Adaptive discontinuous Current Source Driver to achieve switching loss reduction for MHz PFC boost converters
Adaptive control concept for the discontinuous Current Source Drivers (CSDs) is proposed for MHz Power Factor Correction (PFC) boost converters. Compared to the continuous CSDs, the discontinuous CSDs have lower circulating current and less conduction loss. Therefore, the discontinuous CSDs are able to use higher gate drive current to reduce the switching loss further. Using different pre-charge time to build Current Source (CS) inductor currents based on different load conditions, the gate drive currents can be achieved adaptively to the load currents, so that the efficiency of the PFC converter can be improved in a wide operation range. The CS inductor of the discontinuous CSD is as low as 120nH. This reduces the board space of the main MOSFET driver part. An 110V input, 380V/ 200W output, 1MHz PFC boost converter with the proposed adaptive discontinuous CSD was built to verify the advantages. With the discontinuous CSD, at 50% load, an efficiency improvement of 5.1% is achieved over the conventional voltage source driver (VSD), and at full load, an efficiency improvement of 4.8% is achieved. The measured PF values are all above 99% and complying with the industrial requirements.