Qspeed™ Advanced Diodes Power Integrations Qspeed™ Advanced Diodes combine an extremely low reverse recovery charge (QRR) with a very soft recovery waveform. Together, these features help designers improve the performance of their power conversion circuits. Three versions are currently available. The H-Series features the lowest switching loss which provides the highest efficiency. The Q-Series has the highest softness that provides the lowest EMI. The X-Series offers the lowest cost which gives designers the BOM cost reductions they might be looking for.