The Design Of A Near Threshold Start-up Voltage Hysteresis Current Mode BOOST Converter

In recent years, with the extensive research on wireless energy harvesting, especially for various types of environmental energy collection and use, the market demand for switching power supply increasing. How to design a low start-up voltage, low power consumption, high conversion efficiency integrated BOOST type DC- DC converter becomes a popular research hotspot.At first, This paper introduces the basic working principle of a BOOST type DC – DC converter, and gives the detailed comparative analysis of the various feedback mode, switching modulation scheme and power stage model of the system. According to market applications, the hysteresis current mode is adopted as the system feedback control mode. Then, the principle of the low-voltage start-up is explained detailedly, and a new and efficient three-step near threshold voltage start-up circuit model is given, some concrete low power consumption solutions in the chip design are proposed. Then, according to the parameters of the modules determined by front system-level model, all of the module circuit including near threshold voltage start-up circuit, bandgap reference circuit, error amplifier, hysteresis voltage comparator, current detection circuit and over-temperature protection circuit are designed, and the detailed circuit structures are represented, their principles are analyzed. Finally, based on SMIC 0.18?m dual-well CMOS process, the simulation of the module circuits and the whole chip is going on with Spectre software of Cadence.The simulation results show that the proposed BOOST type DC-DC converter works properly, and the parameters and performances of the system meet the design requirements. The minimum input voltage can be as low as 0.35 V, load current range is 0.1-50 m A, output voltage is stabilized at 1.8V, and the output voltage ripple is very small(CCM state, ripple <3m V, DCM state, ripple <10m V). In low input voltage condition(0.35V), the conversion efficiency is over 50%. In the situation of the input voltage being 1.2V, the output voltage being 1.8V, and load current being 25 m A, the conversion efficiency is up to 91%. And the system can switched automatically between CCM and DCM modes according to the output load current. For the purpose of improving the conversation efficiency in light load condition, the thermal shutdown circuit and over-voltage protection circuit are added to ensure the security of chip during operation. What's more, the adoption of anti-ring circuit can inhibit the effect of electron magnetic interference on the performance of chip.