Design Of The Fault Diagnosis Circuit For DC-DC Converters

As DC-DC converters are extensively used in the fields of aeronautics, astronautics, communications, vessels, computers and industrial control, it becomes more and more urgent to ensure security of relevant system, and the key is to design fault diagnosis of DC-DC converters. In recent years, the research dealing with switch fault has extensively attracted academicattention, but the methods of fault diagnosis aimed at switch are not perfect. It is hard to meet switch’s rapid fault diagnosis requirements for high quality applications. Therefore, it is of great value to study the switch fault diagnosis.In this thesis, a switch’s rapid fault diagnosis circuit is proposed, and the thesis is mainly organised in three aspects. Firstly, the switch fault types are analysized, switch fault model is established. Secondly, the fault signal of switch is deduced theoretically, the conclusion is that the differential of output voltage is related to switch failures directly. Finally, the thesis uses the method of output voltage differential to design fault diagnosis circuit, including the circuit of eliminating system transmission delay and fault type identification circuit. And the fault diagnosis strategy is also given. The innovation is that this thesis uses the method of output voltage differential to design fault diagnosis circuit. Compared to traditional methods, the characteristics of the method proposed in this thesis are the shortest diagnosis time, without sensors, wide application range and low-cost.Based on a practical Buck converter, fault diagnosis module is established and verified. Experimental results show that when the switching cycle Ts is 24.2 μs and the output voltage ripple rate is 0.04, the designed fault diagnosis circuit can accurately diagnose the switch open-circuit fault and short-circuit fault, fault diagnosis time is 0.35Ts- The designed scheme can be widely used in various PWM DC-DC converters.