Paralleling Of Power MOSFETs For Higher Power Output

Dynamic current and transition energy unbalance resulting from parameter mismatch between parallel MOSFET branches are mapped over wide operating ranges. Unbalance generator magnitudes are given for HEXFET Power MOSFET data sheet ant typical production batch extremes. Limit functions are defined for unbalance due to ON resistance, gain and threshold voltage mismatch. Q loci are utilized for mapping dynamic load lines and transition energy. A critical product, average gate current times commutation inductance, and a critical inductance ratio, common source to commutation inductances, are identified. For worst case parameter mismatch, modest levels of unbalance are predicted through the use of minimum gate decoupling, dynamic load lines with high Q values, common source inductance or high yield screening. Each technique is evaluated in terms of current unbalance, transition energy, peak turn-off voltage and parasitic oscillations, as appropriate, for various pulse duty cycles and frequency ranges. Results are predicted for a worst case clamped inductive load circuit with an arbitrary number of paralleled IRF150 HEXFET Power MOSFETs.