I was trying to design a current mode boost converter in CCM using a MCP1630 and the specifications of the design are as follow:
Vinmin=2.7V (minimum input voltage). Vinmax=4.2V (maximum input voltage). Vout=5V (Output voltage). Iout=5A (Maximum output current). RL=5 Ohm (load resistor Vout/Iout).
I have calculated the components and they are as follow:
Dmin=0.16 (Minimum duty cycle) Dmax=0.46 (Maximum duty cycle) L=5uH (Inductor value) Ipeak=2.2A (Peak current) C=200uF (Output capacitor) Fc=8kH (Crossover frequency)
The sense resistor is selected to be Rs=0.36 ohm, because the maximum current sense signal for MCP1630 is 0.9V (for Ipeak=2.2A Vsense=Ipeak*Rs=0.36*2.2=0.8v, we let 0.1V as a margin).
For the feedback control I have sellected a type 2 amplifier with the following components:
*Divider network: Rup=Rlow=10k *Refrence voltage Vref=2.5V *C1=2.5nF *C2=15.6pF *R2=100k
I provide the circuit bellow:
Unfortunatly, when I simulated my circuit, I never get 5V at the output, instead I get 3.94 and the duty cycle approaches 90% and I don't know what is the reason for that failure. Please try to figure out where I have mistaken!!
Bellow I provide you with the signals: