UCC28019A: FRA

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Part Number: UCC28019A
Other Parts Discussed in Thread: UCC28019,

Tool/software:

I would like to know how to do FRA analysis for UCC28019.
(Where to insert resistors, applied signal level, etc.)
Input/output conditions are:
Input voltage: 19.2V~28.8V AC
Output voltage: 36V

3 months ago

0 ?? ?? 3 months ago

Prodigy 40 points

UCC28019A

0 Ulrich Goerke 3 months ago in reply to ?? ??

TI__Mastermind 40580 points

Hello,

Frequency Response Analysis can be preformed on a PFC circuit controlled by UCC28019A by following the general principles explained in this reference paper: https://www.ti.com/seclit/ml/slup386/slup386.pdf

There are special consideration for PFC, though, since the bandwidth of the PFC control loop is extraordinarily low compared to most DC-DC converter loops. Also, the output voltage of the usual high-voltage PFC circuits may need to be scaled down to stay within the limits of the test equipment.
And the normal ripple voltage on the PFC output may interfere with FRA measurements at or near the ripple frequency.

In your case, a 36V output may be acceptable to measure directly with the FRA equipment.

For a 36V average output, I recommend to limit the maximum AC input voltage to <24.5Vrms. Higher input voltage will result in peak-charging of the output capacitor and loss of regulation of the output. FRA in such circumstances will be meaningless.

Regards,
Ulrich

0 ?? ?? 3 months ago in reply to Ulrich Goerke

Prodigy 40 points

注入箇所 (弊社追記).pdf

If the measurement is made as shown in the attached document, the waveform in Figure 32 of the data sheet would be obtained. (voltage loop)
Do I need to measure the current loop in Figure.30?
If so, how is it measured?

0 Ning Tan 3 months ago in reply to ?? ??

TI__Genius 12795 points

Please see this YouTube video for voltage loop measurement. TP3 and TP4 are used here.

https://www.youtube.com/watch?v=ZSX-N33hd5M

Please see this YouTube Video for current loop measurement. You need to inject a signal on Isense pin (starting at 4:00 in the video)

https://www.youtube.com/watch?v=lz9O7ZACxQM

0 ?? ?? 3 months ago in reply to Ning Tan

Prodigy 40 points

I have heard it explained before that it is not usual to extend the stability determination of the current loop to no-load, but why not do the same for the voltage loop?

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UCC28019A: FRA