The voltage mode is not the only way of closing the loop. In current mode control, in addition to the feedback voltage, there is an inner feedback loop that monitors the current. A current sense amplifier senses the inductor current and converts it to a voltage. This signal is fed to a comparator together with the output of the error amplifier and the slope compensation. Slope compensation is necessary to avoid sub-harmonic oscillations, the details of this go beyond the scope of this presentation. As in the voltage mode, during each cycle, the PWM comparator modulates the power transferred to the load, but this time the inductor peak current is also changed based on the feedback error voltage. This is the principle of a slope compensated, current mode PWM control, which provides stable switching and cycle-by-cycle current limiting for excellent load and line response.