A monolithic step down converter with frequency-variable protection technique

Motivated by portable electronic equipments which demand compact, light weight, and highly efficient DC/DC converters, a step down converter with a novel on-chip current protecting technique is presented in this paper. Based on the proposed frequency-variable protection technique, the duty cycle become lower when the output current exceeds the first given value (the voltage across RS is greater than 200mV). While, both the pulse width and operating frequency will be decreased quickly if the output current exceeds the second set value (V_RS>220mV). This innovative protection program greatly reduce the chip´s power loss in the case of short circuit. Besides, the chip´s over-temperature protection function is also proposed and analyzed. The results of simulation and typical application testify the feasibility of the proposed technique.