Answer Happy

Consider the buck converter with controller shown in Figure 1. Assume that the de input voltage is 150V. The rated output power 1 kW. The duty cycle is adjusted by the controller to keep the output voltage constant at 50V. The switching frequency is 1kHz. Answer the following questions when the converter operates in steady state. + + Controller + V- + L + i Voi D с V Load V. SW d 11 Figure 1 Buck converter with controller 1. Calculate the inductance if the boundary current happens when the load is 10% of the rated load. (5%) 2. Choose the capacitance if the output ripple voltage is less than 200mV when the load is rated load. Use above calculated inductance. (5%) 3. Calculate the duty cycle, D when the inductance 2mH and the converter output 20% of rated load current.(5%) 4. Calculate the peak current in switch, Idpk , when the load is full load. (5%) 5. If the load draws rated load current, sketch to scale the following waveforms in two cycles. Indicate on each waveform the maximum and minimum values. (10%) a. the voltage waveform across the inductor, VL , b. the current waveform of inductor, il , c. the current waveform of switch, id.