Fumihiro Okazaki

Operational characteristics of a step-down converter applied proposed switching transient waveform modification

Recently, high performance power switching device realize high performance power converter. However, high speed turn-on and turn-off cause electromagnetic interference (EMI). EMI filters or wire shields decrease EMI. However, they take over space of automotive, and cost is expense. Authors have proposed a new method to decrease high-frequency noise at specific frequency band with modification of switching transient slope. In order to realize a step-down converter with modified switching slope, there are several problems such as generating PWM signal with modified slope, feasibility in a real chopper circuit, switching loss and so on. In this paper, a step-down converter applied proposed modified switching slope was successfully realized using MT (Modified Transient)-PWM generator. The operational characteristics were analyzed for resistive load.

Verification of LLC resonant converter applied a current-balancing high-frequency transformer with multi-output windings

DC-DC converters of hybrid vehicles and electric vehicles are required to become smaller and lighter for building roomy and light weight EV. High-frequency switching can be used to miniaturize DC-DC converter. However, the influence of the skin effect and the eddy current become large. Parallel operation of converter is often for current applications using multiple winding transformers in order to reduce of skin effect. However, it is difficult to equalize the each current of converter due to unbalance of winding resistance, drop voltage of diodes and so on. In this paper, the parallel LLC converter applied a current-balancing high-frequency transformer is proposed. The proposed converter can realize nearly equal current even if the stray impedance of secondary circuit of LLC are unbalanced.

H-bridge step-down converter applied proposed switching transient waveform modification to reduce specific harmonics

Authors has proposed a new method to decrease high-frequency noise at specific frequency band with modification of switching transient slope. In this paper, new voltage feedback type VDS controller (gate driver) has proposed to realize modified switching transient to increase stability. In the step-down converter applied propose VDS controller, harmonics reduction effect is obtained about 10 dB in AM radio band. Then, output voltage and switching loss characteristics was measured on the step-down converter applied proposed method. It is verified that these characteristics are same to conventional converter. In addition, the proposed method was applied to H-bridge step-down converter for DC motor drive application. It is verified that MT-PWM is able to realize in H-bridge step-down converter without any major modification through simulations.