摘要
该文设计了一款白光LED驱动DC-DC升压芯片。该设计基于电流控制模式、脉宽调制方式,减小了输出电压的纹波,确保控制环路更加稳定,同时采用同步整流技术,提高了升压转换效率,芯片开关频率为1MHz,保证外围器件可以选择小型的低ESR电容器,从而确保芯片有着更好的集成度。
本文首先讨论了DC-DC转换器的设计背景,阐述了国内电源管理行业面临的机遇与挑战。随后就组成DC-DC转换器的主要控制功能模块以及相应的辅助保护模块的设计进行详细的探讨,包括误差放大器,带隙电路、功率管驱动、振荡器、PWM比较器以及相应的欠压、过压、热关断等保护模块,且一并给出了仿真结果。
本设计采用SANYO 0.6um 1P2M BiCMOS工艺,每个电路模块都通过了功能、性能仿真,达到了所需要的设计指标。整个系统的主要指标为:输入电压范围为2.7~7V,典型开关电流400mA,最大输出电压为14.6V,转换效率为80%,能驱动最多4个串联白光LED,该设计能广泛应用于手机、MP3以及白光LED照明等应用场合。
A boost DC–DC converter was designed for the application of white LED. The method of Current mode Pulse width module was adopted for decreasing the ripple of output voltage and the Technology of synchronous was used for increasing the circuit efficiency. Fixed 1MHz operation frequency of this converter allows the use of small, low ESR capacitors as well as a more integration, which is more important in portable application.
In the paper, the background was introduced at first, the opportunity and challenge for Chinese power management design was illuminated. Then the detail circuits of design were depicted clearly, including Error amplifier, Bandgap, the driver of Power device, oscillator, PWM comparator, over-voltage protector, thermal shutdown and the block for soft-star.
The process of SANYO 1.6um 1 poly 2 metal BiCMOS was used for design. Every circuits pass the functional and performance simulation, and the results of simulation meet the specification. The key specification of this system is: input voltage is range from 2.7V to 7V; the typical switching current is 400mA, the max output voltage is 14.6V, and the efficiency of converter is up to 80%.
The design can be used widely in mobile phone、MP3 and other fields which need the white LED for backlight.
引文
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