The fundamental calculations for InnoSwitch3-CP/PRO are very similar to the InnoSwitch3-CE/EP product family, however, the InnoSwitch3-CP/PRO calculations are structured to satisfy 2 primary objectives. The first objective is to calculate the value of primary magnetizing inductance such that the design guarantees power delivery across all line/load conditions. The second objective is to ensure that the electrical constraints are not violated.
Based on the InnoSwitch3 architecture, the primary magnetizing inductance should be calculated at the valley of the rectified minimum input voltage and full output load. This primary magnetizing inductance is calculated for each output set-points and the highest primary magnetizing is selected as the design inductance: the highest primary magnetizing inductance will ensure power delivery for all output set-points.
Once the primary magnetizing inductance has been selected, the electrical parameters for all set-points are recalculated and their worst case values (min/max) based on the tolerance in the primary magnetizing inductance and current limit are displayed to the user. In case of manual design optimization, the user is responsible to ensure that the electrical parameters do not exceed the limits specified in the datasheet. If the ‘Optimize/Auto Optimize’ feature of PI Expert is used, the tool ensures that the optimized solution does not violate any electrical constraints per the product datasheet.