luminance for an illuminator requires many LEDs to be connected together and a constant current supplied to each LED. Therefore, the LED drive circuit must have constant-output-current control and/or constant-luminance control. We propose an LED drive circuit that consists of a boost-type DC-DC converter with constant-output-current control and constant-luminance control. This circuit is a switching regulator-type circuit controlled by pulse width modulation (PWM). Both the power and the constant-current control can be provided by a single system, without any ballast resistor or auxiliary current control circuit.

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Abstract-Recently, the bi-directional dc-dc converter has been focused on because of the huge demand for diversification of power supply network including battery. The dual active bridge (DAB) dc-dc converter is one of the most popular circuits for bi-directional applications because of its simple structure. However, power efficiency at light load is the intrinsic problem of a bi-directional DAB DC-DC converter. In this paper, the simple solution with digital operation for the problem is proposed and experiments are performed with 1kW system. This method can reduce a switching surge without other circuits such as snubber and improve power efficiency at light load. Therefore it can reduce loss of switching surge and, improve power efficiency. From the results, 37% maximum power efficiency improvement at light load is confirmed. Furthermore, this method is capable of control in the conventional method in the heavy load range. Consequently, it is possible to reduce the switching surge and realize high power efficiency in a wide load range.

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Recently, increased attention is being paid to power supply networks using energy storage devices such as batteries. Network topologies using bi-directional isolated DC-DC converters of low or medium capacity are required for the diversification of power supply networks. The dual active bridge (DAB) DC-DC converter is one of the most effective bi-directional isolated DC-DC converters. However, the circuit has some inherent problems such as degradation of power efficiency and the occurrence of surges during light-load operation. In this paper, we propose a control technique to solve these problems. From the experimental results, it is confirmed that the maximum power efficiency improvement was 16% for a light load. Applying two operation modes, the proposed operation in light load and the conventional operation in heavy load, the circuit can be operated across a full range of road. To switch between the two modes seamlessly, the precise boundary point of the two modes is needed for feedback control. Therefore, a precise static characteristic analysis with loss was carried out. From the results, the loss included simple equivalent circuit model was obtained. The root mean square error between the proposed analysis and the experimental results is within 4%.

This paper presents the analysis of a new multi-oscillated current resonant type DC-DC converter. Current resonant converters have several remarkable features such as high efficiency, small size, low cost and low noise, and are frequently employed in many portable electronic systems such as personal computers, cellular phones and flat panel displays.The current resonant type converter generally employs pulse frequency modulation for constant voltage control in the output. For this reason, the magnetizing current through the converter not only causes a power loss under a light load, but also a loss during stand-by.Therefore, this type of converter has a problem in that the required smaller size cannot be achieved, because an auxiliary source is necessary for stand-by.In order to solve these problems, a new current resonant type power supply is proposed in which two driving methods are employed. In these driving methods, one MOSFET as a main switch is driven by an auxiliary winding of the transformer and another MOSFET as a main switch is driven by the driving IC with a low withstand voltage.Good agreement of the observed and simulated waveforms was confirmed. In addition, eight distinct states and four distinct operating modes, which compose of the sequence of states, were clarified by experimental and simulated analysis.