Fundamentals of PWM Dc-to-Dc Power Conversion Dynamic Performance of PWM Dc-to-Dc Converters
2 Performance of PWM Dc-to-Dc Converters Dc-to-Dc Converter Performance ● Static performance: ● Dynamics performance Stability Frequency-domain response: Time-domain response:
3 Buck Converter Example Stability
4 Stability of Buck Converter Stability
5 Loop Gain Stability
6 Stability of Buck Converter Stability
7 Input-to-Output Frequency Response: ● Input-to-output transfer function: : Laplace transformation of ac component of : Laplace transformation of ac component of Frequency-Domain Performance Criteria
8 Audio-Susceptibility Time-Domain Performance Criteria Audio-susceptibility
9 Input-to-Output Frequency Response Frequency-Domain Performance Criteria
10 Load Current-to-Output Transfer Function: ● Load current-to-output transfer function: : : Laplace transformation of ac component of : Laplace transformation of ac component of Frequency-Domain Performance Criteria
11 Output Impedance Time-Domain Performance Criteria Output impedance
12 Load Current-to-Output Frequency Response Time-Domain Performance Criteria Output impedance
13 Step Load Response ● Transient response of the output voltage due to step change in the input voltage Time-Domain Performance Criteria
14 Output Impedance and Step Load Response Time-Domain Performance Criteria Output impedanceStep load response
15 Step Input Response Time-Domain Performance Criteria ● Transient response of the output voltage due to step change in load current
16 Audio-Susceptibility and Step Input Response Time-Domain Performance Criteria Audio-susceptibility Step input response
17 Definition of Stability ● Stability of transfer function T(s) or stability of an LTI system having T(s) as its transfer function ● T(s) or LTI system is stable if and only if all the roots of the characteristic equation are located in the left-half plane(LHP) of the s-plane Stability Definition
18 Nyquist (Stability) Criterion ● Nyquist(Stability) Criterion: Graphical method to determine the number of RHP roots in 1+T m (s)=0 Nyquist Criterion
19 Application Example ● ● Characteristic equation Nyquist Criterion
20 Stability Analysis of PWM Converters Nyquist Criterion
21 Nyquist Analysis on 1+T m (s)=0 Nyquist Criterion
22 Absolute Stability Nyquist Criterion
23 Stability Analysis Using Bode Plot Nyquist Criterion
24 Marginally Stable Buck Converter
25 Marginally Stable Buck Converter
26 Conditionally Stable System Marginally Stable Buck Converter
27 Effect of Gain and Phase Delay Relative Stability
28 Gain Margin ● Gain margin : the amount of gain increase that can be added to before the system becomes unstable, Stability Margins
29 Phase Margin ● Phase margin : the amount of phase delay that can be added to before the system becomes unstable, Stability Margins
30 Gain Margin and Phase Margin Stability Margins
31 Stability Margins and Closed-Loop Performance ● Proximity to (-1,0) point Small stability margin Nearness of poles to imaginary axis:
32 Buck Converter Example Stability Margins and Closed-Loop Performance
33 Buck Converter Example Stability Margins and Closed-Loop Performance
34 Buck Converter Example: Step Load Response Stability Margins and Closed-Loop Performance