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TMS320F28035: Digital Peak Current Mode Control With Slope Compensation Using the TMS320F2803x

rs
Intellectual 891 points

Part Number: TMS320F28035

Hello,

In the application note "Digital Peak Current Mode Control With Slope Compensation Using the TMS320F2803x"

https://www.ti.com/lit/an/sprabe7a/sprabe7a.pdf

there's some discussion on p.20 about comparing the measured and simulated results. The app note says:

"The gain plot at low frequencies is less than the modeled result. This is due to the combination of the way
in which the frequency response is measured and the discrete time nature of the controller. When the
frequency of the injected signal is low, the input to the discrete time controller does not significantly
change from cycle to cycle and the response cannot be accurately measured."

Wondering if you can point me to additional resources explaining this low frequency measurement phenomenon? I'm looking for a bit more support to better understand it and convince colleagues. 

Thanks!

  • 0
    TI__Genius 12225 points

    You can read about how a frequency response analyzer works by injecting small signals and sweeping the frequency. It is available in literature public domain. In general at low frequencies when the injected signals are small magnitude, the gain calculation is not very accurate and it does not matter much for the control design since the phase shift is very low and the control loop is perfectly stable. At higher frequencies the phase shift increases quickly. So for the control design you want to focus more around the crossover frequency (which is at a higher frequency) and make sure that you have enough phase margin and gain margin.