07 271 Testing DCDC Converters for Stability Description

07 -271 Testing DC/DC Converters for Stability Description: Unstable PWM loop control and dynamic negative resistance at the input have become leading causes of catastrophic failures of DC/DC converters for NASA space missions. DC/DC converter manufacturers ensure the stability of their products only by design and by measuring loop gain/phase margins on open-frame prototypes during design verification. Once the hybrid device is built, it becomes nearly impossible (due to probing difficulties) to make the control loop measurement. Once the hybrid’s lid is installed the test points are no longer available. Characterization of DC/DC converter design stability is not represented in device datasheets or military SMD’s. The goal of this study is to develop a practical method for baselining and monitoring the stability levels of DC/DC converters. Several methods to be studied include using spectral analysis on input and common mode noises, experiments with simultaneous load increased with input voltage decreases, signal recovery technique, and signal detection technique. Schedule/Costs: FY 07 Plans: • Explore the possibility to measure gain/phase margins of units on which Remote-Sense input pins are available. • Identify the ΔPout/-ΔVin relationship which results in a –Rd at the input. • Study oscillation behavior using signal analysis on the effects of input and common-mode noise • Characterize a new stability indicator by understanding the correlationship between a noise spectrum and gain/phase margins. • Develop the technique to recover main switching waveform from input or output voltage noise waveforms. Device samples will be from GSFC residual collection or from leveraging with the NESC DC/DC Converter Reliability project. Deliverables: Technical report on DC/DC converter stability measurement techniques and results found during test method development. NASA and Non-NASA Organizations/Procurements: Lead Center/PI: GSFC, Bright Wang DC-DC converters and testing supplies will be purchased from various standard suppliers. Support will be provided by the GSFC Parts Analysis Lab and Surface Mount Assembly Laboratories.