Design Of A Low Voltage Start-up PWM DC/DC Converter

With the development of electronic technology, the electronic equipment has been used widely in our work and life. Every electronic equipment can not be operated without a reliable power supply because the switch mode power supply (SMPS) has the characteristics of high integration, most cost effective, simple periphery circuit and high efficiency so it has been used broadly.A boost PWM DC/DC converter is designed based on CMOS technology in this thesis. The bandgap-reference. with a low temperature coefficient (TC) of 5 ppm/℃and a high power supply rejection ratio (PSRR) at low frequency provides a stable and precision voltage reference for the whole circuit. The low voltage start-up mode makes the whole circuit start up at a lower input voltage of 0.85V, extending the operation time of the battery. The low voltage start-up module controls the internal NMOS switch under the maximum peak inductor current, with an approximate 1.5μS off-time during start-up, allowing the circuit to start up an output load. The whole circuit also includes the over-temperature protection circuit and the over-current protection circuit.In this thesis, the basic principle of the SMPS is proposed at first. Then the circuit architecture is designed according to the customer's requirement. The sub-block circuits, addition to the whole circuit, are also designed and simulated with Hspice. The result shows that the desired functions and performance are achieved. Finally, the layout is designed with Cadence virtuoso, which is verified by DRC and LVS, with post-layout simulation performed simultaneously.