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I2 Average Current Mode Control for Switching Converters

Fig.1 Proposed I2 average current mode control.
Fig.1 shows the proposed I2 average current mode control structure. The current loop consists of a fast direct feedback loop and a slow integral feedback loop. The integration provides a dynamic offset between vc and vci to eliminate a low frequency control error. Voltage loop is the outer loop for voltage regulation. As the current information is used twice in control loop, following the name V2 control, the proposed control is named as I2 control.
The I2 control can achieve fast and accurate current control, without requiring an external ramp. In CCM, as on-time is fixed, the switching frequency fsw of I2 control is independent on the inductor value.
When the average current is below half of the inductor current ripple, the circuit operates in discontinuous-conduction-mode (DCM). In DCM, the synchronized rectifier is turned off when the inductor current reverses to minimize efficiency loss due to reverse current flow and gate charge switching.

Fig.2 Transient Response of I2 control in CCM.
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