Performance Improvement of a Silicon Partial Power Converter Over a Silicon Carbide Full Power Converter

This article studies the new benefits that partial power processing (PPP) brings to silicon (Si) devices compared to wide bandgap (WBG) technologies. To prove this, the proposed case study consists of an onboard charger (OBC) application in which a Si-based partial power converter (PPC) is compared with a silicon carbide (SiC)-based full power converter (FPC). The OBC application considers three different technologies of lithium-ion batteries and the main comparison metrics are: semiconductor switching, temperature rise of semiconductors, volume, and device losses (efficiency). This last one is oriented to energy losses (Wh) and not to power losses (W) as classical design. An analytical model is used to compute switching and conduction losses. Depending on the operating point, switching events are segregated into zero voltage switching (ZVS), incomplete ZVS (iZVS), and hard switching. It is shown that the Si-based PPC may enter non-ZVS in certain operating conditions. However, its efficiency remains above 99%, producing up to five times lower energy losses than the SiC-based FPC. Also, the case temperature of the semiconductors is halved and a reduction in the volume and electrical stress of the devices is achieved. This permits a global multiobjective optimization. The results are experimentally validated using a 3-kW prototype of SiC-based FPC and Si-based PPC.

I. Introduction

Improved energy efficiency and smaller power converter size are the principal advantages that wide bandgap (WBG) devices offer compared to traditional silicon (Si)-based semiconductors [1], [2]. In addition, these WBG technologies give devices the ability to work at much higher frequencies [typical application of gallium nitride (GaN)] and higher voltages/temperatures [typical application of silicon carbide (SiC)] than the conventional Si semiconductors [3]. In consequence, solar, traction, and electric vehicles (EVs) applications are implementing WBG-based devices on their power converters [4]. On the other hand, the Si technology is considered as a very mature technology, and thus, it still dominates the market of power devices due to its reduced cost and ruggedness. However, when it comes to power density and switching capability, the performance of Si devices has reached its theoretical limitations [5].