WECO. Frequency Response Analyzer. Venable Instruments. - K.H Cho -

Transcription

1 WECO. Frequency Response Analyzer Venable Instruments - K.H Cho -

2 Frequency Response Analyzer FRA??: 어떤선형시스템에정현파신호를가했을때시스템출력신호를조사하는것으로입력신호의주파수를관심있는범위에걸쳐변화시키고그결과로서나타나는응답을연구하는것. 일반적으로입력신호를준다음시간이경과한후과도상태에서정상상태가되었을대입력신호와출력신호의진폭과위상등을통하여시스템의동특성을파악한다. 즉주파수응답은시스템이안정하다는가정하에분석이가능.( 불안정한경우정상상테존재 X)

3 Frequency Response Analyzer Purpose: 1. Measure the EUT in frequency domain (Bode plot). 2. Figure out the character and stability (Phase margin) 3. Help the design and verification for RD or QC

4 CHROMA ATE INC. Products : AC/DC Source, Electronic Load, Power Meter, Automatic Test System, LCR Meter, Only for Time Domain Test.

5 Venable Instruments 1. Professional on Frequency Response Analyzer in USA 2. Focus on the test of power supply in frequency domain 3. Customers:

6 Frequency Domain: Bode Plot Phase margin Gain margin Cross frequency

7 Frequency Domain v.s. Time Domain V I

8 Frequency Domain v.s. Time Domain V I

9 Introduction Operation theory: 1. Input a signal with sweeping frequency. 2. Measure the variable component in particular points. 3. Calculate the data to get Gain and Phase Plots.

10 Frequency Response Analyzer Venable 4325 Main unit: 1. A Generator for output signal 2. Two channels for measurement Control and Analysis Software: 1. Send commands, catch data by GPIB interface 2. Calculate data, get Bode plot for analysis 3. Control Circuit Design Aid for power supply Bode Box: Float the output signal for Injecting to EUT

11 Specification FRA Model 4325: Generator Frequency Range : 1mHz 25MHz(Sine) 1mHz 1MHz(Square) Amplitude : 1mVac 10Vac DC bias : ±10Vdc,10mV Step Isolation : Referenced to chassis ground Measurement Channel : 2, Single Ended GND Range : 10mV - 500V rms, in 11 ranges Accuracy : ±0.05dB, ± KHz Isolation : ± 500V to ground CMRR : > 120dB PC Interface : IEEE-488 (GPIB)

12 Venable FRA 4325 Figures 1. Wide output range, 10mVac 10Vac, ±10Vdc, suitable for different application. 2. Wide measurement range, 10mV 500V. 3. Powerful software: multi-trace, data save, annotation edit 4. Control circuit design aid, frequency domain calculation.

13 Applications Examples: 1. Get the Bode plot of a Power supply. Figure out the stability by cross frequency & Phase margin 2. A process for using Control Circuit Design Aid to get a power supply with good stability. 3. Get an impedance v.s. frequency plot by measuring a capacitor.

14 Example 1 : Loop gain & phase measurement

15 Example 1 : Parameters Setting Control Menu:

16 Injection Point A(actual) = [A(measured) + Zo/Zi] / (1+Zo/Zi) Suitable Point: Zo << Zi, Accuracy: A > B > C Vinput A Vout B Vcc C

17 The Difference for Injection Points

18 Test Result 110V / 220V input, low load / full load output

19 Example 2 : Control Circuit Design Aid

20 Design Aid: Step 1 Connecting for Modulator Measurement

21 Modulator Measurement Modulator connecting Vinput Vout CH1 Vcc CH2 V1 V2

22 Modulator Bode Plot Get modulator Bode plot, set cross frequency:

23 Design Aid: Step 2 Set Phase Margin and select Error Amplifier:

24 Error Amplifier Select Error Amplifier (Controller):

25 Design Aid: Step 3 Calculate the value of resistances and capacitors in the Error Amplifier automatically

26 Design Aid: Step 4 Modify the value of resistances and capacitors

27 Design Aid: Step 5 Show SPICE-like Net List :

28 Design Aid: Step 6 Set Frequency Range for Calculation:

29 Design Aid: Step 7 Get the Error Amplifier Result (present in number):

30 Design Aid: Step 8 Get the Bode plot of Error Amplifier:

31 Multiply Modulator and Error Amplifier in frequency domain: Design Aid: Step 9

32 Design Aid: Step 10 Get the Bode plot of full loop:

33 Design Aid: Step 11 Double check with the result of real circuit:

34 Example 3 : Impedance Measurement

35 Test Result for A Capacitor Measurement of 200uF Capacitor C = 207.4u, R = 84.5 m, L = 93 n

36 Measuring I/O impedance of A Power Supply Load: input impedance: CH2/CH1 Source: output impedance: CH2 /CH1 CH2 CH2

37 Conclusion The advantage for Venable FRA users: 1. Help RD engineers to get a clear picture of stability of their products for improvement. 2. Save a lots of time comparing traditional method (scope and trial & error) 3. Verify the product with enough phase margin. Reduce the uncertainty in mass production. 4. Give a good, professional image to the customers.