Research On DC/DC Converter Radiation-hardened Method Based On Screening

DC/DC converter is one of the most vulnerable units in electronic systems of satellites and spacecrafts. The reliability of DC/DC converters is extensively concerned. There are several shortcomings in the traditional radiation-hardened methods, such as long production cycle, high cost, and not so godd performance as commercial one. Therefore, this paper expects to find a new method named screening to improve the performance of the DC/DC converter.PWM controller is the core of the feedback loop in DC/DC converter with a PWM-based topology. Radiation-induced degradation of the PWM will result in the output instability and even failure of a DC / DC converter. VDMOS is a good switching device and linear amplifier part. Radiation-induced degradation of the VDMOS will lead to the degradation of the efficiency in DC / DC converter. This article begins with the quantitative relationship between the degradation of the discrete devices and the degradation of the overall DC / DC converter. The screening methods for PWM and VDMOS are proposed, which are also verified by simulation. Also a new concept in the reliability engineering PHM is introduced based on which a predication circuit and a DC / DC converter solution are proposed.Based on above works, the main results of this paper are follows:1. Experimental results show that the threshold voltage of VDMOS decreases after exposure to ionizing radiation. When the threshold voltage of N-type VDMOS decreases to less than zero, the off-state leakage current increases significantly, which will result in the decreases of the efficiency in the DC/DC converter. Also the data shows that this is the main reason for the degradation of the efficiency in a DC / DC converter after exposure to ionizing radiation.2. Experimental results show that the reference voltage of PWM increases a little, also the output voltage increases after exposure to ionizing radiation, but there are nothing obvious relationships between that two increases. Theoretical analysis shows that, for the structure of magnetic feedback DC / DC converter, the output voltage is uniquely decided by the reference voltage of the PWM. But for the structure of opto-coupler feedback DC / DC converter, the output voltage is mainly decided by other reference devices.3. Proposed VDMOS and PWM anti-radiation screening solutions, including the anti-radiation screening targets and screening process VDMOS and the PWM.4. Proposed the screening programs of radiation experiments for VDMOS and PWM, which are used to verify the screening solutions. In the screening program, some conditions are determined, such as the total radiation dose, dose rate, bias circuit and test methods, etc.5. Designed the DC / DC converters prediction circuit, also proposed DC / DC converter PHM solution.