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Advanced Stability and Control Loop Compensation in Switch Mode Power Supplies

This presentation by Huyen Tran delves into the intricacies of stability and control loop compensation in switch mode power supplies. It explores potential risks of oscillation in closed-loop control systems and the various methods for stabilizing these loops, including Type 1, Type 2, and Type 3 compensation techniques. The presentation highlights the importance of fine-tuning and transient load testing while providing measurement procedures for accurate closed-loop power supply evaluation. Practical design examples illustrate the stabilization of feedback loops, showcasing critical factors affecting gain and phase margins.

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Advanced Stability and Control Loop Compensation in Switch Mode Power Supplies

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  1. EE136 STABILITY AND CONTROL LOOP COMPENSATION IN SWITCH MODE POWER SUPPLY Present By Huyen Tran

  2. 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

  3. 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.

  4. C1 R1 Vi - Vo OUT + VREF 0 Methods of stabilizing the loop Type 1 Compensation

  5. Methods of stabilizing the loop • Type 2 Compensation

  6. Methods of stabilizing the loop • Type 3 Compensation

  7. Stability testing methods • One of these method is transient load testing -the transfer function changes under different loading conditions.

  8. Set up the transient load test

  9. Analysis for transient test

  10. 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.

  11. Measurement procedure for the closed- loop power supply systems

  12. 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

  13. A typical Bode plot

  14. Design example 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

  15. Design example • calculate Lo and Co And the cutoff frequency of the output LC filter Is

  16. Design example • the frequency of the ESR zero is Then the modulator gain :

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

  18. Design example • 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.

  19. Design example fz = 5kHz, fp =80 kHz, gain 40

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