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EE136. STABILITY AND CONTROL LOOP COMPENSATION IN SWITCH MODE POWER SUPPLY Present By Huyen Tran. STABILITY AND CONTROL LOOP COMPENSATION IN SWITCH MODE POWER SUPPLY. potential risk for oscillation in a closed loop control system methods of stabilizing the loop .

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Ee136

EE136

STABILITY AND CONTROL LOOP COMPENSATION IN SWITCH MODE POWER SUPPLY

Present By Huyen Tran


Stability and control loop compensation in switch mode power supply

STABILITY AND CONTROL LOOP COMPENSATION IN SWITCH MODE POWER SUPPLY

potential risk for oscillation in a closed loop control system

methods of stabilizing the loop


Methods of stabilizing the loop
Methods of stabilizing the loop

  • By Circuit and Mathematical Analysis

    -Required “fine tuning”

  • Interrogative Methods of Loop Stabilization

    -A “difference techniques” can be used to establish the required characteristics of the compensated control amplifier.


Methods of stabilizing the loop1

C1

R1

Vi

-

Vo

OUT

+

VREF

0

Methods of stabilizing the loop

Type 1 Compensation



Methods of stabilizing the loop3
Methods of stabilizing the loop

  • Type 3 Compensation


Stability testing methods
Stability testing methods

  • One of these method is transient load testing

    -the transfer function changes under different loading conditions.




Analysis for transient test1
Analysis for transient test

  • For an under damped response, it will have a poor gain and phase margins and maybe only conditional stable. With this performance, the oscillation may occur.

  • For an over damped response, it is very stable, but does not give the best transient recovery performance.

  • For waveform c, it is stable transient response, and it will provide enough gain and phase margin for most application.



Measurement procedure for the closed loop power supply systems1
Measurement procedure for the closed- loop power supply systems

  • voltmeter V1 is used to measure the ac input of control amplifier

  • voltmeter V2 is used to measure the ac output voltage of power supply for each time changing the frequency



Design example
Design example systems

Stabilizing a Forward Converter Feedback Loop with a Type 2 Error Amplifier

  • V0 = 5V

  • I0(nom) =10A

  • Minimum I0 = 1A

  • Switching frequency = 100 kHz

  • Minimum out put ripple = 50mV


Design example1
Design example systems

  • calculate Lo and Co

And the cutoff frequency of the output LC filter Is


Design example2
Design example systems

  • the frequency of the ESR zero is

Then the modulator gain :


Design example3
Design example systems

  • Then the total open loop gain Gt = Glc + Gm +Gs is draw in fig.1


Design example4
Design example systems

  • At very low frequency, it is a straight line with -1.5dB and then it hit 2 poles at the frequency which is 806 Hz and start rolling down with slope of -40dB/dec until it hit a zero at 2500 Hz, and the line still rolling down but the slope only -20dB/dec.


Design example5
Design example systems

fz = 5kHz, fp =80 kHz, gain 40