Designing CV and CC Compensation for CYPD3184 - KBA227971

Version 4

    Author: SaiK_66           Version: **

     

    Question: How do you design CV and CC compensation in QR and DC modes using CYPD3184

     

    Answer: In isolated applications, an optocoupler is used to transmit the voltage feedback signal from the secondary side; the emitter current of the optocoupler flows through the capacitor to ground to set up the feedback voltage. CYPD3184 has an internal shunt regulator to drive the optocoupler photodiode to couple the control signal to the primary side. Loop compensation is applied on the secondary side as a Type-II compensation network with an R-C network to provide poles and zeros. The R-C network is connected from the feedback pin (FB) to the output of the error amplifier (EA_OUT).

     

    In addition to voltage regulation, CYPD3184 has a constant current (CC) mode feature to regulate the load current to any set current limit. In CC mode, the load current is kept constant by folding the VBUS voltage. CYPD3184 monitors the load current using the internal Low Side Current Sense Amplifier (LSCSA) and varies VBUS such that the load current regulates to the set target. The Type-II compensation network provides a stable operation in CC mode, limiting the overshoot and undershoot of the load current to specific limits during load transients. CC and constant voltage (CV) loops are independent of each other; only one loop acts at a time, based on the mode detected (either CC or CV).

     

    Use the attached design calculator tool to generate the CV and CC compensation values in Discontinuous Conduction Mode (DCM) and Quasi-Resonant Mode (QRM).