1. A diagnosis method of DC/DC converter aging based on the variation of parasitic resistor 1/11 1. Introduction The power converter system supplies power in the fields of industry, home, information and communication. It requires specialized protection equipment to prevent an accident with the power converter because it could bring a great loss of humans and operations, communication troubles, and accident treatment costs. The recent trends of research and development are not the individual measurement but the aspects of systematic and on-line diagnosis. In addition, it has been studied for not only the simple physical quantity of measured data, but also the examination of the variations and progresses using a signal processing method This study presents an indicator for the aging of a power converter system and demonstrates a diagnosis method of a power converter system using t his study. This study proposes a method of DC/DC converter diagnosis by analyzing the variations of model on the variations of parasitic resistor.

2. A diagnosis method of DC/DC converter aging based on the variation of parasitic resistor 2/11 2. Variations of the equivalent resistor of electrolytic condenser due to the aging increment T Co =105°C 0 50 100 150 200 250 300 01000200030004000 time (hours) ESR (m ) ESR t ESR l ESR th tr ESR Increment by aging time 0 100 200 300 400 500 600 -200204060 T Co (°C) ESR (m  ) Case temperature : ESR Increment by environment temperature

3. A diagnosis method of DC/DC converter aging based on the variation of parasitic resistor 3/11 ■ Buck converter considered in the parasitic resistor 3. Defining of the diagnosis indicator(  )

4. A diagnosis method of DC/DC converter aging based on the variation of parasitic resistor 4/11 Vout Vref + white noise PI White noise Vref Σ Σ 4. Measurement of the diagnosis indicator(  ) Circuit constant define Random excitation signal Generation Input/output measurement Estimation by Least square Method Error compensation  measurement Block diagram for the diagnosis indicator measurement Diagnosis algorithm and implementing flow chart Digital Controller DC/DC Converter

5. A diagnosis method of DC/DC converter aging based on the variation of parasitic resistor 5/11 Circuit Parameters Diagnosis DC/DC converter prototypes 5. Diagnosis DC/DC converter prototypes Input voltage V in 24[V] Output voltage V out 5[V] Load resistor R o 10.6[Ω] Inductor parasitic resistor r l 1.2 [mΩ] Condenser series resistor r c 12.5[mΩ] Switching series resistor r t 10.7[mΩ] Diode series resistor r d 6.1[mΩ] Condenser C470[uF]

6. A diagnosis method of DC/DC converter aging based on the variation of parasitic resistor 6/11 6. Input/output Signal Condition of System Identification Input/output level of System Identification - Duty ratio Range : 0.38 Duty ± 0.01 Duty (2.6%) - Output Range : 21V ± 1V (4.7%) Input/output signal condition of System Identification : - Minimum input signal frequency : 2kHz - Sampling rate : 2kHz (10 times over than system cut-off frequency) - System Cut-off Frequency : 100Hz - Running Time : 0.512sec = 500usec * 1024 (System Identification Minimum Date)

7. A diagnosis method of DC/DC converter aging based on the variation of parasitic resistor 7/11 7. Experimental Result (1) Extended waveforms White noise and its response chara- cteristics added in the input signal Output Voltage Duty Ratio 0 0.5 1 1.5 0.7 0.75 0.8 30 20 10 0 21 20 22 0.5 0.3 0 0.1 0.4 0.39 0.38 0.37 0.36 0.512sec Output Voltage

8. A diagnosis method of DC/DC converter aging based on the variation of parasitic resistor 8/11 8. Experimental Result (2) System ID 26% System ID 75% - Digital Filtering Output data, System constant Optimization (increase accuracy 3 times )

9. A diagnosis method of DC/DC converter aging based on the variation of parasitic resistor 9/11 9. Experimental Result (3) Real value and diagnosis result 12m79m112m212m 100m 300m 250m 200m 150m 50m 0m Real measurement Diagnosis result    

10. A diagnosis method of DC/DC converter aging based on the variation of parasitic resistor 10/11 10. Verification (Frequency response) By Impendence Analyzer HP4194A Matlab Simulation result Proposed diagnosis method result ESR= 0.012ESR= 0.067

11. A diagnosis method of DC/DC converter aging based on the variation of parasitic resistor 11/11 11. Conclusion The conclusion of the this research are as follows. 1) A new algorithm is proposed to diagnose for the DC/DC converter of a power converter system. 2) The diagnosis indicators are defined not to diagnose for each element, but for the system. 3) The diagnosis indicator ξ of parasitic property for each element is defined as a diagnosis indicator of diagnosis. 4) The system identification of the power converter system can be used to produce the indicator ξ. 5) The diagnosis algorithm can be verified by the analysis and simulation by using the agreement be-tween the experimental results and the simulation results through the manufactured sample of DC/DC converter.