| Development of microelectronics and communication technology has greatly promoted the research and popularization of consumer electronics. The electronic equipment has become part of people’s lives. No matter the common equipment or the cutting-eage technology instruments, the stable power supply is the pre mise of maintaining their operating. Switching Power Supply can achieve high energy efficiency, stable performance and small size. Because of the high response speed and current protection, the DC-DC converter has been widely adopted in different field.The thesis resesrchs the theory of the Boost DC-DC converter and analyses the reason of unstable process which caused by the changing voltage and inductance c urrent fluctuations. We find the related solutions and design a converter for LED driver. The circuit is a Boost type converter which adopts peak current mode and pluse width modulation. The frequency is 1.7MHz, the range of input voltage is 2.5V~5.5V and the maximum output voltage 20 V. Specially, the output current can be regulated according the requirement and realizes high stability.For achieving the purpose, we have designed the related modules, including bandgap reference, oscillators, adaptive alope aompensation and so on. Considering its reliability, we designed the under voltage lock out circuit and other protection modules to make the chip work in the safe operating area.After the design of the sub- module of the converter, we simulated the circuit by Cadence Spectre base on 0.5μm BCD peocess. The simulation results show the start time is about 240μs. When the output voltage is 15.8V, the average output current is 61.2 mA and the current fluctuation range is ±0.95 mA. When we keep the regulation current resistance constant and change the number of LED, the average output current changes very little. O n the other hand, if we change the regulation current resistance, the output current has inverse proportion ratio changes and the current ripple is still small. This indicates that the circuit can achieve constant current and meet the design requirments basically. |
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