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# A New Inverse Charge Constant On-Time (IQCOT) Control for Noise Performance Improvement in Multiphase Operation

*I*) interacts with the voltage-loop compensator output (

_{sum}*V*) to generate the duty cycle. The issue with this control strategy is that when the duty cycle approaches the ripple cancellation point (where summation of the inductor current ripple becomes zero, i.e.,

_{c}*D*= 0.5 for two-phase operation), the ripples become smaller and smaller. This ripple cancellation effect at different multiphase operations is shown in Fig. 2. Fig 3 illustrates that when the duty is close to the ripple cancellation point (

*D*≈ 0.4 for two phases), the inductor current ripple becomes very small. In that case, any noise in

*V*or

_{c}*I*can create jittering at the output, and control becomes very noise-sensitive.

_{sum}This paper proposes a new COTCM control method based on the inverse charge control concept (IQCOT control). In Fig. 4, a two-phase COTCM control with the proposed structure is shown. In this control, unlike conventional COTCM,

*V*

_{c}-*I*is used to charge a capacitor and in every cycle, the cap voltage (_{sum}*V*) is compared with a_{ramp}*V*to generate the duty cycle for control. The advantage of the proposed IQCOT control is that, as it is not a ripple-based control, when the duty cycle is approaching the ripple cancellation point, and the inductor current ripple becomes very small, there is no noise impact, since modulation depends on the_{TH}*V*signal, which is still very large. Furthermore, at the ripple cancellation point, when the ripple is zero, the converter can still operate normally, as_{ramp}*V*can still be generated by the voltage difference between_{ramp}*V*and_{c}*I*×_{L}*R*. This is shown in Fig. 5, where for four phases, the converter is operating at the ripple cancellation point (at_{i}*D*= 0.25), and the ripple current summation*I*is zero. But_{Lsum}*f*is determined by the_{sw}*V*signal, which is 2_{ramp}*V*in this case. Fig 6 shows the test results for the proposed control. As illustrated, in two-phase operation with*D*= 0.5,*I*is almost negligible._{sum}

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