Control Scheme of Average Current Mode Control of Switching Power Supplies

        For this scheme the circuit diagram shown in the figure below. Its single voltage feedback path is the major advantage of this circuit wherein by comparing the waveform the duty ratio is controlled that is obtained from the resulting error voltage through the operational amplifier along with the ramp that is fixed. To design and analyze owing it to the single loop so this circuit topology is easy. In voltage mode control the modulation is stable due to the high ramp amplitude. Due to low impedance at the output cross-regulation is better compared to current-mode control. Moreover, there are the following disadvantages of this technique and because of their disadvantages this could not be used in certain application these are given below;

        As compared to the current-mode control voltage-mode control has the slow response due to any change by the change in output voltage in input voltage or else load resistance would be first required to be sensed. In the input voltage as well as load resistance the voltage feedback loop will then correct any changes.

In the feedback loop the RC-circuit at the output adds an extra pole. Moreover, through the controller a zero would be required.

With the change in line voltage the open loop gains of the circuit changes.

Figure: boost converter voltage mode control