I try to design a buck-converter in PSIM simulation program. Let me write the circuit's requirements:
Frequency = 80kHz
Ripple < 0.5%
\$V_{input}\$ = 30V
\$V_{out}\$ = 12V
\$R_{load}\$ = 10 \$\Omega\$
Here are my calculations:
\$ D = \frac{V_{input}}{V_s} = \frac{12}{30} = 0.375 \equiv 67.5 \% \$
\$ L_{min} = \frac{(1-D)R}{2f} = \frac{(1-0.375)*10}{2\cdot80\cdot10^{3}} = 39.0625 \mu H \$
\$ C = \frac{1-D}{8\cdot \left(\frac{\Delta V_{o}}{V_o} \right)\cdot f^2} = \frac{1-0.375}{8\times 48.828 \times 10^{-6} \times \left( 80 \cdot 10^3 \right)^2} = 50 \mu F \$
as shown in the figure.
simulate this circuit – Schematic created using CircuitLab
Here is the schematic that I draw in PSIM with the calculated values. I float some of the values.
Simulation results for 2ms run:
Input-Output Voltage Diagram:
Output voltage diagram between 1.2ms and 1.6ms:
What is the problem?
As I calculated above, the output voltage value should be 12V but, when analyse the circuit, it returns about 6 volts. I test this circuit for another values and calculations but result always same. It returns half of the calculated-output voltage value. I couldn't figure it out. Why output voltages are always half of the calculated value?
