The novel ripple-based I2 type control technique for buck converters with constant current output

This paper presents two novel ripple-based I2 type control techniques, I2 constant off-time (I2-CFT) control and I2 constant on-time (I2-COT) control applied for buck converters with constant current output, as well as the detailed introduction of their operating principles and calculation of critical equivalent series resistance (ESR). Afterwards, the merits and weaknesses among the conventional peak current mode (PCM), I2-COT and I2-CFT controlled buck converters are further compared. Research results indicate that I2-CFT control is superior to the other two techniques. Furthermore, fixed frequency I2-CFT control is achieved by bringing in the input voltage feed-forward and output voltage feed-back. Simulation results verify the theoretical analysis and demonstrate the frequency of fixed frequency I2-CFT control is immune to the variation of input voltage, reference current and load.