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frequency response for current mode pwm controller

Midhun M
Prodigy 230 points

Hi

I am using a current mode pwm controller for driving solenoid current is it possible to do a frequency response analysis for current loop in pwm controller.

Please suggest a method to avoid sub harmonic oscillations.

The voltage feedback loop is not used in the design.

Thanks

Midhun

  • 0
    TI__Mastermind 25570 points

    Hello Midhun

    Slope compensation is used in peak current mode controlled systems to prevent sub-harmonic oscillations. There is a lot of published information about this technique including articles at http://www.ti.com/lit/an/snva555/snva555.pdf . the article at https://www.ti.com/seclit/ml/slup113a/slup113a.pdf  has a lot of information about psu control in general.

    Some notes : slope compensation is needed in peak current mode control systems if they operate at > 50% duty cycle. If you keep the duty cycle < 50% then it isn't necessary - although if the system is operating just below 50% duty cycle it may get a little 'jumpy' . It isn't needed in an average current mode controlled system or in a voltage mode controlled system.

    Regards

    Colin