I was experimenting with a low watt boost converter,12V to 100V,50mA using the venerable MC34063A and an external MOSFET switch..I calculated the inductor value to be about 100uH.So I made two inductors using a drum core and toroid ring,both of which are 100uH.The drum core works well,but under load the toroid drops to 60V or so. Is the toroid saturating? If so ,should i use a larger toroid to overcome this problem? TIA.
Just commenting on Janka's idea that a 5:1 ratio is the practical limit to boost converter design. These kinds of limits only apply for continuos mode boost converters. In discontinuous mode, there are no such limits at all, I've built converters of this type with a 50:1 upconverting ratio, while maintaining reasonably high efficiencies. Since control circuits are needed anyways to better stabilize the output of a continuous mode boost converter, it makes little sense to adhere to the continuous mode which has the disadvantage of needing a minimum load at all times. You yourself may be well aware of these considerations.