INTRODUCTION Mobility is a foundation to human social and economic life. Automotive vehicles are a key contributor to the mobility we enjoy today. However, automotive vehicles are also a contributor to issues of global warming and air pollution through tailpipe emissions of CO 2 and pollutants. To combat these issues, the urgent task of automotive development is environmental consciousness: high fuel efficiency, and low emissions. To solve this task, Toyota has been working to develop and popularize Hybrid Vehicles (HV). In 1997, 1 st generation HV , the world’s first mass produced HV , debuted. Its fuel efficiency was twice as much as gasoline engine vehicles. In 2003, a high voltage system using a boost converter was introduced to 2nd generation HV , which achieved high power and high fuel efficiency. In 2009, 3rd generation compact-class HV debuted. Increasing the engine displacement and the power of motor, both the power and fuel efficiency at high speed cruising was improved. Apart from the hybrid systems power train, Toyota is a leader in further improving efficiency through the reduction of size and weight of each unit produced. Now the 4 th generation HV , the first vehicle adopting TNGA (Toyota New Global Architecture), has debuted. Through the reduction in vehicle component size and weight, lowering the center of gravity and the stature, the 4th generation HV achieves high fuel efficiency (40.8km/L, JC08), and a pleasurable driving experience. For this hybrid system, a 4th generation power control unit (PCU) has been newly developed ( Fig 1). The PCU has achieved further reduction in size, the weight and the electronic energy loss than previous generations. This paper explains the specific technologies of the 4th generation PCU to enable this improvement. Fig.1. The 4th generation PCU PCU SPECIFICATIONS AND STRUCTURE HV System Specifications The configuration of the new hybrid system is shown in Fig.2. The basic configuration is same as the previous model. However, a major change is the mounting position of the main and auxiliary batteries enables improvements in an increase in luggage area and the lower center of gravity of car. The battery mounting positions of 4 th generation hybrid system is shown in Fig.3. The specifications of the system are shown in Table.1. The fuel efficiency is improved around 18.2%(JC08) by following items. • Improvement of thermal efficiency of gasoline engine • Reduction in the electronic loss of HV system components • Reduction in the current by the operation of motor at higher speedDevelopment of Power Control Unit for Compact-Class Vehicle Osamu Kitazawa, Takaji Kikuchi, Masaru Nakashima, Yoshiki Tomita, and Hajime Kosugi Toyota Motor Corporation Takahisa Kaneko DENSO Corporation ABSTRACT Toyota Motor Corporation has developed the new compact-class hybrid vehicle (HV). This vehicle incorporates a new hybrid system for the improvement of fuel efficiency. For this system, a new Power Control Unit (PCU) is developed. The feature of the PCU is downsizing, lightweight, and high efficiency. In expectation of rapid popularization of HV , the aptitude for mass production is also improved. The PCU, which plays an important role in the new system, is our main focus in this paper. Its development is described. CITATION: Kitazawa, O., Kikuchi, T., Nakashima, M., Tomita, Y . et al., "Development of Power Control Unit for Compact-Class Vehicle," SAE Int. J. Alt. Power. 5(2):2016, doi:10.4271/2016-01-1227.2016-01-1227 Published 04/05/2016 Copyright © 2016 SAE International doi:10.4271/2016-01-1227 saealtpow.saejournals.org Fig.2. Composition of 4th generation HV system Table.1. Specifications of HV system Fig.3. Placement of 4th generation HV system PCU Mounting PCU mounting space, following the concept of TNGA, was not developed independently for every car type, but in consideration of applications to the many models. Thus, the PCU was mounted upon the transaxle