Introduction of the DC-DC Converter Inductor Selection Tool - Murata

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■Inductor Current Ripple (Want)MPST is structured so that the inductance value which becomes the inductor currentripple is automatically calculated and displayed in the "Recommended Inductance" ofthe output results, by inputting the ideal value in the "Want" field of the "InductorCurrent Ripple" of the input form.■Inductor Current Ripple (Max)When an inductor with poor bias current characteristics is used, the inductancevalue will deteriorate due to the increase in the current (inductor current ripplebecomes higher), which causes unstable operation.In the worst case, there is a risk of causing serious damage to circuits, such asdestruction of ICs.Therefore, the restrictions to "prevent the triangular wave of the amplitude frombecoming larger than it is now in the operating state", and the function (MaxInductance Current Ripple) to select components are provided in MPST.When the "Max Inductance Current Ripple" is specified, inductors in which a currentflows more than the current ripple specified at the time of a maximum load(without having the necessary bias characteristics) will be excluded automaticallyfrom the search results.* The "Min Inductance Current Ripple" is the limiting value to prevent a DC‐DCconverter from having a poor response characteristic due to the inductance beingtoo high.I実 Actual 際の Waveform 波形想 Assumed 定していた Waveform 波形Current waveform when an inductor having poor characteristics isused for the required bias current characteristicst
Viewpoint of Loss in Power InductorsInductor loss in a DC‐DC converter consists of Core Loss (Pcore) and Conductor Loss(Pcond) as shown below.PP cond P coreConductor Loss (Pcond) is the loss which mainly originates in a DC component, and isexpressed as follows using the DC resistance (Rdc) and the current DC component (Idc).2P cond RDCIDCBasically, this value can be calculated if the value of the DC resistance is understood.Conventionally, the power inductor loss was only predicted from this value.On the other hand, the Core Loss (Pcore) is the loss which mainly originates in the ACcomponent, and is expressed as follows using the AC resistance (Rac) and the currentAC component (Irms).P RcoreACI2rmsSince the AC resistance (Rac) and the current AC component (Irms) changesdepending on the conditions, such as the frequency, current amplitude, bias currentand etc., it was difficult to calculate this value accurately.Actually, this Core Loss is a component which can not be disregarded, as there arecases where a value larger than the conductor loss is taken in conditions of highfrequency and low load.Murata established a method to accurately evaluate power inductor loss, bymeasuring the changes in the inductor characteristics caused by the changes of thesecomplicated conditions.We have constructed an environment where the characteristics of inductors caneasily be evaluated, by calculating the values automatically in MPST based on theseevaluation results.
Page 2 and 3: Having trouble selecting power indu
Page 4 and 5: 2 nd stepConfirming the Output Resu
Page 6 and 7: ■Current Wave formComparison betw
Page 8 and 9: ■Frequency -Loss CharacteristicsW
Page 10 and 11: The ideal power inductor can be sel
Page 12 and 13: Supplemental Materials

Introduction of the DC-DC Converter Inductor Selection Tool - Murata

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