DESIGN PHASE: measurement SUB ELEMENT NAME: environmental measurements VARIABLE NAME: [HEMOVEN] DATE: REVISION LETTER: REVISION DATE: APPLICABILITY: all circuits ACTIVITY: Determine survivability, stability*, worse case performance, temperature coefficients of circuit, and take PARD photo over the specified temperature range. OUTPUT: Measurements in laboratory notebook for comparison to specifications and analysis. ALGORITHM: [HEMOVEN] = engineer hours for environmental measurement [HTMOVEN] = technician hours for environmental measurement 0.0+ set up time 0.0* time per stabilized temperature (1+INT(1+ ([UTEMP]-[LTEMP])/25)) number of temperature measurements [UTEMP] upper operating temperature extreme in degrees C [LTEMP] lower operating temperature extreme in degrees C DISCUSSION: Test Cases: -55C to 125C (-55,-25,0,25,50,75,100,125) 8 = 8 ok 0 to 70C (0,25,50,70) 4 = 4 ok -25 to 70C (-25,0,25,50,70) 5 = 4, estimates one too low. Algorithm not exact but probably ok. * A good stability screen for regulators with feedback loops is to apply a square wave to the reference input and observe the closed loop response as as load is varied for each line voltage condition at each temperature. A tendency for instability often shows up as an underdamped ringing response or oscillation on the output. The frequency of ringing, if any, may vary with conditions and should be recorded or photographed. For more details see Power Supply Instability.
Original: Foutz, J., Power Supply Circuit Development Estimating Aid - An Expert System Application, IEEE Applied Power Electronics Conference Record, New Orleans, February 1-5, 1988. Revised 21 February 2001
Copyright © 2001 Jerrold Foutz
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