Ultra-low startup voltage low output ripple high-efficiency hysteretic current mode step-up DC–DC converter

This study proposes a hysteretic current mode step-up DC–DC converter with ultra-low startup voltage, low output ripple and high efficiency, which is suitable to be used as a power supply for an accurately voltage controlled systems, high-efficiency devices and low-voltage supply applications. A startup module is used for operating the switches when the input voltage is not high enough to supply the control circuit. The output ripple is restricted by a fixed-hysteretic current mode controller whether the load is heavy or light. The high efficiency is obtained by applying an auto-mode changed technology under light load. This makes some sub-circuits of the chip enter into the power save mode and shuts down the power switching devices. At the same time, a back-gate diode of the rectifying power metal-oxide semiconductor device is used for maintaining output voltage. The chip has been made with a standard 0.35-μm complementary metal-oxide semiconductor process forming an area of only 960 μm × 820 μm. Experimental results show that the minimum startup voltage is 0.8 V; and the output voltage ripple is <10 mV. Moreover, the peak efficiency is 95% with a heavy load that can prolong battery life.