Daniel Hart Eletrônica de Potência (cap 7 Solucionário), Exercícios de Eletrônica de Potência

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CHAPTER 7 SOLUTIONS

4/03/ 7-1) 7-2)

7-4) Example design

b) The currents in the converter are shown below. The winding currents are for the windings in the ideal transformer model, not the physical windings. The physical primary winding current is the sum of winding #1 and Lm currents.

The current in the physical primary winding is the sum of iL1 and iLm in the model. The physical currents in windings 2 and 3 are the same as in the model.

7-18) The input voltage vx to the filter is Vs(Ns / Np) when either switch is on, and vx is zero when both switches are off. (See Fig. 7-8.) The voltage across Lx is therefore 7-19) 7-20)

Time 3.000ms 3.004ms 3.008ms 3.012ms 3.016ms 3.020ms V(Output) AVG(V(Output)) 29.5V 30.0V 30.5V Output voltage (3.0200m,30.057) (3.0141m,29.697) (3.0041m,30.295) Time 3.000ms 3.005ms 3.010ms 3.015ms 3.020ms I(TX1:3) AVG(I(TX1:3)) -200mA 0A 200mA SEL>> (3.0200m,83.489m) Secondary current I(TX1:1) AVG(I(TX1:1)) 0A 2.0A 4.0A (3.0200m,912.072m) Primary current

Using a nonideal switch and diode produces lower values for the currents. For iLx, the maximum, minimum, and average values in PSpice are 1.446 A, 0.900 A, and 1.17 A, compared to 1.56 A, 1.01 A, and 1.28 A, respectively. However, the peak-to-peak variation in iLx in PSpice matches that of the ideal circuit (0.55 A). Time 3.60ms 3.61ms 3.62ms 3.63ms 3.64ms 3.65ms 3.66ms I(L3) -1.0A 0A 1.0A (3.6115m,539.288m) -I(L2) -2.0A 0A 2.0A (3.6287m,903.647m) (3.6114m,1.4463) I(L1) -2.0A 0A 2.0A (3.6287m,603.330m) (3.6114m,1.5068) I(Lx) 0A 2.0A SEL>> (3.6286m,900.720m) (3.6114m,1.4463)

Using Vs = 6 V as in Example 7-8, the frequency response of the open-loop system shows that the crossover frequency is approximately 16.8 kHz. The phase angle at the crossover frequency is 17°, which is much less than the desired value of at least 45°. Therefore, the system does not have the desired degree of stability.

Frequency 10Hz 100Hz 1.0KHz 10KHz 100KHz DB(V(error)) P(V(error))

• 0 40 80 120 Phase Magnitude (dB) (16.814K,16.866) (16.814K,48.439m) 7-27) a) A frequency response of the circuit yields Vo ≈ -2.5 dB and θ ≈ 103° at 10 kHz.