class: center, middle # EE-464 STATIC POWER CONVERSION-II # Midterm Recitation ## Ozan Keysan ## [keysan.me](http://keysan.me) ### Office: C-113
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Tel: 210 7586 --- # Ex. Mohan 10-3 -- ## In a regulated flyback converter with 1:1 turns ratio, Vo=12V, Vd=12-24V, Pload is 60W, and the switching frequency is 200 kHz. -- ## Calculate the maximum value of the magnetizing inductance Lm that can be used if the converter is always required to operate in a complete demagnetization (i.e. discontinuous conduction mode). --- # Ex. Mohan 10-3 -- ### 1:1 ratio means same as a buck-boost converter -- ### Refer to Mohan Section 7.5.2 --
--- # Solution -- ####1:1 turns ratio, then it is same as a buck converter -- #### Smallest \\(I\_{OB}\\) occurs when \\(V_d\\) is min (Read Mohan Sect. 7.5.2) -- #### \\(D= \dfrac{V_o}{V_o + V_d} = \dfrac{12}{12+12} = 0.5\\) -- #### \\(I_O\\) should be calculated for the highest power (60 W) #### \\(I_O = \dfrac{60}{12}= 5A \\) -- \\(I_{OB} = \dfrac{T\_s V\_o (1-D)^2}{2L} = 5A\\) -- #### \\(L\_m = \dfrac{12 (1-0.5)^2}{200 10^3 2 \, 5} = 1.5 \mu H\\) --- # Ex. Mohan 10-5 -- ### A switch-mode supply with the following specs are designed: ### Vd=48 V ± 10%, ### Vo=5V, ### fs=100kHz, ### Pload=15-50W -- ### A forward converter is operating in continuous conduction mode with the demagnetizing winding (N3=N1). Assume ideal components (except transformer magnetization) --- # Ex. Mohan 10-5 -- ## a) Calculate N2/N1 if the turns ratio is desired to be as small as possible. -- ## b) Calculate the minimum value of filter inductance. --- # Solution -- #### \\(N\_3 = N\_2 \rightarrow D\_{max}=0.5 \quad 43.2 V \lt V\_d \lt 52.8 V \\) -- #### \\( \dfrac{V\_o}{V\_d} = \dfrac{N_2}{N_1} D \\) -- #### \\( \dfrac{V\_o}{V\_{dmin}} = \dfrac{5}{43.2} = \dfrac{N\_2}{N\_1} 0.5 \rightarrow \dfrac{N\_2}{N\_1} = 0.232 \\) -- #### Let's check for maximum Vd #### \\(\dfrac{V\_o}{V\_{dmax}} = \dfrac{N\_2}{N\_1} D\_{min} \rightarrow \dfrac{5}{52.8} =\dfrac{N\_2}{N\_1}D \\) -- #### \\(D = 0.408 \\) Condition satisfied --- ### b) Minimum value of the filter inductance -- #### \\( \dfrac{N\_2}{N\_1} = 0.232 \\) #### \\(P\_{min} = 15 W \rightarrow I\_{omin} = 3A = I\_{Lmin}\\) -- #### At the boundary: #### \\(\dfrac{(V\_d \dfrac{N\_2}{N\_1} - V\_o ) D}{2 L\_{min}} t\_{on}= I\_{omin}\\) -- #### \\( V\_{dmin} = 43.2 \rightarrow D=0.5 \rightarrow L\_{min}=4.18 \mu H\\) -- #### \\( V\_{dmax} = 52.8 \rightarrow D=0.408 \rightarrow L\_{min}=4.93 \mu H\\) #### Therefore \\( L\_{min}=4.93 \mu H \approx 5 \mu H \\) should be used --- # Ex. W.Hart 7.2 -- ### Design a converter to produce and output voltage of 36V from a 3.3V supply. The output current is 0.1 A. -- ### Design for an output ripple voltage of 2%. Include ESR when choosing a capacitor. -- ### Assume for this problem that the ESR is related to the capacitor value by \\(r\_c = 10^{-5}/C\\). -- ### Solution available in the textbook --- # Ex. W.Hart 7.4 -- ### A forward converter of Fig. 7-5a has the following parameters: -- - ### Vs=48V - ### R= 10 Ohm - ### Lx = 0.4 mH, Lm = 5 mH - ### C=100 uF - ### f = 35 kHz - ### N1/N2= 1.5, N1/N3=1 - ### D=0.4 --- # Ex. W.Hart 7.4 ## a) Determine the output voltage, the maximum and minimum currents in Lx, and the output voltage ripple. -- ## b) Determine the peak curren in the transformer primary winding. Verify that the magnetizinf current is reset to zero during each switching period. ### Solution available in the textbook --- # Ex. W.Hart 7.4 --
--- # Ex. W.Hart 7.4 --
--- # Ex. W.Hart 7.4 --
--- # Ex. W.Hart 7.4 --
--- # Ex. W.Hart 8.9 -- ## Design a bipolar PWM single phase inverter that will produce 75 Vrms, 60 Hz output from a 150 Vdc supply. -- ## Rload=12 Ohm, Lload=60mH. Select the switching frequency such that the current THD is less than 10 %. --- # Ex. W.Hart 8.9 --
--- # Ex. W.Hart 8.9 --
### Solution available in the textbook and also in the YouTube Channel --- ## You can download this presentation from: [keysan.me/ee464](http://keysan.me/ee464)