Research And Application Of SEPIC Circuit In Automotive Air-Conditioning System

With the development of science and technology and continuous improvement of the life and production, people put forward higher requirements for car comfort, security, entertainment and convenience. To meet users’demands, electronic equipments in the car are increasing. Therefore, designing power supplying stable output voltage to these electronic devices and make them work well is very important. However at the time of the car starting, the car’s DC power supply voltage is reduced from the normal12V to6V, which cann’t reach the operating voltage of car audio systems, air conditioning systems, etc., making these devices stop running. To keep these devices stable working, electronic devices’power supply module should be able to withstand a wide range of automotive power disturbances, and has a stable output voltage.Based on this, this paper has a research on a DC topology-SEPIC circuit. Analyse the SEPIC circuit open-loop characteristics and derive open-loop transfer function of voltage loop circuit, current loop circuit and the whole system. Through these open-loop transfer functions, this paper simulates the system with Matlab, and analyse the circuit’s closed-loop stability. On this basis, a SEPIC circuit with a stable output voltage of5V was designed. And in conjunction with the circuit, this article has designed a set of car air-conditioning control system, which gets5V power supply from the former SEPIC circuit. According to the test report, when the total car’s power disturbance between4V-40V, the SEPIC circuit can still output stable5V voltage and the automotive air-conditioning control system has been working properly.