Designing a Dynamic Ramp with Invariant Inductor in Current-Mode Control Circuit for Buck Converter

Current-mode control circuit is widely used to achieve better transient response, because the current-mode control circuit contains two feedback signals for a voltage loop and a current loop. A difference between the voltage-mode control circuit and current-mode control circuit, the current-mode control circuit can sense the inductor current signal which causes the control to have a better transient response. However, it also produces a subharmonic issue when the duty cycle is larger than 50%. Designing a dynamic ramp with invariant inductor in current-mode control circuit for buck converter is showed in this chapter. This configuration maintains system stability under a wide range of the input/output voltages without changing the inductor and compensation circuit. The dynamic ramp can be adjusted according to varied the output voltage or the voltage droop between the input voltage and the output voltage to maintain bandwidth and phase margin using the invariant inductor and compensation circuit. Finally, 14-V input voltage, 12-V output voltage, and 24-W output power with the dynamic ramp sampling the output voltage is implemented using MathCAD predictions, SIMPLIS simulation results, and experimental results to verify its viability and superiority.