Research On Multi Mode DC-DC Converter And Diverse Application Circuits

With the rapidly development of semiconductor process, power management IC has become an indispensable part of all electronic equipment, the demand of power management IC (intergrated circuit) is also growing year by year. In recent years, the power IC has matured. High efficiency, flexible working mode, large load current and rapidly transient response DC-DC converter has become a goal of power IC, and a widely application prospect is demanded. With the increasing power value of popular portable power devices, high stability from no load to the full load is necessary in DC-DC design and application.Firstly, the development and application of power IC is introduced in the dissertation, then the basic structure and working principle of buck, boost and buck-boost DC-DC converter are analyzed in detail. The chip is designed based on the system-level application and electrical characteristics. The charactors are analyzed under different operating modes and different application conditions, so a novel compensation network and multi-mode operation are contrived. The converter is simulated by the technology model, and experimented according to the application at last. The contributions are as follows.1. A dual-mode boost converter with constant voltage mode and constant current mode is proposed in this dissertation. A constant voltage is achieved in a wide range of load current, with the load current increasing, and constant current mode is achieved. Dual mode converter output is introduced by an internal multi-mode comparator. The converter has been taped out using 0.35μm CMOS process, and is on the mass production process after test and revision. Together with a charging IC, single inductor and dual loop working mode can be completed. The upper and lower MOS (Metal-oxide-semiconductor) current can be measured by using a high precision mirror current sample inside the converter, accomplish high-precision current sampling and ensuring accurate circuit mode switching.2. Based on the wide input range (2.7V～5.5V) buck-boost converter, a novel internal topology is designed, which is consist of power stage section, feedback loop and logic modules, making sure the normal operation of the converter. A current feedback loop is provided to improve the response speed. With the module above, the circuit can accommodate to the applications of wide input range, large-power, high-precision. Three light-heavy load named PWM/Burst/Sleep modes are introduced. Buck/Boost/Buck-Boost modes can be chosen depending on the value of input voltage. The proposed converter with variable modes obtains higher efficiency compared with conventional buck/boost converter. A loop compensation network is designed through theoretical analysis and simulation. The phase margin of the loop can be selected by the peripheral circuit, so the stability and reliability of the loop are improved. Through the test results, the converter maintains high efficiency in all load condition. Line regulation and load transient are very well in the period of input-mode switching and output-mode switching.3. Based on the buck-boost converter, a novel average current sensing circuit is discussed. The circuit can adjust the operation mode according to the inductor current. By simulation and experiment, the current sensing circuit can realize higher accuray compared with conventional current sensing circuit. High accurate current sensing is benefit to smooth mode switching and high efficiency. The converter is released by 0.18μm CMOS process, and input to market after test and minor changes.4. More popular electronic products are proposed and designed in the dissertation. Dual-loop single-inductance power bank uses a common inductor to drive two working loops. This method overcomes the conventional circuit design methods which every loop is consist of separate inductor and feedback loop. This circuit can achieve cost down under high efficiency and stable operation. Thus, the market competitiveness is improved. The design occupies a relatively large proportion in power bank application. Then, a controller IC design technique is proposed, which the circuit can be applied in large-power power bank, electronic cigarettes and QC2.0 charging application. An automatic power regulator is provided to implement novel function.5. Based on regular DC-DC converter, the dissertation introduces a proposed external components placement and EVB layout method. In buck and boost converters, the placement of peripheral input and output capacitors can influence the switching circuits. Via theoretical analysis and experimental result, the reasonable placement of external capacitors in buck and boost EVBs are obtained respectively.